Re: networking checksum errors again

[Florian Kirstein <xenlist@custom.ray.net>]

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Hallo,

> Regardless of whether or not I use a dom0 kernel or a domU kernel I
> get failed checksum packets whenever I try to route across a virtual
> interface.  I have a pure virtual setup
Ah, I just dived into that recently... Is there a bugzilla id
for that already? I had the same problem as you, Dom0 can't communicate
with DomU due to the checksum errors in a routed setup, everything
works when bridged. But I don't want to bridge :)

> thing on all interfaces, tried changing the code in netback.c to
> force a checksum and have had no luck.   Any else having trouble?
Which netback.c patch did you use? I currently have a working setup
using the "interface.c" patch which removes the NETIF_F_NO_CSUM from
the dev->features in Dom0 (attached). Using this "sum ok" packets go
from Dom0 to DomU (also leaving Dom0 intact), DomU to Dom0 packets
are broken leaving DomU but Dom0 ignores that. Using
ethtool -K eth0 tx off
in DomU I can bring DomU to generate valid sums also, but that's cosmetic
and not needed for a working setup. I'd rather also patch this in the
kernel instead of running ethtool in every DomU but I haven't searched
for that yet. Should be easy, though :)

As far as I understood the discussion, this is not an easy issue and
possibly will be dealt with in in clean way after the 3.0.2 release?
For now I have other problems, the above setup seems to work fine
for me (also for DomU-DomU communication, which of course is routed
over Dom0. Will have to test tunnels/vpn in DomU).

(:ul8er, r@y

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diff -U 3 -r xen-unstable-orig/linux-2.6-xen-sparse/drivers/xen/netback/interface.c xen-unstable/linux-2.6-xen-sparse/drivers/xen/netback/interface.c
--- xen-unstable-orig/linux-2.6-xen-sparse/drivers/xen/netback/interface.c	2006-03-28 06:11:37.000000000 +0200
+++ xen-unstable/linux-2.6-xen-sparse/drivers/xen/netback/interface.c	2006-03-30 08:17:01.000000000 +0200
@@ -101,7 +101,7 @@
 	dev->get_stats       = netif_be_get_stats;
 	dev->open            = net_open;
 	dev->stop            = net_close;
-	dev->features        = NETIF_F_NO_CSUM;
+	dev->features        = 0; /* replaced NETIF_F_NO_CSUM */
 
 	/* Disable queuing. */
 	dev->tx_queue_len = 0;

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