Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754095AbcKYIm0 (ORCPT ); Fri, 25 Nov 2016 03:42:26 -0500 Received: from mx2.suse.de ([195.135.220.15]:45310 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751035AbcKYIcP (ORCPT ); Fri, 25 Nov 2016 03:32:15 -0500 X-Amavis-Alert: BAD HEADER SECTION, Duplicate header field: "References" From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Douglas Caetano dos Santos , "David S . Miller" , Jiri Slaby Subject: [PATCH 3.12 086/127] tcp: fix wrong checksum calculation on MTU probing Date: Fri, 25 Nov 2016 09:29:59 +0100 Message-Id: <511ad85e5eb023f16494d703446f3d7b7f09e879.1480062521.git.jslaby@suse.cz> X-Mailer: git-send-email 2.10.2 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1902 Lines: 53 From: Douglas Caetano dos Santos 3.12-stable review patch. If anyone has any objections, please let me know. =============== [ Upstream commit 2fe664f1fcf7c4da6891f95708a7a56d3c024354 ] With TCP MTU probing enabled and offload TX checksumming disabled, tcp_mtu_probe() calculated the wrong checksum when a fragment being copied into the probe's SKB had an odd length. This was caused by the direct use of skb_copy_and_csum_bits() to calculate the checksum, as it pads the fragment being copied, if needed. When this fragment was not the last, a subsequent call used the previous checksum without considering this padding. The effect was a stale connection in one way, as even retransmissions wouldn't solve the problem, because the checksum was never recalculated for the full SKB length. Signed-off-by: Douglas Caetano dos Santos Signed-off-by: David S. Miller Signed-off-by: Jiri Slaby --- net/ipv4/tcp_output.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index f08921156be8..c807d5790ca1 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -1762,12 +1762,14 @@ static int tcp_mtu_probe(struct sock *sk) len = 0; tcp_for_write_queue_from_safe(skb, next, sk) { copy = min_t(int, skb->len, probe_size - len); - if (nskb->ip_summed) + if (nskb->ip_summed) { skb_copy_bits(skb, 0, skb_put(nskb, copy), copy); - else - nskb->csum = skb_copy_and_csum_bits(skb, 0, - skb_put(nskb, copy), - copy, nskb->csum); + } else { + __wsum csum = skb_copy_and_csum_bits(skb, 0, + skb_put(nskb, copy), + copy, 0); + nskb->csum = csum_block_add(nskb->csum, csum, len); + } if (skb->len <= copy) { /* We've eaten all the data from this skb. -- 2.10.2