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Re: [Qemu-devel] [Qemu-stable] [PATCH V2] net: fix qemu_announce_self no

From: Jason Wang
Subject: Re: [Qemu-devel] [Qemu-stable] [PATCH V2] net: fix qemu_announce_self not emitting packets
Date: Wed, 8 Jun 2016 15:54:53 +0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.8.0

On 2016年06月08日 15:13, Peter Lieven wrote:
Am 08.06.2016 um 08:39 schrieb Jason Wang:

On 2016年06月07日 21:00, Peter Lieven wrote:
commit fefe2a78 accidently dropped the code path for injecting
raw packets. This feature is needed for sending gratuitous ARPs
after an incoming migration has completed. The result is increased
network downtime for vservers where the network card is not virtio-net

Fixes: fefe2a78abde932e0f340b21bded2c86def1d242
Cc: address@hidden
Cc: address@hidden
Signed-off-by: Peter Lieven <address@hidden>
v1->v2: assert that only raw packets with a plain buffer come in. [Paolo]

   net/net.c | 10 +++++++++-
   1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/net/net.c b/net/net.c
index 5f3e5a9..5e1b5fa 100644
--- a/net/net.c
+++ b/net/net.c
@@ -714,6 +714,11 @@ ssize_t qemu_deliver_packet_iov(NetClientState *sender,
       NetClientState *nc = opaque;
       int ret;
   +    /* we currently only support sending raw packets via 
+     * If we want generic raw iov support we need to implement something like
+     * .receive_raw_iov in NetClientInfo first. */
+    assert(!(flags & QEMU_NET_PACKET_FLAG_RAW) || iovcnt == 1);
       if (nc->link_down) {
           return iov_size(iov, iovcnt);
@@ -722,7 +727,10 @@ ssize_t qemu_deliver_packet_iov(NetClientState *sender,
           return 0;
   -    if (nc->info->receive_iov) {
+    if (flags & QEMU_NET_PACKET_FLAG_RAW && nc->info->receive_raw) {
+        /* this is required for qemu_announce_self() */
+        ret = nc->info->receive_raw(nc, iov[0].iov_base, iov[0].iov_len);
+    } else  if (nc->info->receive_iov) {
           ret = nc->info->receive_iov(nc, iov, iovcnt);
       } else {
           ret = nc_sendv_compat(nc, iov, iovcnt, flags);
We still have raw packet support in nv_sendv_compat, can we use it? (and then 
there's no need for the assert above).
Okay, so Version 1 of the patch is more appropiate. I would either use V1 or 
revert fefe2a78. The issue is quite serious
for live migration.


V1 checks iovcnt and call receive_raw with hard coded first iov. Since we have raw packet support in nc_sendv_compat(), I mean when we detect QEMU_NET_PACKET_FLAG_RAW, call nc_sendv_compat() here.

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