From 6ff048ed35ce45e14636893ee690198332695206 Mon Sep 17 00:00:00 2001
From: "jinxue.cgh" <jinxue.cgh@alibaba-inc.com>
Date: Sat, 27 Jun 2020 14:37:35 +0800
Subject: [PATCH] RTC: process twcc before srtp unprotected

---
 trunk/src/app/srs_app_rtc_conn.cpp      | 31 +++++++++++++++----------
 trunk/src/kernel/srs_kernel_rtc_rtp.cpp |  8 ++++++-
 trunk/src/kernel/srs_kernel_rtc_rtp.hpp |  2 ++
 3 files changed, 28 insertions(+), 13 deletions(-)

diff --git a/trunk/src/app/srs_app_rtc_conn.cpp b/trunk/src/app/srs_app_rtc_conn.cpp
index 00013499a..8f4a94bb4 100644
--- a/trunk/src/app/srs_app_rtc_conn.cpp
+++ b/trunk/src/app/srs_app_rtc_conn.cpp
@@ -1196,6 +1196,25 @@ srs_error_t SrsRtcPublisher::on_rtp(char* data, int nb_data)
         return err;
     }
 
+    if (0 != twcc_ext_id_) {
+        SrsBuffer b0(data, nb_data); SrsRtpHeader h0;
+        h0.set_decode_only_header(true);
+        h0.set_extensions(&extension_types_);
+        if ((err = h0.decode(&b0)) != srs_success) {
+            return srs_error_wrap(err, "process twcc to decode rtp header");
+        }
+
+        uint16_t twcc_sn = 0;
+        if ((err = h0.get_twcc_sequence_number(twcc_sn)) == srs_success) {
+            if((err = on_twcc(twcc_sn)) != srs_success) {
+                return srs_error_wrap(err, "fail to process twcc packet");
+            }
+        } else {
+            // TODO: FIXME: process no twcc seq number for audio ssrc
+            srs_error_reset(err);
+        }
+    }
+
     // Decrypt the cipher to plaintext RTP data.
     int nb_unprotected_buf = nb_data;
     char* unprotected_buf = new char[kRtpPacketSize];
@@ -1232,18 +1251,6 @@ srs_error_t SrsRtcPublisher::on_rtp(char* data, int nb_data)
         if ((err = pkt->decode(&b)) != srs_success) {
             return srs_error_wrap(err, "decode rtp packet");
         }
-
-        if (0 != twcc_ext_id_) {
-            uint16_t twcc_sn = 0;
-            if ((err = pkt->header.get_twcc_sequence_number(twcc_sn)) == srs_success) {
-                if((err = on_twcc(twcc_sn))) {
-                    return srs_error_wrap(err, "fail to process twcc packet");
-                }
-            } else {
-                // TODO: FIXME: process no twcc seq number for audio ssrc
-                srs_error_reset(err);
-            }
-        }
     }
 
     // For source to consume packet.
diff --git a/trunk/src/kernel/srs_kernel_rtc_rtp.cpp b/trunk/src/kernel/srs_kernel_rtc_rtp.cpp
index 840db3185..cdcd62e10 100644
--- a/trunk/src/kernel/srs_kernel_rtc_rtp.cpp
+++ b/trunk/src/kernel/srs_kernel_rtc_rtp.cpp
@@ -319,6 +319,7 @@ SrsRtpHeader::SrsRtpHeader()
     sequence         = 0;
     timestamp        = 0;
     ssrc             = 0;
+    decode_only_header_ = false;
 }
 
 SrsRtpHeader::~SrsRtpHeader()
@@ -376,7 +377,7 @@ srs_error_t SrsRtpHeader::decode(SrsBuffer* buf)
         }
     }
 
-    if (padding && !buf->empty()) {
+    if (padding && !buf->empty() && !decode_only_header_) {
         padding_length = *(reinterpret_cast<uint8_t*>(buf->data() + buf->size() - 1));
         if (!buf->require(padding_length)) {
             return srs_error_new(ERROR_RTC_RTP_MUXER, "padding requires %d bytes", padding_length);
@@ -448,6 +449,11 @@ void SrsRtpHeader::set_extensions(const SrsRtpExtensionTypes* extmap)
     }
 }
 
+void SrsRtpHeader::set_decode_only_header(bool only_header)
+{
+    decode_only_header_ = only_header;
+}
+
 srs_error_t SrsRtpHeader::get_twcc_sequence_number(uint16_t& twcc_sn)
 {
     if (extensions_.exists()) {
diff --git a/trunk/src/kernel/srs_kernel_rtc_rtp.hpp b/trunk/src/kernel/srs_kernel_rtc_rtp.hpp
index 5d93e7193..163d6f7a8 100644
--- a/trunk/src/kernel/srs_kernel_rtc_rtp.hpp
+++ b/trunk/src/kernel/srs_kernel_rtc_rtp.hpp
@@ -175,6 +175,7 @@ private:
     uint32_t ssrc;
     uint32_t csrc[15];
     SrsRtpExtensions extensions_;
+    bool decode_only_header_;
 public:
     SrsRtpHeader();
     virtual ~SrsRtpHeader();
@@ -199,6 +200,7 @@ public:
     void set_padding(uint8_t v);
     uint8_t get_padding() const;
     void set_extensions(const SrsRtpExtensionTypes* extmap);
+    void set_decode_only_header(bool only_header);
     srs_error_t get_twcc_sequence_number(uint16_t& twcc_sn);
     srs_error_t set_twcc_sequence_number(uint8_t id, uint16_t sn);
 };