tcp: early_demux fixes

1) Remove a non needed pskb_may_pull() in tcp_v4_early_demux()
   and fix a potential bug if skb->head was reallocated
   (iph & th pointers were not reloaded)

TCP stack will pull/check headers anyway.

2) must reload iph in ip_rcv_finish() after early_demux()
 call since skb->head might have changed.

3) skb->dev->ifindex can be now replaced by skb->skb_iif

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 6 insertions, 8 deletions

diff --git a/net/ipv4/ip_input.c b/net/ipv4/ip_input.c
index 4ebc6feee250..93134b0eab0c 100644
--- a/net/ipv4/ip_input.c
+++ b/net/ipv4/ip_input.c
@@ -326,8 +326,11 @@ static int ip_rcv_finish(struct sk_buff *skb)
 
                 rcu_read_lock();
                 ipprot = rcu_dereference(inet_protos[protocol]);
-                if (ipprot && ipprot->early_demux)
+                if (ipprot && ipprot->early_demux) {
                         ipprot->early_demux(skb);
+                        /* must reload iph, skb->head might have changed */
+                        iph = ip_hdr(skb);
+                }
                 rcu_read_unlock();
         }
 
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 3e30548ac32a..b6b07c93924c 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1686,7 +1686,6 @@ void tcp_v4_early_demux(struct sk_buff *skb)
         struct net *net = dev_net(skb->dev);
         const struct iphdr *iph;
         const struct tcphdr *th;
-        struct net_device *dev;
         struct sock *sk;
 
         if (skb->pkt_type != PACKET_HOST)
@@ -1701,14 +1700,10 @@ void tcp_v4_early_demux(struct sk_buff *skb)
         if (th->doff < sizeof(struct tcphdr) / 4)
                 return;
 
-        if (!pskb_may_pull(skb, ip_hdrlen(skb) + th->doff * 4))
-                return;
-
-        dev = skb->dev;
         sk = __inet_lookup_established(net, &tcp_hashinfo,
                                        iph->saddr, th->source,
                                        iph->daddr, ntohs(th->dest),
-                                       dev->ifindex);
+                                       skb->skb_iif);
         if (sk) {
                 skb->sk = sk;
                 skb->destructor = sock_edemux;
@@ -1718,7 +1713,7 @@ void tcp_v4_early_demux(struct sk_buff *skb)
                         if (dst)
                                 dst = dst_check(dst, 0);
                         if (dst &&
-                            icsk->rx_dst_ifindex == dev->ifindex)
+                            icsk->rx_dst_ifindex == skb->skb_iif)
                                 skb_dst_set_noref(skb, dst);
                 }
         }