ipv4: add a sock pointer to ip_queue_xmit()

ip_queue_xmit() assumes the skb it has to transmit is attached to an
inet socket. Commit 31c70d5956fc ("l2tp: keep original skb ownership")
changed l2tp to not change skb ownership and thus broke this assumption.

One fix is to add a new 'struct sock *sk' parameter to ip_queue_xmit(),
so that we do not assume skb->sk points to the socket used by l2tp
tunnel.

Fixes: 31c70d5956fc ("l2tp: keep original skb ownership")
Reported-by: Zhan Jianyu <nasa4836@gmail.com>
Tested-by: Zhan Jianyu <nasa4836@gmail.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 3 insertions, 2 deletions

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 1a0755fea491..7ad68b860935 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -315,9 +315,9 @@ static void ip_copy_addrs(struct iphdr *iph, const struct flowi4 *fl4)
                sizeof(fl4->saddr) + sizeof(fl4->daddr));
 }
 
-int ip_queue_xmit(struct sk_buff *skb, struct flowi *fl)
+/* 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)
 {
-        struct sock *sk = skb->sk;
         struct inet_sock *inet = inet_sk(sk);
         struct ip_options_rcu *inet_opt;
         struct flowi4 *fl4;
@@ -389,6 +389,7 @@ packet_routed:
         ip_select_ident_more(skb, &rt->dst, sk,
                              (skb_shinfo(skb)->gso_segs ?: 1) - 1);
 
+        /* TODO : should we use skb->sk here instead of sk ? */
         skb->priority = sk->sk_priority;
         skb->mark = sk->sk_mark;