[FFmpeg-devel] [PATCH v3 2/5] avformat/udp: Select output interfaces for ipv6 multicast

[Peter Enderborg via ffmpeg-devel <ffmpeg-devel@ffmpeg.org>]

This fixes two old TODO's in ipv6 multicast handling.
If the system as SIOCGIFINDEX ioctl a helper function to iterate over
all interfaces added to join the multicast group on interface if approperite.

The default value is IN6ADDR_ANY (::) and it then joins all interfaces
that are up and have multicast support. Local address can be
specified and then it join ALL interfaces that use that specific
local address.

Limitations (TODO's)
Handling when network configuration is changed. if up/down etc.

Change-Id: Ifea9c0504469b108de94643a525d9b55fad5466f
Signed-off-by: Peter Enderborg <peterend@axis.com>
---
 libavformat/udp.c | 101 +++++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 99 insertions(+), 2 deletions(-)

diff --git a/libavformat/udp.c b/libavformat/udp.c
index 84f9d3e62e..9ffd55e017 100644
--- a/libavformat/udp.c
+++ b/libavformat/udp.c
@@ -68,6 +68,13 @@
 #include "libavutil/thread.h"
 #endif
 
+#if HAVE_STRUCT_IPV6_MREQ && HAVE_IOCTL_GIFINDEX && defined(IPPROTO_IPV6)
+#include <sys/types.h>
+#include <net/if.h>
+#include <sys/ioctl.h>
+#include <ifaddrs.h>
+#endif
+
 #ifndef IPV6_ADD_MEMBERSHIP
 #define IPV6_ADD_MEMBERSHIP IPV6_JOIN_GROUP
 #define IPV6_DROP_MEMBERSHIP IPV6_LEAVE_GROUP
@@ -205,6 +212,82 @@ static int udp_set_multicast_ttl(int sockfd, int mcastTTL,
 
     return 0;
 }
+#if HAVE_STRUCT_IPV6_MREQ && HAVE_IOCTL_GIFINDEX && defined(IPPROTO_IPV6)
+static int udp_ipv6_mc_devname_membership(int mop, const char *name,
+                                          int iindex_fd,struct in6_addr *mca,
+                                          int sockfd,void *logctx)
+{
+    struct ifreq if_req;
+    strncpy(if_req.ifr_name,name , IFNAMSIZ);
+
+    if (ioctl(iindex_fd, SIOCGIFINDEX, &if_req) != -1) {
+        struct ipv6_mreq mreq6;
+        memcpy(&mreq6.ipv6mr_multiaddr, mca, sizeof(struct in6_addr));
+        mreq6.ipv6mr_interface = if_req.ifr_ifindex;
+
+        switch (mop) {
+        case IPV6_JOIN_GROUP:
+            if (setsockopt(sockfd, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP, &mreq6, sizeof(mreq6)) == 0) {
+                return 1;
+            } else {
+                /* Subscribe for all ipv6 addresses belong to a
+                   interface.It can generate EADDRINUSE but
+                   is accaptable. */
+                if (errno != EADDRINUSE)
+                    ff_log_net_error(logctx, AV_LOG_ERROR, "setsockopt(IPV6_ADD_MEMBERSHIP)");
+            }
+            break;
+        case IPV6_LEAVE_GROUP:
+            if (setsockopt(sockfd, IPPROTO_IPV6, IPV6_DROP_MEMBERSHIP, &mreq6, sizeof(mreq6)) == 0) {
+                return 1;
+            } else {
+                /* Unsubscribe for all ipv6 addresses belong to a
+                   interface. Ignore EADDRNOTAVAIL. */
+                if (errno != EADDRNOTAVAIL)
+                    ff_log_net_error(logctx, AV_LOG_ERROR, "setsockopt(IPV6_DROP_MEMBERSHIP)");
+            }
+            break;
+        default:
+            av_log(logctx, AV_LOG_ERROR, "unknown multicast operation\n");
+        }
+    }
+    return -1;
+}
+
+static int udp_ipv6_multicast_iterate(int sockfd, struct sockaddr_in6 *addr,
+                                      struct sockaddr_in6 *local_addr, int mop, void *logctx)
+{
+    struct in6_addr anyipv6 = IN6ADDR_ANY_INIT;
+    struct ifaddrs *ifal=NULL,*ife=NULL;
+    int iindex_fd = socket(AF_INET, SOCK_STREAM, IPPROTO_IP);
+    int membership_changed = 0;
+
+    if (iindex_fd >= 0 && !getifaddrs(&ifal)) {
+        for(ife=ifal; ife!=NULL; ife=ife->ifa_next) {
+            if (ife->ifa_addr &&
+                (ife->ifa_addr->sa_family == AF_INET6) &&
+                (ife->ifa_flags & IFF_MULTICAST) &&
+                (ife->ifa_flags & IFF_UP)) {
+                if ((!memcmp(&local_addr->sin6_addr, &anyipv6, sizeof(struct in6_addr))) ||
+                    (!memcmp(&local_addr->sin6_addr, &((struct sockaddr_in6 *)ife->ifa_addr)->sin6_addr, sizeof(struct in6_addr)))) {
+                    if (udp_ipv6_mc_devname_membership(mop,ife->ifa_name,
+                                                       iindex_fd, &addr->sin6_addr,
+                                                       sockfd, logctx) == 1)
+                        membership_changed = 1;
+                }
+            }
+        }
+    }
+    freeifaddrs(ifal);
+    close(iindex_fd);
+
+    if (!membership_changed) {
+        av_log(logctx, AV_LOG_ERROR, "no valid interfaces found\n");
+        return AVERROR(EINVAL);
+    }
+    return 0;
+}
+#endif
 
 static int udp_join_multicast_group(int sockfd, struct sockaddr *addr,
                                     struct sockaddr *local_addr, void *logctx)
@@ -226,15 +309,22 @@ static int udp_join_multicast_group(int sockfd, struct sockaddr *addr,
 #endif
 #if HAVE_STRUCT_IPV6_MREQ && defined(IPPROTO_IPV6)
     if (addr->sa_family == AF_INET6) {
+#if HAVE_IOCTL_GIFINDEX
+        return udp_ipv6_multicast_iterate(sockfd,
+                                          (struct sockaddr_in6 *)addr,
+                                          (struct sockaddr_in6 *)local_addr,
+                                          IPV6_JOIN_GROUP,
+                                          logctx);
+#else
         struct ipv6_mreq mreq6;
 
         memcpy(&mreq6.ipv6mr_multiaddr, &(((struct sockaddr_in6 *)addr)->sin6_addr), sizeof(struct in6_addr));
-        //TODO: Interface index should be looked up from local_addr
         mreq6.ipv6mr_interface = 0;
         if (setsockopt(sockfd, IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP, &mreq6, sizeof(mreq6)) < 0) {
             ff_log_net_error(logctx, AV_LOG_ERROR, "setsockopt(IPV6_ADD_MEMBERSHIP)");
             return ff_neterrno();
         }
+#endif
     }
 #endif
     return 0;
@@ -260,15 +350,22 @@ static int udp_leave_multicast_group(int sockfd, struct sockaddr *addr,
 #endif
 #if HAVE_STRUCT_IPV6_MREQ && defined(IPPROTO_IPV6)
     if (addr->sa_family == AF_INET6) {
+#if HAVE_IOCTL_GIFINDEX
+        return udp_ipv6_multicast_iterate(sockfd,
+                                          (struct sockaddr_in6 *)addr,
+                                          (struct sockaddr_in6 *)local_addr,
+                                          IPV6_LEAVE_GROUP,
+                                          logctx);
+#else
         struct ipv6_mreq mreq6;
 
         memcpy(&mreq6.ipv6mr_multiaddr, &(((struct sockaddr_in6 *)addr)->sin6_addr), sizeof(struct in6_addr));
-        //TODO: Interface index should be looked up from local_addr
         mreq6.ipv6mr_interface = 0;
         if (setsockopt(sockfd, IPPROTO_IPV6, IPV6_DROP_MEMBERSHIP, &mreq6, sizeof(mreq6)) < 0) {
             ff_log_net_error(logctx, AV_LOG_ERROR, "setsockopt(IPV6_DROP_MEMBERSHIP)");
             return -1;
         }
+#endif
     }
 #endif
     return 0;
-- 
2.34.1

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