From: Jamie Gloudon <jamie.gloudon@gmail.com>
To: netdev@vger.kernel.org
Subject: BUG: TCPDUMP invalid cksum persists after disabling TCP cksum offload
Date: Tue, 18 Sep 2012 17:14:23 -0400 [thread overview]
Message-ID: <20120918211423.GA19115@darkstar> (raw)
In-Reply-To: <1347998905.2685.29.camel@bwh-desktop.uk.solarflarecom.com>
Hello,
I am seeing that tx checksum offload appears to be still running after disabling the feature with ethtool. I'm using kernel 3.6.0-rc6 and the latest ethtool from the git repo.
The default settings on my e1000e NIC:
# ethtool -k eth1 | grep ': on'
rx-checksumming: on
tx-checksumming: on
tx-checksum-ip-generic: on
scatter-gather: on
tx-scatter-gather: on
tcp-segmentation-offload: on
tx-tcp-segmentation: on
tx-tcp6-segmentation: on
generic-segmentation-offload: on
generic-receive-offload: on
rx-vlan-offload: on
tx-vlan-offload: on
receive-hashing: on
highdma: on [fixed]
rx-vlan-filter: on [fixed]
tx-nocache-copy: on
The results after disabling tcp cksum offload feature:
# ethtool -K eth1 tx off
Actual changes:
tx-checksumming: off
tx-checksum-ip-generic: off
scatter-gather: off
tx-scatter-gather: off [requested on]
tcp-segmentation-offload: off
tx-tcp-segmentation: off [requested on]
tx-tcp6-segmentation: off [requested on]
generic-segmentation-offload: off [requested on]
However, in tcpdump, I'm still observing incorrect tcp checksum:
14:44:38.838711 IP (tos 0x10, ttl 64, id 45798, offset 0, flags [DF], proto TCP
(6), length 60)
1.1.1.2.59748 > 1.1.1.1.23: Flags [S], cksum 0x0433 (incorrect -> 0x4137), seq 318222122, win 14600, options [mss 1460,sackOK,TS val 5447116 ecr 0,nop,wscale 7], length 0
Is this behaviour valid? I'm quite baffled.
Regards,
Jamie Gloudon
next parent reply other threads:[~2012-09-18 21:14 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20120918193208.GA19030@darkstar>
[not found] ` <1347998905.2685.29.camel@bwh-desktop.uk.solarflarecom.com>
2012-09-18 21:14 ` Jamie Gloudon [this message]
2012-09-18 21:46 ` BUG: TCPDUMP invalid cksum persists after disabling TCP cksum offload Vijay Subramanian
2012-09-18 21:54 ` Rick Jones
2012-09-18 22:20 ` Jamie Gloudon
2012-09-19 5:54 ` Eric Dumazet
2012-09-19 6:44 ` [PATCH net-next] net: more accurate network taps in transmit path Eric Dumazet
2012-09-19 15:58 ` Jamie Gloudon
2012-09-19 18:16 ` David Miller
2012-09-19 18:21 ` Eric Dumazet
2012-09-19 19:33 ` David Miller
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