linux-kernel - [PATCH 4.14 142/178] ipv4: ipv4_default

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Date:   Mon, 18 Dec 2017 16:49:38 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <alexander.levin@...izon.com>
Subject: [PATCH 4.14 142/178] ipv4: ipv4_default_advmss() should use route mtu

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

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

From: Eric Dumazet <edumazet@...gle.com>


[ 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@...gle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 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);