tcp: do not use ipv6 header for ipv4 flow

BugLink: https://bugs.launchpad.net/bugs/1826212

[ Upstream commit 89e41309 ]

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: 1397ed35 ("ipv6: add flowinfo for tcp6 pkt_options for all cases")
Fixes: df3687ff ("ipv6: add the IPV6_FL_F_REFLECT flag to IPV6_FL_A_GET")
Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

net/ipv6/tcp_ipv6.c

@@ -1043,11 +1043,11 @@ 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