From a3a1656e9050ef1964764e67e8a13fb669c2dbbc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jos=C3=A9=20Luis=20Mill=C3=A1n?= <jmillan@aliax.net>
Date: Fri, 28 Oct 2022 13:56:18 +0200
Subject: [PATCH] RTCP: Adjust maximum compound packet size (#934)

* RTCP: Adjust maximum compound packet size

Consider IP and transport header sizes on the MTU.

* Update CHANGELOG
---
 CHANGELOG.md                               |  1 +
 worker/include/RTC/RTCP/CompoundPacket.hpp | 13 ++++++++-----
 2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index c7c9637cf10..73d72c17625 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,7 @@
 ### NEXT
 
 * Transport: Remove duplicate call to method (PR #931).
+* RTCP: Adjust maximum compound packet size (PR #934).
 
 
 ### 3.10.12
diff --git a/worker/include/RTC/RTCP/CompoundPacket.hpp b/worker/include/RTC/RTCP/CompoundPacket.hpp
index a250b5c5b84..3e377d394a7 100644
--- a/worker/include/RTC/RTCP/CompoundPacket.hpp
+++ b/worker/include/RTC/RTCP/CompoundPacket.hpp
@@ -17,11 +17,14 @@ namespace RTC
 		class CompoundPacket
 		{
 		public:
-			// Maximum size for a CompundPacket, leaving free space for encryption.
-			// SRTP_MAX_TRAILER_LEN+4 is the maximum number of octects that will be
-			// added to an RTCP packet by srtp_protect_rtcp().
-			// srtp.h: SRTP_MAX_TRAILER_LEN (SRTP_MAX_TAG_LEN + SRTP_MAX_MKI_LEN)
-			constexpr static size_t MaxSize{ RTC::MtuSize - 148u };
+			// Maximum size for a CompundPacket.
+			// * IPv4|Ipv6 header size: 20|40 bytes. IPv6 considered.
+			// * UDP|TCP header size:   8|20  bytes. TCP considered.
+			// * SRTP Encryption: 148 bytes.
+			//    SRTP_MAX_TRAILER_LEN+4 is the maximum number of octects that will be
+			//    added to an RTCP packet by srtp_protect_rtcp().
+			//    srtp.h: SRTP_MAX_TRAILER_LEN (SRTP_MAX_TAG_LEN + SRTP_MAX_MKI_LEN)
+			constexpr static size_t MaxSize{ RTC::MtuSize - 40u - 20u - 148u };
 
 		public:
 			CompoundPacket() = default;