[PATCH net-next] ipv4: ipv4_default_advmss() should use route mtu

[Eric Dumazet]

From: Eric Dumazet <eduma...@google.com>

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 <eduma...@google.com>
---
 net/ipv4/route.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index 
4306db8273742f5e845635419c296823301c4a8b..bc40bd4111969f640603dd7c5b04fdb7fdcd4afd
 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1250,7 +1250,7 @@ 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);