[vlc-devel] [PATCH 1/2] access/rtp: define MSG_TRUNC on recv call if available.

[Ilkka Ollakka]

recv() needs MSG_TRUNC flag so it will tell actual data-size if truncate
would happen additional to setting flag for it.

Tested the adjust of MTU by sending data to localhost via netcat:

cat ~/tmp/myfile.mp3|netcat -u 127.0.0.1 1234

and vlc -Idummy -vv rtp://@127.0.0.1:1234 --sout="#stat"

without this patch the rtp input constantly complains about trunced
input and doesn't adjust the receiving amount.
---
 modules/access/rtp/input.c | 18 +++++++++---------
 1 file changed, 9 insertions(+), 9 deletions(-)

diff --git a/modules/access/rtp/input.c b/modules/access/rtp/input.c
index f22f6655ab..32404a7331 100644
--- a/modules/access/rtp/input.c
+++ b/modules/access/rtp/input.c
@@ -109,6 +109,12 @@ void *rtp_dgram_thread (void *opaque)
     demux_sys_t *sys = demux->p_sys;
     vlc_tick_t deadline = VLC_TICK_INVALID;
     int rtp_fd = sys->fd;
+#ifdef __linux__
+    const int trunc_flag = MSG_TRUNC;
+#else
+    const int trunc_flag = 0;
+#endif
+
     struct iovec iov =
     {
         .iov_len = DEFAULT_MRU,
@@ -149,17 +155,12 @@ void *rtp_dgram_thread (void *opaque)
             }
 
             iov.iov_base = block->p_buffer;
-#ifdef __linux__
-            msg.msg_flags = MSG_TRUNC;
-#else
-            msg.msg_flags = 0;
-#endif
+            msg.msg_flags = trunc_flag;
 
-            ssize_t len = recvmsg (rtp_fd, &msg, 0);
+            ssize_t len = recvmsg (rtp_fd, &msg, trunc_flag);
             if (len != -1)
             {
-#ifdef MSG_TRUNC
-                if (msg.msg_flags & MSG_TRUNC)
+                if (msg.msg_flags & trunc_flag )
                 {
                     msg_Err(demux, "%zd bytes packet truncated (MRU was %zu)",
                             len, iov.iov_len);
@@ -167,7 +168,6 @@ void *rtp_dgram_thread (void *opaque)
                     iov.iov_len = len;
                 }
                 else
-#endif
                     block->i_buffer = len;
 
                 rtp_process (demux, block);
-- 
2.19.0