From b68e47968b581accea9deebd15a2160300452fff Mon Sep 17 00:00:00 2001
From: Ederson de Souza <ederson.desouza@intel.com>
Date: Fri, 3 Apr 2020 10:41:44 -0700
Subject: [PATCH] avtpsink: Log that AVTPDU transmission failure is due
 lateness

As ENOBUFS is not really clear about what is going on, let's check
socket error queue to see if packets are being dropped due being late.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/merge_requests/1004>
---
 ext/avtp/gstavtpsink.c | 52 +++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 51 insertions(+), 1 deletion(-)

diff --git a/ext/avtp/gstavtpsink.c b/ext/avtp/gstavtpsink.c
index a825049d8f..2718ce78c5 100644
--- a/ext/avtp/gstavtpsink.c
+++ b/ext/avtp/gstavtpsink.c
@@ -44,6 +44,7 @@
  */
 
 #include <arpa/inet.h>
+#include <linux/errqueue.h>
 #include <linux/if_packet.h>
 #include <linux/net_tstamp.h>
 #include <net/ethernet.h>
@@ -242,7 +243,7 @@ gst_avtp_sink_init_socket (GstAvtpSink * avtpsink)
   }
 
   txtime_cfg.clockid = CLOCK_TAI;
-  txtime_cfg.flags = 0;
+  txtime_cfg.flags = SOF_TXTIME_REPORT_ERRORS;
   res = setsockopt (fd, SOL_SOCKET, SO_TXTIME, &txtime_cfg,
       sizeof (txtime_cfg));
   if (res < 0) {
@@ -363,6 +364,51 @@ gst_avtp_sink_adjust_time (GstBaseSink * basesink, GstClockTime time)
   return time;
 }
 
+static void
+gst_avtp_sink_process_error_queue (GstAvtpSink * avtpsink, int fd)
+{
+  uint8_t msg_control[CMSG_SPACE (sizeof (struct sock_extended_err))];
+  unsigned char err_buffer[256];
+  struct sock_extended_err *serr;
+  struct cmsghdr *cmsg;
+
+  struct iovec iov = {
+    .iov_base = err_buffer,
+    .iov_len = sizeof (err_buffer)
+  };
+  struct msghdr msg = {
+    .msg_iov = &iov,
+    .msg_iovlen = 1,
+    .msg_control = msg_control,
+    .msg_controllen = sizeof (msg_control)
+  };
+
+  if (recvmsg (fd, &msg, MSG_ERRQUEUE) == -1) {
+    GST_LOG_OBJECT (avtpsink, "Could not get socket errqueue: recvmsg failed");
+    return;
+  }
+
+  cmsg = CMSG_FIRSTHDR (&msg);
+  while (cmsg != NULL) {
+    serr = (void *) CMSG_DATA (cmsg);
+    if (serr->ee_origin == SO_EE_ORIGIN_TXTIME) {
+      switch (serr->ee_code) {
+        case SO_EE_CODE_TXTIME_INVALID_PARAM:
+        case SO_EE_CODE_TXTIME_MISSED:
+          GST_INFO_OBJECT (avtpsink, "AVTPDU dropped due to being late. "
+              "Check stream spec and pipeline settings.");
+          break;
+        default:
+          break;
+      }
+
+      return;
+    }
+
+    cmsg = CMSG_NXTHDR (&msg, cmsg);
+  }
+}
+
 static GstFlowReturn
 gst_avtp_sink_render (GstBaseSink * basesink, GstBuffer * buffer)
 {
@@ -400,6 +446,10 @@ gst_avtp_sink_render (GstBaseSink * basesink, GstBuffer * buffer)
   n = sendmsg (avtpsink->sk_fd, avtpsink->msg, 0);
   if (n < 0) {
     GST_INFO_OBJECT (avtpsink, "Failed to send AVTPDU: %s", strerror (errno));
+
+    if (G_LIKELY (basesink->sync))
+      gst_avtp_sink_process_error_queue (avtpsink, avtpsink->sk_fd);
+
     goto out;
   }
   if (n != info.size) {