netfilter: use actual socket sk rather than skb sk when routing harder

If netfilter changes the packet mark when mangling, the packet is
rerouted using the route_me_harder set of functions. Prior to this
commit, there's one big difference between route_me_harder and the
ordinary initial routing functions, described in the comment above
__ip_queue_xmit():

   /* Note: skb->sk can be different from sk, in case of tunnels */
   int __ip_queue_xmit(struct sock *sk, struct sk_buff *skb, struct flowi *fl,

That function goes on to correctly make use of sk->sk_bound_dev_if,
rather than skb->sk->sk_bound_dev_if. And indeed the comment is true: a
tunnel will receive a packet in ndo_start_xmit with an initial skb->sk.
It will make some transformations to that packet, and then it will send
the encapsulated packet out of a *new* socket. That new socket will
basically always have a different sk_bound_dev_if (otherwise there'd be
a routing loop). So for the purposes of routing the encapsulated packet,
the routing information as it pertains to the socket should come from
that socket's sk, rather than the packet's original skb->sk. For that
reason __ip_queue_xmit() and related functions all do the right thing.

One might argue that all tunnels should just call skb_orphan(skb) before
transmitting the encapsulated packet into the new socket. But tunnels do
*not* do this -- and this is wisely avoided in skb_scrub_packet() too --
because features like TSQ rely on skb->destructor() being called when
that buffer space is truely available again. Calling skb_orphan(skb) too
early would result in buffers filling up unnecessarily and accounting
info being all wrong. Instead, additional routing must take into account
the new sk, just as __ip_queue_xmit() notes.

So, this commit addresses the problem by fishing the correct sk out of
state->sk -- it's already set properly in the call to nf_hook() in
__ip_local_out(), which receives the sk as part of its normal
functionality. So we make sure to plumb state->sk through the various
route_me_harder functions, and then make correct use of it following the
example of __ip_queue_xmit().

Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

diff --git a/include/linux/netfilter_ipv4.h b/include/linux/netfilter_ipv4.h
index 082e2c41b7ff90a8e03c55f2f78c4d1129345760..5b70ca868bb1907165cc68b364534849a3a37f0c 100644 (file)
--- a/include/linux/netfilter_ipv4.h
+++ b/include/linux/netfilter_ipv4.h
@@ -16,7 +16,7 @@ struct ip_rt_info {
        u_int32_t mark;
 };
 
-int ip_route_me_harder(struct net *net, struct sk_buff *skb, unsigned addr_type);
+int ip_route_me_harder(struct net *net, struct sock *sk, struct sk_buff *skb, unsigned addr_type);
 
 struct nf_queue_entry;
 

diff --git a/include/linux/netfilter_ipv6.h b/include/linux/netfilter_ipv6.h
index 9b67394471e1c63462327d5cefdd7ab2701e0acf..48314ade1506f2108e32a56a9bab93599ba67152 100644 (file)
--- a/include/linux/netfilter_ipv6.h
+++ b/include/linux/netfilter_ipv6.h
@@ -42,7 +42,7 @@ struct nf_ipv6_ops {
 #if IS_MODULE(CONFIG_IPV6)
        int (*chk_addr)(struct net *net, const struct in6_addr *addr,
                        const struct net_device *dev, int strict);
-       int (*route_me_harder)(struct net *net, struct sk_buff *skb);
+       int (*route_me_harder)(struct net *net, struct sock *sk, struct sk_buff *skb);
        int (*dev_get_saddr)(struct net *net, const struct net_device *dev,
                       const struct in6_addr *daddr, unsigned int srcprefs,
                       struct in6_addr *saddr);
@@ -143,9 +143,9 @@ static inline int nf_br_ip6_fragment(struct net *net, struct sock *sk,
 #endif
 }
 
-int ip6_route_me_harder(struct net *net, struct sk_buff *skb);
+int ip6_route_me_harder(struct net *net, struct sock *sk, struct sk_buff *skb);
 
-static inline int nf_ip6_route_me_harder(struct net *net, struct sk_buff *skb)
+static inline int nf_ip6_route_me_harder(struct net *net, struct sock *sk, struct sk_buff *skb)
 {
 #if IS_MODULE(CONFIG_IPV6)
        const struct nf_ipv6_ops *v6_ops = nf_get_ipv6_ops();
@@ -153,9 +153,9 @@ static inline int nf_ip6_route_me_harder(struct net *net, struct sk_buff *skb)
        if (!v6_ops)
                return -EHOSTUNREACH;
 
-       return v6_ops->route_me_harder(net, skb);
+       return v6_ops->route_me_harder(net, sk, skb);
 #elif IS_BUILTIN(CONFIG_IPV6)
-       return ip6_route_me_harder(net, skb);
+       return ip6_route_me_harder(net, sk, skb);
 #else
        return -EHOSTUNREACH;
 #endif

diff --git a/net/ipv4/netfilter.c b/net/ipv4/netfilter.c
index a058213b77a787a1aa1c0779ae9017932eaff785..7c841037c53349855f9711a70bd0ac333b8bd716 100644 (file)
--- a/net/ipv4/netfilter.c
+++ b/net/ipv4/netfilter.c
@@ -17,17 +17,19 @@
 #include <net/netfilter/nf_queue.h>
 
 /* route_me_harder function, used by iptable_nat, iptable_mangle + ip_queue */
-int ip_route_me_harder(struct net *net, struct sk_buff *skb, unsigned int addr_type)
+int ip_route_me_harder(struct net *net, struct sock *sk, struct sk_buff *skb, unsigned int addr_type)
 {
        const struct iphdr *iph = ip_hdr(skb);
        struct rtable *rt;
        struct flowi4 fl4 = {};
        __be32 saddr = iph->saddr;
-       const struct sock *sk = skb_to_full_sk(skb);
-       __u8 flags = sk ? inet_sk_flowi_flags(sk) : 0;
+       __u8 flags;
        struct net_device *dev = skb_dst(skb)->dev;
        unsigned int hh_len;
 
+       sk = sk_to_full_sk(sk);
+       flags = sk ? inet_sk_flowi_flags(sk) : 0;
+
        if (addr_type == RTN_UNSPEC)
                addr_type = inet_addr_type_dev_table(net, dev, saddr);
        if (addr_type == RTN_LOCAL || addr_type == RTN_UNICAST)

diff --git a/net/ipv4/netfilter/iptable_mangle.c b/net/ipv4/netfilter/iptable_mangle.c
index f703a717ab1d23bdf94ee0b47d4182ddd7810a4c..83307958927307845951ef5cb2682f05e7b2024b 100644 (file)
--- a/net/ipv4/netfilter/iptable_mangle.c
+++ b/net/ipv4/netfilter/iptable_mangle.c
@@ -62,7 +62,7 @@ ipt_mangle_out(struct sk_buff *skb, const struct nf_hook_state *state)
                    iph->daddr != daddr ||
                    skb->mark != mark ||
                    iph->tos != tos) {
-                       err = ip_route_me_harder(state->net, skb, RTN_UNSPEC);
+                       err = ip_route_me_harder(state->net, state->sk, skb, RTN_UNSPEC);
                        if (err < 0)
                                ret = NF_DROP_ERR(err);
                }

diff --git a/net/ipv4/netfilter/nf_reject_ipv4.c b/net/ipv4/netfilter/nf_reject_ipv4.c
index 9dcfa4e461b65aaada32b4d5e11946ae3ae919c8..93b07739807b270854e663b16ac103b159009d72 100644 (file)
--- a/net/ipv4/netfilter/nf_reject_ipv4.c
+++ b/net/ipv4/netfilter/nf_reject_ipv4.c
@@ -145,7 +145,7 @@ void nf_send_reset(struct net *net, struct sk_buff *oldskb, int hook)
                                   ip4_dst_hoplimit(skb_dst(nskb)));
        nf_reject_ip_tcphdr_put(nskb, oldskb, oth);
 
-       if (ip_route_me_harder(net, nskb, RTN_UNSPEC))
+       if (ip_route_me_harder(net, nskb->sk, nskb, RTN_UNSPEC))
                goto free_nskb;
 
        niph = ip_hdr(nskb);

diff --git a/net/ipv6/netfilter.c b/net/ipv6/netfilter.c
index 6d0e942d082d4ec0f66cb97fb20a7c466a0a0dfa..ab9a279dd6d47d34a3ad68e7cb88d588f2c6eaef 100644 (file)
--- a/net/ipv6/netfilter.c
+++ b/net/ipv6/netfilter.c
@@ -20,10 +20,10 @@
 #include <net/netfilter/ipv6/nf_defrag_ipv6.h>
 #include "../bridge/br_private.h"
 
-int ip6_route_me_harder(struct net *net, struct sk_buff *skb)
+int ip6_route_me_harder(struct net *net, struct sock *sk_partial, struct sk_buff *skb)
 {
        const struct ipv6hdr *iph = ipv6_hdr(skb);
-       struct sock *sk = sk_to_full_sk(skb->sk);
+       struct sock *sk = sk_to_full_sk(sk_partial);
        unsigned int hh_len;
        struct dst_entry *dst;
        int strict = (ipv6_addr_type(&iph->daddr) &
@@ -84,7 +84,7 @@ static int nf_ip6_reroute(struct sk_buff *skb,
                if (!ipv6_addr_equal(&iph->daddr, &rt_info->daddr) ||
                    !ipv6_addr_equal(&iph->saddr, &rt_info->saddr) ||
                    skb->mark != rt_info->mark)
-                       return ip6_route_me_harder(entry->state.net, skb);
+                       return ip6_route_me_harder(entry->state.net, entry->state.sk, skb);
        }
        return 0;
 }

diff --git a/net/ipv6/netfilter/ip6table_mangle.c b/net/ipv6/netfilter/ip6table_mangle.c
index 1a2748611e00388abf30a4127a24adc516cdcd2e..cee74803d7a1ce649c01c71f4d7b6860ff156aa3 100644 (file)
--- a/net/ipv6/netfilter/ip6table_mangle.c
+++ b/net/ipv6/netfilter/ip6table_mangle.c
@@ -57,7 +57,7 @@ ip6t_mangle_out(struct sk_buff *skb, const struct nf_hook_state *state)
             skb->mark != mark ||
             ipv6_hdr(skb)->hop_limit != hop_limit ||
             flowlabel != *((u_int32_t *)ipv6_hdr(skb)))) {
-               err = ip6_route_me_harder(state->net, skb);
+               err = ip6_route_me_harder(state->net, state->sk, skb);
                if (err < 0)
                        ret = NF_DROP_ERR(err);
        }

diff --git a/net/netfilter/ipvs/ip_vs_core.c b/net/netfilter/ipvs/ip_vs_core.c
index cc3c275934f47f4817280897e1bc9f8b5424f178..c0b8215ab3d47a6719cbb0d57cffb7b73326ecad 100644 (file)
--- a/net/netfilter/ipvs/ip_vs_core.c
+++ b/net/netfilter/ipvs/ip_vs_core.c
@@ -742,12 +742,12 @@ static int ip_vs_route_me_harder(struct netns_ipvs *ipvs, int af,
                struct dst_entry *dst = skb_dst(skb);
 
                if (dst->dev && !(dst->dev->flags & IFF_LOOPBACK) &&
-                   ip6_route_me_harder(ipvs->net, skb) != 0)
+                   ip6_route_me_harder(ipvs->net, skb->sk, skb) != 0)
                        return 1;
        } else
 #endif
                if (!(skb_rtable(skb)->rt_flags & RTCF_LOCAL) &&
-                   ip_route_me_harder(ipvs->net, skb, RTN_LOCAL) != 0)
+                   ip_route_me_harder(ipvs->net, skb->sk, skb, RTN_LOCAL) != 0)
                        return 1;
 
        return 0;

diff --git a/net/netfilter/nf_nat_proto.c b/net/netfilter/nf_nat_proto.c
index 59151dc07fdc14fe6fa640cdd0448723d96bcb48..e87b6bd6b3cdb6b79b2d229df4ce3d74f8e374d8 100644 (file)
--- a/net/netfilter/nf_nat_proto.c
+++ b/net/netfilter/nf_nat_proto.c
@@ -715,7 +715,7 @@ nf_nat_ipv4_local_fn(void *priv, struct sk_buff *skb,
 
                if (ct->tuplehash[dir].tuple.dst.u3.ip !=
                    ct->tuplehash[!dir].tuple.src.u3.ip) {
-                       err = ip_route_me_harder(state->net, skb, RTN_UNSPEC);
+                       err = ip_route_me_harder(state->net, state->sk, skb, RTN_UNSPEC);
                        if (err < 0)
                                ret = NF_DROP_ERR(err);
                }
@@ -953,7 +953,7 @@ nf_nat_ipv6_local_fn(void *priv, struct sk_buff *skb,
 
                if (!nf_inet_addr_cmp(&ct->tuplehash[dir].tuple.dst.u3,
                                      &ct->tuplehash[!dir].tuple.src.u3)) {
-                       err = nf_ip6_route_me_harder(state->net, skb);
+                       err = nf_ip6_route_me_harder(state->net, state->sk, skb);
                        if (err < 0)
                                ret = NF_DROP_ERR(err);
                }

diff --git a/net/netfilter/nf_synproxy_core.c b/net/netfilter/nf_synproxy_core.c
index 9cca35d22927382e0323cc7cb8cd16913e8d3e87..d7d34a62d3bf5fb5d7919d855a02a2c1c935b8a0 100644 (file)
--- a/net/netfilter/nf_synproxy_core.c
+++ b/net/netfilter/nf_synproxy_core.c
@@ -446,7 +446,7 @@ synproxy_send_tcp(struct net *net,
 
        skb_dst_set_noref(nskb, skb_dst(skb));
        nskb->protocol = htons(ETH_P_IP);
-       if (ip_route_me_harder(net, nskb, RTN_UNSPEC))
+       if (ip_route_me_harder(net, nskb->sk, nskb, RTN_UNSPEC))
                goto free_nskb;
 
        if (nfct) {

diff --git a/net/netfilter/nft_chain_route.c b/net/netfilter/nft_chain_route.c
index 8826bbe71136c86bd1020e0598bb4509aa793421..edd02cda57fca8713c29f749ceae7e26e83aa9ff 100644 (file)
--- a/net/netfilter/nft_chain_route.c
+++ b/net/netfilter/nft_chain_route.c
@@ -42,7 +42,7 @@ static unsigned int nf_route_table_hook4(void *priv,
                    iph->daddr != daddr ||
                    skb->mark != mark ||
                    iph->tos != tos) {
-                       err = ip_route_me_harder(state->net, skb, RTN_UNSPEC);
+                       err = ip_route_me_harder(state->net, state->sk, skb, RTN_UNSPEC);
                        if (err < 0)
                                ret = NF_DROP_ERR(err);
                }
@@ -92,7 +92,7 @@ static unsigned int nf_route_table_hook6(void *priv,
             skb->mark != mark ||
             ipv6_hdr(skb)->hop_limit != hop_limit ||
             flowlabel != *((u32 *)ipv6_hdr(skb)))) {
-               err = nf_ip6_route_me_harder(state->net, skb);
+               err = nf_ip6_route_me_harder(state->net, state->sk, skb);
                if (err < 0)
                        ret = NF_DROP_ERR(err);
        }

diff --git a/net/netfilter/utils.c b/net/netfilter/utils.c
index cedf47ab3c6f98d13f0397e27a4beeca44d28854..2182d361e273f18818e312e47dda770bf9b4b625 100644 (file)
--- a/net/netfilter/utils.c
+++ b/net/netfilter/utils.c
@@ -191,8 +191,8 @@ static int nf_ip_reroute(struct sk_buff *skb, const struct nf_queue_entry *entry
                      skb->mark == rt_info->mark &&
                      iph->daddr == rt_info->daddr &&
                      iph->saddr == rt_info->saddr))
-                       return ip_route_me_harder(entry->state.net, skb,
-                                                 RTN_UNSPEC);
+                       return ip_route_me_harder(entry->state.net, entry->state.sk,
+                                                 skb, RTN_UNSPEC);
        }
 #endif
        return 0;