From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ted Percival Subject: Regression: TCP connections fail over wireless: bad cksum? Date: Thu, 4 Sep 2014 14:11:52 -0600 Message-ID: <5408C788.4050401@tedp.id.au> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit To: Return-path: Received: from amersmtp2.software.dell.com ([12.106.87.227]:47863 "EHLO amersmtp2.software.dell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752920AbaIDU0K (ORCPT ); Thu, 4 Sep 2014 16:26:10 -0400 Received: from amersmtp2.prod.quest.corp (127.0.0.1) id h135e20171s1 for ; Thu, 4 Sep 2014 13:10:59 -0700 (envelope-from ) Sender: netdev-owner@vger.kernel.org List-ID: Yesterday's linux-next build introduced a problem with wireless networking on my machine. ie. next-20140901 worked fine but next-20140902 does not seem able to sustain a TCP connection over wireless. Wired networking works fine. I am using the brcmsmac driver and the hardware is "Broadcom Corporation BCM4313 802.11b/g/n Wireless LAN Controller (rev 01)". Pings, even large pings (ping -s 16000) work fine but TCP connections hang. I looked through the changes between the bad & good commits from the net & net-next trees and I wonder if some of the changes to checksumming have surfaced a problem with this driver. When I look at a tcpdump, it indicates that all the checksums are wrong (although I don't know if that is just due to hardware offload). Here is a short trace of the hung connection attempt of curl http://lwn.net/ $ sudo tcpdump -vvn -i wlan0 port 80 tcpdump: listening on wlan0, link-type EN10MB (Ethernet), capture size 65535 bytes 13:20:15.120770 IP (tos 0x0, ttl 64, id 22734, offset 0, flags [DF], proto TCP (6), length 60) 10.5.51.93.38035 > 72.51.34.34.80: Flags [S], cksum 0xa7e5 (incorrect -> 0x4fac), seq 2861986597, win 29200, options [mss 1460,sackOK,TS val 142315 ecr 0,nop,wscale 7], length 0 13:20:16.121755 IP (tos 0x0, ttl 64, id 22735, offset 0, flags [DF], proto TCP (6), length 60) 10.5.51.93.38035 > 72.51.34.34.80: Flags [S], cksum 0xa7e5 (incorrect -> 0x4bc3), seq 2861986597, win 29200, options [mss 1460,sackOK,TS val 143316 ecr 0,nop,wscale 7], length 0 13:20:18.125748 IP (tos 0x0, ttl 64, id 22736, offset 0, flags [DF], proto TCP (6), length 60) 10.5.51.93.38035 > 72.51.34.34.80: Flags [S], cksum 0xa7e5 (incorrect -> 0x43ef), seq 2861986597, win 29200, options [mss 1460,sackOK,TS val 145320 ecr 0,nop,wscale 7], length 0 13:20:22.133743 IP (tos 0x0, ttl 64, id 22737, offset 0, flags [DF], proto TCP (6), length 60) 10.5.51.93.38035 > 72.51.34.34.80: Flags [S], cksum 0xa7e5 (incorrect -> 0x3447), seq 2861986597, win 29200, options [mss 1460,sackOK,TS val 149328 ecr 0,nop,wscale 7], length 0 13:20:30.149754 IP (tos 0x0, ttl 64, id 22738, offset 0, flags [DF], proto TCP (6), length 60) 10.5.51.93.38035 > 72.51.34.34.80: Flags [S], cksum 0xa7e5 (incorrect -> 0x14f7), seq 2861986597, win 29200, options [mss 1460,sackOK,TS val 157344 ecr 0,nop,wscale 7], length 0 I don't see anything that looks related in dmesg. The only brcmsmac messages I see are: [ 567.122218] brcmsmac bcma0:0: brcmsmac: brcms_ops_bss_info_changed: associated [ 567.122226] brcmsmac bcma0:0: brcms_ops_bss_info_changed: arp filtering: 1 addresses (implement) [ 567.122231] brcmsmac bcma0:0: brcms_ops_bss_info_changed: qos enabled: true (implement) [ 567.192283] brcmsmac bcma0:0: brcms_ops_bss_info_changed: qos enabled: true (implement) I am writing to linux-netdev rather than linux-wireless because according to Next/SHA1s the wireless & wireless-next trees were not updated between next-20140901 and next-20140902, but the net & net-next trees were updated, so maybe the regression came from there. (I haven't tested next-20140903 because it won't boot for unrelated reasons.) Let me know if I should just file this in Bugzilla or what information I can provide to help track this down, if it hasn't already been identified. The here are the good (-) and bad (+) trees from Next/SHA1s at the next-* tags mentioned earlier that I built from. -net 38ab1fa981d543e1b00f4ffbce4ddb480cd2effe +net cc25f0cbe4409d6a573b1f3bf7020d5b04076ee9 -net-next dace1b54726bffe1c009f7661e3cee6b762f30c8 +net-next 364a9e93243d1785f310c0964af0e24bf1adac03 -- Cheers, -Ted