Rx/tx hardware checksumming statistics?
pyunyh at gmail.com
Mon Aug 11 02:19:17 UTC 2008
On Sat, Aug 09, 2008 at 08:12:42PM +0000, Christian Weisgerber wrote:
> OpenBSD keeps count of the packets that have undergone IPv4 header/
> TCP/UDP checksumming in hardware. These statics are available with
> netstat -s, e.g.:
> 492152 input datagrams checksum-processed by hardware
> 911338 output datagrams checksum-processed by hardware
> This comes in quite handy to check whether checksum offloading
> actually works and which protocols are successfully processed this
I don't think it indicates whether checksum offloading actually
works as OpenBSD blindly set a flag, which was derived from
hardware, to indicate hardware performed the checksum computation.
You can still have a chance that checksum offloading does not work
even if the counter constantly increase over time. In addition,
OpenBSD have a no way to disable checksum offloading feature of
hardware on the fly so you have to rebuild the driver to disable
checksum offloading in case of broken/buggy hardware.
> On FreeBSD, netstat -s does not provide this information. Are these
> statistics available in some other way? How would I check whether
AFAIK there is no such counters in FreeBSD.
> packets have actually been checksummed in hardware?
If checksum offloading didn't work you couldn't get a working
connection at all.
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