dmtcp

dmtcp DMOD library module.

Description

DMOD TCP - builds/parses TCP segments (RFC 793) and implements the three-way handshake (passive and active open), reliable in-order data transfer with a sliding window and retransmission, graceful close, and RST handling on top of dmip. Port reservation works like dmudp's port binding: register an accept handler for a chosen port (dmtcp_listen()) or the first free ephemeral port (dmtcp_listen_any()). See docs/dmtcp.md for the full architecture and known limitations.

Building

Using CMake

mkdir -p build
cd build
cmake ..
cmake --build .

Pass -DDMOD_DIR=/path/to/local/dmod to build against a local dmod checkout instead of fetching develop from GitHub.

Using Make

make DMOD_MODE=DMOD_MODULE DMOD_DIR=/path/to/dmod

Testing

Tests are built automatically alongside the module (see tests/). Once built, run them with ctest:

cd build
ctest --output-on-failure

ctest installs the test module's dependencies with dmf-get and then runs it through dmod_loader. To run it manually instead:

export DMOD_DMF_DIR=$(pwd)/build/dmf
dmf-get install -d ${DMOD_DMF_DIR}/test_dmtcp-local.dmd -y
dmod_loader build/dmf/test_dmtcp.dmf

Usage

#include "dmtcp.h"

static void on_data(dmtcp_conn_t conn, const uint8_t* data, size_t len, void* user_data)
{
    if (data == NULL) { /* peer sent FIN (EOF) */ return; }
    dmtcp_send(conn, data, len); /* echo it back */
}

static void on_accept(dmtcp_conn_t conn, const dmip_addr_t* peer, uint16_t peer_port, dmnetif_iface_t iface)
{
    dmtcp_conn_callbacks_t callbacks = { .on_data = on_data };
    dmtcp_conn_set_callbacks(conn, &callbacks, NULL);
}

uint16_t port;
dmtcp_listen_any(on_accept, &port); /* or dmtcp_listen(7, on_accept) for a fixed port */

API

Function	Description
dmtcp_listen() / _listen_any() / _unlisten()	Reserve a port (or the first free one) and register a handler for incoming connections
dmtcp_connect()	Actively open a connection
dmtcp_send() / _send_space() / _close() / _abort()	Send data (byte-stream, may short-write), query free buffer room, close gracefully, or abort
dmtcp_conn_set_callbacks() / _get_state() / _get_local_endpoint() / _get_peer_endpoint()	Per-connection accessors
dmtcp_build_header() / _parse_header() / _v4_checksum_valid() / _v6_checksum_valid()	Wire-level segment build/parse/checksum

See include/dmtcp.h for the full declarations and docs/api-reference.md for the complete reference.

Documentation

See the docs/ directory:

• dmtcp.md - Architecture and design rationale
• api-reference.md - Complete API documentation

View documentation using dmf-man dmtcp.

Project Structure

dmtcp/
├── docs/              # Documentation (markdown format)
├── include/           # Public headers
│   └── dmtcp.h
├── src/
│   ├── dmtcp.c              # dmod_init()/_deinit(), dmtcp_connect()
│   ├── dmtcp_internal.h     # Private TCB struct and shared plumbing
│   ├── dmtcp_wire.c         # Header build/parse, checksum
│   ├── dmtcp_listen_table.c # dmtcp_listen()/_listen_any()/_unlisten()
│   ├── dmtcp_conn_table.c   # Connection table, TCB lifecycle, accessors
│   ├── dmtcp_output.c       # dmtcp_send(), retransmission timer
│   ├── dmtcp_input.c        # Receive dispatch and state machine
│   └── dmtcp_close.c        # dmtcp_close()/_abort(), TIME_WAIT timer
├── tests/
│   ├── CMakeLists.txt
│   └── dmtcp_test.c
├── CMakeLists.txt
├── Makefile
├── dmtcp.dmr
└── manifest.dmm

Author

Patryk Kubiak

License

MIT