Re: [Qemu-stable] [Qemu-devel] [PATCH V2] net: fix qemu_announce_self not emitting packets

[Jason Wang]

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
> > > with the VIRTIO_NET_F_GUEST_ANNOUNCE feature.
> > >
> > > 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 
> > > qemu_send_packet_raw.
> > > +     * 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.
>
> Peter

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.