wg-quick: remember to rewind DNS settings on failure

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

diff --git a/src/wg-quick.bash b/src/wg-quick.bash
index def78af084332563eafcab32299253c06edb5cf9..b98a18b37758afd3c5e8a6d64cffb6de59bd4fc8 100755 (executable)
--- a/src/wg-quick.bash
+++ b/src/wg-quick.bash
@@ -83,6 +83,7 @@ add_if() {
 
 del_if() {
        local fwmark
+       [[ $HAVE_SET_DNS -eq 0 ]] || unset_dns
        fwmark="$(wg show "$INTERFACE" fwmark)"
        DEFAULT_TABLE=0
        [[ $fwmark != off ]] && DEFAULT_TABLE=$(( fwmark ))
@@ -130,12 +131,16 @@ set_mtu() {
        cmd ip link set mtu $(( mtu - 80 )) dev "$INTERFACE"
 }
 
+HAVE_SET_DNS=0
 set_dns() {
-       [[ ${#DNS[@]} -eq 0 ]] || printf 'nameserver %s\n' "${DNS[@]}" | cmd resolvconf -a "tun.$INTERFACE" -m 0 -x
+       [[ ${#DNS[@]} -gt 0 ]] || return 0
+       printf 'nameserver %s\n' "${DNS[@]}" | cmd resolvconf -a "tun.$INTERFACE" -m 0 -x
+       HAVE_SET_DNS=1
 }
 
 unset_dns() {
-       [[ ${#DNS[@]} -eq 0 ]] || cmd resolvconf -d "tun.$INTERFACE"
+       [[ ${#DNS[@]} -gt 0 ]] || return 0
+       cmd resolvconf -d "tun.$INTERFACE"
 }
 
 add_route() {
@@ -254,8 +259,8 @@ cmd_down() {
        [[ " $(wg show interfaces) " == *" $INTERFACE "* ]] || die "\`$INTERFACE' is not a WireGuard interface"
        execute_hooks "${PRE_DOWN[@]}"
        [[ $SAVE_CONFIG -eq 0 ]] || save_config
-       unset_dns
        del_if
+       unset_dns
        execute_hooks "${POST_DOWN[@]}"
 }