netfilter: factor out packet duplication for IPv4/IPv6

Extracted from the xtables TEE target. This creates two new modules for IPv4
and IPv6 that are shared between the TEE target and the new nf_tables dup
expressions.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 6 insertions, 152 deletions

diff --git a/net/netfilter/xt_TEE.c b/net/netfilter/xt_TEE.c
index 0ed9fb61d470..49fee6aa2c0a 100644
--- a/net/netfilter/xt_TEE.c
+++ b/net/netfilter/xt_TEE.c
@@ -10,23 +10,14 @@
  *	modify it under the terms of the GNU General Public License
  *	version 2 or later, as published by the Free Software Foundation.
  */
-#include <linux/ip.h>
 #include <linux/module.h>
-#include <linux/percpu.h>
-#include <linux/route.h>
 #include <linux/skbuff.h>
-#include <linux/notifier.h>
-#include <net/checksum.h>
-#include <net/icmp.h>
-#include <net/ip.h>
-#include <net/ipv6.h>
-#include <net/ip6_route.h>
-#include <net/route.h>
+#include <linux/route.h>
 #include <linux/netfilter/x_tables.h>
+#include <net/route.h>
+#include <net/netfilter/ipv4/nf_dup_ipv4.h>
+#include <net/netfilter/ipv6/nf_dup_ipv6.h>
 #include <linux/netfilter/xt_TEE.h>
-#if IS_ENABLED(CONFIG_NF_CONNTRACK)
-#include <net/netfilter/nf_conntrack.h>
-#endif
 
 struct xt_tee_priv {
 	struct notifier_block	notifier;
@@ -36,161 +27,24 @@ struct xt_tee_priv {
 
 static const union nf_inet_addr tee_zero_address;
 
-static struct net *pick_net(struct sk_buff *skb)
-{
-#ifdef CONFIG_NET_NS
-	const struct dst_entry *dst;
-
-	if (skb->dev != NULL)
-		return dev_net(skb->dev);
-	dst = skb_dst(skb);
-	if (dst != NULL && dst->dev != NULL)
-		return dev_net(dst->dev);
-#endif
-	return &init_net;
-}
-
-static bool
-tee_tg_route4(struct sk_buff *skb, const struct xt_tee_tginfo *info)
-{
-	const struct iphdr *iph = ip_hdr(skb);
-	struct net *net = pick_net(skb);
-	struct rtable *rt;
-	struct flowi4 fl4;
-
-	memset(&fl4, 0, sizeof(fl4));
-	if (info->priv) {
-		if (info->priv->oif == -1)
-			return false;
-		fl4.flowi4_oif = info->priv->oif;
-	}
-	fl4.daddr = info->gw.ip;
-	fl4.flowi4_tos = RT_TOS(iph->tos);
-	fl4.flowi4_scope = RT_SCOPE_UNIVERSE;
-	fl4.flowi4_flags = FLOWI_FLAG_KNOWN_NH;
-	rt = ip_route_output_key(net, &fl4);
-	if (IS_ERR(rt))
-		return false;
-
-	skb_dst_drop(skb);
-	skb_dst_set(skb, &rt->dst);
-	skb->dev      = rt->dst.dev;
-	skb->protocol = htons(ETH_P_IP);
-	return true;
-}
-
 static unsigned int
 tee_tg4(struct sk_buff *skb, const struct xt_action_param *par)
 {
 	const struct xt_tee_tginfo *info = par->targinfo;
-	struct iphdr *iph;
 
-	if (__this_cpu_read(nf_skb_duplicated))
-		return XT_CONTINUE;
-	/*
-	 * Copy the skb, and route the copy. Will later return %XT_CONTINUE for
-	 * the original skb, which should continue on its way as if nothing has
-	 * happened. The copy should be independently delivered to the TEE
-	 * --gateway.
-	 */
-	skb = pskb_copy(skb, GFP_ATOMIC);
-	if (skb == NULL)
-		return XT_CONTINUE;
-
-#if IS_ENABLED(CONFIG_NF_CONNTRACK)
-	/* Avoid counting cloned packets towards the original connection. */
-	nf_conntrack_put(skb->nfct);
-	skb->nfct     = &nf_ct_untracked_get()->ct_general;
-	skb->nfctinfo = IP_CT_NEW;
-	nf_conntrack_get(skb->nfct);
-#endif
-	/*
-	 * If we are in PREROUTING/INPUT, the checksum must be recalculated
-	 * since the length could have changed as a result of defragmentation.
-	 *
-	 * We also decrease the TTL to mitigate potential TEE loops
-	 * between two hosts.
-	 *
-	 * Set %IP_DF so that the original source is notified of a potentially
-	 * decreased MTU on the clone route. IPv6 does this too.
-	 */
-	iph = ip_hdr(skb);
-	iph->frag_off |= htons(IP_DF);
-	if (par->hooknum == NF_INET_PRE_ROUTING ||
-	    par->hooknum == NF_INET_LOCAL_IN)
-		--iph->ttl;
-	ip_send_check(iph);
+	nf_dup_ipv4(skb, par->hooknum, &info->gw.in, info->priv->oif);
 
-	if (tee_tg_route4(skb, info)) {
-		__this_cpu_write(nf_skb_duplicated, true);
-		ip_local_out(skb);
-		__this_cpu_write(nf_skb_duplicated, false);
-	} else {
-		kfree_skb(skb);
-	}
 	return XT_CONTINUE;
 }
 
 #if IS_ENABLED(CONFIG_IPV6)
-static bool
-tee_tg_route6(struct sk_buff *skb, const struct xt_tee_tginfo *info)
-{
-	const struct ipv6hdr *iph = ipv6_hdr(skb);
-	struct net *net = pick_net(skb);
-	struct dst_entry *dst;
-	struct flowi6 fl6;
-
-	memset(&fl6, 0, sizeof(fl6));
-	if (info->priv) {
-		if (info->priv->oif == -1)
-			return false;
-		fl6.flowi6_oif = info->priv->oif;
-	}
-	fl6.daddr = info->gw.in6;
-	fl6.flowlabel = ((iph->flow_lbl[0] & 0xF) << 16) |
-			   (iph->flow_lbl[1] << 8) | iph->flow_lbl[2];
-	fl6.flowi6_flags = FLOWI_FLAG_KNOWN_NH;
-	dst = ip6_route_output(net, NULL, &fl6);
-	if (dst->error) {
-		dst_release(dst);
-		return false;
-	}
-	skb_dst_drop(skb);
-	skb_dst_set(skb, dst);
-	skb->dev      = dst->dev;
-	skb->protocol = htons(ETH_P_IPV6);
-	return true;
-}
-
 static unsigned int
 tee_tg6(struct sk_buff *skb, const struct xt_action_param *par)
 {
 	const struct xt_tee_tginfo *info = par->targinfo;
 
-	if (__this_cpu_read(nf_skb_duplicated))
-		return XT_CONTINUE;
-	skb = pskb_copy(skb, GFP_ATOMIC);
-	if (skb == NULL)
-		return XT_CONTINUE;
+	nf_dup_ipv6(skb, par->hooknum, &info->gw.in6, info->priv->oif);
 
-#if IS_ENABLED(CONFIG_NF_CONNTRACK)
-	nf_conntrack_put(skb->nfct);
-	skb->nfct     = &nf_ct_untracked_get()->ct_general;
-	skb->nfctinfo = IP_CT_NEW;
-	nf_conntrack_get(skb->nfct);
-#endif
-	if (par->hooknum == NF_INET_PRE_ROUTING ||
-	    par->hooknum == NF_INET_LOCAL_IN) {
-		struct ipv6hdr *iph = ipv6_hdr(skb);
-		--iph->hop_limit;
-	}
-	if (tee_tg_route6(skb, info)) {
-		__this_cpu_write(nf_skb_duplicated, true);
-		ip6_local_out(skb);
-		__this_cpu_write(nf_skb_duplicated, false);
-	} else {
-		kfree_skb(skb);
-	}
 	return XT_CONTINUE;
 }
 #endif