# erlang_quic

Pure Erlang QUIC implementation (RFC 9000/9001).

## Features

- TLS 1.3 handshake (RFC 8446)
- Stream multiplexing (bidirectional and unidirectional)
- Key update support (RFC 9001 Section 6)
- Connection migration with active path migration API (RFC 9000 Section 9)
- 0-RTT early data support with session resumption (RFC 9001 Section 4.6)
- DATAGRAM frame support for unreliable data (RFC 9221)
- QUIC v2 support (RFC 9369)
- Server mode with listener and pooled listeners (SO_REUSEPORT)
- QUIC-LB load balancer support with routable CIDs (RFC 9312)
- Retry packet handling for address validation (RFC 9000 Section 8.1)
- Stateless reset support (RFC 9000 Section 10.3)
- Flow control (connection and stream level)
- Congestion control (NewReno, CUBIC, BBR with ECN support)
- HyStart++ slow start (RFC 9406)
- Loss detection and packet retransmission (RFC 9002)
- QLOG tracing support for debug visibility
- UDP packet batching (GSO/GRO)
- Client certificate verification

## Requirements

- Erlang/OTP 26.0 or later
- rebar3

## Installation

Add to your `rebar.config` dependencies:

```erlang
{deps, [
    {quic, {git, "https://github.com/benoitc/erlang_quic.git", {branch, "main"}}}
]}.
```

## Quick Start

### Client

```erlang
%% Connect to a QUIC server
{ok, ConnRef} = quic:connect(<<"example.com">>, 443, #{
    alpn => [<<"h3">>],
    verify => false
}, self()),

%% Wait for connection
receive
    {quic, ConnRef, {connected, Info}} ->
        io:format("Connected: ~p~n", [Info])
end,

%% Open a bidirectional stream
{ok, StreamId} = quic:open_stream(ConnRef),

%% Send data on the stream
ok = quic:send_data(ConnRef, StreamId, <<"Hello, QUIC!">>, true),

%% Receive data
receive
    {quic, ConnRef, {stream_data, StreamId, Data, _Fin}} ->
        io:format("Received: ~p~n", [Data])
end,

%% Close connection
quic:close(ConnRef, normal).
```

### Server

```erlang
%% Load certificate and key
{ok, CertDer} = file:read_file("server.crt"),
{ok, KeyDer} = file:read_file("server.key"),

%% Start a named server (recommended)
{ok, _Pid} = quic:start_server(my_server, 4433, #{
    cert => CertDer,
    key => KeyDer,
    alpn => [<<"h3">>]
}),

%% Get the port (useful if 0 was specified for ephemeral port)
{ok, Port} = quic:get_server_port(my_server),
io:format("Listening on port ~p~n", [Port]),

%% Incoming connections are handled automatically
%% The server spawns quic_connection processes for each client

%% Stop the server when done
quic:stop_server(my_server).
```

Alternatively, use the low-level listener API directly:

```erlang
{ok, Listener} = quic_listener:start_link(4433, #{
    cert => CertDer,
    key => KeyDer,
    alpn => [<<"h3">>]
}),
Port = quic_listener:get_port(Listener).
```

## Messages

The owner process receives messages in the format `{quic, ConnRef, Event}`:

| Event | Description |
|-------|-------------|
| `{connected, Info}` | Connection established |
| `{stream_opened, StreamId}` | New stream opened by peer |
| `{stream_data, StreamId, Data, Fin}` | Data received on stream |
| `{stream_reset, StreamId, ErrorCode}` | Stream reset by peer |
| `{closed, Reason}` | Connection closed |
| `{transport_error, Code, Reason}` | Transport error |
| `{session_ticket, Ticket}` | Session ticket for 0-RTT resumption |
| `{datagram, Data}` | Datagram received (RFC 9221) |
| `{stop_sending, StreamId, ErrorCode}` | Stop sending requested by peer |
| `{send_ready, StreamId}` | Stream ready for writing |

## API Reference

See [docs/features.md](docs/features.md) for the complete API reference and feature list.

### Quick Reference

**Connection:** `quic:connect/4`, `quic:close/2`, `quic:peername/1`, `quic:migrate/1`

**Streams:** `quic:open_stream/1`, `quic:send_data/4`, `quic:reset_stream/3`

**Server:** `quic:start_server/3`, `quic:stop_server/1`, `quic:get_server_port/1`

**Datagrams:** `quic:send_datagram/2` (RFC 9221)

**Load Balancer:** `quic_lb:new_config/1`, `quic_lb:generate_cid/1` (RFC 9312)

## Building

```bash
rebar3 compile
```

## Formatting

```bash
rebar3 fmt
```

## Static analysis tools

```bash
rebar3 lint
rebar3 xref
rebar3 dialyzer
```

## Testing

```bash
# Run unit tests
rebar3 eunit

# Run property-based tests
rebar3 proper

# Run all tests
rebar3 eunit && rebar3 proper
```

## Interoperability

This implementation passes all 10 [QUIC Interop Runner](https://github.com/quic-interop/quic-interop-runner) test cases. See [docs/features.md](docs/features.md) for the full test matrix and [interop/README.md](interop/README.md) for details on running interop tests.

## Documentation

Generate documentation with:

```bash
rebar3 ex_doc
```

## License

Apache License 2.0

## Author

Benoit Chesneau