On 2024/10/09 16:41, Jason Wang wrote:
On Tue, Oct 8, 2024 at 2:52 PM Akihiko Odaki <akihiko.od...@daynix.com> wrote:
ipvtap and macvtap create a file for each interface unlike tuntap, which
creates one file shared by all interfaces. Try to open a file dedicated
to the interface first for ipvtap and macvtap.
Management layers usually pass these fds via SCM_RIGHTS. Is this for
testing purposes? (Note that we can use something like -netdev
tap,fd=10 10<>/dev/tap0).
I used this for testing.
Signed-off-by: Akihiko Odaki <akihiko.od...@daynix.com>
---
net/tap-linux.c | 17 ++++++++++++++---
1 file changed, 14 insertions(+), 3 deletions(-)
diff --git a/net/tap-linux.c b/net/tap-linux.c
index 1226d5fda2d9..22ec2f45d2b7 100644
--- a/net/tap-linux.c
+++ b/net/tap-linux.c
@@ -45,10 +45,21 @@ int tap_open(char *ifname, int ifname_size, int *vnet_hdr,
int len = sizeof(struct virtio_net_hdr);
unsigned int features;
- fd = RETRY_ON_EINTR(open(PATH_NET_TUN, O_RDWR));
+
+ ret = if_nametoindex(ifname);
+ if (ret) {
+ g_autofree char *file = g_strdup_printf("/dev/tap%d", ret);
+ fd = open(file, O_RDWR);
+ } else {
+ fd = -1;
+ }
+
if (fd < 0) {
- error_setg_errno(errp, errno, "could not open %s", PATH_NET_TUN);
- return -1;
+ fd = RETRY_ON_EINTR(open(PATH_NET_TUN, O_RDWR));
Any reason tuntap were tried after the macvtap/ipvtap?
If we try tuntap first, we will know that it is not tuntap when calling
TUNSETIFF. We will need to call TUNGETFEATURES and TUNSETVNETHDRSZ again
in such a case because they precede TUNSETIFF. Calling them twice is
troublesome.
This is also consistent with libvirt. libvirt first checks if
g_strdup_printf("/dev/tap%d", ifindex) exists, and falls back to tuntap
otherwise.
Regards,
Akihiko Odaki
+ if (fd < 0) {
+ error_setg_errno(errp, errno, "could not open %s", PATH_NET_TUN);
+ return -1;
+ }
}
memset(&ifr, 0, sizeof(ifr));
ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
---
base-commit: 31669121a01a14732f57c49400bc239cf9fd505f
change-id: 20241008-macvtap-b152e5abb457
Best regards,
--
Akihiko Odaki <akihiko.od...@daynix.com>
Thanks
