[PATCH 5.10 45/57] ipv6: Fix tcp socket connection with DSCP.

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

From: Guillaume Nault <gnault@redhat.com>

commit 8230680f36fd1525303d1117768c8852314c488c upstream.

Take into account the IPV6_TCLASS socket option (DSCP) in
tcp_v6_connect(). Otherwise fib6_rule_match() can't properly
match the DSCP value, resulting in invalid route lookup.

For example:

  ip route add unreachable table main 2001:db8::10/124

  ip route add table 100 2001:db8::10/124 dev eth0
  ip -6 rule add dsfield 0x04 table 100

  echo test | socat - TCP6:[2001:db8::11]:54321,ipv6-tclass=0x04

Without this patch, socat fails at connect() time ("No route to host")
because the fib-rule doesn't jump to table 100 and the lookup ends up
being done in the main table.

Fixes: 2cc67cc731d9 ("[IPV6] ROUTE: Routing by Traffic Class.")
Signed-off-by: Guillaume Nault <gnault@redhat.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: David Ahern <dsahern@kernel.org>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/ipv6/tcp_ipv6.c |    1 +
 1 file changed, 1 insertion(+)

--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -269,6 +269,7 @@ static int tcp_v6_connect(struct sock *s
 	fl6.flowi6_proto = IPPROTO_TCP;
 	fl6.daddr = sk->sk_v6_daddr;
 	fl6.saddr = saddr ? *saddr : np->saddr;
+	fl6.flowlabel = ip6_make_flowinfo(np->tclass, np->flow_label);
 	fl6.flowi6_oif = sk->sk_bound_dev_if;
 	fl6.flowi6_mark = sk->sk_mark;
 	fl6.fl6_dport = usin->sin6_port;