[FFmpeg-cvslog] avformat/udp: Fix IP_MULTICAST_TTL for BSD compatibility

[Limin Wang]

ffmpeg | branch: master | Limin Wang <lance.lmwang at gmail.com> | Mon Feb  7 08:08:18 2022 +0800| [268d00bb87c544c6a89edf3b3f986ed4f639ce7a] | committer: Limin Wang

avformat/udp: Fix IP_MULTICAST_TTL for BSD compatibility

Suggested by zhilizhao, vlc project has solved the compatibility by
the same way, so I borrowed the comments from vlc project.

Fixes ticket #9449

Reviewed-by: Marton Balint <cus at passwd.hu>
Signed-off-by: Limin Wang <lance.lmwang at gmail.com>

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=268d00bb87c544c6a89edf3b3f986ed4f639ce7a
---

 libavformat/udp.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/libavformat/udp.c b/libavformat/udp.c
index a2c01b3ec9..143f4b92c0 100644
--- a/libavformat/udp.c
+++ b/libavformat/udp.c
@@ -164,6 +164,10 @@ static int udp_set_multicast_ttl(int sockfd, int mcastTTL,
 {
     int protocol, cmd;
 
+    /* There is some confusion in the world whether IP_MULTICAST_TTL
+     * takes a byte or an int as an argument.
+     * BSD seems to indicate byte so we are going with that and use
+     * int and fall back to byte to be safe */
     switch (addr->sa_family) {
 #ifdef IP_MULTICAST_TTL
         case AF_INET:
@@ -182,8 +186,14 @@ static int udp_set_multicast_ttl(int sockfd, int mcastTTL,
     }
 
     if (setsockopt(sockfd, protocol, cmd, &mcastTTL, sizeof(mcastTTL)) < 0) {
-        ff_log_net_error(logctx, AV_LOG_ERROR, "setsockopt(IPV4/IPV6 MULTICAST TTL)");
-        return ff_neterrno();
+        /* BSD compatibility */
+        unsigned char ttl = (unsigned char) mcastTTL;
+
+        ff_log_net_error(logctx, AV_LOG_DEBUG, "setsockopt(IPV4/IPV6 MULTICAST TTL)");
+        if (setsockopt(sockfd, protocol, cmd, &ttl, sizeof(ttl)) < 0) {
+            ff_log_net_error(logctx, AV_LOG_ERROR, "setsockopt(IPV4/IPV6 MULTICAST TTL)");
+            return ff_neterrno();
+        }
     }
 
     return 0;