libvlc: add basic UPnP adapter discovery

This fixes #398 (closed) for execution on iOS and tvOS devices

Resources/MobileVLCKit/patches/0031-upnp-add-basic-network-interface-discovery-for-iOS-a.patch

+From b0c79859d5de6f99f711be12449699d6cc028f58 Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?Felix=20Paul=20K=C3=BChne?= <felix@feepk.net>
+Date: Wed, 1 Jul 2020 13:45:29 +0200
+Subject: [PATCH 31/31] upnp: add basic network interface discovery for iOS and
+ tvOS
+
+---
+ modules/services_discovery/upnp.cpp | 47 +++++++++++++++++++++++++++--
+ 1 file changed, 45 insertions(+), 2 deletions(-)
+
+diff --git a/modules/services_discovery/upnp.cpp b/modules/services_discovery/upnp.cpp
+index 13c1eb7971..3e7e39a225 100644
+--- a/modules/services_discovery/upnp.cpp
++++ b/modules/services_discovery/upnp.cpp
+@@ -1621,9 +1621,52 @@ inline char *getPreferedAdapter()
+ }
+ #else
+ 
+-static char *getPreferedAdapter()
++inline bool necessaryFlagsSetOnInterface(struct ifaddrs *anInterface, const char *nameToCompare)
+ {
+-    return NULL;
++    if (strncmp (anInterface->ifa_name, nameToCompare, strlen(nameToCompare)) == 0) {
++        unsigned int flags = anInterface->ifa_flags;
++        if( (flags & IFF_UP) && (flags & IFF_RUNNING) && !(flags & IFF_LOOPBACK) ) {
++            return true;
++        }
++    }
++    return false;
++}
++
++inline char *getPreferedAdapter()
++{
++    struct ifaddrs *listOfInterfaces = NULL;
++    struct ifaddrs *anInterface = NULL;
++    int ret = getifaddrs(&listOfInterfaces);
++    char *adapterName = NULL;
++
++    if (ret == 0) {
++        anInterface = listOfInterfaces;
++
++        while (anInterface != NULL) {
++            bool ret = necessaryFlagsSetOnInterface(anInterface, "en0");
++            if (ret) {
++                adapterName = strdup(anInterface->ifa_name);
++                break;
++            }
++
++            ret = necessaryFlagsSetOnInterface(anInterface, "en1");
++            if (ret) {
++                adapterName = strdup(anInterface->ifa_name);
++                break;
++            }
++
++            ret = necessaryFlagsSetOnInterface(anInterface, "bridge100");
++            if (ret) {
++                adapterName = strdup(anInterface->ifa_name);
++                break;
++            }
++
++            anInterface = anInterface->ifa_next;
++        }
++    }
++    freeifaddrs(listOfInterfaces);
++
++    return adapterName;
+ }
+ 
+ #endif
+-- 
+2.21.1 (Apple Git-122.3)
+