libconvert 
An LD_PRELOAD library that turns an existing client, using TCP sockets, into
a Convert client. See the IETF draft draft-ietf-tcpm-converters-05 for more information.
This is work in progress. The LD_PRELOAD client and the underlying library currently only support the Connect TLV and the Error TLV. This repository does not yet include a server-side Transport Converter.
Future work:
- Sample server-side Transport Converter
- Support Extended TCP Header TLV and Converter bypass.
- Support Info TLV and the Supported TCP Extensions TLV.
- Support Cookie TLV.
Requirements
- Requires Linux >= 4.5 (leverages the TCP Fast Open infrastructure).
- Configure
$ sysctl -w net.ipv4.tcp_fastopen=5to enable sending data in the opening SYN, regardless of cookie availability.
Build & usage
Fetch the Git submodules:
$ git submodule init && git submodule update
The easiest way to build and run the tests is with the provided Dockerfile (which contains all deps):
$ docker build -t tessares.net/libconvert .
$ docker run --cap-add=NET_ADMIN --sysctl net.ipv4.tcp_fastopen=5 -v $PWD:/lc -t tessares.net/libconvert /bin/bash -c "mkdir -p /lc/build && cd /lc/build && cmake .. && make && make test"
Otherwise, assuming all deps are installed, build and run the tests with CMake as follows:
$ mkdir -p build && cd build && cmake .. && make && make test
Usage (assuming a Transport Converter listening at 192.0.2.1:1234):
$ CONVERT_ADDR=192.0.2.1 CONVERT_PORT=1234 LD_PRELOAD=./libconvert_client.so curl https://www.tessares.net
Currently tested with curl & wget on both Centos 7 and Ubuntu {16,18,19}
Contributing
Code contributions are more than welcome.
Upon change, please run uncrustify (0.68) and validate that cppcheck is still happy:
$ uncrustify -c uncrustify.cfg -l C --replace --no-backup convert*.{h,c}
$ cppcheck -I/usr/include -q --language=c --std=c99 --enable=warning,style,performance,portability -j "$(nproc)" --suppress=unusedStructMember ./convert*.{h,c}
To contribute to the Convert protocol, see this Github repository, which tracks the evolution of the 0-RTT TCP Converter Internet draft.
To ease troubleshooting, download the 0-RTT TCP Convert Wireshark dissector plugin.
Contact
License
This project is licensed under the 3-Clause BSD License - see the LICENSE file for details.