libre README

libre is a Generic library for real-time communications with async IO support.

• Copyright (C) 2010 - 2020 Creytiv.com
• Copyright (C) 2020 - 2026 Baresip Foundation (https://github.com/baresip)

Features

• SIP Stack (RFC 3261)
• SDP
• RTP and RTCP
• SRTP and SRTCP (Secure RTP)
• DNS-Client
• STUN/TURN/ICE stack
• BFCP
• HTTP-stack with client/server
• Websockets
• Async I/O (select, epoll, kqueue)
• UDP/TCP/TLS/DTLS transport
• JSON parser
• Real Time Messaging Protocol (RTMP)

Building

libre is using CMake. CMake and OpenSSL development headers must be installed before building.

Build with debug enabled

$ cmake -B build
$ cmake --build build -j
$ sudo cmake --install build
$ sudo ldconfig

Build/run tests

cmake -B build && cmake --build build -t retest -j
build/test/retest -rv

On some distributions, /usr/local/lib may not be included in ld.so.conf. You can check with grep "/usr/local/lib" /etc/ld.so.conf.d/*.conf and add if necessary:

$ echo "/usr/local/lib" | sudo tee /etc/ld.so.conf.d/libc.conf
$ sudo ldconfig

Build with release

$ cmake -B build -DCMAKE_BUILD_TYPE=Release 
$ cmake --build build -j
$ sudo cmake --install build
$ sudo ldconfig

Build with clang compiler

$ cmake -B build -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++
$ cmake --build build -j
$ sudo cmake --install build
$ sudo ldconfig

Examples

Coding examples are available from the redemo project.

License

The libre project is using the BSD license.

Contributing

Patches can sent via Github Pull-Requests

Design goals

• Portable POSIX source code (ISO C99 and C11 standard)
• Robust, fast, low memory footprint
• RFC compliance
• IPv4 and IPv6 support

Modules

legend:

• stable - code complete; stable code and stable API
• testing - code complete, but API might change
• unstable - code complete but not completely tested
• development - code is under development

Features

• RFC 1321 - The MD5 Message-Digest Algorithm
• RFC 1886 - DNS Extensions to support IP version 6
• RFC 2616 - Hypertext Transfer Protocol -- HTTP/1.1
• RFC 2617 - HTTP Authentication: Basic and Digest Access Authentication
• RFC 2782 - A DNS RR for Specifying the Location of Services (DNS SRV)
• RFC 2915 - The Naming Authority Pointer (NAPTR) DNS Resource Record
• RFC 3261 - SIP: Session Initiation Protocol
• RFC 3262 - SIP Reliability of Provisional Responses
• RFC 3263 - Locating SIP Servers
• RFC 3264 - An Offer/Answer Model with SDP
• RFC 3265 - SIP-Specific Event Notification
• RFC 3311 - The SIP UPDATE Method
• RFC 3327 - SIP Extension Header Field for Registering Non-Adjacent Contacts
• RFC 3428 - SIP Extension for Instant Messaging
• RFC 3489 - STUN - Simple Traversal of UDP Through NATs
• RFC 3515 - The SIP Refer Method
• RFC 3550 - RTP: A Transport Protocol for Real-Time Applications
• RFC 3551 - RTP Profile for Audio and Video Conferences with Minimal Control
• RFC 3555 - MIME Type Registration of RTP Payload Formats
• RFC 3556 - SDP Bandwidth Modifiers for RTCP Bandwidth
• RFC 3581 - An Extension to SIP for Symmetric Response Routing
• RFC 3605 - RTCP attribute in SDP
• RFC 3611 - RTCP Extended Reports
• RFC 3711 - The Secure Real-time Transport Protocol (SRTP)
• RFC 3969 - The IANA URI Parameter Registry for SIP
• RFC 3994 - Indication of Message Composition for Instant Messaging
• RFC 4566 - SDP: Session Description Protocol
• RFC 4582 - The Binary Floor Control Protocol (BFCP)
• RFC 4582bis - The Binary Floor Control Protocol (BFCP)
• RFC 4585 - Extended RTP Profile for RTCP-Based Feedback
• RFC 4733 - RTP Payload for DTMF Digits, Telephony Tones, and Teleph. Signals
• RFC 4961 - Symmetric RTP / RTP Control Protocol (RTCP)
• RFC 5104 - Codec Control Messages in AVPF
• RFC 5118 - SIP Torture Test Messages for IPv6
• RFC 5245 - Interactive Connectivity Establishment (ICE)
• RFC 5246 - The TLS Protocol Version 1.2
• RFC 5389 - Session Traversal Utilities for NAT (STUN)
• RFC 5626 - Managing Client-Initiated Connections in SIP
• RFC 5761 - Multiplexing RTP Data and Control Packets on a Single Port
• RFC 5766 - Traversal Using Relays around NAT (TURN)
• RFC 5768 - Indicating Support for ICE in SIP
• RFC 5769 - Test vectors for STUN
• RFC 6026 - Correct Transaction Handling for 2xx Resp. to SIP INVITE Requests
• RFC 6156 - TURN Extension for IPv6
• RFC 6188 - The Use of AES-192 and AES-256 in Secure RTP
• RFC 6455 - The WebSocket Protocol
• RFC 7159 - JavaScript Object Notation (JSON)
• RFC 7350 - DTLS as Transport for STUN
• RFC 7616 - HTTP Digest Access Authentication
• RFC 7714 - AES-GCM Authenticated Encryption in SRTP
• AV1-RTP - RTP Payload Format For AV1

Supported platforms

Known bugs

macOS clang-1600.0.26.3 (Xcode 16.0) and clang-1600.0.26.4 (Xcode 16.1) have a optimization bug:

• https://github.com/baresip/re/pull/1399
• https://github.com/baresip/baresip/issues/3240

Support types

• Tier 1: Officially supported and tested with CI. Any contributed patch MUST NOT break such systems.

• Tier 2: Officially supported, but not necessarily tested with CI. These systems are maintained to the best of collaborators ability, without being a top priority.

• Tier 3: Community maintained. These systems may inadvertently break and the community and interested parties are expected to help with the maintenance.

Supported versions of C Standard library

• Android bionic
• BSD libc
• GNU C Library (glibc)
• Windows C Run-Time Libraries (CRT)
• uClibc
• musl

Supported compilers:

• gcc 9 or later
• MSVC 2022
• clang 9.x or later

Supported versions of OpenSSL

• OpenSSL version 3.x.x and 4.x.x
• LibreSSL version 4.x

Coding guidelines

• Use enum for constants where appropriate
• Use const as much as possible (where appropriate)
• Use C99 data types (intN_t, uintN_t, bool)
• Hide data-types in .c files where possible (use struct foo)
• Avoid malloc/free, use mem_alloc/mem_deref instead
• CVS/svn/git tags are NOT allowed in the code!
• Avoid bit-fields in structs which are not portable
• Use dummy handlers for timing-critical callbacks
• return err, return alloced objects as pointer-pointers
• in allocating functions, first arg is always double pointer
• Use POSIX error-codes; EINVAL for invalid args, EBADMSG for parse errors and EPROTO for protocol errors

Transport protocols

Related projects

• librem
• retest
• baresip

References

https://github.com/creytiv/re