[PATCH 4.14 142/178] ipv4: ipv4_default_advmss() should use route mtu

[Greg Kroah-Hartman]

4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <edumazet@xxxxxxxxxx>


[ 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@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/ipv4/route.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1254,7 +1254,7 @@ static void set_class_tag(struct rtable
 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);