From 032a74a1c0fcdd5fd1c69e56126b4c857ee36611 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?C=C3=A9dric=20Le=20Goater?= Date: Tue, 24 Jun 2014 19:11:32 +0200 Subject: [PATCH] virtio-net: byteswap virtio-net header MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 [ Ported from PowerKVM, Greg Kurz ] Signed-off-by: Greg Kurz Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin --- hw/net/virtio-net.c | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/hw/net/virtio-net.c b/hw/net/virtio-net.c index e51d753cee..ea1a081993 100644 --- a/hw/net/virtio-net.c +++ b/hw/net/virtio-net.c @@ -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