// net — minimal TCP. Sketched against the Linux syscall numbers
// 41 (socket), 42 (connect), 43 (accept), 49 (bind), 50 (listen).
// Real applications will want addrinfo + DNS; we leave that to
// higher layers.

package net;

@symbol("rt_syscall") fn syscall0(num: i64) i64;
@symbol("rt_syscall") fn syscall3(num: i64, a: i64, b: i64, c: i64) i64;

def AF_INET:    i32 = 2;
def SOCK_STREAM:i32 = 1;
def IPPROTO_TCP:i32 = 6;

def SYS_SOCKET:  i64 = 41;
def SYS_CONNECT: i64 = 42;
def SYS_ACCEPT:  i64 = 43;
def SYS_BIND:    i64 = 49;
def SYS_LISTEN:  i64 = 50;

// sockaddrin is laid out by the kernel: family u16, port u16 (BE),
// addr u32 (BE), padding 8B = 16B total. Caller fills it.
type sockaddrin = struct {
	family: u16,
	port:   u16,
	addr:   u32,
	pad0:   u64,
};

export fn socket() i32 = {
	return syscall3(SYS_SOCKET, AF_INET: i64, SOCK_STREAM: i64,
	    IPPROTO_TCP: i64): i32;
};

export fn connect(fd: i32, sa: *sockaddrin) i32 = {
	return syscall3(SYS_CONNECT, fd: i64, sa: i64, 16): i32;
};

export fn bind(fd: i32, sa: *sockaddrin) i32 = {
	return syscall3(SYS_BIND, fd: i64, sa: i64, 16): i32;
};

export fn listen(fd: i32, backlog: i32) i32 = {
	return syscall3(SYS_LISTEN, fd: i64, backlog: i64, 0): i32;
};

// Byte-order conversions live in lib/endian (Hare's endian::htonu16
// is the canonical name). Use `endian.htonu16` to put a port into
// network order.