IAPP: Set SO_REUSEADDR on listening socket

Make it possible for several instances of hostapd to listen on the same
network interface.

Signed-off-by: Petko Bordjukov <bordjukov@gmail.com>

src/ap/iapp.c

@@ -381,6 +381,7 @@ struct iapp_data * iapp_init(struct hostapd_data *hapd, const char *iface)
 	struct sockaddr_in *paddr, uaddr;
 	struct iapp_data *iapp;
 	struct ip_mreqn mreq;
+	int reuseaddr = 1;
 
 	iapp = os_zalloc(sizeof(*iapp));
 	if (iapp == NULL)
@@ -443,6 +444,18 @@ struct iapp_data * iapp_init(struct hostapd_data *hapd, const char *iface)
 	os_memset(&uaddr, 0, sizeof(uaddr));
 	uaddr.sin_family = AF_INET;
 	uaddr.sin_port = htons(IAPP_UDP_PORT);
+
+	if (setsockopt(iapp->udp_sock, SOL_SOCKET, SO_REUSEADDR, &reuseaddr,
+		       sizeof(reuseaddr)) < 0) {
+		wpa_printf(MSG_INFO,
+			   "iapp_init - setsockopt[UDP,SO_REUSEADDR]: %s",
+			   strerror(errno));
+		/*
+		 * Ignore this and try to continue. This is fine for single
+		 * BSS cases, but may fail if multiple BSSes enable IAPP.
+		 */
+	}
+
 	if (bind(iapp->udp_sock, (struct sockaddr *) &uaddr,
 		 sizeof(uaddr)) < 0) {
 		wpa_printf(MSG_INFO, "iapp_init - bind[UDP]: %s",