In order to be useable by kvmtool, a macvtap interface requires
some minimal configuration (basically setting up the offload bits).
This requires skipping some of the low level TUN/TAP setup.
To avoid adding yet another option, we extend the 'tapif' option
to detect the use of a file (such as /dev/tap23).
Assuming you've run the following as root:
# ip link add link eth0 name kvmtap0 type macvtap mode bridge
# chgrp kvm /dev/tap$(< /sys/class/net/kvmtap0/ifindex)
# chmod g+rw /dev/tap$(< /sys/class/net/kvmtap0/ifindex)
it is fairly easy to have a script that does the following:
#!/bin/sh
addr=$(< /sys/class/net/kvmtap0/address)
tap=/dev/tap$(< /sys/class/net/kvmtap0/ifindex)
kvmtool/lkvm run --console virtio \
-k /boot/zImage \
-p "console=hvc0 earlyprintk" \
-n trans=mmio,mode=tap,tapif=$tap,guest_mac=$addr
and you now have your VM running, directly attached to the network.
This patch also removes the TUNSETNOCSUM ioctl that has declared
obsolete for quite some time now...
Signed-off-by: Marc Zyngier <[email protected]>
---
tools/kvm/virtio/net.c | 40 ++++++++++++++++++++++++++--------------
1 file changed, 26 insertions(+), 14 deletions(-)
diff --git a/tools/kvm/virtio/net.c b/tools/kvm/virtio/net.c
index ecdb94e..25b9496 100644
--- a/tools/kvm/virtio/net.c
+++ b/tools/kvm/virtio/net.c
@@ -276,6 +276,23 @@ static void virtio_net_handle_callback(struct kvm *kvm,
struct net_dev *ndev, in
mutex_unlock(&ndev->io_lock[queue]);
}
+static int virtio_net_request_tap(struct net_dev *ndev, struct ifreq *ifr,
+ const char *tapname)
+{
+ int ret;
+
+ memset(ifr, 0, sizeof(*ifr));
+ ifr->ifr_flags = IFF_TAP | IFF_NO_PI | IFF_VNET_HDR;
+ if (tapname)
+ strncpy(ifr->ifr_name, tapname, sizeof(ifr->ifr_name));
+
+ ret = ioctl(ndev->tap_fd, TUNSETIFF, &ifr);
+
+ if (ret >= 0)
+ strncpy(ndev->tap_name, ifr->ifr_name, sizeof(ndev->tap_name));
+ return ret;
+}
+
static bool virtio_net__tap_init(struct net_dev *ndev)
{
int sock = socket(AF_INET, SOCK_STREAM, 0);
@@ -284,6 +301,8 @@ static bool virtio_net__tap_init(struct net_dev *ndev)
struct ifreq ifr;
const struct virtio_net_params *params = ndev->params;
bool skipconf = !!params->tapif;
+ bool macvtap = skipconf && (params->tapif[0] == '/');
+ const char *tap_file = "/dev/net/tun";
/* Did the user already gave us the FD? */
if (params->fd) {
@@ -291,28 +310,21 @@ static bool virtio_net__tap_init(struct net_dev *ndev)
return 1;
}
- ndev->tap_fd = open("/dev/net/tun", O_RDWR);
+ if (macvtap)
+ tap_file = params->tapif;
+
+ ndev->tap_fd = open(tap_file, O_RDWR);
if (ndev->tap_fd < 0) {
- pr_warning("Unable to open /dev/net/tun");
+ pr_warning("Unable to open %s", tap_file);
goto fail;
}
- memset(&ifr, 0, sizeof(ifr));
- ifr.ifr_flags = IFF_TAP | IFF_NO_PI | IFF_VNET_HDR;
- if (params->tapif)
- strncpy(ifr.ifr_name, params->tapif, sizeof(ifr.ifr_name));
- if (ioctl(ndev->tap_fd, TUNSETIFF, &ifr) < 0) {
+ if (!macvtap &&
+ virtio_net_request_tap(ndev, &ifr, params->tapif) < 0) {
pr_warning("Config tap device error. Are you root?");
goto fail;
}
- strncpy(ndev->tap_name, ifr.ifr_name, sizeof(ndev->tap_name));
-
- if (ioctl(ndev->tap_fd, TUNSETNOCSUM, 1) < 0) {
- pr_warning("Config tap device TUNSETNOCSUM error");
- goto fail;
- }
-
hdr_len = has_virtio_feature(ndev, VIRTIO_NET_F_MRG_RXBUF) ?
sizeof(struct virtio_net_hdr_mrg_rxbuf) :
sizeof(struct virtio_net_hdr);
--
2.1.4
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