netdev - [PATCH net] tcp: do not use ipv6 header for ipv4 flow

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Date:   Tue, 19 Mar 2019 05:45:35 -0700
From:   Eric Dumazet <edumazet@...gle.com>
To:     "David S . Miller" <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>
Subject: [PATCH net] tcp: do not use ipv6 header for ipv4 flow

When a dual stack tcp listener accepts an ipv4 flow,
it should not attempt to use an ipv6 header or tcp_v6_iif() helper.

Fixes: 1397ed35f22d ("ipv6: add flowinfo for tcp6 pkt_options for all cases")
Fixes: df3687ffc665 ("ipv6: add the IPV6_FL_F_REFLECT flag to IPV6_FL_A_GET")
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 net/ipv6/tcp_ipv6.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 57ef69a1088908fc624ecfca99a728fa296ae0bf..44d431849d391d6903d263ae547fc9bed1e67aa7 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1110,11 +1110,11 @@ static struct sock *tcp_v6_syn_recv_sock(const struct sock *sk, struct sk_buff *
 		newnp->ipv6_fl_list = NULL;
 		newnp->pktoptions  = NULL;
 		newnp->opt	   = NULL;
-		newnp->mcast_oif   = tcp_v6_iif(skb);
-		newnp->mcast_hops  = ipv6_hdr(skb)->hop_limit;
-		newnp->rcv_flowinfo = ip6_flowinfo(ipv6_hdr(skb));
+		newnp->mcast_oif   = inet_iif(skb);
+		newnp->mcast_hops  = ip_hdr(skb)->ttl;
+		newnp->rcv_flowinfo = 0;
 		if (np->repflow)
-			newnp->flow_label = ip6_flowlabel(ipv6_hdr(skb));
+			newnp->flow_label = 0;
 
 		/*
 		 * No need to charge this sock to the relevant IPv6 refcnt debug socks count
-- 
2.21.0.225.g810b269d1ac-goog