P2P: Derive group interface name bit more sensibly

The interface name for the P2P group interface is derived from the
P2P management interface. When the P2P management interface is a
P2P Device interface, i.e., p2p-dev-wlanX, the name for the group
interface is abbreviated to p2p-X (X being group index). When the
P2P management interface starts with p2p-dev- use its postfix
instead. So P2P management interface p2p-dev-wlan3 results in group
interface name p2p-wlan3-0.

Signed-hostap: Arend van Spriel <arend@broadcom.com>

wpa_supplicant/p2p_supplicant.c

@@ -61,6 +61,8 @@
 #define P2P_CONCURRENT_SEARCH_DELAY 500
 #endif /* P2P_CONCURRENT_SEARCH_DELAY */
 
+#define P2P_MGMT_DEVICE_PREFIX		"p2p-dev-"
+
 enum p2p_group_removal_reason {
 	P2P_GROUP_REMOVAL_UNKNOWN,
 	P2P_GROUP_REMOVAL_SILENT,
@@ -983,6 +985,26 @@ static void wpas_p2p_clone_config(struct wpa_supplicant *dst,
 }
 
 
+static void wpas_p2p_get_group_ifname(struct wpa_supplicant *wpa_s,
+				      char *ifname, size_t len)
+{
+	char *ifname_ptr = wpa_s->ifname;
+
+	if (os_strncmp(wpa_s->ifname, P2P_MGMT_DEVICE_PREFIX,
+		       os_strlen(P2P_MGMT_DEVICE_PREFIX)) == 0) {
+		ifname_ptr = os_strrchr(wpa_s->ifname, '-') + 1;
+	}
+
+	os_snprintf(ifname, len, "p2p-%s-%d", ifname_ptr, wpa_s->p2p_group_idx);
+	if (os_strlen(ifname) >= IFNAMSIZ &&
+	    os_strlen(wpa_s->ifname) < IFNAMSIZ) {
+		/* Try to avoid going over the IFNAMSIZ length limit */
+		os_snprintf(ifname, sizeof(ifname), "p2p-%d",
+			    wpa_s->p2p_group_idx);
+	}
+}
+
+
 static int wpas_p2p_add_group_interface(struct wpa_supplicant *wpa_s,
 					enum wpa_driver_if_type type)
 {
@@ -1000,14 +1022,7 @@ static int wpas_p2p_add_group_interface(struct wpa_supplicant *wpa_s,
 		return 0;
 	}
 
-	os_snprintf(ifname, sizeof(ifname), "p2p-%s-%d", wpa_s->ifname,
-		    wpa_s->p2p_group_idx);
-	if (os_strlen(ifname) >= IFNAMSIZ &&
-	    os_strlen(wpa_s->ifname) < IFNAMSIZ) {
-		/* Try to avoid going over the IFNAMSIZ length limit */
-		os_snprintf(ifname, sizeof(ifname), "p2p-%d",
-			    wpa_s->p2p_group_idx);
-	}
+	wpas_p2p_get_group_ifname(wpa_s, ifname, sizeof(ifname));
 	force_ifname[0] = '\0';
 
 	wpa_printf(MSG_DEBUG, "P2P: Create a new interface %s for the group",
@@ -2983,7 +2998,8 @@ int wpas_p2p_add_p2pdev_interface(struct wpa_supplicant *wpa_s)
 	char force_name[100];
 	int ret;
 
-	os_snprintf(ifname, sizeof(ifname), "p2p-dev-%s", wpa_s->ifname);
+	os_snprintf(ifname, sizeof(ifname), P2P_MGMT_DEVICE_PREFIX "%s",
+		    wpa_s->ifname);
 	force_name[0] = '\0';
 	wpa_s->pending_interface_type = WPA_IF_P2P_DEVICE;
 	ret = wpa_drv_if_add(wpa_s, WPA_IF_P2P_DEVICE, ifname, NULL, NULL,