netdev - [PATCH net-next] sock: Reset dst when changing sk

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Date:   Wed, 7 Nov 2018 16:33:27 -0600
From:   David Barmann <david.barmann@...ckpath.com>
To:     netdev@...r.kernel.org
Subject: [PATCH net-next] sock: Reset dst when changing sk_mark via setsockopt

When setting the SO_MARK socket option, the dst needs to be reset so
that a new route lookup is performed.

This fixes the case where an application wants to change routing by
setting a new sk_mark.  If this is done after some packets have already
been sent, the dst is cached and has no effect.

Signed-off-by: David Barmann <david.barmann@...ckpath.com>
---
 net/core/sock.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/net/core/sock.c b/net/core/sock.c
index 6fcc4bc07d19..187badac24a3 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -950,10 +950,14 @@ int sock_setsockopt(struct socket *sock, int level, int optname,
 			clear_bit(SOCK_PASSSEC, &sock->flags);
 		break;
 	case SO_MARK:
-		if (!ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN))
+		if (!ns_capable(sock_net(sk)->user_ns, CAP_NET_ADMIN)) {
 			ret = -EPERM;
-		else
+		} else {
+			struct dst_entry *dst = sk_dst_get(sk);
 			sk->sk_mark = val;
+			sk_dst_reset(sk);
+			dst_release(dst);
+		}
 		break;
 
 	case SO_RXQ_OVFL:
-- 
2.14.4