Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux-2.6

19 files changed, 1528 insertions, 846 deletions

diff --git a/net/dccp/ackvec.c b/net/dccp/ackvec.c
index 1e8be246ad15..01e4d39fa232 100644
--- a/net/dccp/ackvec.c
+++ b/net/dccp/ackvec.c
@@ -12,7 +12,6 @@
 #include "ackvec.h"
 #include "dccp.h"
 
-#include <linux/dccp.h>
 #include <linux/init.h>
 #include <linux/errno.h>
 #include <linux/kernel.h>
@@ -68,7 +67,7 @@ int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
 	struct dccp_sock *dp = dccp_sk(sk);
 	struct dccp_ackvec *av = dp->dccps_hc_rx_ackvec;
 	/* Figure out how many options do we need to represent the ackvec */
-	const u16 nr_opts = DIV_ROUND_UP(av->av_vec_len, DCCP_MAX_ACKVEC_OPT_LEN);
+	const u8 nr_opts = DIV_ROUND_UP(av->av_vec_len, DCCP_SINGLE_OPT_MAXLEN);
 	u16 len = av->av_vec_len + 2 * nr_opts, i;
 	u32 elapsed_time;
 	const unsigned char *tail, *from;
@@ -100,8 +99,8 @@ int dccp_insert_option_ackvec(struct sock *sk, struct sk_buff *skb)
 	for (i = 0; i < nr_opts; ++i) {
 		int copylen = len;
 
-		if (len > DCCP_MAX_ACKVEC_OPT_LEN)
-			copylen = DCCP_MAX_ACKVEC_OPT_LEN;
+		if (len > DCCP_SINGLE_OPT_MAXLEN)
+			copylen = DCCP_SINGLE_OPT_MAXLEN;
 
 		*to++ = DCCPO_ACK_VECTOR_0;
 		*to++ = copylen + 2;
@@ -432,7 +431,7 @@ found:
 int dccp_ackvec_parse(struct sock *sk, const struct sk_buff *skb,
 		      u64 *ackno, const u8 opt, const u8 *value, const u8 len)
 {
-	if (len > DCCP_MAX_ACKVEC_OPT_LEN)
+	if (len > DCCP_SINGLE_OPT_MAXLEN)
 		return -1;
 
 	/* dccp_ackvector_print(DCCP_SKB_CB(skb)->dccpd_ack_seq, value, len); */
diff --git a/net/dccp/ackvec.h b/net/dccp/ackvec.h
index bcb64fb4acef..4ccee030524e 100644
--- a/net/dccp/ackvec.h
+++ b/net/dccp/ackvec.h
@@ -11,15 +11,14 @@
  *	published by the Free Software Foundation.
  */
 
+#include <linux/dccp.h>
 #include <linux/compiler.h>
 #include <linux/ktime.h>
 #include <linux/list.h>
 #include <linux/types.h>
 
-/* Read about the ECN nonce to see why it is 253 */
-#define DCCP_MAX_ACKVEC_OPT_LEN 253
 /* We can spread an ack vector across multiple options */
-#define DCCP_MAX_ACKVEC_LEN (DCCP_MAX_ACKVEC_OPT_LEN * 2)
+#define DCCP_MAX_ACKVEC_LEN (DCCP_SINGLE_OPT_MAXLEN * 2)
 
 #define DCCP_ACKVEC_STATE_RECEIVED	0
 #define DCCP_ACKVEC_STATE_ECN_MARKED	(1 << 6)
diff --git a/net/dccp/ccid.c b/net/dccp/ccid.c
index 8fe931a3d7a1..bcc643f992ae 100644
--- a/net/dccp/ccid.c
+++ b/net/dccp/ccid.c
@@ -13,6 +13,13 @@
 
 #include "ccid.h"
 
+static u8 builtin_ccids[] = {
+	DCCPC_CCID2,		/* CCID2 is supported by default */
+#if defined(CONFIG_IP_DCCP_CCID3) || defined(CONFIG_IP_DCCP_CCID3_MODULE)
+	DCCPC_CCID3,
+#endif
+};
+
 static struct ccid_operations *ccids[CCID_MAX];
 #if defined(CONFIG_SMP) || defined(CONFIG_PREEMPT)
 static atomic_t ccids_lockct = ATOMIC_INIT(0);
@@ -86,6 +93,47 @@ static void ccid_kmem_cache_destroy(struct kmem_cache *slab)
 	}
 }
 
+/* check that up to @array_len members in @ccid_array are supported */
+bool ccid_support_check(u8 const *ccid_array, u8 array_len)
+{
+	u8 i, j, found;
+
+	for (i = 0, found = 0; i < array_len; i++, found = 0) {
+		for (j = 0; !found && j < ARRAY_SIZE(builtin_ccids); j++)
+			found = (ccid_array[i] == builtin_ccids[j]);
+		if (!found)
+			return false;
+	}
+	return true;
+}
+
+/**
+ * ccid_get_builtin_ccids  -  Provide copy of `builtin' CCID array
+ * @ccid_array: pointer to copy into
+ * @array_len: value to return length into
+ * This function allocates memory - caller must see that it is freed after use.
+ */
+int ccid_get_builtin_ccids(u8 **ccid_array, u8 *array_len)
+{
+	*ccid_array = kmemdup(builtin_ccids, sizeof(builtin_ccids), gfp_any());
+	if (*ccid_array == NULL)
+		return -ENOBUFS;
+	*array_len = ARRAY_SIZE(builtin_ccids);
+	return 0;
+}
+
+int ccid_getsockopt_builtin_ccids(struct sock *sk, int len,
+				    char __user *optval, int __user *optlen)
+{
+	if (len < sizeof(builtin_ccids))
+		return -EINVAL;
+
+	if (put_user(sizeof(builtin_ccids), optlen) ||
+	    copy_to_user(optval, builtin_ccids, sizeof(builtin_ccids)))
+		return -EFAULT;
+	return 0;
+}
+
 int ccid_register(struct ccid_operations *ccid_ops)
 {
 	int err = -ENOBUFS;
@@ -205,20 +253,6 @@ out_module_put:
 
 EXPORT_SYMBOL_GPL(ccid_new);
 
-struct ccid *ccid_hc_rx_new(unsigned char id, struct sock *sk, gfp_t gfp)
-{
-	return ccid_new(id, sk, 1, gfp);
-}
-
-EXPORT_SYMBOL_GPL(ccid_hc_rx_new);
-
-struct ccid *ccid_hc_tx_new(unsigned char id,struct sock *sk,  gfp_t gfp)
-{
-	return ccid_new(id, sk, 0, gfp);
-}
-
-EXPORT_SYMBOL_GPL(ccid_hc_tx_new);
-
 static void ccid_delete(struct ccid *ccid, struct sock *sk, int rx)
 {
 	struct ccid_operations *ccid_ops;
diff --git a/net/dccp/ccid.h b/net/dccp/ccid.h
index fdeae7b57319..18f69423a708 100644
--- a/net/dccp/ccid.h
+++ b/net/dccp/ccid.h
@@ -103,13 +103,31 @@ static inline void *ccid_priv(const struct ccid *ccid)
 	return (void *)ccid->ccid_priv;
 }
 
+extern bool ccid_support_check(u8 const *ccid_array, u8 array_len);
+extern int  ccid_get_builtin_ccids(u8 **ccid_array, u8 *array_len);
+extern int  ccid_getsockopt_builtin_ccids(struct sock *sk, int len,
+					  char __user *, int __user *);
+
 extern struct ccid *ccid_new(unsigned char id, struct sock *sk, int rx,
 			     gfp_t gfp);
 
-extern struct ccid *ccid_hc_rx_new(unsigned char id, struct sock *sk,
-				   gfp_t gfp);
-extern struct ccid *ccid_hc_tx_new(unsigned char id, struct sock *sk,
-				   gfp_t gfp);
+static inline int ccid_get_current_rx_ccid(struct dccp_sock *dp)
+{
+	struct ccid *ccid = dp->dccps_hc_rx_ccid;
+
+	if (ccid == NULL || ccid->ccid_ops == NULL)
+		return -1;
+	return ccid->ccid_ops->ccid_id;
+}
+
+static inline int ccid_get_current_tx_ccid(struct dccp_sock *dp)
+{
+	struct ccid *ccid = dp->dccps_hc_tx_ccid;
+
+	if (ccid == NULL || ccid->ccid_ops == NULL)
+		return -1;
+	return ccid->ccid_ops->ccid_id;
+}
 
 extern void ccid_hc_rx_delete(struct ccid *ccid, struct sock *sk);
 extern void ccid_hc_tx_delete(struct ccid *ccid, struct sock *sk);
diff --git a/net/dccp/ccids/ccid2.c b/net/dccp/ccids/ccid2.c
index 9a430734530c..c9ea19a4d85e 100644
--- a/net/dccp/ccids/ccid2.c
+++ b/net/dccp/ccids/ccid2.c
@@ -25,7 +25,7 @@
 /*
  * This implementation should follow RFC 4341
  */
-
+#include "../feat.h"
 #include "../ccid.h"
 #include "../dccp.h"
 #include "ccid2.h"
@@ -147,8 +147,8 @@ static void ccid2_change_l_ack_ratio(struct sock *sk, u32 val)
 		DCCP_WARN("Limiting Ack Ratio (%u) to %u\n", val, max_ratio);
 		val = max_ratio;
 	}
-	if (val > 0xFFFF)		/* RFC 4340, 11.3 */
-		val = 0xFFFF;
+	if (val > DCCPF_ACK_RATIO_MAX)
+		val = DCCPF_ACK_RATIO_MAX;
 
 	if (val == dp->dccps_l_ack_ratio)
 		return;
diff --git a/net/dccp/dccp.h b/net/dccp/dccp.h
index b4bc6e095a0e..0bc4c9a02e19 100644
--- a/net/dccp/dccp.h
+++ b/net/dccp/dccp.h
@@ -49,7 +49,7 @@ extern int dccp_debug;
 
 extern struct inet_hashinfo dccp_hashinfo;
 
-extern atomic_t dccp_orphan_count;
+extern struct percpu_counter dccp_orphan_count;
 
 extern void dccp_time_wait(struct sock *sk, int state, int timeo);
 
@@ -98,9 +98,6 @@ extern int  sysctl_dccp_retries2;
 extern int  sysctl_dccp_feat_sequence_window;
 extern int  sysctl_dccp_feat_rx_ccid;
 extern int  sysctl_dccp_feat_tx_ccid;
-extern int  sysctl_dccp_feat_ack_ratio;
-extern int  sysctl_dccp_feat_send_ack_vector;
-extern int  sysctl_dccp_feat_send_ndp_count;
 extern int  sysctl_dccp_tx_qlen;
 extern int  sysctl_dccp_sync_ratelimit;
 
@@ -252,7 +249,8 @@ extern const char *dccp_state_name(const int state);
 extern void dccp_set_state(struct sock *sk, const int state);
 extern void dccp_done(struct sock *sk);
 
-extern void dccp_reqsk_init(struct request_sock *req, struct sk_buff *skb);
+extern int  dccp_reqsk_init(struct request_sock *rq, struct dccp_sock const *dp,
+			    struct sk_buff const *skb);
 
 extern int dccp_v4_conn_request(struct sock *sk, struct sk_buff *skb);
 
@@ -435,12 +433,19 @@ static inline int dccp_ack_pending(const struct sock *sk)
 	const struct dccp_sock *dp = dccp_sk(sk);
 	return dp->dccps_timestamp_echo != 0 ||
 #ifdef CONFIG_IP_DCCP_ACKVEC
-	       (dccp_msk(sk)->dccpms_send_ack_vector &&
+	       (dp->dccps_hc_rx_ackvec != NULL &&
 		dccp_ackvec_pending(dp->dccps_hc_rx_ackvec)) ||
 #endif
 	       inet_csk_ack_scheduled(sk);
 }
 
+extern int  dccp_feat_finalise_settings(struct dccp_sock *dp);
+extern int  dccp_feat_server_ccid_dependencies(struct dccp_request_sock *dreq);
+extern int  dccp_feat_insert_opts(struct dccp_sock*, struct dccp_request_sock*,
+				  struct sk_buff *skb);
+extern int  dccp_feat_activate_values(struct sock *sk, struct list_head *fn);
+extern void dccp_feat_list_purge(struct list_head *fn_list);
+
 extern int dccp_insert_options(struct sock *sk, struct sk_buff *skb);
 extern int dccp_insert_options_rsk(struct dccp_request_sock*, struct sk_buff*);
 extern int dccp_insert_option_elapsed_time(struct sock *sk,
diff --git a/net/dccp/diag.c b/net/dccp/diag.c
index d8a3509b26f6..b21f261da75e 100644
--- a/net/dccp/diag.c
+++ b/net/dccp/diag.c
@@ -29,11 +29,14 @@ static void dccp_get_info(struct sock *sk, struct tcp_info *info)
 	info->tcpi_backoff	= icsk->icsk_backoff;
 	info->tcpi_pmtu		= icsk->icsk_pmtu_cookie;
 
-	if (dccp_msk(sk)->dccpms_send_ack_vector)
+	if (dp->dccps_hc_rx_ackvec != NULL)
 		info->tcpi_options |= TCPI_OPT_SACK;
 
-	ccid_hc_rx_get_info(dp->dccps_hc_rx_ccid, sk, info);
-	ccid_hc_tx_get_info(dp->dccps_hc_tx_ccid, sk, info);
+	if (dp->dccps_hc_rx_ccid != NULL)
+		ccid_hc_rx_get_info(dp->dccps_hc_rx_ccid, sk, info);
+
+	if (dp->dccps_hc_tx_ccid != NULL)
+		ccid_hc_tx_get_info(dp->dccps_hc_tx_ccid, sk, info);
 }
 
 static void dccp_diag_get_info(struct sock *sk, struct inet_diag_msg *r,
@@ -45,7 +48,7 @@ static void dccp_diag_get_info(struct sock *sk, struct inet_diag_msg *r,
 		dccp_get_info(sk, _info);
 }
 
-static struct inet_diag_handler dccp_diag_handler = {
+static const struct inet_diag_handler dccp_diag_handler = {
 	.idiag_hashinfo	 = &dccp_hashinfo,
 	.idiag_get_info	 = dccp_diag_get_info,
 	.idiag_type	 = DCCPDIAG_GETSOCK,
diff --git a/net/dccp/feat.c b/net/dccp/feat.c
index 933a0ecf8d46..30f9fb76b921 100644
--- a/net/dccp/feat.c
+++ b/net/dccp/feat.c
@@ -1,11 +1,17 @@
 /*
  *  net/dccp/feat.c
  *
- *  An implementation of the DCCP protocol
- *  Andrea Bittau <a.bittau@cs.ucl.ac.uk>
+ *  Feature negotiation for the DCCP protocol (RFC 4340, section 6)
+ *
+ *  Copyright (c) 2008 Gerrit Renker <gerrit@erg.abdn.ac.uk>
+ *  Rewrote from scratch, some bits from earlier code by
+ *  Copyright (c) 2005 Andrea Bittau <a.bittau@cs.ucl.ac.uk>
+ *
  *
  *  ASSUMPTIONS
  *  -----------
+ *  o Feature negotiation is coordinated with connection setup (as in TCP), wild
+ *    changes of parameters of an established connection are not supported.
  *  o All currently known SP features have 1-byte quantities. If in the future
  *    extensions of RFCs 4340..42 define features with item lengths larger than
  *    one byte, a feature-specific extension of the code will be required.
@@ -15,597 +21,1185 @@
  *  as published by the Free Software Foundation; either version
  *  2 of the License, or (at your option) any later version.
  */
-
 #include <linux/module.h>
-
 #include "ccid.h"
 #include "feat.h"
 
-#define DCCP_FEAT_SP_NOAGREE (-123)
-
-int dccp_feat_change(struct dccp_minisock *dmsk, u8 type, u8 feature,
-		     u8 *val, u8 len, gfp_t gfp)
-{
-	struct dccp_opt_pend *opt;
-
-	dccp_feat_debug(type, feature, *val);
-
-	if (len > 3) {
-		DCCP_WARN("invalid length %d\n", len);
-		return -EINVAL;
-	}
-	/* XXX add further sanity checks */
-
-	/* check if that feature is already being negotiated */
-	list_for_each_entry(opt, &dmsk->dccpms_pending, dccpop_node) {
-		/* ok we found a negotiation for this option already */
-		if (opt->dccpop_feat == feature && opt->dccpop_type == type) {
-			dccp_pr_debug("Replacing old\n");
-			/* replace */
-			BUG_ON(opt->dccpop_val == NULL);
-			kfree(opt->dccpop_val);
-			opt->dccpop_val	 = val;
-			opt->dccpop_len	 = len;
-			opt->dccpop_conf = 0;
-			return 0;
-		}
-	}
-
-	/* negotiation for a new feature */
-	opt = kmalloc(sizeof(*opt), gfp);
-	if (opt == NULL)
-		return -ENOMEM;
-
-	opt->dccpop_type = type;
-	opt->dccpop_feat = feature;
-	opt->dccpop_len	 = len;
-	opt->dccpop_val	 = val;
-	opt->dccpop_conf = 0;
-	opt->dccpop_sc	 = NULL;
-
-	BUG_ON(opt->dccpop_val == NULL);
-
-	list_add_tail(&opt->dccpop_node, &dmsk->dccpms_pending);
-	return 0;
-}
-
-EXPORT_SYMBOL_GPL(dccp_feat_change);
-
-static int dccp_feat_update_ccid(struct sock *sk, u8 type, u8 new_ccid_nr)
+/*
+ * Feature activation handlers.
+ *
+ * These all use an u64 argument, to provide enough room for NN/SP features. At
+ * this stage the negotiated values have been checked to be within their range.
+ */
+static int dccp_hdlr_ccid(struct sock *sk, u64 ccid, bool rx)
 {
 	struct dccp_sock *dp = dccp_sk(sk);
-	struct dccp_minisock *dmsk = dccp_msk(sk);
-	/* figure out if we are changing our CCID or the peer's */
-	const int rx = type == DCCPO_CHANGE_R;
-	const u8 ccid_nr = rx ? dmsk->dccpms_rx_ccid : dmsk->dccpms_tx_ccid;
-	struct ccid *new_ccid;
+	struct ccid *new_ccid = ccid_new(ccid, sk, rx, gfp_any());
 
-	/* Check if nothing is being changed. */
-	if (ccid_nr == new_ccid_nr)
-		return 0;
-
-	new_ccid = ccid_new(new_ccid_nr, sk, rx, GFP_ATOMIC);
 	if (new_ccid == NULL)
 		return -ENOMEM;
 
 	if (rx) {
 		ccid_hc_rx_delete(dp->dccps_hc_rx_ccid, sk);
 		dp->dccps_hc_rx_ccid = new_ccid;
-		dmsk->dccpms_rx_ccid = new_ccid_nr;
 	} else {
 		ccid_hc_tx_delete(dp->dccps_hc_tx_ccid, sk);
 		dp->dccps_hc_tx_ccid = new_ccid;
-		dmsk->dccpms_tx_ccid = new_ccid_nr;
 	}
+	return 0;
+}
 
+static int dccp_hdlr_seq_win(struct sock *sk, u64 seq_win, bool rx)
+{
+	if (!rx)
+		dccp_msk(sk)->dccpms_sequence_window = seq_win;
 	return 0;
 }
 
-static int dccp_feat_update(struct sock *sk, u8 type, u8 feat, u8 val)
+static int dccp_hdlr_ack_ratio(struct sock *sk, u64 ratio, bool rx)
 {
-	dccp_feat_debug(type, feat, val);
+	if (rx)
+		dccp_sk(sk)->dccps_r_ack_ratio = ratio;
+	else
+		dccp_sk(sk)->dccps_l_ack_ratio = ratio;
+	return 0;
+}
 
-	switch (feat) {
-	case DCCPF_CCID:
-		return dccp_feat_update_ccid(sk, type, val);
-	default:
-		dccp_pr_debug("UNIMPLEMENTED: %s(%d, ...)\n",
-			      dccp_feat_typename(type), feat);
-		break;
+static int dccp_hdlr_ackvec(struct sock *sk, u64 enable, bool rx)
+{
+	struct dccp_sock *dp = dccp_sk(sk);
+
+	if (rx) {
+		if (enable && dp->dccps_hc_rx_ackvec == NULL) {
+			dp->dccps_hc_rx_ackvec = dccp_ackvec_alloc(gfp_any());
+			if (dp->dccps_hc_rx_ackvec == NULL)
+				return -ENOMEM;
+		} else if (!enable) {
+			dccp_ackvec_free(dp->dccps_hc_rx_ackvec);
+			dp->dccps_hc_rx_ackvec = NULL;
+		}
 	}
 	return 0;
 }
 
-static int dccp_feat_reconcile(struct sock *sk, struct dccp_opt_pend *opt,
-			       u8 *rpref, u8 rlen)
+static int dccp_hdlr_ndp(struct sock *sk, u64 enable, bool rx)
 {
-	struct dccp_sock *dp = dccp_sk(sk);
-	u8 *spref, slen, *res = NULL;
-	int i, j, rc, agree = 1;
+	if (!rx)
+		dccp_sk(sk)->dccps_send_ndp_count = (enable > 0);
+	return 0;
+}
 
-	BUG_ON(rpref == NULL);
+/*
+ * Minimum Checksum Coverage is located at the RX side (9.2.1). This means that
+ * `rx' holds when the sending peer informs about his partial coverage via a
+ * ChangeR() option. In the other case, we are the sender and the receiver
+ * announces its coverage via ChangeL() options. The policy here is to honour
+ * such communication by enabling the corresponding partial coverage - but only
+ * if it has not been set manually before; the warning here means that all
+ * packets will be dropped.
+ */
+static int dccp_hdlr_min_cscov(struct sock *sk, u64 cscov, bool rx)
+{
+	struct dccp_sock *dp = dccp_sk(sk);
 
-	/* check if we are the black sheep */
-	if (dp->dccps_role == DCCP_ROLE_CLIENT) {
-		spref = rpref;
-		slen  = rlen;
-		rpref = opt->dccpop_val;
-		rlen  = opt->dccpop_len;
-	} else {
-		spref = opt->dccpop_val;
-		slen  = opt->dccpop_len;
+	if (rx)
+		dp->dccps_pcrlen = cscov;
+	else {
+		if (dp->dccps_pcslen == 0)
+			dp->dccps_pcslen = cscov;
+		else if (cscov > dp->dccps_pcslen)
+			DCCP_WARN("CsCov %u too small, peer requires >= %u\n",
+				  dp->dccps_pcslen, (u8)cscov);
 	}
-	/*
-	 * Now we have server preference list in spref and client preference in
-	 * rpref
-	 */
-	BUG_ON(spref == NULL);
-	BUG_ON(rpref == NULL);
+	return 0;
+}
 
-	/* FIXME sanity check vals */
+static const struct {
+	u8			feat_num;		/* DCCPF_xxx */
+	enum dccp_feat_type	rxtx;			/* RX or TX  */
+	enum dccp_feat_type	reconciliation;		/* SP or NN  */
+	u8			default_value;		/* as in 6.4 */
+	int (*activation_hdlr)(struct sock *sk, u64 val, bool rx);
+/*
+ *    Lookup table for location and type of features (from RFC 4340/4342)
+ *  +--------------------------+----+-----+----+----+---------+-----------+
+ *  | Feature                  | Location | Reconc. | Initial |  Section  |
+ *  |                          | RX | TX  | SP | NN |  Value  | Reference |
+ *  +--------------------------+----+-----+----+----+---------+-----------+
+ *  | DCCPF_CCID               |    |  X  | X  |    |   2     | 10        |
+ *  | DCCPF_SHORT_SEQNOS       |    |  X  | X  |    |   0     |  7.6.1    |
+ *  | DCCPF_SEQUENCE_WINDOW    |    |  X  |    | X  | 100     |  7.5.2    |
+ *  | DCCPF_ECN_INCAPABLE      | X  |     | X  |    |   0     | 12.1      |
+ *  | DCCPF_ACK_RATIO          |    |  X  |    | X  |   2     | 11.3      |
+ *  | DCCPF_SEND_ACK_VECTOR    | X  |     | X  |    |   0     | 11.5      |
+ *  | DCCPF_SEND_NDP_COUNT     |    |  X  | X  |    |   0     |  7.7.2    |
+ *  | DCCPF_MIN_CSUM_COVER     | X  |     | X  |    |   0     |  9.2.1    |
+ *  | DCCPF_DATA_CHECKSUM      | X  |     | X  |    |   0     |  9.3.1    |
+ *  | DCCPF_SEND_LEV_RATE      | X  |     | X  |    |   0     | 4342/8.4  |
+ *  +--------------------------+----+-----+----+----+---------+-----------+
+ */
+} dccp_feat_table[] = {
+	{ DCCPF_CCID,		 FEAT_AT_TX, FEAT_SP, 2,   dccp_hdlr_ccid     },
+	{ DCCPF_SHORT_SEQNOS,	 FEAT_AT_TX, FEAT_SP, 0,   NULL },
+	{ DCCPF_SEQUENCE_WINDOW, FEAT_AT_TX, FEAT_NN, 100, dccp_hdlr_seq_win  },
+	{ DCCPF_ECN_INCAPABLE,	 FEAT_AT_RX, FEAT_SP, 0,   NULL },
+	{ DCCPF_ACK_RATIO,	 FEAT_AT_TX, FEAT_NN, 2,   dccp_hdlr_ack_ratio},
+	{ DCCPF_SEND_ACK_VECTOR, FEAT_AT_RX, FEAT_SP, 0,   dccp_hdlr_ackvec   },
+	{ DCCPF_SEND_NDP_COUNT,  FEAT_AT_TX, FEAT_SP, 0,   dccp_hdlr_ndp      },
+	{ DCCPF_MIN_CSUM_COVER,  FEAT_AT_RX, FEAT_SP, 0,   dccp_hdlr_min_cscov},
+	{ DCCPF_DATA_CHECKSUM,	 FEAT_AT_RX, FEAT_SP, 0,   NULL },
+	{ DCCPF_SEND_LEV_RATE,	 FEAT_AT_RX, FEAT_SP, 0,   NULL },
+};
+#define DCCP_FEAT_SUPPORTED_MAX		ARRAY_SIZE(dccp_feat_table)
+
+/**
+ * dccp_feat_index  -  Hash function to map feature number into array position
+ * Returns consecutive array index or -1 if the feature is not understood.
+ */
+static int dccp_feat_index(u8 feat_num)
+{
+	/* The first 9 entries are occupied by the types from RFC 4340, 6.4 */
+	if (feat_num > DCCPF_RESERVED && feat_num <= DCCPF_DATA_CHECKSUM)
+		return feat_num - 1;
 
-	/* Are values in any order?  XXX Lame "algorithm" here */
-	for (i = 0; i < slen; i++) {
-		for (j = 0; j < rlen; j++) {
-			if (spref[i] == rpref[j]) {
-				res = &spref[i];
-				break;
-			}
-		}
-		if (res)
-			break;
+	/*
+	 * Other features: add cases for new feature types here after adding
+	 * them to the above table.
+	 */
+	switch (feat_num) {
+	case DCCPF_SEND_LEV_RATE:
+			return DCCP_FEAT_SUPPORTED_MAX - 1;
 	}
+	return -1;
+}
 
-	/* we didn't agree on anything */
-	if (res == NULL) {
-		/* confirm previous value */
-		switch (opt->dccpop_feat) {
-		case DCCPF_CCID:
-			/* XXX did i get this right? =P */
-			if (opt->dccpop_type == DCCPO_CHANGE_L)
-				res = &dccp_msk(sk)->dccpms_tx_ccid;
-			else
-				res = &dccp_msk(sk)->dccpms_rx_ccid;
-			break;
+static u8 dccp_feat_type(u8 feat_num)
+{
+	int idx = dccp_feat_index(feat_num);
 
-		default:
-			DCCP_BUG("Fell through, feat=%d", opt->dccpop_feat);
-			/* XXX implement res */
-			return -EFAULT;
-		}
+	if (idx < 0)
+		return FEAT_UNKNOWN;
+	return dccp_feat_table[idx].reconciliation;
+}
 
-		dccp_pr_debug("Don't agree... reconfirming %d\n", *res);
-		agree = 0; /* this is used for mandatory options... */
-	}
+static int dccp_feat_default_value(u8 feat_num)
+{
+	int idx = dccp_feat_index(feat_num);
+	/*
+	 * There are no default values for unknown features, so encountering a
+	 * negative index here indicates a serious problem somewhere else.
+	 */
+	DCCP_BUG_ON(idx < 0);
 
-	/* need to put result and our preference list */
-	rlen = 1 + opt->dccpop_len;
-	rpref = kmalloc(rlen, GFP_ATOMIC);
-	if (rpref == NULL)
-		return -ENOMEM;
+	return idx < 0 ? 0 : dccp_feat_table[idx].default_value;
+}
 
-	*rpref = *res;
-	memcpy(&rpref[1], opt->dccpop_val, opt->dccpop_len);
+static int __dccp_feat_activate(struct sock *sk, const int idx,
+				const bool is_local, dccp_feat_val const *fval)
+{
+	bool rx;
+	u64 val;
 
-	/* put it in the "confirm queue" */
-	if (opt->dccpop_sc == NULL) {
-		opt->dccpop_sc = kmalloc(sizeof(*opt->dccpop_sc), GFP_ATOMIC);
-		if (opt->dccpop_sc == NULL) {
-			kfree(rpref);
-			return -ENOMEM;
+	if (idx < 0 || idx >= DCCP_FEAT_SUPPORTED_MAX)
+		return -1;
+	if (dccp_feat_table[idx].activation_hdlr == NULL)
+		return 0;
+
+	if (fval == NULL) {
+		val = dccp_feat_table[idx].default_value;
+	} else if (dccp_feat_table[idx].reconciliation == FEAT_SP) {
+		if (fval->sp.vec == NULL) {
+			/*
+			 * This can happen when an empty Confirm is sent
+			 * for an SP (i.e. known) feature. In this case
+			 * we would be using the default anyway.
+			 */
+			DCCP_CRIT("Feature #%d undefined: using default", idx);
+			val = dccp_feat_table[idx].default_value;
+		} else {
+			val = fval->sp.vec[0];
 		}
 	} else {
-		/* recycle the confirm slot */
-		BUG_ON(opt->dccpop_sc->dccpoc_val == NULL);
-		kfree(opt->dccpop_sc->dccpoc_val);
-		dccp_pr_debug("recycling confirm slot\n");
+		val = fval->nn;
 	}
-	memset(opt->dccpop_sc, 0, sizeof(*opt->dccpop_sc));
 
-	opt->dccpop_sc->dccpoc_val = rpref;
-	opt->dccpop_sc->dccpoc_len = rlen;
+	/* Location is RX if this is a local-RX or remote-TX feature */
+	rx = (is_local == (dccp_feat_table[idx].rxtx == FEAT_AT_RX));
 
-	/* update the option on our side [we are about to send the confirm] */
-	rc = dccp_feat_update(sk, opt->dccpop_type, opt->dccpop_feat, *res);
-	if (rc) {
-		kfree(opt->dccpop_sc->dccpoc_val);
-		kfree(opt->dccpop_sc);
-		opt->dccpop_sc = NULL;
-		return rc;
-	}
+	return dccp_feat_table[idx].activation_hdlr(sk, val, rx);
+}
 
-	dccp_pr_debug("Will confirm %d\n", *rpref);
+/* Test for "Req'd" feature (RFC 4340, 6.4) */
+static inline int dccp_feat_must_be_understood(u8 feat_num)
+{
+	return	feat_num == DCCPF_CCID || feat_num == DCCPF_SHORT_SEQNOS ||
+		feat_num == DCCPF_SEQUENCE_WINDOW;
+}
 
-	/* say we want to change to X but we just got a confirm X, suppress our
-	 * change
-	 */
-	if (!opt->dccpop_conf) {
-		if (*opt->dccpop_val == *res)
-			opt->dccpop_conf = 1;
-		dccp_pr_debug("won't ask for change of same feature\n");
+/* copy constructor, fval must not already contain allocated memory */
+static int dccp_feat_clone_sp_val(dccp_feat_val *fval, u8 const *val, u8 len)
+{
+	fval->sp.len = len;
+	if (fval->sp.len > 0) {
+		fval->sp.vec = kmemdup(val, len, gfp_any());
+		if (fval->sp.vec == NULL) {
+			fval->sp.len = 0;
+			return -ENOBUFS;
+		}
 	}
+	return 0;
+}
 
-	return agree ? 0 : DCCP_FEAT_SP_NOAGREE; /* used for mandatory opts */
+static void dccp_feat_val_destructor(u8 feat_num, dccp_feat_val *val)
+{
+	if (unlikely(val == NULL))
+		return;
+	if (dccp_feat_type(feat_num) == FEAT_SP)
+		kfree(val->sp.vec);
+	memset(val, 0, sizeof(*val));
 }
 
-static int dccp_feat_sp(struct sock *sk, u8 type, u8 feature, u8 *val, u8 len)
+static struct dccp_feat_entry *
+	      dccp_feat_clone_entry(struct dccp_feat_entry const *original)
 {
-	struct dccp_minisock *dmsk = dccp_msk(sk);
-	struct dccp_opt_pend *opt;
-	int rc = 1;
-	u8 t;
+	struct dccp_feat_entry *new;
+	u8 type = dccp_feat_type(original->feat_num);
 
-	/*
-	 * We received a CHANGE.  We gotta match it against our own preference
-	 * list.  If we got a CHANGE_R it means it's a change for us, so we need
-	 * to compare our CHANGE_L list.
-	 */
-	if (type == DCCPO_CHANGE_L)
-		t = DCCPO_CHANGE_R;
-	else
-		t = DCCPO_CHANGE_L;
+	if (type == FEAT_UNKNOWN)
+		return NULL;
 
-	/* find our preference list for this feature */
-	list_for_each_entry(opt, &dmsk->dccpms_pending, dccpop_node) {
-		if (opt->dccpop_type != t || opt->dccpop_feat != feature)
-			continue;
+	new = kmemdup(original, sizeof(struct dccp_feat_entry), gfp_any());
+	if (new == NULL)
+		return NULL;
 
-		/* find the winner from the two preference lists */
-		rc = dccp_feat_reconcile(sk, opt, val, len);
-		break;
+	if (type == FEAT_SP && dccp_feat_clone_sp_val(&new->val,
+						      original->val.sp.vec,
+						      original->val.sp.len)) {
+		kfree(new);
+		return NULL;
 	}
+	return new;
+}
 
-	/* We didn't deal with the change.  This can happen if we have no
-	 * preference list for the feature.  In fact, it just shouldn't
-	 * happen---if we understand a feature, we should have a preference list
-	 * with at least the default value.
-	 */
-	BUG_ON(rc == 1);
+static void dccp_feat_entry_destructor(struct dccp_feat_entry *entry)
+{
+	if (entry != NULL) {
+		dccp_feat_val_destructor(entry->feat_num, &entry->val);
+		kfree(entry);
+	}
+}
 
-	return rc;
+/*
+ * List management functions
+ *
+ * Feature negotiation lists rely on and maintain the following invariants:
+ * - each feat_num in the list is known, i.e. we know its type and default value
+ * - each feat_num/is_local combination is unique (old entries are overwritten)
+ * - SP values are always freshly allocated
+ * - list is sorted in increasing order of feature number (faster lookup)
+ */
+static struct dccp_feat_entry *dccp_feat_list_lookup(struct list_head *fn_list,
+						     u8 feat_num, bool is_local)
+{
+	struct dccp_feat_entry *entry;
+
+	list_for_each_entry(entry, fn_list, node) {
+		if (entry->feat_num == feat_num && entry->is_local == is_local)
+			return entry;
+		else if (entry->feat_num > feat_num)
+			break;
+	}
+	return NULL;
 }
 
-static int dccp_feat_nn(struct sock *sk, u8 type, u8 feature, u8 *val, u8 len)
+/**
+ * dccp_feat_entry_new  -  Central list update routine (called by all others)
+ * @head:  list to add to
+ * @feat:  feature number
+ * @local: whether the local (1) or remote feature with number @feat is meant
+ * This is the only constructor and serves to ensure the above invariants.
+ */
+static struct dccp_feat_entry *
+	      dccp_feat_entry_new(struct list_head *head, u8 feat, bool local)
 {
-	struct dccp_opt_pend *opt;
-	struct dccp_minisock *dmsk = dccp_msk(sk);
-	u8 *copy;
-	int rc;
+	struct dccp_feat_entry *entry;
+
+	list_for_each_entry(entry, head, node)
+		if (entry->feat_num == feat && entry->is_local == local) {
+			dccp_feat_val_destructor(entry->feat_num, &entry->val);
+			return entry;
+		} else if (entry->feat_num > feat) {
+			head = &entry->node;
+			break;
+		}
 
-	/* NN features must be Change L (sec. 6.3.2) */
-	if (type != DCCPO_CHANGE_L) {
-		dccp_pr_debug("received %s for NN feature %d\n",
-				dccp_feat_typename(type), feature);
-		return -EFAULT;
+	entry = kmalloc(sizeof(*entry), gfp_any());
+	if (entry != NULL) {
+		entry->feat_num = feat;
+		entry->is_local = local;
+		list_add_tail(&entry->node, head);
 	}
+	return entry;
+}
 
-	/* XXX sanity check opt val */
+/**
+ * dccp_feat_push_change  -  Add/overwrite a Change option in the list
+ * @fn_list: feature-negotiation list to update
+ * @feat: one of %dccp_feature_numbers
+ * @local: whether local (1) or remote (0) @feat_num is meant
+ * @needs_mandatory: whether to use Mandatory feature negotiation options
+ * @fval: pointer to NN/SP value to be inserted (will be copied)
+ */
+static int dccp_feat_push_change(struct list_head *fn_list, u8 feat, u8 local,
+				 u8 mandatory, dccp_feat_val *fval)
+{
+	struct dccp_feat_entry *new = dccp_feat_entry_new(fn_list, feat, local);
 
-	/* copy option so we can confirm it */
-	opt = kzalloc(sizeof(*opt), GFP_ATOMIC);
-	if (opt == NULL)
+	if (new == NULL)
 		return -ENOMEM;
 
-	copy = kmemdup(val, len, GFP_ATOMIC);
-	if (copy == NULL) {
-		kfree(opt);
-		return -ENOMEM;
-	}
+	new->feat_num	     = feat;
+	new->is_local	     = local;
+	new->state	     = FEAT_INITIALISING;
+	new->needs_confirm   = 0;
+	new->empty_confirm   = 0;
+	new->val	     = *fval;
+	new->needs_mandatory = mandatory;
 
-	opt->dccpop_type = DCCPO_CONFIRM_R; /* NN can only confirm R */
-	opt->dccpop_feat = feature;
-	opt->dccpop_val	 = copy;
-	opt->dccpop_len	 = len;
+	return 0;
+}
 
-	/* change feature */
-	rc = dccp_feat_update(sk, type, feature, *val);
-	if (rc) {
-		kfree(opt->dccpop_val);
-		kfree(opt);
-		return rc;
-	}
+/**
+ * dccp_feat_push_confirm  -  Add a Confirm entry to the FN list
+ * @fn_list: feature-negotiation list to add to
+ * @feat: one of %dccp_feature_numbers
+ * @local: whether local (1) or remote (0) @feat_num is being confirmed
+ * @fval: pointer to NN/SP value to be inserted or NULL
+ * Returns 0 on success, a Reset code for further processing otherwise.
+ */
+static int dccp_feat_push_confirm(struct list_head *fn_list, u8 feat, u8 local,
+				  dccp_feat_val *fval)
+{
+	struct dccp_feat_entry *new = dccp_feat_entry_new(fn_list, feat, local);
 
-	dccp_feat_debug(type, feature, *copy);
+	if (new == NULL)
+		return DCCP_RESET_CODE_TOO_BUSY;
 
-	list_add_tail(&opt->dccpop_node, &dmsk->dccpms_conf);
+	new->feat_num	     = feat;
+	new->is_local	     = local;
+	new->state	     = FEAT_STABLE;	/* transition in 6.6.2 */
+	new->needs_confirm   = 1;
+	new->empty_confirm   = (fval == NULL);
+	new->val.nn	     = 0;		/* zeroes the whole structure */
+	if (!new->empty_confirm)
+		new->val     = *fval;
+	new->needs_mandatory = 0;
 
 	return 0;
 }
 
-static void dccp_feat_empty_confirm(struct dccp_minisock *dmsk,
-				    u8 type, u8 feature)
+static int dccp_push_empty_confirm(struct list_head *fn_list, u8 feat, u8 local)
 {
-	/* XXX check if other confirms for that are queued and recycle slot */
-	struct dccp_opt_pend *opt = kzalloc(sizeof(*opt), GFP_ATOMIC);
+	return dccp_feat_push_confirm(fn_list, feat, local, NULL);
+}
 
-	if (opt == NULL) {
-		/* XXX what do we do?  Ignoring should be fine.  It's a change
-		 * after all =P
-		 */
-		return;
-	}
+static inline void dccp_feat_list_pop(struct dccp_feat_entry *entry)
+{
+	list_del(&entry->node);
+	dccp_feat_entry_destructor(entry);
+}
 
-	switch (type) {
-	case DCCPO_CHANGE_L:
-		opt->dccpop_type = DCCPO_CONFIRM_R;
-		break;
-	case DCCPO_CHANGE_R:
-		opt->dccpop_type = DCCPO_CONFIRM_L;
-		break;
-	default:
-		DCCP_WARN("invalid type %d\n", type);
-		kfree(opt);
-		return;
+void dccp_feat_list_purge(struct list_head *fn_list)
+{
+	struct dccp_feat_entry *entry, *next;
+
+	list_for_each_entry_safe(entry, next, fn_list, node)
+		dccp_feat_entry_destructor(entry);
+	INIT_LIST_HEAD(fn_list);
+}
+EXPORT_SYMBOL_GPL(dccp_feat_list_purge);
+
+/* generate @to as full clone of @from - @to must not contain any nodes */
+int dccp_feat_clone_list(struct list_head const *from, struct list_head *to)
+{
+	struct dccp_feat_entry *entry, *new;
+
+	INIT_LIST_HEAD(to);
+	list_for_each_entry(entry, from, node) {
+		new = dccp_feat_clone_entry(entry);
+		if (new == NULL)
+			goto cloning_failed;
+		list_add_tail(&new->node, to);
 	}
-	opt->dccpop_feat = feature;
-	opt->dccpop_val	 = NULL;
-	opt->dccpop_len	 = 0;
+	return 0;
+
+cloning_failed:
+	dccp_feat_list_purge(to);
+	return -ENOMEM;
+}
 
-	/* change feature */
-	dccp_pr_debug("Empty %s(%d)\n", dccp_feat_typename(type), feature);
+/**
+ * dccp_feat_valid_nn_length  -  Enforce length constraints on NN options
+ * Length is between 0 and %DCCP_OPTVAL_MAXLEN. Used for outgoing packets only,
+ * incoming options are accepted as long as their values are valid.
+ */
+static u8 dccp_feat_valid_nn_length(u8 feat_num)
+{
+	if (feat_num == DCCPF_ACK_RATIO)	/* RFC 4340, 11.3 and 6.6.8 */
+		return 2;
+	if (feat_num == DCCPF_SEQUENCE_WINDOW)	/* RFC 4340, 7.5.2 and 6.5  */
+		return 6;
+	return 0;
+}
 
-	list_add_tail(&opt->dccpop_node, &dmsk->dccpms_conf);
+static u8 dccp_feat_is_valid_nn_val(u8 feat_num, u64 val)
+{
+	switch (feat_num) {
+	case DCCPF_ACK_RATIO:
+		return val <= DCCPF_ACK_RATIO_MAX;
+	case DCCPF_SEQUENCE_WINDOW:
+		return val >= DCCPF_SEQ_WMIN && val <= DCCPF_SEQ_WMAX;
+	}
+	return 0;	/* feature unknown - so we can't tell */
 }
 
-static void dccp_feat_flush_confirm(struct sock *sk)
+/* check that SP values are within the ranges defined in RFC 4340 */
+static u8 dccp_feat_is_valid_sp_val(u8 feat_num, u8 val)
 {
-	struct dccp_minisock *dmsk = dccp_msk(sk);
-	/* Check if there is anything to confirm in the first place */
-	int yes = !list_empty(&dmsk->dccpms_conf);
+	switch (feat_num) {
+	case DCCPF_CCID:
+		return val == DCCPC_CCID2 || val == DCCPC_CCID3;
+	/* Type-check Boolean feature values: */
+	case DCCPF_SHORT_SEQNOS:
+	case DCCPF_ECN_INCAPABLE:
+	case DCCPF_SEND_ACK_VECTOR:
+	case DCCPF_SEND_NDP_COUNT:
+	case DCCPF_DATA_CHECKSUM:
+	case DCCPF_SEND_LEV_RATE:
+		return val < 2;
+	case DCCPF_MIN_CSUM_COVER:
+		return val < 16;
+	}
+	return 0;			/* feature unknown */
+}
 
-	if (!yes) {
-		struct dccp_opt_pend *opt;
+static u8 dccp_feat_sp_list_ok(u8 feat_num, u8 const *sp_list, u8 sp_len)
+{
+	if (sp_list == NULL || sp_len < 1)
+		return 0;
+	while (sp_len--)
+		if (!dccp_feat_is_valid_sp_val(feat_num, *sp_list++))
+			return 0;
+	return 1;
+}
 
-		list_for_each_entry(opt, &dmsk->dccpms_pending, dccpop_node) {
-			if (opt->dccpop_conf) {
-				yes = 1;
-				break;
+/**
+ * dccp_feat_insert_opts  -  Generate FN options from current list state
+ * @skb: next sk_buff to be sent to the peer
+ * @dp: for client during handshake and general negotiation
+ * @dreq: used by the server only (all Changes/Confirms in LISTEN/RESPOND)
+ */
+int dccp_feat_insert_opts(struct dccp_sock *dp, struct dccp_request_sock *dreq,
+			  struct sk_buff *skb)
+{
+	struct list_head *fn = dreq ? &dreq->dreq_featneg : &dp->dccps_featneg;
+	struct dccp_feat_entry *pos, *next;
+	u8 opt, type, len, *ptr, nn_in_nbo[DCCP_OPTVAL_MAXLEN];
+	bool rpt;
+
+	/* put entries into @skb in the order they appear in the list */
+	list_for_each_entry_safe_reverse(pos, next, fn, node) {
+		opt  = dccp_feat_genopt(pos);
+		type = dccp_feat_type(pos->feat_num);
+		rpt  = false;
+
+		if (pos->empty_confirm) {
+			len = 0;
+			ptr = NULL;
+		} else {
+			if (type == FEAT_SP) {
+				len = pos->val.sp.len;
+				ptr = pos->val.sp.vec;
+				rpt = pos->needs_confirm;
+			} else if (type == FEAT_NN) {
+				len = dccp_feat_valid_nn_length(pos->feat_num);
+				ptr = nn_in_nbo;
+				dccp_encode_value_var(pos->val.nn, ptr, len);
+			} else {
+				DCCP_BUG("unknown feature %u", pos->feat_num);
+				return -1;
 			}
 		}
+
+		if (dccp_insert_fn_opt(skb, opt, pos->feat_num, ptr, len, rpt))
+			return -1;
+		if (pos->needs_mandatory && dccp_insert_option_mandatory(skb))
+			return -1;
+		/*
+		 * Enter CHANGING after transmitting the Change option (6.6.2).
+		 */
+		if (pos->state == FEAT_INITIALISING)
+			pos->state = FEAT_CHANGING;
 	}
+	return 0;
+}
 
-	if (!yes)
-		return;
+/**
+ * __feat_register_nn  -  Register new NN value on socket
+ * @fn: feature-negotiation list to register with
+ * @feat: an NN feature from %dccp_feature_numbers
+ * @mandatory: use Mandatory option if 1
+ * @nn_val: value to register (restricted to 4 bytes)
+ * Note that NN features are local by definition (RFC 4340, 6.3.2).
+ */
+static int __feat_register_nn(struct list_head *fn, u8 feat,
+			      u8 mandatory, u64 nn_val)
+{
+	dccp_feat_val fval = { .nn = nn_val };
 
-	/* OK there is something to confirm... */
-	/* XXX check if packet is in flight?  Send delayed ack?? */
-	if (sk->sk_state == DCCP_OPEN)
-		dccp_send_ack(sk);
+	if (dccp_feat_type(feat) != FEAT_NN ||
+	    !dccp_feat_is_valid_nn_val(feat, nn_val))
+		return -EINVAL;
+
+	/* Don't bother with default values, they will be activated anyway. */
+	if (nn_val - (u64)dccp_feat_default_value(feat) == 0)
+		return 0;
+
+	return dccp_feat_push_change(fn, feat, 1, mandatory, &fval);
 }
 
-int dccp_feat_change_recv(struct sock *sk, u8 type, u8 feature, u8 *val, u8 len)
+/**
+ * __feat_register_sp  -  Register new SP value/list on socket
+ * @fn: feature-negotiation list to register with
+ * @feat: an SP feature from %dccp_feature_numbers
+ * @is_local: whether the local (1) or the remote (0) @feat is meant
+ * @mandatory: use Mandatory option if 1
+ * @sp_val: SP value followed by optional preference list
+ * @sp_len: length of @sp_val in bytes
+ */
+static int __feat_register_sp(struct list_head *fn, u8 feat, u8 is_local,
+			      u8 mandatory, u8 const *sp_val, u8 sp_len)
 {
-	int rc;
+	dccp_feat_val fval;
 
-	dccp_feat_debug(type, feature, *val);
+	if (dccp_feat_type(feat) != FEAT_SP ||
+	    !dccp_feat_sp_list_ok(feat, sp_val, sp_len))
+		return -EINVAL;
 
-	/* figure out if it's SP or NN feature */
-	switch (feature) {
-	/* deal with SP features */
-	case DCCPF_CCID:
-		rc = dccp_feat_sp(sk, type, feature, val, len);
-		break;
+	/* Avoid negotiating alien CCIDs by only advertising supported ones */
+	if (feat == DCCPF_CCID && !ccid_support_check(sp_val, sp_len))
+		return -EOPNOTSUPP;
 
-	/* deal with NN features */
-	case DCCPF_ACK_RATIO:
-		rc = dccp_feat_nn(sk, type, feature, val, len);
-		break;
+	if (dccp_feat_clone_sp_val(&fval, sp_val, sp_len))
+		return -ENOMEM;
 
-	/* XXX implement other features */
-	default:
-		dccp_pr_debug("UNIMPLEMENTED: not handling %s(%d, ...)\n",
-			      dccp_feat_typename(type), feature);
-		rc = -EFAULT;
-		break;
-	}
+	return dccp_feat_push_change(fn, feat, is_local, mandatory, &fval);
+}
 
-	/* check if there were problems changing features */
-	if (rc) {
-		/* If we don't agree on SP, we sent a confirm for old value.
-		 * However we propagate rc to caller in case option was
-		 * mandatory
+/**
+ * dccp_feat_register_sp  -  Register requests to change SP feature values
+ * @sk: client or listening socket
+ * @feat: one of %dccp_feature_numbers
+ * @is_local: whether the local (1) or remote (0) @feat is meant
+ * @list: array of preferred values, in descending order of preference
+ * @len: length of @list in bytes
+ */
+int dccp_feat_register_sp(struct sock *sk, u8 feat, u8 is_local,
+			  u8 const *list, u8 len)
+{	 /* any changes must be registered before establishing the connection */
+	if (sk->sk_state != DCCP_CLOSED)
+		return -EISCONN;
+	if (dccp_feat_type(feat) != FEAT_SP)
+		return -EINVAL;
+	return __feat_register_sp(&dccp_sk(sk)->dccps_featneg, feat, is_local,
+				  0, list, len);
+}
+
+/* Analogous to dccp_feat_register_sp(), but for non-negotiable values */
+int dccp_feat_register_nn(struct sock *sk, u8 feat, u64 val)
+{
+	/* any changes must be registered before establishing the connection */
+	if (sk->sk_state != DCCP_CLOSED)
+		return -EISCONN;
+	if (dccp_feat_type(feat) != FEAT_NN)
+		return -EINVAL;
+	return __feat_register_nn(&dccp_sk(sk)->dccps_featneg, feat, 0, val);
+}
+
+/*
+ *	Tracking features whose value depend on the choice of CCID
+ *
+ * This is designed with an extension in mind so that a list walk could be done
+ * before activating any features. However, the existing framework was found to
+ * work satisfactorily up until now, the automatic verification is left open.
+ * When adding new CCIDs, add a corresponding dependency table here.
+ */
+static const struct ccid_dependency *dccp_feat_ccid_deps(u8 ccid, bool is_local)
+{
+	static const struct ccid_dependency ccid2_dependencies[2][2] = {
+		/*
+		 * CCID2 mandates Ack Vectors (RFC 4341, 4.): as CCID is a TX
+		 * feature and Send Ack Vector is an RX feature, `is_local'
+		 * needs to be reversed.
 		 */
-		if (rc != DCCP_FEAT_SP_NOAGREE)
-			dccp_feat_empty_confirm(dccp_msk(sk), type, feature);
+		{	/* Dependencies of the receiver-side (remote) CCID2 */
+			{
+				.dependent_feat	= DCCPF_SEND_ACK_VECTOR,
+				.is_local	= true,
+				.is_mandatory	= true,
+				.val		= 1
+			},
+			{ 0, 0, 0, 0 }
+		},
+		{	/* Dependencies of the sender-side (local) CCID2 */
+			{
+				.dependent_feat	= DCCPF_SEND_ACK_VECTOR,
+				.is_local	= false,
+				.is_mandatory	= true,
+				.val		= 1
+			},
+			{ 0, 0, 0, 0 }
+		}
+	};
+	static const struct ccid_dependency ccid3_dependencies[2][5] = {
+		{	/*
+			 * Dependencies of the receiver-side CCID3
+			 */
+			{	/* locally disable Ack Vectors */
+				.dependent_feat	= DCCPF_SEND_ACK_VECTOR,
+				.is_local	= true,
+				.is_mandatory	= false,
+				.val		= 0
+			},
+			{	/* see below why Send Loss Event Rate is on */
+				.dependent_feat	= DCCPF_SEND_LEV_RATE,
+				.is_local	= true,
+				.is_mandatory	= true,
+				.val		= 1
+			},
+			{	/* NDP Count is needed as per RFC 4342, 6.1.1 */
+				.dependent_feat	= DCCPF_SEND_NDP_COUNT,
+				.is_local	= false,
+				.is_mandatory	= true,
+				.val		= 1
+			},
+			{ 0, 0, 0, 0 },
+		},
+		{	/*
+			 * CCID3 at the TX side: we request that the HC-receiver
+			 * will not send Ack Vectors (they will be ignored, so
+			 * Mandatory is not set); we enable Send Loss Event Rate
+			 * (Mandatory since the implementation does not support
+			 * the Loss Intervals option of RFC 4342, 8.6).
+			 * The last two options are for peer's information only.
+			*/
+			{
+				.dependent_feat	= DCCPF_SEND_ACK_VECTOR,
+				.is_local	= false,
+				.is_mandatory	= false,
+				.val		= 0
+			},
+			{
+				.dependent_feat	= DCCPF_SEND_LEV_RATE,
+				.is_local	= false,
+				.is_mandatory	= true,
+				.val		= 1
+			},
+			{	/* this CCID does not support Ack Ratio */
+				.dependent_feat	= DCCPF_ACK_RATIO,
+				.is_local	= true,
+				.is_mandatory	= false,
+				.val		= 0
+			},
+			{	/* tell receiver we are sending NDP counts */
+				.dependent_feat	= DCCPF_SEND_NDP_COUNT,
+				.is_local	= true,
+				.is_mandatory	= false,
+				.val		= 1
+			},
+			{ 0, 0, 0, 0 }
+		}
+	};
+	switch (ccid) {
+	case DCCPC_CCID2:
+		return ccid2_dependencies[is_local];
+	case DCCPC_CCID3:
+		return ccid3_dependencies[is_local];
+	default:
+		return NULL;
 	}
+}
 
-	/* generate the confirm [if required] */
-	dccp_feat_flush_confirm(sk);
-
+/**
+ * dccp_feat_propagate_ccid - Resolve dependencies of features on choice of CCID
+ * @fn: feature-negotiation list to update
+ * @id: CCID number to track
+ * @is_local: whether TX CCID (1) or RX CCID (0) is meant
+ * This function needs to be called after registering all other features.
+ */
+static int dccp_feat_propagate_ccid(struct list_head *fn, u8 id, bool is_local)
+{
+	const struct ccid_dependency *table = dccp_feat_ccid_deps(id, is_local);
+	int i, rc = (table == NULL);
+
+	for (i = 0; rc == 0 && table[i].dependent_feat != DCCPF_RESERVED; i++)
+		if (dccp_feat_type(table[i].dependent_feat) == FEAT_SP)
+			rc = __feat_register_sp(fn, table[i].dependent_feat,
+						    table[i].is_local,
+						    table[i].is_mandatory,
+						    &table[i].val, 1);
+		else
+			rc = __feat_register_nn(fn, table[i].dependent_feat,
+						    table[i].is_mandatory,
+						    table[i].val);
 	return rc;
 }
 
-EXPORT_SYMBOL_GPL(dccp_feat_change_recv);
+/**
+ * dccp_feat_finalise_settings  -  Finalise settings before starting negotiation
+ * @dp: client or listening socket (settings will be inherited)
+ * This is called after all registrations (socket initialisation, sysctls, and
+ * sockopt calls), and before sending the first packet containing Change options
+ * (ie. client-Request or server-Response), to ensure internal consistency.
+ */
+int dccp_feat_finalise_settings(struct dccp_sock *dp)
+{
+	struct list_head *fn = &dp->dccps_featneg;
+	struct dccp_feat_entry *entry;
+	int i = 2, ccids[2] = { -1, -1 };
 
-int dccp_feat_confirm_recv(struct sock *sk, u8 type, u8 feature,
-			   u8 *val, u8 len)
+	/*
+	 * Propagating CCIDs:
+	 * 1) not useful to propagate CCID settings if this host advertises more
+	 *    than one CCID: the choice of CCID  may still change - if this is
+	 *    the client, or if this is the server and the client sends
+	 *    singleton CCID values.
+	 * 2) since is that propagate_ccid changes the list, we defer changing
+	 *    the sorted list until after the traversal.
+	 */
+	list_for_each_entry(entry, fn, node)
+		if (entry->feat_num == DCCPF_CCID && entry->val.sp.len == 1)
+			ccids[entry->is_local] = entry->val.sp.vec[0];
+	while (i--)
+		if (ccids[i] > 0 && dccp_feat_propagate_ccid(fn, ccids[i], i))
+			return -1;
+	return 0;
+}
+
+/**
+ * dccp_feat_server_ccid_dependencies  -  Resolve CCID-dependent features
+ * It is the server which resolves the dependencies once the CCID has been
+ * fully negotiated. If no CCID has been negotiated, it uses the default CCID.
+ */
+int dccp_feat_server_ccid_dependencies(struct dccp_request_sock *dreq)
 {
-	u8 t;
-	struct dccp_opt_pend *opt;
-	struct dccp_minisock *dmsk = dccp_msk(sk);
-	int found = 0;
-	int all_confirmed = 1;
+	struct list_head *fn = &dreq->dreq_featneg;
+	struct dccp_feat_entry *entry;
+	u8 is_local, ccid;
 
-	dccp_feat_debug(type, feature, *val);
+	for (is_local = 0; is_local <= 1; is_local++) {
+		entry = dccp_feat_list_lookup(fn, DCCPF_CCID, is_local);
 
-	/* locate our change request */
-	switch (type) {
-	case DCCPO_CONFIRM_L: t = DCCPO_CHANGE_R; break;
-	case DCCPO_CONFIRM_R: t = DCCPO_CHANGE_L; break;
-	default:	      DCCP_WARN("invalid type %d\n", type);
-			      return 1;
+		if (entry != NULL && !entry->empty_confirm)
+			ccid = entry->val.sp.vec[0];
+		else
+			ccid = dccp_feat_default_value(DCCPF_CCID);
 
+		if (dccp_feat_propagate_ccid(fn, ccid, is_local))
+			return -1;
 	}
-	/* XXX sanity check feature value */
+	return 0;
+}
 
-	list_for_each_entry(opt, &dmsk->dccpms_pending, dccpop_node) {
-		if (!opt->dccpop_conf && opt->dccpop_type == t &&
-		    opt->dccpop_feat == feature) {
-			found = 1;
-			dccp_pr_debug("feature %d found\n", opt->dccpop_feat);
+/* Select the first entry in @servlist that also occurs in @clilist (6.3.1) */
+static int dccp_feat_preflist_match(u8 *servlist, u8 slen, u8 *clilist, u8 clen)
+{
+	u8 c, s;
 
-			/* XXX do sanity check */
+	for (s = 0; s < slen; s++)
+		for (c = 0; c < clen; c++)
+			if (servlist[s] == clilist[c])
+				return servlist[s];
+	return -1;
+}
 
-			opt->dccpop_conf = 1;
+/**
+ * dccp_feat_prefer  -  Move preferred entry to the start of array
+ * Reorder the @array_len elements in @array so that @preferred_value comes
+ * first. Returns >0 to indicate that @preferred_value does occur in @array.
+ */
+static u8 dccp_feat_prefer(u8 preferred_value, u8 *array, u8 array_len)
+{
+	u8 i, does_occur = 0;
 
-			/* We got a confirmation---change the option */
-			dccp_feat_update(sk, opt->dccpop_type,
-					 opt->dccpop_feat, *val);
+	if (array != NULL) {
+		for (i = 0; i < array_len; i++)
+			if (array[i] == preferred_value) {
+				array[i] = array[0];
+				does_occur++;
+			}
+		if (does_occur)
+			array[0] = preferred_value;
+	}
+	return does_occur;
+}
 
-			/* XXX check the return value of dccp_feat_update */
-			break;
-		}
+/**
+ * dccp_feat_reconcile  -  Reconcile SP preference lists
+ *  @fval: SP list to reconcile into
+ *  @arr: received SP preference list
+ *  @len: length of @arr in bytes
+ *  @is_server: whether this side is the server (and @fv is the server's list)
+ *  @reorder: whether to reorder the list in @fv after reconciling with @arr
+ * When successful, > 0 is returned and the reconciled list is in @fval.
+ * A value of 0 means that negotiation failed (no shared entry).
+ */
+static int dccp_feat_reconcile(dccp_feat_val *fv, u8 *arr, u8 len,
+			       bool is_server, bool reorder)
+{
+	int rc;
 
-		if (!opt->dccpop_conf)
-			all_confirmed = 0;
+	if (!fv->sp.vec || !arr) {
+		DCCP_CRIT("NULL feature value or array");
+		return 0;
 	}
 
-	/* fix re-transmit timer */
-	/* XXX gotta make sure that no option negotiation occurs during
-	 * connection shutdown.  Consider that the CLOSEREQ is sent and timer is
-	 * on.  if all options are confirmed it might kill timer which should
-	 * remain alive until close is received.
-	 */
-	if (all_confirmed) {
-		dccp_pr_debug("clear feat negotiation timer %p\n", sk);
-		inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
-	}
+	if (is_server)
+		rc = dccp_feat_preflist_match(fv->sp.vec, fv->sp.len, arr, len);
+	else
+		rc = dccp_feat_preflist_match(arr, len, fv->sp.vec, fv->sp.len);
 
-	if (!found)
-		dccp_pr_debug("%s(%d, ...) never requested\n",
-			      dccp_feat_typename(type), feature);
-	return 0;
-}
+	if (!reorder)
+		return rc;
+	if (rc < 0)
+		return 0;
 
-EXPORT_SYMBOL_GPL(dccp_feat_confirm_recv);
+	/*
+	 * Reorder list: used for activating features and in dccp_insert_fn_opt.
+	 */
+	return dccp_feat_prefer(rc, fv->sp.vec, fv->sp.len);
+}
 
-void dccp_feat_clean(struct dccp_minisock *dmsk)
+/**
+ * dccp_feat_change_recv  -  Process incoming ChangeL/R options
+ * @fn: feature-negotiation list to update
+ * @is_mandatory: whether the Change was preceded by a Mandatory option
+ * @opt: %DCCPO_CHANGE_L or %DCCPO_CHANGE_R
+ * @feat: one of %dccp_feature_numbers
+ * @val: NN value or SP value/preference list
+ * @len: length of @val in bytes
+ * @server: whether this node is the server (1) or the client (0)
+ */
+static u8 dccp_feat_change_recv(struct list_head *fn, u8 is_mandatory, u8 opt,
+				u8 feat, u8 *val, u8 len, const bool server)
 {
-	struct dccp_opt_pend *opt, *next;
+	u8 defval, type = dccp_feat_type(feat);
+	const bool local = (opt == DCCPO_CHANGE_R);
+	struct dccp_feat_entry *entry;
+	dccp_feat_val fval;
 
-	list_for_each_entry_safe(opt, next, &dmsk->dccpms_pending,
-				 dccpop_node) {
-		BUG_ON(opt->dccpop_val == NULL);
-		kfree(opt->dccpop_val);
+	if (len == 0 || type == FEAT_UNKNOWN)		/* 6.1 and 6.6.8 */
+		goto unknown_feature_or_value;
+
+	/*
+	 *	Negotiation of NN features: Change R is invalid, so there is no
+	 *	simultaneous negotiation; hence we do not look up in the list.
+	 */
+	if (type == FEAT_NN) {
+		if (local || len > sizeof(fval.nn))
+			goto unknown_feature_or_value;
+
+		/* 6.3.2: "The feature remote MUST accept any valid value..." */
+		fval.nn = dccp_decode_value_var(val, len);
+		if (!dccp_feat_is_valid_nn_val(feat, fval.nn))
+			goto unknown_feature_or_value;
+
+		return dccp_feat_push_confirm(fn, feat, local, &fval);
+	}
+
+	/*
+	 *	Unidirectional/simultaneous negotiation of SP features (6.3.1)
+	 */
+	entry = dccp_feat_list_lookup(fn, feat, local);
+	if (entry == NULL) {
+		/*
+		 * No particular preferences have been registered. We deal with
+		 * this situation by assuming that all valid values are equally
+		 * acceptable, and apply the following checks:
+		 * - if the peer's list is a singleton, we accept a valid value;
+		 * - if we are the server, we first try to see if the peer (the
+		 *   client) advertises the default value. If yes, we use it,
+		 *   otherwise we accept the preferred value;
+		 * - else if we are the client, we use the first list element.
+		 */
+		if (dccp_feat_clone_sp_val(&fval, val, 1))
+			return DCCP_RESET_CODE_TOO_BUSY;
+
+		if (len > 1 && server) {
+			defval = dccp_feat_default_value(feat);
+			if (dccp_feat_preflist_match(&defval, 1, val, len) > -1)
+				fval.sp.vec[0] = defval;
+		} else if (!dccp_feat_is_valid_sp_val(feat, fval.sp.vec[0])) {
+			kfree(fval.sp.vec);
+			goto unknown_feature_or_value;
+		}
 
-		if (opt->dccpop_sc != NULL) {
-			BUG_ON(opt->dccpop_sc->dccpoc_val == NULL);
-			kfree(opt->dccpop_sc->dccpoc_val);
-			kfree(opt->dccpop_sc);
+		/* Treat unsupported CCIDs like invalid values */
+		if (feat == DCCPF_CCID && !ccid_support_check(fval.sp.vec, 1)) {
+			kfree(fval.sp.vec);
+			goto not_valid_or_not_known;
 		}
 
-		kfree(opt);
+		return dccp_feat_push_confirm(fn, feat, local, &fval);
+
+	} else if (entry->state == FEAT_UNSTABLE) {	/* 6.6.2 */
+		return 0;
 	}
-	INIT_LIST_HEAD(&dmsk->dccpms_pending);
 
-	list_for_each_entry_safe(opt, next, &dmsk->dccpms_conf, dccpop_node) {
-		BUG_ON(opt == NULL);
-		if (opt->dccpop_val != NULL)
-			kfree(opt->dccpop_val);
-		kfree(opt);
+	if (dccp_feat_reconcile(&entry->val, val, len, server, true)) {
+		entry->empty_confirm = 0;
+	} else if (is_mandatory) {
+		return DCCP_RESET_CODE_MANDATORY_ERROR;
+	} else if (entry->state == FEAT_INITIALISING) {
+		/*
+		 * Failed simultaneous negotiation (server only): try to `save'
+		 * the connection by checking whether entry contains the default
+		 * value for @feat. If yes, send an empty Confirm to signal that
+		 * the received Change was not understood - which implies using
+		 * the default value.
+		 * If this also fails, we use Reset as the last resort.
+		 */
+		WARN_ON(!server);
+		defval = dccp_feat_default_value(feat);
+		if (!dccp_feat_reconcile(&entry->val, &defval, 1, server, true))
+			return DCCP_RESET_CODE_OPTION_ERROR;
+		entry->empty_confirm = 1;
 	}
-	INIT_LIST_HEAD(&dmsk->dccpms_conf);
-}
+	entry->needs_confirm   = 1;
+	entry->needs_mandatory = 0;
+	entry->state	       = FEAT_STABLE;
+	return 0;
 
-EXPORT_SYMBOL_GPL(dccp_feat_clean);
+unknown_feature_or_value:
+	if (!is_mandatory)
+		return dccp_push_empty_confirm(fn, feat, local);
 
-/* this is to be called only when a listening sock creates its child.  It is
- * assumed by the function---the confirm is not duplicated, but rather it is
- * "passed on".
+not_valid_or_not_known:
+	return is_mandatory ? DCCP_RESET_CODE_MANDATORY_ERROR
+			    : DCCP_RESET_CODE_OPTION_ERROR;
+}
+
+/**
+ * dccp_feat_confirm_recv  -  Process received Confirm options
+ * @fn: feature-negotiation list to update
+ * @is_mandatory: whether @opt was preceded by a Mandatory option
+ * @opt: %DCCPO_CONFIRM_L or %DCCPO_CONFIRM_R
+ * @feat: one of %dccp_feature_numbers
+ * @val: NN value or SP value/preference list
+ * @len: length of @val in bytes
+ * @server: whether this node is server (1) or client (0)
  */
-int dccp_feat_clone(struct sock *oldsk, struct sock *newsk)
+static u8 dccp_feat_confirm_recv(struct list_head *fn, u8 is_mandatory, u8 opt,
+				 u8 feat, u8 *val, u8 len, const bool server)
 {
-	struct dccp_minisock *olddmsk = dccp_msk(oldsk);
-	struct dccp_minisock *newdmsk = dccp_msk(newsk);
-	struct dccp_opt_pend *opt;
-	int rc = 0;
+	u8 *plist, plen, type = dccp_feat_type(feat);
+	const bool local = (opt == DCCPO_CONFIRM_R);
+	struct dccp_feat_entry *entry = dccp_feat_list_lookup(fn, feat, local);
 
-	INIT_LIST_HEAD(&newdmsk->dccpms_pending);
-	INIT_LIST_HEAD(&newdmsk->dccpms_conf);
+	if (entry == NULL) {	/* nothing queued: ignore or handle error */
+		if (is_mandatory && type == FEAT_UNKNOWN)
+			return DCCP_RESET_CODE_MANDATORY_ERROR;
+
+		if (!local && type == FEAT_NN)		/* 6.3.2 */
+			goto confirmation_failed;
+		return 0;
+	}
 
-	list_for_each_entry(opt, &olddmsk->dccpms_pending, dccpop_node) {
-		struct dccp_opt_pend *newopt;
-		/* copy the value of the option */
-		u8 *val = kmemdup(opt->dccpop_val, opt->dccpop_len, GFP_ATOMIC);
+	if (entry->state != FEAT_CHANGING)		/* 6.6.2 */
+		return 0;
 
-		if (val == NULL)
-			goto out_clean;
+	if (len == 0) {
+		if (dccp_feat_must_be_understood(feat))	/* 6.6.7 */
+			goto confirmation_failed;
+		/*
+		 * Empty Confirm during connection setup: this means reverting
+		 * to the `old' value, which in this case is the default. Since
+		 * we handle default values automatically when no other values
+		 * have been set, we revert to the old value by removing this
+		 * entry from the list.
+		 */
+		dccp_feat_list_pop(entry);
+		return 0;
+	}
 
-		newopt = kmemdup(opt, sizeof(*newopt), GFP_ATOMIC);
-		if (newopt == NULL) {
-			kfree(val);
-			goto out_clean;
-		}
+	if (type == FEAT_NN) {
+		if (len > sizeof(entry->val.nn))
+			goto confirmation_failed;
 
-		/* insert the option */
-		newopt->dccpop_val = val;
-		list_add_tail(&newopt->dccpop_node, &newdmsk->dccpms_pending);
+		if (entry->val.nn == dccp_decode_value_var(val, len))
+			goto confirmation_succeeded;
 
-		/* XXX what happens with backlogs and multiple connections at
-		 * once...
-		 */
-		/* the master socket no longer needs to worry about confirms */
-		opt->dccpop_sc = NULL; /* it's not a memleak---new socket has it */
+		DCCP_WARN("Bogus Confirm for non-existing value\n");
+		goto confirmation_failed;
+	}
 
-		/* reset state for a new socket */
-		opt->dccpop_conf = 0;
+	/*
+	 * Parsing SP Confirms: the first element of @val is the preferred
+	 * SP value which the peer confirms, the remainder depends on @len.
+	 * Note that only the confirmed value need to be a valid SP value.
+	 */
+	if (!dccp_feat_is_valid_sp_val(feat, *val))
+		goto confirmation_failed;
+
+	if (len == 1) {		/* peer didn't supply a preference list */
+		plist = val;
+		plen  = len;
+	} else {		/* preferred value + preference list */
+		plist = val + 1;
+		plen  = len - 1;
 	}
 
-	/* XXX not doing anything about the conf queue */
+	/* Check whether the peer got the reconciliation right (6.6.8) */
+	if (dccp_feat_reconcile(&entry->val, plist, plen, server, 0) != *val) {
+		DCCP_WARN("Confirm selected the wrong value %u\n", *val);
+		return DCCP_RESET_CODE_OPTION_ERROR;
+	}
+	entry->val.sp.vec[0] = *val;
 
-out:
-	return rc;
+confirmation_succeeded:
+	entry->state = FEAT_STABLE;
+	return 0;
 
-out_clean:
-	dccp_feat_clean(newdmsk);
-	rc = -ENOMEM;
-	goto out;
+confirmation_failed:
+	DCCP_WARN("Confirmation failed\n");
+	return is_mandatory ? DCCP_RESET_CODE_MANDATORY_ERROR
+			    : DCCP_RESET_CODE_OPTION_ERROR;
 }
 
-EXPORT_SYMBOL_GPL(dccp_feat_clone);
-
-static int __dccp_feat_init(struct dccp_minisock *dmsk, u8 type, u8 feat,
-			    u8 *val, u8 len)
+/**
+ * dccp_feat_parse_options  -  Process Feature-Negotiation Options
+ * @sk: for general use and used by the client during connection setup
+ * @dreq: used by the server during connection setup
+ * @mandatory: whether @opt was preceded by a Mandatory option
+ * @opt: %DCCPO_CHANGE_L | %DCCPO_CHANGE_R | %DCCPO_CONFIRM_L | %DCCPO_CONFIRM_R
+ * @feat: one of %dccp_feature_numbers
+ * @val: value contents of @opt
+ * @len: length of @val in bytes
+ * Returns 0 on success, a Reset code for ending the connection otherwise.
+ */
+int dccp_feat_parse_options(struct sock *sk, struct dccp_request_sock *dreq,
+			    u8 mandatory, u8 opt, u8 feat, u8 *val, u8 len)
 {
-	int rc = -ENOMEM;
-	u8 *copy = kmemdup(val, len, GFP_KERNEL);
+	struct dccp_sock *dp = dccp_sk(sk);
+	struct list_head *fn = dreq ? &dreq->dreq_featneg : &dp->dccps_featneg;
+	bool server = false;
 
-	if (copy != NULL) {
-		rc = dccp_feat_change(dmsk, type, feat, copy, len, GFP_KERNEL);
-		if (rc)
-			kfree(copy);
+	switch (sk->sk_state) {
+	/*
+	 *	Negotiation during connection setup
+	 */
+	case DCCP_LISTEN:
+		server = true;			/* fall through */
+	case DCCP_REQUESTING:
+		switch (opt) {
+		case DCCPO_CHANGE_L:
+		case DCCPO_CHANGE_R:
+			return dccp_feat_change_recv(fn, mandatory, opt, feat,
+						     val, len, server);
+		case DCCPO_CONFIRM_R:
+		case DCCPO_CONFIRM_L:
+			return dccp_feat_confirm_recv(fn, mandatory, opt, feat,
+						      val, len, server);
+		}
 	}
-	return rc;
+	return 0;	/* ignore FN options in all other states */
 }
 
-int dccp_feat_init(struct dccp_minisock *dmsk)
+int dccp_feat_init(struct sock *sk)
 {
+	struct dccp_sock *dp = dccp_sk(sk);
+	struct dccp_minisock *dmsk = dccp_msk(sk);
 	int rc;
 
-	INIT_LIST_HEAD(&dmsk->dccpms_pending);
-	INIT_LIST_HEAD(&dmsk->dccpms_conf);
-
-	/* CCID L */
-	rc = __dccp_feat_init(dmsk, DCCPO_CHANGE_L, DCCPF_CCID,
-			      &dmsk->dccpms_tx_ccid, 1);
-	if (rc)
-		goto out;
-
-	/* CCID R */
-	rc = __dccp_feat_init(dmsk, DCCPO_CHANGE_R, DCCPF_CCID,
-			      &dmsk->dccpms_rx_ccid, 1);
-	if (rc)
-		goto out;
+	INIT_LIST_HEAD(&dmsk->dccpms_pending);	/* XXX no longer used */
+	INIT_LIST_HEAD(&dmsk->dccpms_conf);	/* XXX no longer used */
 
 	/* Ack ratio */
-	rc = __dccp_feat_init(dmsk, DCCPO_CHANGE_L, DCCPF_ACK_RATIO,
-			      &dmsk->dccpms_ack_ratio, 1);
-out:
+	rc = __feat_register_nn(&dp->dccps_featneg, DCCPF_ACK_RATIO, 0,
+				dp->dccps_l_ack_ratio);
 	return rc;
 }
 
 EXPORT_SYMBOL_GPL(dccp_feat_init);
 
+int dccp_feat_activate_values(struct sock *sk, struct list_head *fn_list)
+{
+	struct dccp_sock *dp = dccp_sk(sk);
+	struct dccp_feat_entry *cur, *next;
+	int idx;
+	dccp_feat_val *fvals[DCCP_FEAT_SUPPORTED_MAX][2] = {
+		 [0 ... DCCP_FEAT_SUPPORTED_MAX-1] = { NULL, NULL }
+	};
+
+	list_for_each_entry(cur, fn_list, node) {
+		/*
+		 * An empty Confirm means that either an unknown feature type
+		 * or an invalid value was present. In the first case there is
+		 * nothing to activate, in the other the default value is used.
+		 */
+		if (cur->empty_confirm)
+			continue;
+
+		idx = dccp_feat_index(cur->feat_num);
+		if (idx < 0) {
+			DCCP_BUG("Unknown feature %u", cur->feat_num);
+			goto activation_failed;
+		}
+		if (cur->state != FEAT_STABLE) {
+			DCCP_CRIT("Negotiation of %s %u failed in state %u",
+				  cur->is_local ? "local" : "remote",
+				  cur->feat_num, cur->state);
+			goto activation_failed;
+		}
+		fvals[idx][cur->is_local] = &cur->val;
+	}
+
+	/*
+	 * Activate in decreasing order of index, so that the CCIDs are always
+	 * activated as the last feature. This avoids the case where a CCID
+	 * relies on the initialisation of one or more features that it depends
+	 * on (e.g. Send NDP Count, Send Ack Vector, and Ack Ratio features).
+	 */
+	for (idx = DCCP_FEAT_SUPPORTED_MAX; --idx >= 0;)
+		if (__dccp_feat_activate(sk, idx, 0, fvals[idx][0]) ||
+		    __dccp_feat_activate(sk, idx, 1, fvals[idx][1])) {
+			DCCP_CRIT("Could not activate %d", idx);
+			goto activation_failed;
+		}
+
+	/* Clean up Change options which have been confirmed already */
+	list_for_each_entry_safe(cur, next, fn_list, node)
+		if (!cur->needs_confirm)
+			dccp_feat_list_pop(cur);
+
+	dccp_pr_debug("Activation OK\n");
+	return 0;
+
+activation_failed:
+	/*
+	 * We clean up everything that may have been allocated, since
+	 * it is difficult to track at which stage negotiation failed.
+	 * This is ok, since all allocation functions below are robust
+	 * against NULL arguments.
+	 */
+	ccid_hc_rx_delete(dp->dccps_hc_rx_ccid, sk);
+	ccid_hc_tx_delete(dp->dccps_hc_tx_ccid, sk);
+	dp->dccps_hc_rx_ccid = dp->dccps_hc_tx_ccid = NULL;
+	dccp_ackvec_free(dp->dccps_hc_rx_ackvec);
+	dp->dccps_hc_rx_ackvec = NULL;
+	return -1;
+}
+
 #ifdef CONFIG_IP_DCCP_DEBUG
 const char *dccp_feat_typename(const u8 type)
 {
@@ -639,6 +1233,8 @@ const char *dccp_feat_name(const u8 feat)
 	if (feat > DCCPF_DATA_CHECKSUM && feat < DCCPF_MIN_CCID_SPECIFIC)
 		return feature_names[DCCPF_RESERVED];
 
+	if (feat ==  DCCPF_SEND_LEV_RATE)
+		return "Send Loss Event Rate";
 	if (feat >= DCCPF_MIN_CCID_SPECIFIC)
 		return "CCID-specific";
 
diff --git a/net/dccp/feat.h b/net/dccp/feat.h
index e272222c7ace..9b46e2a7866e 100644
--- a/net/dccp/feat.h
+++ b/net/dccp/feat.h
@@ -3,17 +3,103 @@
 /*
  *  net/dccp/feat.h
  *
- *  An implementation of the DCCP protocol
+ *  Feature negotiation for the DCCP protocol (RFC 4340, section 6)
+ *  Copyright (c) 2008 Gerrit Renker <gerrit@erg.abdn.ac.uk>
  *  Copyright (c) 2005 Andrea Bittau <a.bittau@cs.ucl.ac.uk>
  *
- *	This program is free software; you can redistribute it and/or modify it
- *	under the terms of the GNU General Public License version 2 as
- *	published by the Free Software Foundation.
+ *  This program is free software; you can redistribute it and/or modify it
+ *  under the terms of the GNU General Public License version 2 as
+ *  published by the Free Software Foundation.
  */
-
 #include <linux/types.h>
 #include "dccp.h"
 
+/*
+ * Known limit values
+ */
+/* Ack Ratio takes 2-byte integer values (11.3) */
+#define DCCPF_ACK_RATIO_MAX	0xFFFF
+/* Wmin=32 and Wmax=2^46-1 from 7.5.2 */
+#define DCCPF_SEQ_WMIN		32
+#define DCCPF_SEQ_WMAX		0x3FFFFFFFFFFFull
+/* Maximum number of SP values that fit in a single (Confirm) option */
+#define DCCP_FEAT_MAX_SP_VALS	(DCCP_SINGLE_OPT_MAXLEN - 2)
+
+enum dccp_feat_type {
+	FEAT_AT_RX   = 1,	/* located at RX side of half-connection  */
+	FEAT_AT_TX   = 2,	/* located at TX side of half-connection  */
+	FEAT_SP      = 4,	/* server-priority reconciliation (6.3.1) */
+	FEAT_NN	     = 8,	/* non-negotiable reconciliation (6.3.2)  */
+	FEAT_UNKNOWN = 0xFF	/* not understood or invalid feature	  */
+};
+
+enum dccp_feat_state {
+	FEAT_DEFAULT = 0,	/* using default values from 6.4 */
+	FEAT_INITIALISING,	/* feature is being initialised  */
+	FEAT_CHANGING,		/* Change sent but not confirmed yet */
+	FEAT_UNSTABLE,		/* local modification in state CHANGING */
+	FEAT_STABLE		/* both ends (think they) agree */
+};
+
+/**
+ * dccp_feat_val  -  Container for SP or NN feature values
+ * @nn:     single NN value
+ * @sp.vec: single SP value plus optional preference list
+ * @sp.len: length of @sp.vec in bytes
+ */
+typedef union {
+	u64 nn;
+	struct {
+		u8	*vec;
+		u8	len;
+	}   sp;
+} dccp_feat_val;
+
+/**
+ * struct feat_entry  -  Data structure to perform feature negotiation
+ * @val: feature's current value (SP features may have preference list)
+ * @state: feature's current state
+ * @feat_num: one of %dccp_feature_numbers
+ * @needs_mandatory: whether Mandatory options should be sent
+ * @needs_confirm: whether to send a Confirm instead of a Change
+ * @empty_confirm: whether to send an empty Confirm (depends on @needs_confirm)
+ * @is_local: feature location (1) or feature-remote (0)
+ * @node: list pointers, entries arranged in FIFO order
+ */
+struct dccp_feat_entry {
+	dccp_feat_val           val;
+	enum dccp_feat_state    state:8;
+	u8                      feat_num;
+
+	bool			needs_mandatory,
+				needs_confirm,
+				empty_confirm,
+				is_local;
+
+	struct list_head	node;
+};
+
+static inline u8 dccp_feat_genopt(struct dccp_feat_entry *entry)
+{
+	if (entry->needs_confirm)
+		return entry->is_local ? DCCPO_CONFIRM_L : DCCPO_CONFIRM_R;
+	return entry->is_local ? DCCPO_CHANGE_L : DCCPO_CHANGE_R;
+}
+
+/**
+ * struct ccid_dependency  -  Track changes resulting from choosing a CCID
+ * @dependent_feat: one of %dccp_feature_numbers
+ * @is_local: local (1) or remote (0) @dependent_feat
+ * @is_mandatory: whether presence of @dependent_feat is mission-critical or not
+ * @val: corresponding default value for @dependent_feat (u8 is sufficient here)
+ */
+struct ccid_dependency {
+	u8	dependent_feat;
+	bool	is_local:1,
+		is_mandatory:1;
+	u8	val;
+};
+
 #ifdef CONFIG_IP_DCCP_DEBUG
 extern const char *dccp_feat_typename(const u8 type);
 extern const char *dccp_feat_name(const u8 feat);
@@ -27,14 +113,30 @@ static inline void dccp_feat_debug(const u8 type, const u8 feat, const u8 val)
 #define dccp_feat_debug(type, feat, val)
 #endif /* CONFIG_IP_DCCP_DEBUG */
 
-extern int  dccp_feat_change(struct dccp_minisock *dmsk, u8 type, u8 feature,
-			     u8 *val, u8 len, gfp_t gfp);
-extern int  dccp_feat_change_recv(struct sock *sk, u8 type, u8 feature,
-				  u8 *val, u8 len);
-extern int  dccp_feat_confirm_recv(struct sock *sk, u8 type, u8 feature,
-				   u8 *val, u8 len);
-extern void dccp_feat_clean(struct dccp_minisock *dmsk);
-extern int  dccp_feat_clone(struct sock *oldsk, struct sock *newsk);
-extern int  dccp_feat_init(struct dccp_minisock *dmsk);
+extern int  dccp_feat_register_sp(struct sock *sk, u8 feat, u8 is_local,
+				  u8 const *list, u8 len);
+extern int  dccp_feat_register_nn(struct sock *sk, u8 feat, u64 val);
+extern int  dccp_feat_parse_options(struct sock *, struct dccp_request_sock *,
+				    u8 mand, u8 opt, u8 feat, u8 *val, u8 len);
+extern int  dccp_feat_clone_list(struct list_head const *, struct list_head *);
+extern int  dccp_feat_init(struct sock *sk);
+
+/*
+ * Encoding variable-length options and their maximum length.
+ *
+ * This affects NN options (SP options are all u8) and other variable-length
+ * options (see table 3 in RFC 4340). The limit is currently given the Sequence
+ * Window NN value (sec. 7.5.2) and the NDP count (sec. 7.7) option, all other
+ * options consume less than 6 bytes (timestamps are 4 bytes).
+ * When updating this constant (e.g. due to new internet drafts / RFCs), make
+ * sure that you also update all code which refers to it.
+ */
+#define DCCP_OPTVAL_MAXLEN	6
+
+extern void dccp_encode_value_var(const u64 value, u8 *to, const u8 len);
+extern u64  dccp_decode_value_var(const u8 *bf, const u8 len);
 
+extern int  dccp_insert_option_mandatory(struct sk_buff *skb);
+extern int  dccp_insert_fn_opt(struct sk_buff *skb, u8 type, u8 feat,
+			       u8 *val, u8 len, bool repeat_first);
 #endif /* _DCCP_FEAT_H */
diff --git a/net/dccp/input.c b/net/dccp/input.c
index 779d0ed9ae94..5eb443f656c1 100644
--- a/net/dccp/input.c
+++ b/net/dccp/input.c
@@ -163,7 +163,7 @@ static void dccp_event_ack_recv(struct sock *sk, struct sk_buff *skb)
 {
 	struct dccp_sock *dp = dccp_sk(sk);
 
-	if (dccp_msk(sk)->dccpms_send_ack_vector)
+	if (dp->dccps_hc_rx_ackvec != NULL)
 		dccp_ackvec_check_rcv_ackno(dp->dccps_hc_rx_ackvec, sk,
 					    DCCP_SKB_CB(skb)->dccpd_ack_seq);
 }
@@ -375,7 +375,7 @@ int dccp_rcv_established(struct sock *sk, struct sk_buff *skb,
 	if (DCCP_SKB_CB(skb)->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
 		dccp_event_ack_recv(sk, skb);
 
-	if (dccp_msk(sk)->dccpms_send_ack_vector &&
+	if (dp->dccps_hc_rx_ackvec != NULL &&
 	    dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
 			    DCCP_SKB_CB(skb)->dccpd_seq,
 			    DCCP_ACKVEC_STATE_RECEIVED))
@@ -421,20 +421,19 @@ static int dccp_rcv_request_sent_state_process(struct sock *sk,
 			goto out_invalid_packet;
 		}
 
+		/*
+		 * If option processing (Step 8) failed, return 1 here so that
+		 * dccp_v4_do_rcv() sends a Reset. The Reset code depends on
+		 * the option type and is set in dccp_parse_options().
+		 */
 		if (dccp_parse_options(sk, NULL, skb))
-			goto out_invalid_packet;
+			return 1;
 
 		/* Obtain usec RTT sample from SYN exchange (used by CCID 3) */
 		if (likely(dp->dccps_options_received.dccpor_timestamp_echo))
 			dp->dccps_syn_rtt = dccp_sample_rtt(sk, 10 * (tstamp -
 			    dp->dccps_options_received.dccpor_timestamp_echo));
 
-		if (dccp_msk(sk)->dccpms_send_ack_vector &&
-		    dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
-				    DCCP_SKB_CB(skb)->dccpd_seq,
-				    DCCP_ACKVEC_STATE_RECEIVED))
-			goto out_invalid_packet; /* FIXME: change error code */
-
 		/* Stop the REQUEST timer */
 		inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS);
 		WARN_ON(sk->sk_send_head == NULL);
@@ -475,6 +474,15 @@ static int dccp_rcv_request_sent_state_process(struct sock *sk,
 		 */
 		dccp_set_state(sk, DCCP_PARTOPEN);
 
+		/*
+		 * If feature negotiation was successful, activate features now;
+		 * an activation failure means that this host could not activate
+		 * one ore more features (e.g. insufficient memory), which would
+		 * leave at least one feature in an undefined state.
+		 */
+		if (dccp_feat_activate_values(sk, &dp->dccps_featneg))
+			goto unable_to_proceed;
+
 		/* Make sure socket is routed, for correct metrics. */
 		icsk->icsk_af_ops->rebuild_header(sk);
 
@@ -509,6 +517,16 @@ out_invalid_packet:
 	/* dccp_v4_do_rcv will send a reset */
 	DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_PACKET_ERROR;
 	return 1;
+
+unable_to_proceed:
+	DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_ABORTED;
+	/*
+	 * We mark this socket as no longer usable, so that the loop in
+	 * dccp_sendmsg() terminates and the application gets notified.
+	 */
+	dccp_set_state(sk, DCCP_CLOSED);
+	sk->sk_err = ECOMM;
+	return 1;
 }
 
 static int dccp_rcv_respond_partopen_state_process(struct sock *sk,
@@ -590,8 +608,6 @@ int dccp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
 			if (inet_csk(sk)->icsk_af_ops->conn_request(sk,
 								    skb) < 0)
 				return 1;
-
-			/* FIXME: do congestion control initialization */
 			goto discard;
 		}
 		if (dh->dccph_type == DCCP_PKT_RESET)
@@ -602,7 +618,7 @@ int dccp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
 		return 1;
 	}
 
-	if (sk->sk_state != DCCP_REQUESTING) {
+	if (sk->sk_state != DCCP_REQUESTING && sk->sk_state != DCCP_RESPOND) {
 		if (dccp_check_seqno(sk, skb))
 			goto discard;
 
@@ -615,7 +631,7 @@ int dccp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
 		if (dcb->dccpd_ack_seq != DCCP_PKT_WITHOUT_ACK_SEQ)
 			dccp_event_ack_recv(sk, skb);
 
-		if (dccp_msk(sk)->dccpms_send_ack_vector &&
+		if (dp->dccps_hc_rx_ackvec != NULL &&
 		    dccp_ackvec_add(dp->dccps_hc_rx_ackvec, sk,
 				    DCCP_SKB_CB(skb)->dccpd_seq,
 				    DCCP_ACKVEC_STATE_RECEIVED))
@@ -667,8 +683,6 @@ int dccp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
 		return 1;
 
 	case DCCP_REQUESTING:
-		/* FIXME: do congestion control initialization */
-
 		queued = dccp_rcv_request_sent_state_process(sk, skb, dh, len);
 		if (queued >= 0)
 			return queued;
diff --git a/net/dccp/ipv4.c b/net/dccp/ipv4.c
index e3dfddab21cc..d1dd95289b89 100644
--- a/net/dccp/ipv4.c
+++ b/net/dccp/ipv4.c
@@ -545,6 +545,7 @@ out:
 
 static void dccp_v4_reqsk_destructor(struct request_sock *req)
 {
+	dccp_feat_list_purge(&dccp_rsk(req)->dreq_featneg);
 	kfree(inet_rsk(req)->opt);
 }
 
@@ -595,7 +596,8 @@ int dccp_v4_conn_request(struct sock *sk, struct sk_buff *skb)
 	if (req == NULL)
 		goto drop;
 
-	dccp_reqsk_init(req, skb);
+	if (dccp_reqsk_init(req, dccp_sk(sk), skb))
+		goto drop_and_free;
 
 	dreq = dccp_rsk(req);
 	if (dccp_parse_options(sk, dreq, skb))
@@ -792,12 +794,10 @@ static int dccp_v4_rcv(struct sk_buff *skb)
 	DCCP_SKB_CB(skb)->dccpd_seq  = dccp_hdr_seq(dh);
 	DCCP_SKB_CB(skb)->dccpd_type = dh->dccph_type;
 
-	dccp_pr_debug("%8.8s "
-		      "src=%u.%u.%u.%u@%-5d "
-		      "dst=%u.%u.%u.%u@%-5d seq=%llu",
+	dccp_pr_debug("%8.8s src=%pI4@%-5d dst=%pI4@%-5d seq=%llu",
 		      dccp_packet_name(dh->dccph_type),
-		      NIPQUAD(iph->saddr), ntohs(dh->dccph_sport),
-		      NIPQUAD(iph->daddr), ntohs(dh->dccph_dport),
+		      &iph->saddr, ntohs(dh->dccph_sport),
+		      &iph->daddr, ntohs(dh->dccph_dport),
 		      (unsigned long long) DCCP_SKB_CB(skb)->dccpd_seq);
 
 	if (dccp_packet_without_ack(skb)) {
@@ -938,6 +938,7 @@ static struct proto dccp_v4_prot = {
 	.orphan_count		= &dccp_orphan_count,
 	.max_header		= MAX_DCCP_HEADER,
 	.obj_size		= sizeof(struct dccp_sock),
+	.slab_flags		= SLAB_DESTROY_BY_RCU,
 	.rsk_prot		= &dccp_request_sock_ops,
 	.twsk_prot		= &dccp_timewait_sock_ops,
 	.h.hashinfo		= &dccp_hashinfo,
diff --git a/net/dccp/ipv6.c b/net/dccp/ipv6.c
index d4ce1224e008..b963f35c65f6 100644
--- a/net/dccp/ipv6.c
+++ b/net/dccp/ipv6.c
@@ -168,7 +168,7 @@ static void dccp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
 				goto out;
 			}
 
-			err = xfrm_lookup(&dst, &fl, sk, 0);
+			err = xfrm_lookup(net, &dst, &fl, sk, 0);
 			if (err < 0) {
 				sk->sk_err_soft = -err;
 				goto out;
@@ -279,7 +279,7 @@ static int dccp_v6_send_response(struct sock *sk, struct request_sock *req)
 	if (final_p)
 		ipv6_addr_copy(&fl.fl6_dst, final_p);
 
-	err = xfrm_lookup(&dst, &fl, sk, 0);
+	err = xfrm_lookup(sock_net(sk), &dst, &fl, sk, 0);
 	if (err < 0)
 		goto done;
 
@@ -304,6 +304,7 @@ done:
 
 static void dccp_v6_reqsk_destructor(struct request_sock *req)
 {
+	dccp_feat_list_purge(&dccp_rsk(req)->dreq_featneg);
 	if (inet6_rsk(req)->pktopts != NULL)
 		kfree_skb(inet6_rsk(req)->pktopts);
 }
@@ -342,7 +343,7 @@ static void dccp_v6_ctl_send_reset(struct sock *sk, struct sk_buff *rxskb)
 
 	/* sk = NULL, but it is safe for now. RST socket required. */
 	if (!ip6_dst_lookup(ctl_sk, &skb->dst, &fl)) {
-		if (xfrm_lookup(&skb->dst, &fl, NULL, 0) >= 0) {
+		if (xfrm_lookup(net, &skb->dst, &fl, NULL, 0) >= 0) {
 			ip6_xmit(ctl_sk, skb, &fl, NULL, 0);
 			DCCP_INC_STATS_BH(DCCP_MIB_OUTSEGS);
 			DCCP_INC_STATS_BH(DCCP_MIB_OUTRSTS);
@@ -426,7 +427,8 @@ static int dccp_v6_conn_request(struct sock *sk, struct sk_buff *skb)
 	if (req == NULL)
 		goto drop;
 
-	dccp_reqsk_init(req, skb);
+	if (dccp_reqsk_init(req, dccp_sk(sk), skb))
+		goto drop_and_free;
 
 	dreq = dccp_rsk(req);
 	if (dccp_parse_options(sk, dreq, skb))
@@ -567,7 +569,7 @@ static struct sock *dccp_v6_request_recv_sock(struct sock *sk,
 		if (final_p)
 			ipv6_addr_copy(&fl.fl6_dst, final_p);
 
-		if ((xfrm_lookup(&dst, &fl, sk, 0)) < 0)
+		if ((xfrm_lookup(sock_net(sk), &dst, &fl, sk, 0)) < 0)
 			goto out;
 	}
 
@@ -1002,7 +1004,7 @@ static int dccp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
 	if (final_p)
 		ipv6_addr_copy(&fl.fl6_dst, final_p);
 
-	err = __xfrm_lookup(&dst, &fl, sk, XFRM_LOOKUP_WAIT);
+	err = __xfrm_lookup(sock_net(sk), &dst, &fl, sk, XFRM_LOOKUP_WAIT);
 	if (err < 0) {
 		if (err == -EREMOTE)
 			err = ip6_dst_blackhole(sk, &dst, &fl);
@@ -1138,6 +1140,7 @@ static struct proto dccp_v6_prot = {
 	.orphan_count	   = &dccp_orphan_count,
 	.max_header	   = MAX_DCCP_HEADER,
 	.obj_size	   = sizeof(struct dccp6_sock),
+	.slab_flags	   = SLAB_DESTROY_BY_RCU,
 	.rsk_prot	   = &dccp6_request_sock_ops,
 	.twsk_prot	   = &dccp6_timewait_sock_ops,
 	.h.hashinfo	   = &dccp_hashinfo,
diff --git a/net/dccp/minisocks.c b/net/dccp/minisocks.c
index e6bf99e3e41a..6821ae33dd37 100644
--- a/net/dccp/minisocks.c
+++ b/net/dccp/minisocks.c
@@ -45,11 +45,6 @@ EXPORT_SYMBOL_GPL(dccp_death_row);
 void dccp_minisock_init(struct dccp_minisock *dmsk)
 {
 	dmsk->dccpms_sequence_window = sysctl_dccp_feat_sequence_window;
-	dmsk->dccpms_rx_ccid	     = sysctl_dccp_feat_rx_ccid;
-	dmsk->dccpms_tx_ccid	     = sysctl_dccp_feat_tx_ccid;
-	dmsk->dccpms_ack_ratio	     = sysctl_dccp_feat_ack_ratio;
-	dmsk->dccpms_send_ack_vector = sysctl_dccp_feat_send_ack_vector;
-	dmsk->dccpms_send_ndp_count  = sysctl_dccp_feat_send_ndp_count;
 }
 
 void dccp_time_wait(struct sock *sk, int state, int timeo)
@@ -112,7 +107,7 @@ struct sock *dccp_create_openreq_child(struct sock *sk,
 	struct sock *newsk = inet_csk_clone(sk, req, GFP_ATOMIC);
 
 	if (newsk != NULL) {
-		const struct dccp_request_sock *dreq = dccp_rsk(req);
+		struct dccp_request_sock *dreq = dccp_rsk(req);
 		struct inet_connection_sock *newicsk = inet_csk(newsk);
 		struct dccp_sock *newdp = dccp_sk(newsk);
 		struct dccp_minisock *newdmsk = dccp_msk(newsk);
@@ -125,35 +120,7 @@ struct sock *dccp_create_openreq_child(struct sock *sk,
 		newdp->dccps_timestamp_time = dreq->dreq_timestamp_time;
 		newicsk->icsk_rto	    = DCCP_TIMEOUT_INIT;
 
-		if (dccp_feat_clone(sk, newsk))
-			goto out_free;
-
-		if (newdmsk->dccpms_send_ack_vector) {
-			newdp->dccps_hc_rx_ackvec =
-						dccp_ackvec_alloc(GFP_ATOMIC);
-			if (unlikely(newdp->dccps_hc_rx_ackvec == NULL))
-				goto out_free;
-		}
-
-		newdp->dccps_hc_rx_ccid =
-			    ccid_hc_rx_new(newdmsk->dccpms_rx_ccid,
-					   newsk, GFP_ATOMIC);
-		newdp->dccps_hc_tx_ccid =
-			    ccid_hc_tx_new(newdmsk->dccpms_tx_ccid,
-					   newsk, GFP_ATOMIC);
-		if (unlikely(newdp->dccps_hc_rx_ccid == NULL ||
-			     newdp->dccps_hc_tx_ccid == NULL)) {
-			dccp_ackvec_free(newdp->dccps_hc_rx_ackvec);
-			ccid_hc_rx_delete(newdp->dccps_hc_rx_ccid, newsk);
-			ccid_hc_tx_delete(newdp->dccps_hc_tx_ccid, newsk);
-out_free:
-			/* It is still raw copy of parent, so invalidate
-			 * destructor and make plain sk_free() */
-			newsk->sk_destruct = NULL;
-			sk_free(newsk);
-			return NULL;
-		}
-
+		INIT_LIST_HEAD(&newdp->dccps_featneg);
 		/*
 		 * Step 3: Process LISTEN state
 		 *
@@ -184,6 +151,17 @@ out_free:
 		dccp_set_seqno(&newdp->dccps_awl,
 			       max48(newdp->dccps_awl, newdp->dccps_iss));
 
+		/*
+		 * Activate features after initialising the sequence numbers,
+		 * since CCID initialisation may depend on GSS, ISR, ISS etc.
+		 */
+		if (dccp_feat_activate_values(newsk, &dreq->dreq_featneg)) {
+			/* It is still raw copy of parent, so invalidate
+			 * destructor and make plain sk_free() */
+			newsk->sk_destruct = NULL;
+			sk_free(newsk);
+			return NULL;
+		}
 		dccp_init_xmit_timers(newsk);
 
 		DCCP_INC_STATS_BH(DCCP_MIB_PASSIVEOPENS);
@@ -304,7 +282,8 @@ void dccp_reqsk_send_ack(struct sock *sk, struct sk_buff *skb,
 
 EXPORT_SYMBOL_GPL(dccp_reqsk_send_ack);
 
-void dccp_reqsk_init(struct request_sock *req, struct sk_buff *skb)
+int dccp_reqsk_init(struct request_sock *req,
+		    struct dccp_sock const *dp, struct sk_buff const *skb)
 {
 	struct dccp_request_sock *dreq = dccp_rsk(req);
 
@@ -313,6 +292,9 @@ void dccp_reqsk_init(struct request_sock *req, struct sk_buff *skb)
 	inet_rsk(req)->acked	  = 0;
 	req->rcv_wnd		  = sysctl_dccp_feat_sequence_window;
 	dreq->dreq_timestamp_echo = 0;
+
+	/* inherit feature negotiation options from listening socket */
+	return dccp_feat_clone_list(&dp->dccps_featneg, &dreq->dreq_featneg);
 }
 
 EXPORT_SYMBOL_GPL(dccp_reqsk_init);
diff --git a/net/dccp/options.c b/net/dccp/options.c
index 0809b63cb055..7b1165c21f51 100644
--- a/net/dccp/options.c
+++ b/net/dccp/options.c
@@ -26,20 +26,21 @@
 int sysctl_dccp_feat_sequence_window = DCCPF_INITIAL_SEQUENCE_WINDOW;
 int sysctl_dccp_feat_rx_ccid	      = DCCPF_INITIAL_CCID;
 int sysctl_dccp_feat_tx_ccid	      = DCCPF_INITIAL_CCID;
-int sysctl_dccp_feat_ack_ratio	      = DCCPF_INITIAL_ACK_RATIO;
-int sysctl_dccp_feat_send_ack_vector = DCCPF_INITIAL_SEND_ACK_VECTOR;
-int sysctl_dccp_feat_send_ndp_count  = DCCPF_INITIAL_SEND_NDP_COUNT;
 
-static u32 dccp_decode_value_var(const unsigned char *bf, const u8 len)
+u64 dccp_decode_value_var(const u8 *bf, const u8 len)
 {
-	u32 value = 0;
+	u64 value = 0;
 
+	if (len >= DCCP_OPTVAL_MAXLEN)
+		value += ((u64)*bf++) << 40;
+	if (len > 4)
+		value += ((u64)*bf++) << 32;
 	if (len > 3)
-		value += *bf++ << 24;
+		value += ((u64)*bf++) << 24;
 	if (len > 2)
-		value += *bf++ << 16;
+		value += ((u64)*bf++) << 16;
 	if (len > 1)
-		value += *bf++ << 8;
+		value += ((u64)*bf++) << 8;
 	if (len > 0)
 		value += *bf;
 
@@ -64,7 +65,7 @@ int dccp_parse_options(struct sock *sk, struct dccp_request_sock *dreq,
 					(dh->dccph_doff * 4);
 	struct dccp_options_received *opt_recv = &dp->dccps_options_received;
 	unsigned char opt, len;
-	unsigned char *value;
+	unsigned char *uninitialized_var(value);
 	u32 elapsed_time;
 	__be32 opt_val;
 	int rc;
@@ -131,41 +132,19 @@ int dccp_parse_options(struct sock *sk, struct dccp_request_sock *dreq,
 			dccp_pr_debug("%s opt: NDP count=%llu\n", dccp_role(sk),
 				      (unsigned long long)opt_recv->dccpor_ndp);
 			break;
-		case DCCPO_CHANGE_L:
-			/* fall through */
-		case DCCPO_CHANGE_R:
-			if (pkt_type == DCCP_PKT_DATA)
+		case DCCPO_CHANGE_L ... DCCPO_CONFIRM_R:
+			if (pkt_type == DCCP_PKT_DATA)      /* RFC 4340, 6 */
 				break;
-			if (len < 2)
-				goto out_invalid_option;
-			rc = dccp_feat_change_recv(sk, opt, *value, value + 1,
-						   len - 1);
-			/*
-			 * When there is a change error, change_recv is
-			 * responsible for dealing with it.  i.e. reply with an
-			 * empty confirm.
-			 * If the change was mandatory, then we need to die.
-			 */
-			if (rc && mandatory)
-				goto out_invalid_option;
-			break;
-		case DCCPO_CONFIRM_L:
-			/* fall through */
-		case DCCPO_CONFIRM_R:
-			if (pkt_type == DCCP_PKT_DATA)
-				break;
-			if (len < 2)	/* FIXME this disallows empty confirm */
-				goto out_invalid_option;
-			if (dccp_feat_confirm_recv(sk, opt, *value,
-						   value + 1, len - 1))
-				goto out_invalid_option;
+			rc = dccp_feat_parse_options(sk, dreq, mandatory, opt,
+						    *value, value + 1, len - 1);
+			if (rc)
+				goto out_featneg_failed;
 			break;
 		case DCCPO_ACK_VECTOR_0:
 		case DCCPO_ACK_VECTOR_1:
 			if (dccp_packet_without_ack(skb))   /* RFC 4340, 11.4 */
 				break;
-
-			if (dccp_msk(sk)->dccpms_send_ack_vector &&
+			if (dp->dccps_hc_rx_ackvec != NULL &&
 			    dccp_ackvec_parse(sk, skb, &ackno, opt, value, len))
 				goto out_invalid_option;
 			break;
@@ -289,8 +268,10 @@ out_nonsensical_length:
 
 out_invalid_option:
 	DCCP_INC_STATS_BH(DCCP_MIB_INVALIDOPT);
-	DCCP_SKB_CB(skb)->dccpd_reset_code = DCCP_RESET_CODE_OPTION_ERROR;
-	DCCP_WARN("DCCP(%p): invalid option %d, len=%d", sk, opt, len);
+	rc = DCCP_RESET_CODE_OPTION_ERROR;
+out_featneg_failed:
+	DCCP_WARN("DCCP(%p): Option %d (len=%d) error=%u\n", sk, opt, len, rc);
+	DCCP_SKB_CB(skb)->dccpd_reset_code = rc;
 	DCCP_SKB_CB(skb)->dccpd_reset_data[0] = opt;
 	DCCP_SKB_CB(skb)->dccpd_reset_data[1] = len > 0 ? value[0] : 0;
 	DCCP_SKB_CB(skb)->dccpd_reset_data[2] = len > 1 ? value[1] : 0;
@@ -299,9 +280,12 @@ out_invalid_option:
 
 EXPORT_SYMBOL_GPL(dccp_parse_options);
 
-static void dccp_encode_value_var(const u32 value, unsigned char *to,
-				  const unsigned int len)
+void dccp_encode_value_var(const u64 value, u8 *to, const u8 len)
 {
+	if (len >= DCCP_OPTVAL_MAXLEN)
+		*to++ = (value & 0xFF0000000000ull) >> 40;
+	if (len > 4)
+		*to++ = (value & 0xFF00000000ull) >> 32;
 	if (len > 3)
 		*to++ = (value & 0xFF000000) >> 24;
 	if (len > 2)
@@ -461,23 +445,61 @@ static int dccp_insert_option_timestamp_echo(struct dccp_sock *dp,
 	return 0;
 }
 
-static int dccp_insert_feat_opt(struct sk_buff *skb, u8 type, u8 feat,
-				u8 *val, u8 len)
+/**
+ * dccp_insert_option_mandatory  -  Mandatory option (5.8.2)
+ * Note that since we are using skb_push, this function needs to be called
+ * _after_ inserting the option it is supposed to influence (stack order).
+ */
+int dccp_insert_option_mandatory(struct sk_buff *skb)
+{
+	if (DCCP_SKB_CB(skb)->dccpd_opt_len >= DCCP_MAX_OPT_LEN)
+		return -1;
+
+	DCCP_SKB_CB(skb)->dccpd_opt_len++;
+	*skb_push(skb, 1) = DCCPO_MANDATORY;
+	return 0;
+}
+
+/**
+ * dccp_insert_fn_opt  -  Insert single Feature-Negotiation option into @skb
+ * @type: %DCCPO_CHANGE_L, %DCCPO_CHANGE_R, %DCCPO_CONFIRM_L, %DCCPO_CONFIRM_R
+ * @feat: one out of %dccp_feature_numbers
+ * @val: NN value or SP array (preferred element first) to copy
+ * @len: true length of @val in bytes (excluding first element repetition)
+ * @repeat_first: whether to copy the first element of @val twice
+ * The last argument is used to construct Confirm options, where the preferred
+ * value and the preference list appear separately (RFC 4340, 6.3.1). Preference
+ * lists are kept such that the preferred entry is always first, so we only need
+ * to copy twice, and avoid the overhead of cloning into a bigger array.
+ */
+int dccp_insert_fn_opt(struct sk_buff *skb, u8 type, u8 feat,
+		       u8 *val, u8 len, bool repeat_first)
 {
-	u8 *to;
+	u8 tot_len, *to;
 
-	if (DCCP_SKB_CB(skb)->dccpd_opt_len + len + 3 > DCCP_MAX_OPT_LEN) {
-		DCCP_WARN("packet too small for feature %d option!\n", feat);
+	/* take the `Feature' field and possible repetition into account */
+	if (len > (DCCP_SINGLE_OPT_MAXLEN - 2)) {
+		DCCP_WARN("length %u for feature %u too large\n", len, feat);
 		return -1;
 	}
 
-	DCCP_SKB_CB(skb)->dccpd_opt_len += len + 3;
+	if (unlikely(val == NULL || len == 0))
+		len = repeat_first = 0;
+	tot_len = 3 + repeat_first + len;
+
+	if (DCCP_SKB_CB(skb)->dccpd_opt_len + tot_len > DCCP_MAX_OPT_LEN) {
+		DCCP_WARN("packet too small for feature %d option!\n", feat);
+		return -1;
+	}
+	DCCP_SKB_CB(skb)->dccpd_opt_len += tot_len;
 
-	to    = skb_push(skb, len + 3);
+	to    = skb_push(skb, tot_len);
 	*to++ = type;
-	*to++ = len + 3;
+	*to++ = tot_len;
 	*to++ = feat;
 
+	if (repeat_first)
+		*to++ = *val;
 	if (len)
 		memcpy(to, val, len);
 
@@ -487,69 +509,6 @@ static int dccp_insert_feat_opt(struct sk_buff *skb, u8 type, u8 feat,
 	return 0;
 }
 
-static int dccp_insert_options_feat(struct sock *sk, struct sk_buff *skb)
-{
-	struct dccp_sock *dp = dccp_sk(sk);
-	struct dccp_minisock *dmsk = dccp_msk(sk);
-	struct dccp_opt_pend *opt, *next;
-	int change = 0;
-
-	/* confirm any options [NN opts] */
-	list_for_each_entry_safe(opt, next, &dmsk->dccpms_conf, dccpop_node) {
-		dccp_insert_feat_opt(skb, opt->dccpop_type,
-				     opt->dccpop_feat, opt->dccpop_val,
-				     opt->dccpop_len);
-		/* fear empty confirms */
-		if (opt->dccpop_val)
-			kfree(opt->dccpop_val);
-		kfree(opt);
-	}
-	INIT_LIST_HEAD(&dmsk->dccpms_conf);
-
-	/* see which features we need to send */
-	list_for_each_entry(opt, &dmsk->dccpms_pending, dccpop_node) {
-		/* see if we need to send any confirm */
-		if (opt->dccpop_sc) {
-			dccp_insert_feat_opt(skb, opt->dccpop_type + 1,
-					     opt->dccpop_feat,
-					     opt->dccpop_sc->dccpoc_val,
-					     opt->dccpop_sc->dccpoc_len);
-
-			BUG_ON(!opt->dccpop_sc->dccpoc_val);
-			kfree(opt->dccpop_sc->dccpoc_val);
-			kfree(opt->dccpop_sc);
-			opt->dccpop_sc = NULL;
-		}
-
-		/* any option not confirmed, re-send it */
-		if (!opt->dccpop_conf) {
-			dccp_insert_feat_opt(skb, opt->dccpop_type,
-					     opt->dccpop_feat, opt->dccpop_val,
-					     opt->dccpop_len);
-			change++;
-		}
-	}
-
-	/* Retransmit timer.
-	 * If this is the master listening sock, we don't set a timer on it.  It
-	 * should be fine because if the dude doesn't receive our RESPONSE
-	 * [which will contain the CHANGE] he will send another REQUEST which
-	 * will "retrnasmit" the change.
-	 */
-	if (change && dp->dccps_role != DCCP_ROLE_LISTEN) {
-		dccp_pr_debug("reset feat negotiation timer %p\n", sk);
-
-		/* XXX don't reset the timer on re-transmissions.  I.e. reset it
-		 * only when sending new stuff i guess.  Currently the timer
-		 * never backs off because on re-transmission it just resets it!
-		 */
-		inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS,
-					  inet_csk(sk)->icsk_rto, DCCP_RTO_MAX);
-	}
-
-	return 0;
-}
-
 /* The length of all options needs to be a multiple of 4 (5.8) */
 static void dccp_insert_option_padding(struct sk_buff *skb)
 {
@@ -565,19 +524,31 @@ static void dccp_insert_option_padding(struct sk_buff *skb)
 int dccp_insert_options(struct sock *sk, struct sk_buff *skb)
 {
 	struct dccp_sock *dp = dccp_sk(sk);
-	struct dccp_minisock *dmsk = dccp_msk(sk);
 
 	DCCP_SKB_CB(skb)->dccpd_opt_len = 0;
 
-	if (dmsk->dccpms_send_ndp_count &&
-	    dccp_insert_option_ndp(sk, skb))
+	if (dp->dccps_send_ndp_count && dccp_insert_option_ndp(sk, skb))
 		return -1;
 
-	if (!dccp_packet_without_ack(skb)) {
-		if (dmsk->dccpms_send_ack_vector &&
-		    dccp_ackvec_pending(dp->dccps_hc_rx_ackvec) &&
-		    dccp_insert_option_ackvec(sk, skb))
+	if (DCCP_SKB_CB(skb)->dccpd_type != DCCP_PKT_DATA) {
+
+		/* Feature Negotiation */
+		if (dccp_feat_insert_opts(dp, NULL, skb))
 			return -1;
+
+		if (DCCP_SKB_CB(skb)->dccpd_type == DCCP_PKT_REQUEST) {
+			/*
+			 * Obtain RTT sample from Request/Response exchange.
+			 * This is currently used in CCID 3 initialisation.
+			 */
+			if (dccp_insert_option_timestamp(sk, skb))
+				return -1;
+
+		} else if (dp->dccps_hc_rx_ackvec != NULL &&
+			   dccp_ackvec_pending(dp->dccps_hc_rx_ackvec) &&
+			   dccp_insert_option_ackvec(sk, skb)) {
+				return -1;
+		}
 	}
 
 	if (dp->dccps_hc_rx_insert_options) {
@@ -586,21 +557,6 @@ int dccp_insert_options(struct sock *sk, struct sk_buff *skb)
 		dp->dccps_hc_rx_insert_options = 0;
 	}
 
-	/* Feature negotiation */
-	/* Data packets can't do feat negotiation */
-	if (DCCP_SKB_CB(skb)->dccpd_type != DCCP_PKT_DATA &&
-	    DCCP_SKB_CB(skb)->dccpd_type != DCCP_PKT_DATAACK &&
-	    dccp_insert_options_feat(sk, skb))
-		return -1;
-
-	/*
-	 * Obtain RTT sample from Request/Response exchange.
-	 * This is currently used in CCID 3 initialisation.
-	 */
-	if (DCCP_SKB_CB(skb)->dccpd_type == DCCP_PKT_REQUEST &&
-	    dccp_insert_option_timestamp(sk, skb))
-		return -1;
-
 	if (dp->dccps_timestamp_echo != 0 &&
 	    dccp_insert_option_timestamp_echo(dp, NULL, skb))
 		return -1;
@@ -613,6 +569,9 @@ int dccp_insert_options_rsk(struct dccp_request_sock *dreq, struct sk_buff *skb)
 {
 	DCCP_SKB_CB(skb)->dccpd_opt_len = 0;
 
+	if (dccp_feat_insert_opts(NULL, dreq, skb))
+		return -1;
+
 	if (dreq->dreq_timestamp_echo != 0 &&
 	    dccp_insert_option_timestamp_echo(NULL, dreq, skb))
 		return -1;
diff --git a/net/dccp/output.c b/net/dccp/output.c
index 809d803d5006..22a618af4893 100644
--- a/net/dccp/output.c
+++ b/net/dccp/output.c
@@ -175,7 +175,7 @@ unsigned int dccp_sync_mss(struct sock *sk, u32 pmtu)
 	 * make it a multiple of 4
 	 */
 
-	cur_mps -= ((5 + 6 + 10 + 6 + 6 + 6 + 3) / 4) * 4;
+	cur_mps -= roundup(5 + 6 + 10 + 6 + 6 + 6, 4);
 
 	/* And store cached results */
 	icsk->icsk_pmtu_cookie = pmtu;
@@ -339,10 +339,12 @@ struct sk_buff *dccp_make_response(struct sock *sk, struct dst_entry *dst,
 	DCCP_SKB_CB(skb)->dccpd_type = DCCP_PKT_RESPONSE;
 	DCCP_SKB_CB(skb)->dccpd_seq  = dreq->dreq_iss;
 
-	if (dccp_insert_options_rsk(dreq, skb)) {
-		kfree_skb(skb);
-		return NULL;
-	}
+	/* Resolve feature dependencies resulting from choice of CCID */
+	if (dccp_feat_server_ccid_dependencies(dreq))
+		goto response_failed;
+
+	if (dccp_insert_options_rsk(dreq, skb))
+		goto response_failed;
 
 	/* Build and checksum header */
 	dh = dccp_zeroed_hdr(skb, dccp_header_size);
@@ -363,6 +365,9 @@ struct sk_buff *dccp_make_response(struct sock *sk, struct dst_entry *dst,
 	inet_rsk(req)->acked = 1;
 	DCCP_INC_STATS(DCCP_MIB_OUTSEGS);
 	return skb;
+response_failed:
+	kfree_skb(skb);
+	return NULL;
 }
 
 EXPORT_SYMBOL_GPL(dccp_make_response);
@@ -469,6 +474,10 @@ int dccp_connect(struct sock *sk)
 	struct sk_buff *skb;
 	struct inet_connection_sock *icsk = inet_csk(sk);
 
+	/* do not connect if feature negotiation setup fails */
+	if (dccp_feat_finalise_settings(dccp_sk(sk)))
+		return -EPROTO;
+
 	dccp_connect_init(sk);
 
 	skb = alloc_skb(sk->sk_prot->max_header, sk->sk_allocation);
diff --git a/net/dccp/probe.c b/net/dccp/probe.c
index 81368a7f5379..37731da41481 100644
--- a/net/dccp/probe.c
+++ b/net/dccp/probe.c
@@ -74,30 +74,27 @@ static void printl(const char *fmt, ...)
 static int jdccp_sendmsg(struct kiocb *iocb, struct sock *sk,
 			 struct msghdr *msg, size_t size)
 {
-	const struct dccp_minisock *dmsk = dccp_msk(sk);
 	const struct inet_sock *inet = inet_sk(sk);
-	const struct ccid3_hc_tx_sock *hctx;
+	struct ccid3_hc_tx_sock *hctx = NULL;
 
-	if (dmsk->dccpms_tx_ccid == DCCPC_CCID3)
+	if (ccid_get_current_tx_ccid(dccp_sk(sk)) == DCCPC_CCID3)
 		hctx = ccid3_hc_tx_sk(sk);
-	else
-		hctx = NULL;
 
 	if (port == 0 || ntohs(inet->dport) == port ||
 	    ntohs(inet->sport) == port) {
 		if (hctx)
-			printl("%d.%d.%d.%d:%u %d.%d.%d.%d:%u %d %d %d %d %u "
+			printl("%pI4:%u %pI4:%u %d %d %d %d %u "
 			       "%llu %llu %d\n",
-			       NIPQUAD(inet->saddr), ntohs(inet->sport),
-			       NIPQUAD(inet->daddr), ntohs(inet->dport), size,
+			       &inet->saddr, ntohs(inet->sport),
+			       &inet->daddr, ntohs(inet->dport), size,
 			       hctx->ccid3hctx_s, hctx->ccid3hctx_rtt,
 			       hctx->ccid3hctx_p, hctx->ccid3hctx_x_calc,
 			       hctx->ccid3hctx_x_recv >> 6,
 			       hctx->ccid3hctx_x >> 6, hctx->ccid3hctx_t_ipi);
 		else
-			printl("%d.%d.%d.%d:%u %d.%d.%d.%d:%u %d\n",
-			       NIPQUAD(inet->saddr), ntohs(inet->sport),
-			       NIPQUAD(inet->daddr), ntohs(inet->dport), size);
+			printl("%pI4:%u %pI4:%u %d\n",
+			       &inet->saddr, ntohs(inet->sport),
+			       &inet->daddr, ntohs(inet->dport), size);
 	}
 
 	jprobe_return();
diff --git a/net/dccp/proto.c b/net/dccp/proto.c
index d0bd34819761..d5c2bacb713c 100644
--- a/net/dccp/proto.c
+++ b/net/dccp/proto.c
@@ -40,16 +40,10 @@ DEFINE_SNMP_STAT(struct dccp_mib, dccp_statistics) __read_mostly;
 
 EXPORT_SYMBOL_GPL(dccp_statistics);
 
-atomic_t dccp_orphan_count = ATOMIC_INIT(0);
-
+struct percpu_counter dccp_orphan_count;
 EXPORT_SYMBOL_GPL(dccp_orphan_count);
 
-struct inet_hashinfo __cacheline_aligned dccp_hashinfo = {
-	.lhash_lock	= RW_LOCK_UNLOCKED,
-	.lhash_users	= ATOMIC_INIT(0),
-	.lhash_wait = __WAIT_QUEUE_HEAD_INITIALIZER(dccp_hashinfo.lhash_wait),
-};
-
+struct inet_hashinfo dccp_hashinfo;
 EXPORT_SYMBOL_GPL(dccp_hashinfo);
 
 /* the maximum queue length for tx in packets. 0 is no limit */
@@ -67,6 +61,9 @@ void dccp_set_state(struct sock *sk, const int state)
 	case DCCP_OPEN:
 		if (oldstate != DCCP_OPEN)
 			DCCP_INC_STATS(DCCP_MIB_CURRESTAB);
+		/* Client retransmits all Confirm options until entering OPEN */
+		if (oldstate == DCCP_PARTOPEN)
+			dccp_feat_list_purge(&dccp_sk(sk)->dccps_featneg);
 		break;
 
 	case DCCP_CLOSED:
@@ -175,7 +172,6 @@ EXPORT_SYMBOL_GPL(dccp_state_name);
 int dccp_init_sock(struct sock *sk, const __u8 ctl_sock_initialized)
 {
 	struct dccp_sock *dp = dccp_sk(sk);
-	struct dccp_minisock *dmsk = dccp_msk(sk);
 	struct inet_connection_sock *icsk = inet_csk(sk);
 
 	dccp_minisock_init(&dp->dccps_minisock);
@@ -193,45 +189,10 @@ int dccp_init_sock(struct sock *sk, const __u8 ctl_sock_initialized)
 
 	dccp_init_xmit_timers(sk);
 
-	/*
-	 * FIXME: We're hardcoding the CCID, and doing this at this point makes
-	 * the listening (master) sock get CCID control blocks, which is not
-	 * necessary, but for now, to not mess with the test userspace apps,
-	 * lets leave it here, later the real solution is to do this in a
-	 * setsockopt(CCIDs-I-want/accept). -acme
-	 */
-	if (likely(ctl_sock_initialized)) {
-		int rc = dccp_feat_init(dmsk);
-
-		if (rc)
-			return rc;
-
-		if (dmsk->dccpms_send_ack_vector) {
-			dp->dccps_hc_rx_ackvec = dccp_ackvec_alloc(GFP_KERNEL);
-			if (dp->dccps_hc_rx_ackvec == NULL)
-				return -ENOMEM;
-		}
-		dp->dccps_hc_rx_ccid = ccid_hc_rx_new(dmsk->dccpms_rx_ccid,
-						      sk, GFP_KERNEL);
-		dp->dccps_hc_tx_ccid = ccid_hc_tx_new(dmsk->dccpms_tx_ccid,
-						      sk, GFP_KERNEL);
-		if (unlikely(dp->dccps_hc_rx_ccid == NULL ||
-			     dp->dccps_hc_tx_ccid == NULL)) {
-			ccid_hc_rx_delete(dp->dccps_hc_rx_ccid, sk);
-			ccid_hc_tx_delete(dp->dccps_hc_tx_ccid, sk);
-			if (dmsk->dccpms_send_ack_vector) {
-				dccp_ackvec_free(dp->dccps_hc_rx_ackvec);
-				dp->dccps_hc_rx_ackvec = NULL;
-			}
-			dp->dccps_hc_rx_ccid = dp->dccps_hc_tx_ccid = NULL;
-			return -ENOMEM;
-		}
-	} else {
-		/* control socket doesn't need feat nego */
-		INIT_LIST_HEAD(&dmsk->dccpms_pending);
-		INIT_LIST_HEAD(&dmsk->dccpms_conf);
-	}
-
+	INIT_LIST_HEAD(&dp->dccps_featneg);
+	/* control socket doesn't need feat nego */
+	if (likely(ctl_sock_initialized))
+		return dccp_feat_init(sk);
 	return 0;
 }
 
@@ -240,7 +201,6 @@ EXPORT_SYMBOL_GPL(dccp_init_sock);
 void dccp_destroy_sock(struct sock *sk)
 {
 	struct dccp_sock *dp = dccp_sk(sk);
-	struct dccp_minisock *dmsk = dccp_msk(sk);
 
 	/*
 	 * DCCP doesn't use sk_write_queue, just sk_send_head
@@ -258,7 +218,7 @@ void dccp_destroy_sock(struct sock *sk)
 	kfree(dp->dccps_service_list);
 	dp->dccps_service_list = NULL;
 
-	if (dmsk->dccpms_send_ack_vector) {
+	if (dp->dccps_hc_rx_ackvec != NULL) {
 		dccp_ackvec_free(dp->dccps_hc_rx_ackvec);
 		dp->dccps_hc_rx_ackvec = NULL;
 	}
@@ -267,7 +227,7 @@ void dccp_destroy_sock(struct sock *sk)
 	dp->dccps_hc_rx_ccid = dp->dccps_hc_tx_ccid = NULL;
 
 	/* clean up feature negotiation state */
-	dccp_feat_clean(dmsk);
+	dccp_feat_list_purge(&dp->dccps_featneg);
 }
 
 EXPORT_SYMBOL_GPL(dccp_destroy_sock);
@@ -277,6 +237,9 @@ static inline int dccp_listen_start(struct sock *sk, int backlog)
 	struct dccp_sock *dp = dccp_sk(sk);
 
 	dp->dccps_role = DCCP_ROLE_LISTEN;
+	/* do not start to listen if feature negotiation setup fails */
+	if (dccp_feat_finalise_settings(dp))
+		return -EPROTO;
 	return inet_csk_listen_start(sk, backlog);
 }
 
@@ -466,42 +429,70 @@ static int dccp_setsockopt_service(struct sock *sk, const __be32 service,
 	return 0;
 }
 
-/* byte 1 is feature.  the rest is the preference list */
-static int dccp_setsockopt_change(struct sock *sk, int type,
-				  struct dccp_so_feat __user *optval)
+static int dccp_setsockopt_cscov(struct sock *sk, int cscov, bool rx)
 {
-	struct dccp_so_feat opt;
-	u8 *val;
-	int rc;
+	u8 *list, len;
+	int i, rc;
 
-	if (copy_from_user(&opt, optval, sizeof(opt)))
-		return -EFAULT;
+	if (cscov < 0 || cscov > 15)
+		return -EINVAL;
 	/*
-	 * rfc4340: 6.1. Change Options
+	 * Populate a list of permissible values, in the range cscov...15. This
+	 * is necessary since feature negotiation of single values only works if
+	 * both sides incidentally choose the same value. Since the list starts
+	 * lowest-value first, negotiation will pick the smallest shared value.
 	 */
-	if (opt.dccpsf_len < 1)
+	if (cscov == 0)
+		return 0;
+	len = 16 - cscov;
+
+	list = kmalloc(len, GFP_KERNEL);
+	if (list == NULL)
+		return -ENOBUFS;
+
+	for (i = 0; i < len; i++)
+		list[i] = cscov++;
+
+	rc = dccp_feat_register_sp(sk, DCCPF_MIN_CSUM_COVER, rx, list, len);
+
+	if (rc == 0) {
+		if (rx)
+			dccp_sk(sk)->dccps_pcrlen = cscov;
+		else
+			dccp_sk(sk)->dccps_pcslen = cscov;
+	}
+	kfree(list);
+	return rc;
+}
+
+static int dccp_setsockopt_ccid(struct sock *sk, int type,
+				char __user *optval, int optlen)
+{
+	u8 *val;
+	int rc = 0;
+
+	if (optlen < 1 || optlen > DCCP_FEAT_MAX_SP_VALS)
 		return -EINVAL;
 
-	val = kmalloc(opt.dccpsf_len, GFP_KERNEL);
-	if (!val)
+	val = kmalloc(optlen, GFP_KERNEL);
+	if (val == NULL)
 		return -ENOMEM;
 
-	if (copy_from_user(val, opt.dccpsf_val, opt.dccpsf_len)) {
-		rc = -EFAULT;
-		goto out_free_val;
+	if (copy_from_user(val, optval, optlen)) {
+		kfree(val);
+		return -EFAULT;
 	}
 
-	rc = dccp_feat_change(dccp_msk(sk), type, opt.dccpsf_feat,
-			      val, opt.dccpsf_len, GFP_KERNEL);
-	if (rc)
-		goto out_free_val;
+	lock_sock(sk);
+	if (type == DCCP_SOCKOPT_TX_CCID || type == DCCP_SOCKOPT_CCID)
+		rc = dccp_feat_register_sp(sk, DCCPF_CCID, 1, val, optlen);
 
-out:
-	return rc;
+	if (!rc && (type == DCCP_SOCKOPT_RX_CCID || type == DCCP_SOCKOPT_CCID))
+		rc = dccp_feat_register_sp(sk, DCCPF_CCID, 0, val, optlen);
+	release_sock(sk);
 
-out_free_val:
 	kfree(val);
-	goto out;
+	return rc;
 }
 
 static int do_dccp_setsockopt(struct sock *sk, int level, int optname,
@@ -510,7 +501,21 @@ static int do_dccp_setsockopt(struct sock *sk, int level, int optname,
 	struct dccp_sock *dp = dccp_sk(sk);
 	int val, err = 0;
 
-	if (optlen < sizeof(int))
+	switch (optname) {
+	case DCCP_SOCKOPT_PACKET_SIZE:
+		DCCP_WARN("sockopt(PACKET_SIZE) is deprecated: fix your app\n");
+		return 0;
+	case DCCP_SOCKOPT_CHANGE_L:
+	case DCCP_SOCKOPT_CHANGE_R:
+		DCCP_WARN("sockopt(CHANGE_L/R) is deprecated: fix your app\n");
+		return 0;
+	case DCCP_SOCKOPT_CCID:
+	case DCCP_SOCKOPT_RX_CCID:
+	case DCCP_SOCKOPT_TX_CCID:
+		return dccp_setsockopt_ccid(sk, optname, optval, optlen);
+	}
+
+	if (optlen < (int)sizeof(int))
 		return -EINVAL;
 
 	if (get_user(val, (int __user *)optval))
@@ -521,53 +526,24 @@ static int do_dccp_setsockopt(struct sock *sk, int level, int optname,
 
 	lock_sock(sk);
 	switch (optname) {
-	case DCCP_SOCKOPT_PACKET_SIZE:
-		DCCP_WARN("sockopt(PACKET_SIZE) is deprecated: fix your app\n");
-		err = 0;
-		break;
-	case DCCP_SOCKOPT_CHANGE_L:
-		if (optlen != sizeof(struct dccp_so_feat))
-			err = -EINVAL;
-		else
-			err = dccp_setsockopt_change(sk, DCCPO_CHANGE_L,
-						     (struct dccp_so_feat __user *)
-						     optval);
-		break;
-	case DCCP_SOCKOPT_CHANGE_R:
-		if (optlen != sizeof(struct dccp_so_feat))
-			err = -EINVAL;
-		else
-			err = dccp_setsockopt_change(sk, DCCPO_CHANGE_R,
-						     (struct dccp_so_feat __user *)
-						     optval);
-		break;
 	case DCCP_SOCKOPT_SERVER_TIMEWAIT:
 		if (dp->dccps_role != DCCP_ROLE_SERVER)
 			err = -EOPNOTSUPP;
 		else
 			dp->dccps_server_timewait = (val != 0);
 		break;
-	case DCCP_SOCKOPT_SEND_CSCOV:	/* sender side, RFC 4340, sec. 9.2 */
-		if (val < 0 || val > 15)
-			err = -EINVAL;
-		else
-			dp->dccps_pcslen = val;
+	case DCCP_SOCKOPT_SEND_CSCOV:
+		err = dccp_setsockopt_cscov(sk, val, false);
 		break;
-	case DCCP_SOCKOPT_RECV_CSCOV:	/* receiver side, RFC 4340 sec. 9.2.1 */
-		if (val < 0 || val > 15)
-			err = -EINVAL;
-		else {
-			dp->dccps_pcrlen = val;
-			/* FIXME: add feature negotiation,
-			 * ChangeL(MinimumChecksumCoverage, val) */
-		}
+	case DCCP_SOCKOPT_RECV_CSCOV:
+		err = dccp_setsockopt_cscov(sk, val, true);
 		break;
 	default:
 		err = -ENOPROTOOPT;
 		break;
 	}
-
 	release_sock(sk);
+
 	return err;
 }
 
@@ -648,6 +624,18 @@ static int do_dccp_getsockopt(struct sock *sk, int level, int optname,
 	case DCCP_SOCKOPT_GET_CUR_MPS:
 		val = dp->dccps_mss_cache;
 		break;
+	case DCCP_SOCKOPT_AVAILABLE_CCIDS:
+		return ccid_getsockopt_builtin_ccids(sk, len, optval, optlen);
+	case DCCP_SOCKOPT_TX_CCID:
+		val = ccid_get_current_tx_ccid(dp);
+		if (val < 0)
+			return -ENOPROTOOPT;
+		break;
+	case DCCP_SOCKOPT_RX_CCID:
+		val = ccid_get_current_rx_ccid(dp);
+		if (val < 0)
+			return -ENOPROTOOPT;
+		break;
 	case DCCP_SOCKOPT_SERVER_TIMEWAIT:
 		val = dp->dccps_server_timewait;
 		break;
@@ -976,7 +964,7 @@ adjudge_to_death:
 	state = sk->sk_state;
 	sock_hold(sk);
 	sock_orphan(sk);
-	atomic_inc(sk->sk_prot->orphan_count);
+	percpu_counter_inc(sk->sk_prot->orphan_count);
 
 	/*
 	 * It is the last release_sock in its life. It will remove backlog.
@@ -1040,17 +1028,21 @@ static int __init dccp_init(void)
 {
 	unsigned long goal;
 	int ehash_order, bhash_order, i;
-	int rc = -ENOBUFS;
+	int rc;
 
 	BUILD_BUG_ON(sizeof(struct dccp_skb_cb) >
 		     FIELD_SIZEOF(struct sk_buff, cb));
-
+	rc = percpu_counter_init(&dccp_orphan_count, 0);
+	if (rc)
+		goto out;
+	rc = -ENOBUFS;
+	inet_hashinfo_init(&dccp_hashinfo);
 	dccp_hashinfo.bind_bucket_cachep =
 		kmem_cache_create("dccp_bind_bucket",
 				  sizeof(struct inet_bind_bucket), 0,
 				  SLAB_HWCACHE_ALIGN, NULL);
 	if (!dccp_hashinfo.bind_bucket_cachep)
-		goto out;
+		goto out_free_percpu;
 
 	/*
 	 * Size and allocate the main established and bind bucket
@@ -1084,8 +1076,8 @@ static int __init dccp_init(void)
 	}
 
 	for (i = 0; i < dccp_hashinfo.ehash_size; i++) {
-		INIT_HLIST_HEAD(&dccp_hashinfo.ehash[i].chain);
-		INIT_HLIST_HEAD(&dccp_hashinfo.ehash[i].twchain);
+		INIT_HLIST_NULLS_HEAD(&dccp_hashinfo.ehash[i].chain, i);
+		INIT_HLIST_NULLS_HEAD(&dccp_hashinfo.ehash[i].twchain, i);
 	}
 
 	if (inet_ehash_locks_alloc(&dccp_hashinfo))
@@ -1143,6 +1135,8 @@ out_free_dccp_ehash:
 out_free_bind_bucket_cachep:
 	kmem_cache_destroy(dccp_hashinfo.bind_bucket_cachep);
 	dccp_hashinfo.bind_bucket_cachep = NULL;
+out_free_percpu:
+	percpu_counter_destroy(&dccp_orphan_count);
 	goto out;
 }
 
diff --git a/net/dccp/sysctl.c b/net/dccp/sysctl.c
index 21295993fdb8..018e210875e1 100644
--- a/net/dccp/sysctl.c
+++ b/net/dccp/sysctl.c
@@ -41,27 +41,6 @@ static struct ctl_table dccp_default_table[] = {
 		.proc_handler	= proc_dointvec,
 	},
 	{
-		.procname	= "ack_ratio",
-		.data		= &sysctl_dccp_feat_ack_ratio,
-		.maxlen		= sizeof(sysctl_dccp_feat_ack_ratio),
-		.mode		= 0644,
-		.proc_handler	= proc_dointvec,
-	},
-	{
-		.procname	= "send_ackvec",
-		.data		= &sysctl_dccp_feat_send_ack_vector,
-		.maxlen		= sizeof(sysctl_dccp_feat_send_ack_vector),
-		.mode		= 0644,
-		.proc_handler	= proc_dointvec,
-	},
-	{
-		.procname	= "send_ndp",
-		.data		= &sysctl_dccp_feat_send_ndp_count,
-		.maxlen		= sizeof(sysctl_dccp_feat_send_ndp_count),
-		.mode		= 0644,
-		.proc_handler	= proc_dointvec,
-	},
-	{
 		.procname	= "request_retries",
 		.data		= &sysctl_dccp_request_retries,
 		.maxlen		= sizeof(sysctl_dccp_request_retries),
diff --git a/net/dccp/timer.c b/net/dccp/timer.c
index 54b3c7e9e016..162d1e683c39 100644
--- a/net/dccp/timer.c
+++ b/net/dccp/timer.c
@@ -87,17 +87,6 @@ static void dccp_retransmit_timer(struct sock *sk)
 {
 	struct inet_connection_sock *icsk = inet_csk(sk);
 
-	/* retransmit timer is used for feature negotiation throughout
-	 * connection.  In this case, no packet is re-transmitted, but rather an
-	 * ack is generated and pending changes are placed into its options.
-	 */
-	if (sk->sk_send_head == NULL) {
-		dccp_pr_debug("feat negotiation retransmit timeout %p\n", sk);
-		if (sk->sk_state == DCCP_OPEN)
-			dccp_send_ack(sk);
-		goto backoff;
-	}
-
 	/*
 	 * More than than 4MSL (8 minutes) has passed, a RESET(aborted) was
 	 * sent, no need to retransmit, this sock is dead.
@@ -126,7 +115,6 @@ static void dccp_retransmit_timer(struct sock *sk)
 		return;
 	}
 
-backoff:
 	icsk->icsk_backoff++;
 
 	icsk->icsk_rto = min(icsk->icsk_rto << 1, DCCP_RTO_MAX);