wg-quick: freebsd: workaround SIOCGIFSTATUS race in FreeBSD kernel

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

diff --git a/src/wg-quick/freebsd.bash b/src/wg-quick/freebsd.bash
index 9d3a40260e793d3905cb0cbec6c89bf625eda824..72e0bd046ad0717b2e403a52666a218542ebacf5 100755 (executable)
--- a/src/wg-quick/freebsd.bash
+++ b/src/wg-quick/freebsd.bash
@@ -137,18 +137,30 @@ del_routes() {
        done
 }
 
+if_exists() {
+       # HACK: The goal is simply to determine whether or not the interface exists. The
+       # straight-forward way of doing this would be `ifconfig $INTERFACE`, but this
+       # invokes the SIOCGIFSTATUS ioctl, which races with interface shutdown inside
+       # the tun driver, resulting in a kernel panic. So we work around it the stupid
+       # way by using the one utility that appears to call if_nametoindex fairly early
+       # and fails if it doesn't exist: `arp`.
+       if arp -i "$INTERFACE" -a -n >/dev/null 2>&1; then
+               return 0
+       else
+               return 1
+       fi
+}
+
 del_if() {
-       local line monitor_pid
        [[ $HAVE_SET_DNS -eq 0 ]] || unset_dns
-       exec 39< <(exec route -n monitor 2>/dev/null)
-       monitor_pid=$!
        cmd rm -f "/var/run/wireguard/$INTERFACE.sock"
-       while ifconfig "$INTERFACE" >/dev/null 2>&1; do
-               while read -r line; do
-                       [[ $line =~ ^RTM_IFANNOUNCE:.* ]] && break
-               done <&39
+       while if_exists; do
+               # HACK: it would be nice to `route monitor` here and wait for RTM_IFANNOUNCE
+               # but it turns out that the announcement is made before the interface
+               # disappears so we sometimes get a hang. So, we're instead left with polling
+               # in a sleep loop like this.
+               sleep 0.1
        done
-       kill $monitor_pid
 }
 
 up_if() {
@@ -274,7 +286,8 @@ monitor_daemon() {
        # endpoints change.
        while read -r event; do
                [[ $event == RTM_* ]] || continue
-               ifconfig "$INTERFACE" >/dev/null 2>&1 || break
+               [[ -e /var/run/wireguard/$INTERFACE.sock ]] || break
+               if_exists || break
                [[ $AUTO_ROUTE4 -eq 1 || $AUTO_ROUTE6 -eq 1 ]] && set_endpoint_direct_route
                # TODO: set the mtu as well, but only if up
        done < <(route -n monitor)) & disown