if_bridge turns off checksum offload of members?

Andrew Thompson thompsa at FreeBSD.org
Tue Jul 1 01:24:10 UTC 2008

On Mon, Jun 30, 2008 at 07:16:29PM +0900, Pyun YongHyeon wrote:
> On Mon, Jun 30, 2008 at 12:11:40PM +0300, Stefan Lambrev wrote:
>  > Greetings,
>  > 
>  > I just noticed, that when I add em network card to bridge the checksum 
>  > offload is turned off.
>  > I even put in my rc.conf:
>  > ifconfig_em0="rxcsum up"
>  > ifconfig_em1="rxcsum up"
>  > but after reboot both em0 and em1 have this feature disabled.
>  > 
>  > Is this expected behavior? Should I care about csum in bridge mode?
>  > I noticed that enabling checksum offload manually improve things little btw.
>  > 
> AFAIK this is intended one, bridge(4) turns off Tx side checksum
> offload by default. I think disabling Tx checksum offload is
> required as not all members of a bridge may be able to do checksum
> offload. The same is true for TSO but it seems that bridge(4)
> doesn't disable it.
> If all members of bridge have the same hardware capability I think
> bridge(4) may not need to disable Tx side hardware assistance. I
> guess bridge(4) can scan every interface capabilities in a member
> and can decide what hardware assistance can be activated instead of
> blindly turning off Tx side hardware assistance.

This patch should do that, are you able to test it Stefan?

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