Support a script to be executed when the device goes up

This adds the `ifup_script` config option. The script receives the
following environment variables as input:

- NET_DEVICE: The name of the network device of the VPN.
- DNS_SUFFIX: DNS domain search prefix, if provided by the VPN server.
- DNS_SERVERS: A list of the DNS server addresses if provided by the VPN
  server.

src/config.c

@@ -267,6 +267,9 @@ int load_config(struct vpn_config *cfg, const char *filename)
 		} else if (strcmp(key, "realm") == 0) {
 			strncpy(cfg->realm, val, FIELD_SIZE - 1);
 			cfg->realm[FIELD_SIZE] = '\0';
+		} else if (strcmp(key, "ifup-script") == 0) {
+			strncpy(cfg->ifup_script, val, MAXPATHLEN - 1);
+			cfg->ifup_script[MAXPATHLEN] = '\0';
 		} else if (strcmp(key, "set-dns") == 0) {
 			int set_dns = strtob(val);
 

src/config.h

@@ -21,6 +21,7 @@
 #include <errno.h>
 #include <string.h>
 #include <sys/types.h>
+#include <sys/param.h>
 #include <netinet/in.h>
 
 #define ERR_CFG_UNKNOWN		-1
@@ -57,6 +58,7 @@ struct x509_digest {
 };
 
 #define FIELD_SIZE	64
+#define SCRIPT_PATH	MAXPATHLEN
 #define COOKIE_SIZE	4096
 
 struct vpn_config {
@@ -70,6 +72,7 @@ struct vpn_config {
 	unsigned int  otp_delay;
 	char		*pinentry;
 	char		realm[FIELD_SIZE + 1];
+	char		ifup_script[SCRIPT_PATH + 1];
 
 	int	set_routes;
 	int	set_dns;

src/tunnel.c

@@ -101,13 +101,39 @@ static int ofv_append_varr(struct ofv_varr *p, const char *x)
 	return 0;
 }
 
+static int ipv4_run_ifup_script(struct tunnel *tunnel)
+{
+	char ns[32];
+
+	setenv("NET_DEVICE", tunnel->ppp_iface, 0);
+
+	ns[0] = '\0';
+
+	if (tunnel->ipv4.ns1_addr.s_addr != 0)
+		strncat(ns, inet_ntoa(tunnel->ipv4.ns1_addr), 15);
+
+	if (tunnel->ipv4.ns2_addr.s_addr != 0) {
+		strcpy(ns, " ");
+		strncat(ns, inet_ntoa(tunnel->ipv4.ns2_addr), 15);
+	}
+
+	setenv("DNS_SERVERS", ns, 0);
+
+	if (tunnel->ipv4.dns_suffix != NULL)
+		setenv("DNS_SUFFIX", tunnel->ipv4.dns_suffix, 0);
+	else
+		setenv("DNS_SUFFIX", "", 0);
+
+	return system(tunnel->config->ifup_script);
+}
+
 static int on_ppp_if_up(struct tunnel *tunnel)
 {
+	int ret;
+
 	log_info("Interface %s is UP.\n", tunnel->ppp_iface);
 
 	if (tunnel->config->set_routes) {
-		int ret;
-
 		log_info("Setting new routes...\n");
 
 		ret = ipv4_set_tunnel_routes(tunnel);
@@ -121,6 +147,13 @@ static int on_ppp_if_up(struct tunnel *tunnel)
 		ipv4_add_nameservers_to_resolv_conf(tunnel);
 	}
 
+	if (tunnel->config->ifup_script) {
+		log_info("Running `ifup` script...\n");
+		ret = ipv4_run_ifup_script(tunnel);
+		if (ret != 0)
+			log_warn("The `ifup` script failed. Please check your logs.\n");
+	}
+
 	log_info("Tunnel is up and running.\n");
 
 #if HAVE_SYSTEMD