Subject: Re: [PATCH] net: tun: convert to hw_features

From: Rusty Russell <[email-masked]>
Date: Wed, 20 Apr 2011 12:52:24 +0930

On Tue, 19 Apr 2011 18:13:10 +0200 (CEST), Michał Mirosław <[email-masked]> wrote:
> This changes offload setting behaviour to what I think is correct:
>  - offloads set via ethtool mean what admin wants to use (by default
>    he wants 'em all)
>  - offloads set via ioctl() mean what userspace is expecting to get
>    (this limits which admin wishes are granted)
>  - TUN_NOCHECKSUM is ignored, as it might cause broken packets when
>    forwarded (ip_summed == CHECKSUM_UNNECESSARY means that checksum
>    was verified, not that it can be ignored)
> 
> If TUN_NOCHECKSUM is implemented, it should set skb->csum_* and
> skb->ip_summed (= CHECKSUM_PARTIAL) for known protocols and let others
> be verified by kernel when necessary.
> 
> TUN_NOCHECKSUM handling was introduced by commit
> f43798c27684ab925adde7d8acc34c78c6e50df8:
> 
>     tun: Allow GSO using virtio_net_hdr

Err, not in my git tree!  It predates git in fact.

Since tap requires privs, I wouldn't worry about invalid packets too
much.

Thanks,
Rusty.