On Thu, May 23, 2024 at 10:59:32AM +0100, Richard W.M. Jones wrote:On Wed, May 22, 2024 at 10:59:05PM +0200, Stefano Brivio wrote:Reading the next patch, I see that fd_tap_listen *isn't* the --fd option ... However that doesn't change the analysis.It has nothing to do with tap_sock_unix_init(). It used to be there as that function could be called multiple times per passt instance, but it's not the case anymore. This also takes care of the fact that, with --fd, we wouldn't set the initial MAC address, so we would need to wait for the guest to send us an ARP packet before we could exchange data. Fixes: 6b4e68383c66 ("passt, tap: Add --fd option") Signed-off-by: Stefano Brivio <sbrivio(a)redhat.com> --- tap.c | 12 ++++++------ 1 file changed, 6 insertions(+), 6 deletions(-) diff --git a/tap.c b/tap.c index 91fd2e2..177fe26 100644 --- a/tap.c +++ b/tap.c @@ -1111,12 +1111,6 @@ static void tap_sock_unix_init(struct ctx *c) if (fd < 0) die("UNIX socket: %s", strerror(errno)); - /* In passt mode, we don't know the guest's MAC until it sends - * us packets. Use the broadcast address so our first packets - * will reach it. - */ - memset(&c->mac_guest, 0xff, sizeof(c->mac_guest)); - for (i = 1; i < UNIX_SOCK_MAX; i++) { char *path = addr.sun_path; int ex, ret; @@ -1312,6 +1306,12 @@ void tap_sock_init(struct ctx *c) if (c->mode == MODE_PASST) { if (c->fd_tap_listen == -1) tap_sock_unix_init(c); + + /* In passt mode, we don't know the guest's MAC address until it + * sends us packets. Use the broadcast address so that our + * first packets will reach it. + */ + memset(&c->mac_guest, 0xff, sizeof(c->mac_guest)); } else { tap_sock_tun_init(c); }Reading tap.c, the effect of this is that memset will also be called when c->fd_tap_listen is set (the --fd option). As c cannot be NULLand c->mac_guest exists, this seems safe. Acked-by: Richard W.M. Jones <rjones(a)redhat.com>Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com nbdkit - Flexible, fast NBD server with plugins https://gitlab.com/nbdkit/nbdkit