This PR implements the UEFI TCPv4 protocol, building upon #1130. As-is, the code performs well in a custom bootloader.

Overview

This implementation adds support for the EFI_TCP4_PROTOCOL and EFI_TCP4_SERVICE_BINDING_PROTOCOL as defined in the UEFI specification (Section 28.1). It enables UEFI applications to establish TCP connections, transmit and receive data over the network.

Changes

uefi-raw

• Complete protocol structure definitions matching UEFI spec.
• TCP connection states enum (Closed, Listen, SynSent, Established, etc.)
• Configuration structure for client mode only.
• I/O token structures for async operations
• Fragment table support for scatter-gather I/O (hard-coded for single fragment buffer at the moment)
• IPv4 mode data structures for network configuration

uefi

• Tcpv4ServiceBinding for creating TCP protocol instances
• Tcpv4 protocol wrapper with higher-level API
• Automatic DHCP-aware configuration with retry logic
• Event-based async I/O handling
• Convenience methods like receive_exact() for reading exact byte counts
• Proper lifetime management for all operations (best effort, needs review)

Key Features

1. Connection Modes: Support for both client and server TCP connections

   • Client mode with remote IP and port configuration
   • Server mode foundation (accept functionality pending)

2. Async Operations: All I/O operations wrap async operations in high-level sync interface

   • Transmit and receive operations with completion tokens
   • Proper event waiting and status checking

3. DHCP Integration: Automatic retry logic when DHCP is still configuring the network

   • Handles NO_MAPPING status during network initialization
   • Configurable timeout with 10-second maximum wait

Example Usage

use alloc::string::String;
use uefi::{
    boot, print, println,
    proto::network::tcpv4::{Tcpv4, Tcpv4ServiceBinding},
};
use uefi_raw::{
    Ipv4Address,
    protocol::network::tcpv4::{Tcpv4ClientConnectionModeParams, Tcpv4ConnectionMode},
};

let addr = Ipv4Address([192, 0, 2, 2]);
let port = 5050;

println!("Connecting to {addr:?}:{port}...");
let mut tcp = {
    let tcp_svc_handle = boot::get_handle_for_protocol::<Tcpv4ServiceBinding>()?;
    let mut tcp_svc_proto =
        boot::open_protocol_exclusive::<Tcpv4ServiceBinding>(tcp_svc_handle)?;
    let tcp_proto_handle = tcp_svc_proto.create_child()?;
    let mut tcp_proto = boot::open_protocol_exclusive::<Tcpv4>(tcp_proto_handle)?;
    tcp_proto
        .configure(Tcpv4ConnectionMode::Client(
            Tcpv4ClientConnectionModeParams::new(addr, port),
        ))
        .expect("configure failed");
    tcp_proto.connect()?;
    tcp_proto
};

let tx_msg = "Hello";
println!("Sending {tx_msg:?} over TCP...");
tcp.transmit(tx_msg.as_bytes())?;

print!("Received ");
let mut buf = [0_u8; 64];
let n = tcp.receive(&mut buf)?;
let rx_string = String::from_utf8_lossy(&buf[..n]);
println!("{rx_string:?}");

Current Limitations

• Server accept functionality uses UnmodelledPtr (implementation pending)
• Close and cancel operations use UnmodelledPtr (implementation pending)
• Some network configuration options not fully exposed in safe API

Future Work

• Implement close and cancel operations
• Improve TCP configuration support
• Create integration tests with test TCP server
• Complete server mode (accept) implementation (low priority)

Checklist

• Sensible git history (for example, squash "typo" or "fix" commits). See the Rewriting History guide for help.
• Update the changelog (if necessary)

Closes #1130