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tap: More detailed error reporting in tap_ns_tun()

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There are several possible failure points in tap_ns_tun(), but if anything
goes wrong, we just set tun_ns_fd to -1 resulting in the same error
message.

Add more detailed error reporting to the various failure points.  At the
same time, we know this is only called from tap_sock_tun_init() which will
terminate pasta if we fail, so we can simplify things a little because we
don't need to close() the fd on the failure paths.

Link: https://bugs.passt.top/show_bug.cgi?id=69
Link: https://github.com/containers/podman/issues/19428
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
This commit is contained in:
David Gibson 2023-08-02 13:15:41 +10:00 committed by Stefano Brivio
parent 6920adda0d
commit 7bc9b66fc2
1 changed files with 16 additions and 9 deletions
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25
tap.c
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@ -1171,7 +1171,7 @@ static int tun_ns_fd = -1;
* tap_ns_tun() - Get tuntap fd in namespace
* @c: Execution context
*
* Return: 0
* Return: 0 on success, exits on failure
*
* #syscalls:pasta ioctl openat
*/
@ -1180,17 +1180,24 @@ static int tap_ns_tun(void *arg)
struct ifreq ifr = { .ifr_flags = IFF_TAP | IFF_NO_PI };
int flags = O_RDWR | O_NONBLOCK | O_CLOEXEC;
struct ctx *c = (struct ctx *)arg;
int fd, rc;
tun_ns_fd = -1;
memcpy(ifr.ifr_name, c->pasta_ifn, IFNAMSIZ);
ns_enter(c);
if ((tun_ns_fd = open("/dev/net/tun", flags)) < 0 ||
ioctl(tun_ns_fd, TUNSETIFF, &ifr) ||
!(c->pasta_ifi = if_nametoindex(c->pasta_ifn))) {
if (tun_ns_fd != -1)
close(tun_ns_fd);
tun_ns_fd = -1;
}
fd = open("/dev/net/tun", flags);
if (fd < 0)
die("Failed to open() /dev/net/tun: %s", strerror(errno));
rc = ioctl(fd, TUNSETIFF, &ifr);
if (rc < 0)
die("TUNSETIFF failed: %s", strerror(errno));
if (!(c->pasta_ifi = if_nametoindex(c->pasta_ifn)))
die("Tap device opened but no network interface found");
tun_ns_fd = fd;
return 0;
}
@ -1205,7 +1212,7 @@ static void tap_sock_tun_init(struct ctx *c)
NS_CALL(tap_ns_tun, c);
if (tun_ns_fd == -1)
die("Failed to open tun socket in namespace");
die("Failed to set up tap device in namespace");
pasta_ns_conf(c);