Allow netdev_del followed by netdev_add to re-peer a NIC and its netdev: (qemu) info network virtio-net-pci.0: type=nic,model=virtio-net-pci,macaddr=52:54:00:12:34:56 \ netdev0: type=user,net=10.0.2.0,restrict=off
(qemu) netdev_del netdev0 (qemu) netdev_add socket,id=netdev0,listen=:1234 (qemu) info network virtio-net-pci.0: type=nic,model=virtio-net-pci,macaddr=52:54:00:12:34:56 \ netdev0: type=socket, This makes it possible to switch netdev while the guest is running. It is not necessary to reset the NIC. Note that the NIC's link goes down in netdev_del and back up again in netdev_add. Therefore the guest becomes aware that the network has changed, although this depends on the emulated NIC model providing link status change interrupts. Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com> --- This patch addresses the netdev hotplug issue that has been discussed previously on the mailing list: https://www.redhat.com/archives/libvir-list/2012-October/msg00629.html Initially I thought we need to add a new monitor command. After looking at the code it seems that simply allowing netdev_del followed by netdev_add (as suggested by Laine) is the simplest way to solve the problem. No new monitor commands are necessary. The current code is not safe with virtio-net + tap, where the virtio-net device reports offload features from the tap device to the guest. If you try to switch to a -netdev user or -netdev socket device, those offload capabilities are not present and network communication will fail. Laine: Please try this out and see if it works for your use case. net.c | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) diff --git a/net.c b/net.c index ae4bc0d..d7c60b0 100644 --- a/net.c +++ b/net.c @@ -619,6 +619,19 @@ static int (* const net_client_init_fun[NET_CLIENT_OPTIONS_KIND_MAX])( [NET_CLIENT_OPTIONS_KIND_HUBPORT] = net_init_hubport, }; +static NICState *net_find_nic_for_peername(const char *name) +{ + NetClientState *nc; + QTAILQ_FOREACH(nc, &net_clients, next) { + if (nc->info->type != NET_CLIENT_OPTIONS_KIND_NIC) { + continue; + } + if (nc->peer && strcmp(nc->peer->name, name) == 0) { + return (NICState *)nc; + } + } + return NULL; +} static int net_client_init1(const void *object, int is_netdev, Error **errp) { @@ -678,6 +691,25 @@ static int net_client_init1(const void *object, int is_netdev, Error **errp) NetClientOptionsKind_lookup[opts->kind]); return -1; } + + /* Peer with existing nic if netdev name matches */ + if (is_netdev && opts->kind != NET_CLIENT_OPTIONS_KIND_NIC) { + NICState *nic = net_find_nic_for_peername(name); + if (nic && nic->peer_deleted) { + NetClientState *netdev = qemu_find_netdev(name); + + /* TODO vnet_hdr compatibility check */ + + qemu_free_net_client(nic->nc.peer); + nic->nc.peer = netdev; + netdev->peer = &nic->nc; + nic->peer_deleted = false; + nic->nc.link_down = false; + if (nic->nc.info->link_status_changed) { + nic->nc.info->link_status_changed(&nic->nc); + } + } + } } return 0; } -- 1.7.11.7
