Re: [Qemu-devel] Re: [PATCH] Fix TAP networking on host kernels without IFF_VNET_HDR support

[Pierre Riteau <Pierre.Riteau@irisa.fr>]

On 24 nov. 2009, at 11:28, Mark McLoughlin wrote:

> On Tue, 2009-11-24 at 10:06 +0100, Pierre Riteau wrote:
>> vnet_hdr is initialized at 1 by default. We need to reset it to 0 if
>> the kernel doesn't support IFF_VNET_HDR.
>> 
>> Signed-off-by: Pierre Riteau <Pierre.Riteau@irisa.fr>
> 
> Thanks Pierre, I see why this is needed now
> 
> Acked-by: Mark McLoughlin <markmc@redhat.com>
> 
> Cheers,
> Mark.


Thanks for your rapid answer!

BTW, every time I run qemu I see this error message:

    TUNSETOFFLOAD ioctl() failed: Invalid argument

It is caused by the piece of code at the end of net/tap-linux.c:

    if (ioctl(fd, TUNSETOFFLOAD, offload) != 0) {
        offload &= ~TUN_F_UFO;
        if (ioctl(fd, TUNSETOFFLOAD, offload) != 0) {
            fprintf(stderr, "TUNSETOFFLOAD ioctl() failed: %s\n",
                    strerror(errno));
        }
    }

Isn't there a way to detect whether the kernel supports the TUNSETOFFLOAD ioctl at all?

-- 
Pierre Riteau -- http://perso.univ-rennes1.fr/pierre.riteau/