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kvmtool: Add minimal support for macvtap

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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 <marc.zyngier@arm.com>
Signed-off-by: Will Deacon <will.deacon@arm.com>
This commit is contained in:
Marc Zyngier
2015-03-27 13:48:18 +00:00
committed by Will Deacon
parent 9c2e1d1a08
commit d2a7ddff46
1 changed files with 26 additions and 14 deletions
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40
virtio/net.c
View File

@@ -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);