ipv4: ipv4_default_advmss() should use route mtu

[ Upstream commit 164a5e7ad531e181334a3d3f03d0d5ad20d6faea ]

ipv4_default_advmss() incorrectly uses the device MTU instead
of the route provided one. IPv6 has the proper behavior,
lets harmonize the two protocols.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 647cfc972bde0f0455b8581734a6591484659409..804bead564db8e08d756fa11ef1981f3908396c1 100644 (file)
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1254,7 +1254,7 @@ static void set_class_tag(struct rtable *rt, u32 tag)
 static unsigned int ipv4_default_advmss(const struct dst_entry *dst)
 {
        unsigned int header_size = sizeof(struct tcphdr) + sizeof(struct iphdr);
-       unsigned int advmss = max_t(unsigned int, dst->dev->mtu - header_size,
+       unsigned int advmss = max_t(unsigned int, ipv4_mtu(dst) - header_size,
                                    ip_rt_min_advmss);
 
        return min(advmss, IPV4_MAX_PMTU - header_size);