nl80211: Ignore netlink interface down if interface is up

The netlink event processing is delayed since they are only returned
after control returns to eloop. This can result in netlink down events
being processed at a point when the interface has is actually still
there (the first event on new interface is down) and that can result in
odd behavior especially when the resulting interface-disabled event is
delivered to AP mode interface with wpa_supplicant.

Work around this by filtering netlink down events if the matching
interface is up at the time the netlink event is processed. This fixes
an issue brought up by commit 36d84860bbe09641f782fcc21b09e5a6952b4629.

src/drivers/driver_nl80211.c

@@ -601,6 +601,14 @@ static void wpa_driver_nl80211_event_rtm_newlink(void *ctx,
 		   (ifi->ifi_flags & IFF_DORMANT) ? "[DORMANT]" : "");
 
 	if (!drv->if_disabled && !(ifi->ifi_flags & IFF_UP)) {
+		char namebuf[IFNAMSIZ];
+		if (if_indextoname(ifi->ifi_index, namebuf) &&
+		    linux_iface_up(drv->global->ioctl_sock,
+				   drv->first_bss.ifname) > 0) {
+			wpa_printf(MSG_DEBUG, "nl80211: Ignore interface down "
+				   "event since interface %s is up", namebuf);
+			return;
+		}
 		wpa_printf(MSG_DEBUG, "nl80211: Interface down");
 		if (drv->ignore_if_down_event) {
 			wpa_printf(MSG_DEBUG, "nl80211: Ignore interface down "

src/drivers/linux_ioctl.c

@@ -60,6 +60,28 @@ int linux_set_iface_flags(int sock, const char *ifname, int dev_up)
 }
 
 
+int linux_iface_up(int sock, const char *ifname)
+{
+	struct ifreq ifr;
+	int ret;
+
+	if (sock < 0)
+		return -1;
+
+	os_memset(&ifr, 0, sizeof(ifr));
+	os_strlcpy(ifr.ifr_name, ifname, IFNAMSIZ);
+
+	if (ioctl(sock, SIOCGIFFLAGS, &ifr) != 0) {
+		ret = errno ? -errno : -999;
+		wpa_printf(MSG_ERROR, "Could not read interface %s flags: %s",
+			   ifname, strerror(errno));
+		return ret;
+	}
+
+	return !!(ifr.ifr_flags & IFF_UP);
+}
+
+
 int linux_get_ifhwaddr(int sock, const char *ifname, u8 *addr)
 {
 	struct ifreq ifr;

src/drivers/linux_ioctl.h

@@ -16,6 +16,7 @@
 #define LINUX_IOCTL_H
 
 int linux_set_iface_flags(int sock, const char *ifname, int dev_up);
+int linux_iface_up(int sock, const char *ifname);
 int linux_get_ifhwaddr(int sock, const char *ifname, u8 *addr);
 int linux_set_ifhwaddr(int sock, const char *ifname, const u8 *addr);
 int linux_br_add(int sock, const char *brname);