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virtio-net: byteswap virtio-net header 

TCP connectivity fails when the guest has a different endianness.
The packets are silently dropped on the host by the tap backend
when they are read from user space because the endianness of the
virtio-net header is in the wrong order. These lines may appear
in the guest console:

[  454.709327] skbuff: bad partial csum: csum=8704/4096 len=74
[  455.702554] skbuff: bad partial csum: csum=8704/4096 len=74

The issue that got first spotted with a ppc64le PowerKVM guest,
but it also exists for the less common case of a x86_64 guest run
by a big-endian ppc64 TCG hypervisor.

Signed-off-by: Cédric Le Goater <clg@fr.ibm.com>
[ Ported from PowerKVM,
  Greg Kurz <gkurz@linux.vnet.ibm.com> ]
Signed-off-by: Greg Kurz <gkurz@linux.vnet.ibm.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Cédric Le Goater 2014-06-24 19:11:32 +02:00 committed by Michael S. Tsirkin
parent a628fc8dae
commit 032a74a1c0
1 changed files with 17 additions and 0 deletions
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17
hw/net/virtio-net.c
View File

@ -875,6 +875,14 @@ static int virtio_net_has_buffers(VirtIONetQueue *q, int bufsize)
return 1;
}
static void virtio_net_hdr_swap(struct virtio_net_hdr *hdr)
{
tswap16s(&hdr->hdr_len);
tswap16s(&hdr->gso_size);
tswap16s(&hdr->csum_start);
tswap16s(&hdr->csum_offset);
}
/* dhclient uses AF_PACKET but doesn't pass auxdata to the kernel so
* it never finds out that the packets don't have valid checksums. This
* causes dhclient to get upset. Fedora's carried a patch for ages to
@ -910,6 +918,7 @@ static void receive_header(VirtIONet *n, const struct iovec *iov, int iov_cnt,
void *wbuf = (void *)buf;
work_around_broken_dhclient(wbuf, wbuf + n->host_hdr_len,
size - n->host_hdr_len);
virtio_net_hdr_swap(wbuf);
iov_from_buf(iov, iov_cnt, 0, buf, sizeof(struct virtio_net_hdr));
} else {
struct virtio_net_hdr hdr = {
@ -1118,6 +1127,14 @@ static int32_t virtio_net_flush_tx(VirtIONetQueue *q)
exit(1);
}
if (n->has_vnet_hdr) {
if (out_sg[0].iov_len < n->guest_hdr_len) {
error_report("virtio-net header incorrect");
exit(1);
}
virtio_net_hdr_swap((void *) out_sg[0].iov_base);
}
/*
* If host wants to see the guest header as is, we can
* pass it on unchanged. Otherwise, copy just the parts