From mboxrd@z Thu Jan  1 00:00:00 1970
From: Thomas Graf <tgraf@suug.ch>
Subject: Re: skb_checksum_help
Date: Tue, 25 Jan 2005 22:15:24 +0100
Message-ID: <20050125211524.GH31837@postel.suug.ch>
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* Ben Greear <41F6B090.6020602@candelatech.com> 2005-01-25 12:48
> Thomas Graf wrote:
> >NETIF_F_IP_CSUM|NETIF_F_HW_CSUM:
> >  Assuming that the vlan accel code can always do the checksumming
> >  if the card can do it.
> 
> I am leery of assuming these things for all drivers and all chipsets.
> 
> Maybe the driver itself could tell vlan code what sorts of flags it
> can set?  That takes the guess-work out, and each driver can add
> the features support as it is verified to work.  If any particular
> hacks need to be used (ie, maybe chipset foo.rev-1a can't handle one
> particular thing), then the VLAN code doesn't have to care.
> 
> 	new_dev->features = real_dev->vlan_features;
> 
* David S. Miller <20050125125019.5ca32de1.davem@davemloft.net> 2005-01-25 12:50
> I bet there are cards that don't have VLAN hw assist yet
> can properly checksum such packets.  One example I am counting
> on to fit this property is the 3c59x.
> 
> This is why I'm suggesting some kind of inheritance indication
> explicitly from the real_dev driver.  Perhaps even something
> like:
> 
> 	unsigned int vlan_inherited_features;
> 
> in the netdev struct.

I thought about this too and actually implemented it but it means to
change all relevant drivers and the only feature that might be
driver specific is checksumming, given I didn't make any mistakes
while checking the drivers for pskb compatibility. Therefore I tried
to avoid it but it seems we can't get around it.

Any objections in inheriting SG|NO_CSUM|HIGH_DMA|FRAGLIST|TSO by
default or leave it to the driver as well?