net: sched: add mpls manipulation actions to TC

Currently, TC offers the ability to match on the MPLS fields of a packet
through the use of the flow_dissector_key_mpls struct. However, as yet, TC
actions do not allow the modification or manipulation of such fields.

Add a new module that registers TC action ops to allow manipulation of
MPLS. This includes the ability to push and pop headers as well as modify
the contents of new or existing headers. A further action to decrement the
TTL field of an MPLS header is also provided with a new helper added to
support this.

Examples of the usage of the new action with flower rules to push and pop
MPLS labels are:

tc filter add dev eth0 protocol ip parent ffff: flower \
    action mpls push protocol mpls_uc label 123  \
    action mirred egress redirect dev eth1

tc filter add dev eth0 protocol mpls_uc parent ffff: flower \
    action mpls pop protocol ipv4  \
    action mirred egress redirect dev eth1

Signed-off-by: John Hurley <john.hurley@netronome.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Simon Horman <simon.horman@netronome.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Acked-by: Cong Wang <xiyou.wangcong@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

4 files changed, 448 insertions, 0 deletions

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 93443a01ab39..6f1e31f674a3 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -59,6 +59,7 @@
 #include <linux/errqueue.h>
 #include <linux/prefetch.h>
 #include <linux/if_vlan.h>
+#include <linux/mpls.h>
 
 #include <net/protocol.h>
 #include <net/dst.h>
@@ -5565,6 +5566,35 @@ int skb_mpls_update_lse(struct sk_buff *skb, __be32 mpls_lse)
 EXPORT_SYMBOL_GPL(skb_mpls_update_lse);
 
 /**
+ * skb_mpls_dec_ttl() - decrement the TTL of the outermost MPLS header
+ *
+ * @skb: buffer
+ *
+ * Expects skb->data at mac header.
+ *
+ * Returns 0 on success, -errno otherwise.
+ */
+int skb_mpls_dec_ttl(struct sk_buff *skb)
+{
+	u32 lse;
+	u8 ttl;
+
+	if (unlikely(!eth_p_mpls(skb->protocol)))
+		return -EINVAL;
+
+	lse = be32_to_cpu(mpls_hdr(skb)->label_stack_entry);
+	ttl = (lse & MPLS_LS_TTL_MASK) >> MPLS_LS_TTL_SHIFT;
+	if (!--ttl)
+		return -EINVAL;
+
+	lse &= ~MPLS_LS_TTL_MASK;
+	lse |= ttl << MPLS_LS_TTL_SHIFT;
+
+	return skb_mpls_update_lse(skb, cpu_to_be32(lse));
+}
+EXPORT_SYMBOL_GPL(skb_mpls_dec_ttl);
+
+/**
  * alloc_skb_with_frags - allocate skb with page frags
  *
  * @header_len: size of linear part
diff --git a/net/sched/Kconfig b/net/sched/Kconfig
index 360fdd3eaa77..731f5fbc2a3c 100644
--- a/net/sched/Kconfig
+++ b/net/sched/Kconfig
@@ -842,6 +842,17 @@ config NET_ACT_CSUM
 	  To compile this code as a module, choose M here: the
 	  module will be called act_csum.
 
+config NET_ACT_MPLS
+	tristate "MPLS manipulation"
+	depends on NET_CLS_ACT
+	help
+	  Say Y here to push or pop MPLS headers.
+
+	  If unsure, say N.
+
+	  To compile this code as a module, choose M here: the
+	  module will be called act_mpls.
+
 config NET_ACT_VLAN
         tristate "Vlan manipulation"
         depends on NET_CLS_ACT
diff --git a/net/sched/Makefile b/net/sched/Makefile
index d54bfcbd7981..c26603606c22 100644
--- a/net/sched/Makefile
+++ b/net/sched/Makefile
@@ -18,6 +18,7 @@ obj-$(CONFIG_NET_ACT_PEDIT)	+= act_pedit.o
 obj-$(CONFIG_NET_ACT_SIMP)	+= act_simple.o
 obj-$(CONFIG_NET_ACT_SKBEDIT)	+= act_skbedit.o
 obj-$(CONFIG_NET_ACT_CSUM)	+= act_csum.o
+obj-$(CONFIG_NET_ACT_MPLS)	+= act_mpls.o
 obj-$(CONFIG_NET_ACT_VLAN)	+= act_vlan.o
 obj-$(CONFIG_NET_ACT_BPF)	+= act_bpf.o
 obj-$(CONFIG_NET_ACT_CONNMARK)	+= act_connmark.o
diff --git a/net/sched/act_mpls.c b/net/sched/act_mpls.c
new file mode 100644
index 000000000000..ca2597ce4ac9
--- /dev/null
+++ b/net/sched/act_mpls.c
@@ -0,0 +1,406 @@
+// SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
+/* Copyright (C) 2019 Netronome Systems, Inc. */
+
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/mpls.h>
+#include <linux/rtnetlink.h>
+#include <linux/skbuff.h>
+#include <linux/tc_act/tc_mpls.h>
+#include <net/mpls.h>
+#include <net/netlink.h>
+#include <net/pkt_sched.h>
+#include <net/pkt_cls.h>
+#include <net/tc_act/tc_mpls.h>
+
+static unsigned int mpls_net_id;
+static struct tc_action_ops act_mpls_ops;
+
+#define ACT_MPLS_TTL_DEFAULT	255
+
+static __be32 tcf_mpls_get_lse(struct mpls_shim_hdr *lse,
+			       struct tcf_mpls_params *p, bool set_bos)
+{
+	u32 new_lse = 0;
+
+	if (lse)
+		new_lse = be32_to_cpu(lse->label_stack_entry);
+
+	if (p->tcfm_label != ACT_MPLS_LABEL_NOT_SET) {
+		new_lse &= ~MPLS_LS_LABEL_MASK;
+		new_lse |= p->tcfm_label << MPLS_LS_LABEL_SHIFT;
+	}
+	if (p->tcfm_ttl) {
+		new_lse &= ~MPLS_LS_TTL_MASK;
+		new_lse |= p->tcfm_ttl << MPLS_LS_TTL_SHIFT;
+	}
+	if (p->tcfm_tc != ACT_MPLS_TC_NOT_SET) {
+		new_lse &= ~MPLS_LS_TC_MASK;
+		new_lse |= p->tcfm_tc << MPLS_LS_TC_SHIFT;
+	}
+	if (p->tcfm_bos != ACT_MPLS_BOS_NOT_SET) {
+		new_lse &= ~MPLS_LS_S_MASK;
+		new_lse |= p->tcfm_bos << MPLS_LS_S_SHIFT;
+	} else if (set_bos) {
+		new_lse |= 1 << MPLS_LS_S_SHIFT;
+	}
+
+	return cpu_to_be32(new_lse);
+}
+
+static int tcf_mpls_act(struct sk_buff *skb, const struct tc_action *a,
+			struct tcf_result *res)
+{
+	struct tcf_mpls *m = to_mpls(a);
+	struct tcf_mpls_params *p;
+	__be32 new_lse;
+	int ret;
+
+	tcf_lastuse_update(&m->tcf_tm);
+	bstats_cpu_update(this_cpu_ptr(m->common.cpu_bstats), skb);
+
+	/* Ensure 'data' points at mac_header prior calling mpls manipulating
+	 * functions.
+	 */
+	if (skb_at_tc_ingress(skb))
+		skb_push_rcsum(skb, skb->mac_len);
+
+	ret = READ_ONCE(m->tcf_action);
+
+	p = rcu_dereference_bh(m->mpls_p);
+
+	switch (p->tcfm_action) {
+	case TCA_MPLS_ACT_POP:
+		if (skb_mpls_pop(skb, p->tcfm_proto))
+			goto drop;
+		break;
+	case TCA_MPLS_ACT_PUSH:
+		new_lse = tcf_mpls_get_lse(NULL, p, !eth_p_mpls(skb->protocol));
+		if (skb_mpls_push(skb, new_lse, p->tcfm_proto))
+			goto drop;
+		break;
+	case TCA_MPLS_ACT_MODIFY:
+		new_lse = tcf_mpls_get_lse(mpls_hdr(skb), p, false);
+		if (skb_mpls_update_lse(skb, new_lse))
+			goto drop;
+		break;
+	case TCA_MPLS_ACT_DEC_TTL:
+		if (skb_mpls_dec_ttl(skb))
+			goto drop;
+		break;
+	}
+
+	if (skb_at_tc_ingress(skb))
+		skb_pull_rcsum(skb, skb->mac_len);
+
+	return ret;
+
+drop:
+	qstats_drop_inc(this_cpu_ptr(m->common.cpu_qstats));
+	return TC_ACT_SHOT;
+}
+
+static int valid_label(const struct nlattr *attr,
+		       struct netlink_ext_ack *extack)
+{
+	const u32 *label = nla_data(attr);
+
+	if (*label & ~MPLS_LABEL_MASK || *label == MPLS_LABEL_IMPLNULL) {
+		NL_SET_ERR_MSG_MOD(extack, "MPLS label out of range");
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
+static const struct nla_policy mpls_policy[TCA_MPLS_MAX + 1] = {
+	[TCA_MPLS_UNSPEC]	= { .strict_start_type = TCA_MPLS_UNSPEC + 1 },
+	[TCA_MPLS_PARMS]	= NLA_POLICY_EXACT_LEN(sizeof(struct tc_mpls)),
+	[TCA_MPLS_PROTO]	= { .type = NLA_U16 },
+	[TCA_MPLS_LABEL]	= NLA_POLICY_VALIDATE_FN(NLA_U32, valid_label),
+	[TCA_MPLS_TC]		= NLA_POLICY_RANGE(NLA_U8, 0, 7),
+	[TCA_MPLS_TTL]		= NLA_POLICY_MIN(NLA_U8, 1),
+	[TCA_MPLS_BOS]		= NLA_POLICY_RANGE(NLA_U8, 0, 1),
+};
+
+static int tcf_mpls_init(struct net *net, struct nlattr *nla,
+			 struct nlattr *est, struct tc_action **a,
+			 int ovr, int bind, bool rtnl_held,
+			 struct tcf_proto *tp, struct netlink_ext_ack *extack)
+{
+	struct tc_action_net *tn = net_generic(net, mpls_net_id);
+	struct nlattr *tb[TCA_MPLS_MAX + 1];
+	struct tcf_chain *goto_ch = NULL;
+	struct tcf_mpls_params *p;
+	struct tc_mpls *parm;
+	bool exists = false;
+	struct tcf_mpls *m;
+	int ret = 0, err;
+	u8 mpls_ttl = 0;
+
+	if (!nla) {
+		NL_SET_ERR_MSG_MOD(extack, "Missing netlink attributes");
+		return -EINVAL;
+	}
+
+	err = nla_parse_nested(tb, TCA_MPLS_MAX, nla, mpls_policy, extack);
+	if (err < 0)
+		return err;
+
+	if (!tb[TCA_MPLS_PARMS]) {
+		NL_SET_ERR_MSG_MOD(extack, "No MPLS params");
+		return -EINVAL;
+	}
+	parm = nla_data(tb[TCA_MPLS_PARMS]);
+
+	/* Verify parameters against action type. */
+	switch (parm->m_action) {
+	case TCA_MPLS_ACT_POP:
+		if (!tb[TCA_MPLS_PROTO]) {
+			NL_SET_ERR_MSG_MOD(extack, "Protocol must be set for MPLS pop");
+			return -EINVAL;
+		}
+		if (!eth_proto_is_802_3(nla_get_be16(tb[TCA_MPLS_PROTO]))) {
+			NL_SET_ERR_MSG_MOD(extack, "Invalid protocol type for MPLS pop");
+			return -EINVAL;
+		}
+		if (tb[TCA_MPLS_LABEL] || tb[TCA_MPLS_TTL] || tb[TCA_MPLS_TC] ||
+		    tb[TCA_MPLS_BOS]) {
+			NL_SET_ERR_MSG_MOD(extack, "Label, TTL, TC or BOS cannot be used with MPLS pop");
+			return -EINVAL;
+		}
+		break;
+	case TCA_MPLS_ACT_DEC_TTL:
+		if (tb[TCA_MPLS_PROTO] || tb[TCA_MPLS_LABEL] ||
+		    tb[TCA_MPLS_TTL] || tb[TCA_MPLS_TC] || tb[TCA_MPLS_BOS]) {
+			NL_SET_ERR_MSG_MOD(extack, "Label, TTL, TC, BOS or protocol cannot be used with MPLS dec_ttl");
+			return -EINVAL;
+		}
+		break;
+	case TCA_MPLS_ACT_PUSH:
+		if (!tb[TCA_MPLS_LABEL]) {
+			NL_SET_ERR_MSG_MOD(extack, "Label is required for MPLS push");
+			return -EINVAL;
+		}
+		if (tb[TCA_MPLS_PROTO] &&
+		    !eth_p_mpls(nla_get_be16(tb[TCA_MPLS_PROTO]))) {
+			NL_SET_ERR_MSG_MOD(extack, "Protocol must be an MPLS type for MPLS push");
+			return -EPROTONOSUPPORT;
+		}
+		/* Push needs a TTL - if not specified, set a default value. */
+		if (!tb[TCA_MPLS_TTL]) {
+#if IS_ENABLED(CONFIG_MPLS)
+			mpls_ttl = net->mpls.default_ttl ?
+				   net->mpls.default_ttl : ACT_MPLS_TTL_DEFAULT;
+#else
+			mpls_ttl = ACT_MPLS_TTL_DEFAULT;
+#endif
+		}
+		break;
+	case TCA_MPLS_ACT_MODIFY:
+		if (tb[TCA_MPLS_PROTO]) {
+			NL_SET_ERR_MSG_MOD(extack, "Protocol cannot be used with MPLS modify");
+			return -EINVAL;
+		}
+		break;
+	default:
+		NL_SET_ERR_MSG_MOD(extack, "Unknown MPLS action");
+		return -EINVAL;
+	}
+
+	err = tcf_idr_check_alloc(tn, &parm->index, a, bind);
+	if (err < 0)
+		return err;
+	exists = err;
+	if (exists && bind)
+		return 0;
+
+	if (!exists) {
+		ret = tcf_idr_create(tn, parm->index, est, a,
+				     &act_mpls_ops, bind, true);
+		if (ret) {
+			tcf_idr_cleanup(tn, parm->index);
+			return ret;
+		}
+
+		ret = ACT_P_CREATED;
+	} else if (!ovr) {
+		tcf_idr_release(*a, bind);
+		return -EEXIST;
+	}
+
+	err = tcf_action_check_ctrlact(parm->action, tp, &goto_ch, extack);
+	if (err < 0)
+		goto release_idr;
+
+	m = to_mpls(*a);
+
+	p = kzalloc(sizeof(*p), GFP_KERNEL);
+	if (!p) {
+		err = -ENOMEM;
+		goto put_chain;
+	}
+
+	p->tcfm_action = parm->m_action;
+	p->tcfm_label = tb[TCA_MPLS_LABEL] ? nla_get_u32(tb[TCA_MPLS_LABEL]) :
+					     ACT_MPLS_LABEL_NOT_SET;
+	p->tcfm_tc = tb[TCA_MPLS_TC] ? nla_get_u8(tb[TCA_MPLS_TC]) :
+				       ACT_MPLS_TC_NOT_SET;
+	p->tcfm_ttl = tb[TCA_MPLS_TTL] ? nla_get_u8(tb[TCA_MPLS_TTL]) :
+					 mpls_ttl;
+	p->tcfm_bos = tb[TCA_MPLS_BOS] ? nla_get_u8(tb[TCA_MPLS_BOS]) :
+					 ACT_MPLS_BOS_NOT_SET;
+	p->tcfm_proto = tb[TCA_MPLS_PROTO] ? nla_get_be16(tb[TCA_MPLS_PROTO]) :
+					     htons(ETH_P_MPLS_UC);
+
+	spin_lock_bh(&m->tcf_lock);
+	goto_ch = tcf_action_set_ctrlact(*a, parm->action, goto_ch);
+	rcu_swap_protected(m->mpls_p, p, lockdep_is_held(&m->tcf_lock));
+	spin_unlock_bh(&m->tcf_lock);
+
+	if (goto_ch)
+		tcf_chain_put_by_act(goto_ch);
+	if (p)
+		kfree_rcu(p, rcu);
+
+	if (ret == ACT_P_CREATED)
+		tcf_idr_insert(tn, *a);
+	return ret;
+put_chain:
+	if (goto_ch)
+		tcf_chain_put_by_act(goto_ch);
+release_idr:
+	tcf_idr_release(*a, bind);
+	return err;
+}
+
+static void tcf_mpls_cleanup(struct tc_action *a)
+{
+	struct tcf_mpls *m = to_mpls(a);
+	struct tcf_mpls_params *p;
+
+	p = rcu_dereference_protected(m->mpls_p, 1);
+	if (p)
+		kfree_rcu(p, rcu);
+}
+
+static int tcf_mpls_dump(struct sk_buff *skb, struct tc_action *a,
+			 int bind, int ref)
+{
+	unsigned char *b = skb_tail_pointer(skb);
+	struct tcf_mpls *m = to_mpls(a);
+	struct tcf_mpls_params *p;
+	struct tc_mpls opt = {
+		.index    = m->tcf_index,
+		.refcnt   = refcount_read(&m->tcf_refcnt) - ref,
+		.bindcnt  = atomic_read(&m->tcf_bindcnt) - bind,
+	};
+	struct tcf_t t;
+
+	spin_lock_bh(&m->tcf_lock);
+	opt.action = m->tcf_action;
+	p = rcu_dereference_protected(m->mpls_p, lockdep_is_held(&m->tcf_lock));
+	opt.m_action = p->tcfm_action;
+
+	if (nla_put(skb, TCA_MPLS_PARMS, sizeof(opt), &opt))
+		goto nla_put_failure;
+
+	if (p->tcfm_label != ACT_MPLS_LABEL_NOT_SET &&
+	    nla_put_u32(skb, TCA_MPLS_LABEL, p->tcfm_label))
+		goto nla_put_failure;
+
+	if (p->tcfm_tc != ACT_MPLS_TC_NOT_SET &&
+	    nla_put_u8(skb, TCA_MPLS_TC, p->tcfm_tc))
+		goto nla_put_failure;
+
+	if (p->tcfm_ttl && nla_put_u8(skb, TCA_MPLS_TTL, p->tcfm_ttl))
+		goto nla_put_failure;
+
+	if (p->tcfm_bos != ACT_MPLS_BOS_NOT_SET &&
+	    nla_put_u8(skb, TCA_MPLS_BOS, p->tcfm_bos))
+		goto nla_put_failure;
+
+	if (nla_put_be16(skb, TCA_MPLS_PROTO, p->tcfm_proto))
+		goto nla_put_failure;
+
+	tcf_tm_dump(&t, &m->tcf_tm);
+
+	if (nla_put_64bit(skb, TCA_MPLS_TM, sizeof(t), &t, TCA_MPLS_PAD))
+		goto nla_put_failure;
+
+	spin_unlock_bh(&m->tcf_lock);
+
+	return skb->len;
+
+nla_put_failure:
+	spin_unlock_bh(&m->tcf_lock);
+	nlmsg_trim(skb, b);
+	return -EMSGSIZE;
+}
+
+static int tcf_mpls_walker(struct net *net, struct sk_buff *skb,
+			   struct netlink_callback *cb, int type,
+			   const struct tc_action_ops *ops,
+			   struct netlink_ext_ack *extack)
+{
+	struct tc_action_net *tn = net_generic(net, mpls_net_id);
+
+	return tcf_generic_walker(tn, skb, cb, type, ops, extack);
+}
+
+static int tcf_mpls_search(struct net *net, struct tc_action **a, u32 index)
+{
+	struct tc_action_net *tn = net_generic(net, mpls_net_id);
+
+	return tcf_idr_search(tn, a, index);
+}
+
+static struct tc_action_ops act_mpls_ops = {
+	.kind		=	"mpls",
+	.id		=	TCA_ID_MPLS,
+	.owner		=	THIS_MODULE,
+	.act		=	tcf_mpls_act,
+	.dump		=	tcf_mpls_dump,
+	.init		=	tcf_mpls_init,
+	.cleanup	=	tcf_mpls_cleanup,
+	.walk		=	tcf_mpls_walker,
+	.lookup		=	tcf_mpls_search,
+	.size		=	sizeof(struct tcf_mpls),
+};
+
+static __net_init int mpls_init_net(struct net *net)
+{
+	struct tc_action_net *tn = net_generic(net, mpls_net_id);
+
+	return tc_action_net_init(tn, &act_mpls_ops);
+}
+
+static void __net_exit mpls_exit_net(struct list_head *net_list)
+{
+	tc_action_net_exit(net_list, mpls_net_id);
+}
+
+static struct pernet_operations mpls_net_ops = {
+	.init = mpls_init_net,
+	.exit_batch = mpls_exit_net,
+	.id   = &mpls_net_id,
+	.size = sizeof(struct tc_action_net),
+};
+
+static int __init mpls_init_module(void)
+{
+	return tcf_register_action(&act_mpls_ops, &mpls_net_ops);
+}
+
+static void __exit mpls_cleanup_module(void)
+{
+	tcf_unregister_action(&act_mpls_ops, &mpls_net_ops);
+}
+
+module_init(mpls_init_module);
+module_exit(mpls_cleanup_module);
+
+MODULE_AUTHOR("Netronome Systems <oss-drivers@netronome.com>");
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("MPLS manipulation actions");