Rusty Russell wrote:
> On Thursday 26 June 2008 05:07:18 Anthony Liguori wrote:
>> Rusty Russell wrote:
>>> @@ -1563,6 +1561,16 @@ static void setup_tun_net(char *arg)
>>>     /* Tell Guest what MAC address to use. */
>>>     add_feature(dev, VIRTIO_NET_F_MAC);
>>>     add_feature(dev, VIRTIO_F_NOTIFY_ON_EMPTY);
>>> +   /* Expect Guest to handle everything except UFO */
>>> +   add_feature(dev, VIRTIO_NET_F_CSUM);
>> You're setting this feature twice.
> 
> Hmm, not in the version here?
> 
>>> +   add_feature(dev, VIRTIO_NET_F_GUEST_CSUM);
>> You set this feature, but I never see the virtio-net driver acknowledge
>> the feature.  Curiously, my implementation with KVM is struggling
>> because UDP packet checksums are not correct so the DHCP client is
>> ignoring them.  If I disable CSUM offload, things it works fine (using
>> the virtio-net header).  The problem is only host=>guest, guest=>host is
>> fine.
> 
> OK, found this: wrong args to skb_partial_csum_set.  It was found by Mark 
> McLoughlin before, I just lost the fix when I extracted this into a separate 
> patch.  I chose to move the call to skb_partial_csum_set(), rather than use 
> his fix (which assumed a tap not tun device).
> 
> Here's two fixes on top of previous patch:
> 
> diff -u b/drivers/net/tun.c b/drivers/net/tun.c
> --- b/drivers/net/tun.c       Thu Jun 26 00:21:59 2008 +1000
> +++ b/drivers/net/tun.c       Thu Jun 26 14:35:03 2008 +1000
> @@ -298,11 +298,11 @@
>               if ((len -= sizeof(gso)) > count)
>                       return -EINVAL;
>  
> -             if (gso.hdr_len > len)
> -                     return -EINVAL;
> -
>               if (memcpy_fromiovec((void *)&gso, iv, sizeof(gso)))
>                       return -EFAULT;
> +
> +             if (gso.hdr_len > len)
> +                     return -EINVAL;
>       }

Yep, looks better now.

>  
>       if ((tun->flags & TUN_TYPE_MASK) == TUN_TAP_DEV) {
> @@ -324,6 +324,16 @@
>               return -EFAULT;
>       }
>  
> +     if (gso.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) {
> +             if (!skb_partial_csum_set(skb, gso.csum_start,
> +                                       gso.csum_offset)) {
> +                     tun->dev->stats.rx_dropped++;
> +                     kfree_skb(skb);
> +                     return -EINVAL;
> +             }
> +     } else if (tun->flags & TUN_NOCHECKSUM)
> +             skb->ip_summed = CHECKSUM_UNNECESSARY;
> +
>       switch (tun->flags & TUN_TYPE_MASK) {
>       case TUN_TUN_DEV:
>               skb_reset_mac_header(skb);
> @@ -335,16 +345,6 @@
>               break;
>       };
>  
> -     if (gso.flags & VIRTIO_NET_HDR_F_NEEDS_CSUM) {
> -             if (!skb_partial_csum_set(skb, gso.csum_start,
> -                                       gso.csum_offset)) {
> -                     tun->dev->stats.rx_dropped++;
> -                     kfree_skb(skb);
> -                     return -EINVAL;
> -             }
> -     } else if (tun->flags & TUN_NOCHECKSUM)
> -             skb->ip_summed = CHECKSUM_UNNECESSARY;
> -
>       if (gso.gso_type != VIRTIO_NET_HDR_GSO_NONE) {
>               pr_debug("GSO!\n");
>               switch (gso.gso_type & ~VIRTIO_NET_HDR_GSO_ECN) {

Do you want to resent the GSO patch with all the latest fixes ? ie other
things (stat counters) I pointed out in the prev email.
I'll ack it.

Thanx
Max
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