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;
}
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) {
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