Handle tun/tap device returning EPERM or EBUSY.

Often when tun/tap is used any errors during setup will be confuse tinc
and it will then assume it is an Ethertap device. Try to avoid this by
checking errno after a failed TUNSETIFF; if it's EPERM or EBUSY then
we can be sure it was not an Ethertap device, and we should report an
error instead.

Closes #157 on GitHub.

diff --git a/src/linux/device.c b/src/linux/device.c
index f75f4bd..990de6a 100644 (file)
--- a/src/linux/device.c
+++ b/src/linux/device.c
@@ -125,6 +125,9 @@ static bool setup_device(void) {
                ifrname[IFNAMSIZ - 1] = 0;
                free(iface);
                iface = xstrdup(ifrname);
+       } else if(errno == EPERM || errno == EBUSY) {
+               logger(LOG_ERR, "Error while trying to configure %s: %s", device, strerror(errno));
+               return false;
        } else if(!ioctl(device_fd, (('T' << 8) | 202), &ifr)) {
                logger(LOG_WARNING, "Old ioctl() request was needed for %s", device);
                strncpy(ifrname, ifr.ifr_name, IFNAMSIZ);