Hi Patrick,
I noticed another problem with the macvlan driver.
In the function dev_forward_skb the test always succeed in the second
condition making the packet to be dropped.
...
if (unlikely(!(dev-flags IFF_UP) ||
(skb-len (dev-mtu + dev-hard_header_len + VLAN_HLEN {
...
When tracing I have the following values:
skb-len = 2962
and
dev-mtu + dev-hard_header_len + VLAN_HLEN = 1518
Do you have any idea where that could be come from ?
Thanks
-- Daniel
On 03/08/2011 03:41 PM, Patrick McHardy wrote:
Am 02.03.2011 19:33, schrieb Daniel Lezcano:
On 03/02/2011 07:03 PM, Patrick McHardy wrote:
Am 02.03.2011 17:03, schrieb Daniel Lezcano:
On 03/02/2011 12:03 PM, Patrick McHardy wrote:
Am 01.03.2011 21:04, schrieb Daniel Lezcano:
On 03/01/2011 05:51 PM, Patrick McHardy wrote:
Patrick, do you have any suggestions to fix this ?
Since the frames are only looped back locally, I suppose the easiest
fix would be to mark them with CHECKSUM_UNNECESSARY. Alternatively
we need to complete the checksum manually, similar to what
dev_hard_start_xmit() does.
That sounds very simple to fix, maybe too much simple :)
I did the following change:
--- linux-next.orig/drivers/net/macvlan.c
+++ linux-next/drivers/net/macvlan.c
@@ -222,6 +222,7 @@ static int macvlan_queue_xmit(struct sk_
if (vlan-mode == MACVLAN_MODE_BRIDGE) {
const struct ethhdr *eth = (void *)skb-data;
+ skb-ip_summed = CHECKSUM_UNNECESSARY;
/* send to other bridge ports directly */
if (is_multicast_ether_addr(eth-h_dest)) {
and that fixed the problem. Do you think it is acceptable ?
The only problem I see is if the packets are bridged to a
different networking device (or redirected using the mirred
action), in this case the checksum will not be completed.
This would be a very strange setup though and probably wouldn't
be using dummy as lower device, so I'm not sure we have to
worry about this case.
I am not sure to get it, do you say the patch is correct ?
Its correct with a short-coming that doesn't seem to matter.
If my understanding is correct, the packet will be flagged
CHECKSUM_UNNECESSARY only for the macvlan devices, right ?
Only for packets bridged between macvlan devices. A setup like
the following would cause problems:
br0
|
.--.
| |
macvlan0macvlan1eth0
| |
---.---
dummy0
In this case packets sent from macvlan0 will show up on
eth0 with incorrect setups. However this setup doesn't
seem realistic to me, you would simply use eth0 instead
of dummy0.
Ok, I understand. thanks for the clarification.
By the way, this problem occurs for any lower device with offloading
capabilities with a macvlan port in bridge mode.
True. This doesn't affect outgoing packets since their checksum
will be completed in dev_hard_start_xmit(), but it affects
packets bridged between macvlans.
One last question. In the case of broadcast packets with maclvan in
bridge mode.
We will have the packets going through each macvlan port and also to the
lower-device, right ?
For the latter, don't we have a problem if the packet is flagged
CHECKSUM_UNNECESSARY ?
Shouldn't we restore the ip_summed field before sending through
dev_queue_xmit ?
Yes, that seems correct in order to have dev_hard_start_xmit() complete
the checksum if necessary.
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