l2tp: take PMTU from tunnel UDP socket

[ Upstream commit f34c4a35d87949fbb0e0f31eba3c054e9f8199ba ]

When l2tp driver tries to get PMTU for the tunnel destination, it uses
the pointer to struct sock that represents PPPoX socket, while it
should use the pointer that represents UDP socket of the tunnel.

Signed-off-by: Dmitry Petukhov <dmgenp@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/l2tp/l2tp_ppp.c b/net/l2tp/l2tp_ppp.c
index 22112754ba0633d9793d2f0dc23b4ce4c201a2e4..4e38a81e48ee060d54946c271a022b0d06de5558 100644 (file)
--- a/net/l2tp/l2tp_ppp.c
+++ b/net/l2tp/l2tp_ppp.c
@@ -772,9 +772,9 @@ static int pppol2tp_connect(struct socket *sock, struct sockaddr *uservaddr,
        session->deref = pppol2tp_session_sock_put;
 
        /* If PMTU discovery was enabled, use the MTU that was discovered */
-       dst = sk_dst_get(sk);
+       dst = sk_dst_get(tunnel->sock);
        if (dst != NULL) {
-               u32 pmtu = dst_mtu(__sk_dst_get(sk));
+               u32 pmtu = dst_mtu(__sk_dst_get(tunnel->sock));
                if (pmtu != 0)
                        session->mtu = session->mru = pmtu -
                                PPPOL2TP_HEADER_OVERHEAD;