wg-quick: allow for saving existing interface

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

src/wg-quick.8

@@ -9,6 +9,8 @@ wg-quick - set up a WireGuard interface simply
 .I up
 |
 .I down
+|
+.I save
 ] [
 .I CONFIG_FILE
 |
@@ -24,7 +26,8 @@ Use \fIup\fP to add and set up an interface, and use \fIdown\fP to tear down and
 an interface. Running \fIup\fP adds a WireGuard interface, brings up the interface with the
 supplied IP addresses, sets up mtu and routes, and optionally runs pre/post up scripts. Running \fIdown\fP
 optionally saves the current configuration, removes the WireGuard interface, and optionally
-runs pre/post down scripts.
+runs pre/post down scripts. Running \fIsave\fP saves the configuration of an existing
+interface without bringing the interface down.
 
 \fICONFIG_FILE\fP is a configuration file, whose filename is the interface name
 followed by `.conf'. Otherwise, \fIINTERFACE\fP is an interface name, with configuration

src/wg-quick.bash

@@ -213,7 +213,7 @@ execute_hooks() {
 
 cmd_usage() {
 	cat >&2 <<-_EOF
-	Usage: $PROGRAM [ up | down ] [ CONFIG_FILE | INTERFACE ]
+	Usage: $PROGRAM [ up | down | save ] [ CONFIG_FILE | INTERFACE ]
 
 	  CONFIG_FILE is a configuration file, whose filename is the interface name
 	  followed by \`.conf'. Otherwise, INTERFACE is an interface name, with
@@ -264,6 +264,11 @@ cmd_down() {
 	execute_hooks "${POST_DOWN[@]}"
 }
 
+cmd_save() {
+	[[ " $(wg show interfaces) " == *" $INTERFACE "* ]] || die "\`$INTERFACE' is not a WireGuard interface"
+	save_config
+}
+
 # ~~ function override insertion point ~~
 
 if [[ $# -eq 1 && ( $1 == --help || $1 == -h || $1 == help ) ]]; then
@@ -276,6 +281,10 @@ elif [[ $# -eq 2 && $1 == down ]]; then
 	auto_su
 	parse_options "$2"
 	cmd_down
+elif [[ $# -eq 2 && $1 == save ]]; then
+	auto_su
+	parse_options "$2"
+	cmd_save
 else
 	cmd_usage
 	exit 1