[PATCH v2 41/42] wireguard: Fix FQDN by using the resolved IP as the gateway

This fixes the hostname use with WireGuard by using the resolved IP as
the gateway for the ipaddress. This address will be sent to connmand for
setting up the routes and DNS will be otherwise broken if the FQDN is
set "as is" as the gateway.

By returning also the resolved IP in string format in the initial
resolve, and setting it as the gateway for the address for the interface
in in the ipaddress.c the FQDN using WireGuard services can be used.
---
 vpn/plugins/wireguard.c | 80 +++++++++++++++++++++++++----------------
 1 file changed, 50 insertions(+), 30 deletions(-)

diff --git a/vpn/plugins/wireguard.c b/vpn/plugins/wireguard.c
index a99d0b75..123fd3ab 100644
--- a/vpn/plugins/wireguard.c
+++ b/vpn/plugins/wireguard.c
@@ -249,10 +249,35 @@ static int get_endpoint_addr(const char *host, const char *port, int flags,
 	return 0;
 }
 
+static const char *endpoint_to_str(struct wg_peer *peer, char *buf,
+							socklen_t len)
+{
+	struct sockaddr_u *addr;
+	int family;
+
+	addr = (struct sockaddr_u *)&peer->endpoint.addr;
+	family = peer->endpoint.addr.sa_family;
+
+	switch (family) {
+	case AF_INET:
+		return inet_ntop(family, &addr->sin.sin_addr, buf, len);
+	case AF_INET6:
+		return inet_ntop(family, &addr->sin6.sin6_addr, buf, len);
+	default:
+		break;
+	}
+
+	return NULL;
+}
+
 static int parse_endpoint_hostname(const char *host, const char *port,
-							struct sockaddr_u *addr)
+							struct wg_peer *peer,
+							char **gateway_resolved)
 {
+	struct sockaddr_u *addr;
 	char **tokens;
+	const char *gw = NULL;
+	char buf[INET6_ADDRSTRLEN] = { 0 };
 	unsigned int len;
 	int err;
 
@@ -271,9 +296,21 @@ static int parse_endpoint_hostname(const char *host, const char *port,
 
 	DBG("using host %s", tokens[0]);
 
+	addr = (struct sockaddr_u *)&peer->endpoint.addr;
+
 	err = get_endpoint_addr(tokens[0], port, 0, addr);
-	if (!err)
+	if (!err) {
+		/*
+		 * In case the endpoint is an host address use the resolved
+		 * IP address as gateway for DNS over WireGuard to work.
+		 */
+		if (connman_inet_check_ipaddress(tokens[0]) <= 0)
+			gw = endpoint_to_str(peer, buf, INET6_ADDRSTRLEN);
+
 		DBG("success");
+	}
+
+	*gateway_resolved = gw ? g_strdup(gw) : g_strdup(tokens[0]);
 
 	g_strfreev(tokens);
 
@@ -651,27 +688,6 @@ static gboolean wg_dns_reresolve_cb(gpointer user_data)
 	return G_SOURCE_REMOVE;
 }
 
-static const char *endpoint_to_str(struct wg_peer *peer, char *buf,
-							socklen_t len)
-{
-	struct sockaddr_u *addr;
-	int family;
-
-	addr = (struct sockaddr_u *)&peer->endpoint.addr;
-	family = peer->endpoint.addr.sa_family;
-
-	switch (family) {
-	case AF_INET:
-		return inet_ntop(family, &addr->sin.sin_addr, buf, len);
-	case AF_INET6:
-		return inet_ntop(family, &addr->sin6.sin6_addr, buf, len);
-	default:
-		break;
-	}
-
-	return NULL;
-}
-
 static gboolean wg_route_setup_cb(gpointer user_data)
 {
 	struct wireguard_info *info = user_data;
@@ -770,7 +786,9 @@ static int wg_connect(struct vpn_provider *provider,
 {
 	struct wg_ipaddresses ipaddresses = { 0 };
 	struct wireguard_info *info;
-	const char *option, *gateway;
+	const char *option;
+	const char *endpoint;
+	char *gateway = NULL;
 	char *ifname;
 	bool do_split_routing = true;
 	int err = -EINVAL;
@@ -859,21 +877,20 @@ static int wg_connect(struct vpn_provider *provider,
 	if (!option)
 		option = "51820";
 
-	gateway = vpn_provider_get_string(provider, "Host");
+	endpoint = vpn_provider_get_string(provider, "Host");
 	/*
 	 * Use the resolve timeout only with re-resolve. Here the network
 	 * is setup as the transport is used. In succeeding attempts resolving
 	 * is needed as it is done over potentially misconfigured WireGuard
 	 * connection that may end up blocking vpnd with getaddrinfo().
 	 */
-	err = parse_endpoint_hostname(gateway, option,
-			(struct sockaddr_u *)&info->peer.endpoint.addr);
+	err = parse_endpoint_hostname(endpoint, option, &info->peer, &gateway);
 	if (err) {
-		DBG("Failed to parse endpoint %s:%s", gateway, option);
+		DBG("Failed to parse endpoint %s:%s", endpoint, option);
 		goto error;
 	}
 
-	info->endpoint_fqdn = g_strdup(gateway);
+	info->endpoint_fqdn = g_strdup(endpoint);
 	info->port = g_strdup(option);
 
 	option = vpn_provider_get_string(provider, "WireGuard.Address");
@@ -881,11 +898,14 @@ static int wg_connect(struct vpn_provider *provider,
 		DBG("Missing WireGuard.Address configuration");
 		goto error;
 	}
+
 	err = parse_addresses(option, gateway, &ipaddresses);
 	if (err) {
-		DBG("Failed to parse addresses %s gateway %s", option, gateway);
+		DBG("Failed to parse addresses %s endpoint %s gateway %s",
+						option, endpoint, gateway);
 		goto error;
 	}
+	g_free(gateway);
 
 	ifname = get_ifname();
 	if (!ifname) {
-- 
2.39.5