From 6174173f81e10e400b55d4e6f6d94608dc4174b0 Mon Sep 17 00:00:00 2001
From: Victor Boivie <boivie@webrtc.org>
Date: Mon, 10 May 2021 17:22:42 +0200
Subject: [PATCH] sctp: dcsctp: Print SCTP packets to logs

When verbose logs are enabled, SCTP packets will be dumped to debug
logs, allowing text2pcap to be used to generate PCAP files.

First start Chrome with verbose logs, and write those to file:

  /path/to/chrome --enable-logging=stderr --v=4 2> out.log

Then extract the SCTP_PACKET traces and run text2pcap:

  grep SCTP_PACKET out.log > sctp.log

  text2pcap -n -i 132 -D -t '%H:%M:%S.' sctp.log sctp.pcapng

You may have to cut away more from the beginning if the debug logs
contain additional timestamps and more, e.g. like:

  grep SCTP_PACKET out.log | cut -d ' ' -f 2- > sctp.log

Note that if there are multiple RTCPeerConnection objects created, each
will print out their packets to log, so to filter for a specific one:

  grep "SCTP_PACKET DcSctpTransport0" out.log > sctp.log

Bug: webrtc:12614
Change-Id: Ibbceaf33719d09e7606247cb0496ddd827ea58bb
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/218200
Commit-Queue: Victor Boivie <boivie@webrtc.org>
Reviewed-by: Florent Castelli <orphis@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#33999}
---
 media/sctp/dcsctp_transport.cc | 51 ++++++++++++++++++++++++++++++++--
 1 file changed, 49 insertions(+), 2 deletions(-)

diff --git a/media/sctp/dcsctp_transport.cc b/media/sctp/dcsctp_transport.cc
index 7cbc43f48e..f0ec69a766 100644
--- a/media/sctp/dcsctp_transport.cc
+++ b/media/sctp/dcsctp_transport.cc
@@ -19,10 +19,13 @@
 #include "absl/types/optional.h"
 #include "api/array_view.h"
 #include "media/base/media_channel.h"
+#include "net/dcsctp/public/packet_observer.h"
 #include "net/dcsctp/public/types.h"
 #include "net/dcsctp/socket/dcsctp_socket.h"
 #include "p2p/base/packet_transport_internal.h"
 #include "rtc_base/checks.h"
+#include "rtc_base/logging.h"
+#include "rtc_base/strings/string_builder.h"
 #include "rtc_base/thread.h"
 #include "rtc_base/trace_event.h"
 #include "system_wrappers/include/clock.h"
@@ -76,6 +79,45 @@ bool IsEmptyPPID(dcsctp::PPID ppid) {
          webrtc_ppid == WebrtcPPID::kBinaryEmpty;
 }
 
+// Print outs all sent and received packets to the logs, at LS_VERBOSE severity.
+class TextPcapPacketObserver : public dcsctp::PacketObserver {
+ public:
+  explicit TextPcapPacketObserver(absl::string_view name) : name_(name) {}
+
+  void OnSentPacket(dcsctp::TimeMs now, rtc::ArrayView<const uint8_t> payload) {
+    PrintPacket("O ", now, payload);
+  }
+
+  void OnReceivedPacket(dcsctp::TimeMs now,
+                        rtc::ArrayView<const uint8_t> payload) {
+    PrintPacket("I ", now, payload);
+  }
+
+ private:
+  void PrintPacket(absl::string_view prefix,
+                   dcsctp::TimeMs now,
+                   rtc::ArrayView<const uint8_t> payload) {
+    rtc::StringBuilder s;
+    s << prefix;
+    int64_t remaining = *now % (24 * 60 * 60 * 1000);
+    int hours = remaining / (60 * 60 * 1000);
+    remaining = remaining % (60 * 60 * 1000);
+    int minutes = remaining / (60 * 1000);
+    remaining = remaining % (60 * 1000);
+    int seconds = remaining / 1000;
+    int ms = remaining % 1000;
+    s.AppendFormat("%02d:%02d:%02d.%03d", hours, minutes, seconds, ms);
+    s << " 0000";
+    for (uint8_t byte : payload) {
+      s.AppendFormat(" %02x", byte);
+    }
+    s << " # SCTP_PACKET " << name_;
+    RTC_LOG(LS_VERBOSE) << s.str();
+  }
+
+  const std::string name_;
+};
+
 }  // namespace
 
 DcSctpTransport::DcSctpTransport(rtc::Thread* network_thread,
@@ -130,8 +172,13 @@ bool DcSctpTransport::Start(int local_sctp_port,
     options.remote_port = remote_sctp_port;
     options.max_message_size = max_message_size;
 
-    socket_ = std::make_unique<dcsctp::DcSctpSocket>(debug_name_, *this,
-                                                     nullptr, options);
+    std::unique_ptr<dcsctp::PacketObserver> packet_observer;
+    if (RTC_LOG_CHECK_LEVEL(LS_VERBOSE)) {
+      packet_observer = std::make_unique<TextPcapPacketObserver>(debug_name_);
+    }
+
+    socket_ = std::make_unique<dcsctp::DcSctpSocket>(
+        debug_name_, *this, std::move(packet_observer), options);
   } else {
     if (local_sctp_port != socket_->options().local_port ||
         remote_sctp_port != socket_->options().remote_port) {