From d749c9cbffd666956694f307d237e018c464d973 Mon Sep 17 00:00:00 2001
From: Hannes Frederic Sowa <hannes@stressinduktion.org>
Date: Tue, 27 Oct 2015 22:40:39 +0100
Subject: [PATCH] ipv4: no CHECKSUM_PARTIAL on MSG_MORE corked sockets

We cannot reliable calculate packet size on MSG_MORE corked sockets
and thus cannot decide if they are going to be fragmented later on,
so better not use CHECKSUM_PARTIAL in the first place.

Cc: Eric Dumazet <edumazet@google.com>
Cc: Vlad Yasevich <vyasevich@gmail.com>
Cc: Benjamin Coddington <bcodding@redhat.com>
Cc: Tom Herbert <tom@herbertland.com>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
 net/ipv4/ip_output.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 50e29737b584..0b024178edd3 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -911,6 +911,7 @@ static int __ip_append_data(struct sock *sk,
 	if (transhdrlen &&
 	    length + fragheaderlen <= mtu &&
 	    rt->dst.dev->features & NETIF_F_V4_CSUM &&
+	    !(flags & MSG_MORE) &&
 	    !exthdrlen)
 		csummode = CHECKSUM_PARTIAL;