wasi-libc/libc-bottom-half/sources/listen.c

#include <errno.h>
#include <netinet/in.h>

#include <wasi/api.h>
#include <wasi/descriptor_table.h>
#include <wasi/sockets_utils.h>

int tcp_listen(tcp_socket_t *socket, int backlog)
{
	network_error_code_t error;
	tcp_borrow_tcp_socket_t socket_borrow =
		tcp_borrow_tcp_socket(socket->socket);

	switch (socket->state.tag) {
	case TCP_SOCKET_STATE_UNBOUND: {
		// Socket is not explicitly bound by the user. We'll do it for them:

		network_ip_socket_address_t any =
			__wasi_sockets_utils__any_addr(socket->family);
		int result = __wasi_sockets_utils__tcp_bind(socket, &any);
		if (result != 0) {
			return result;
		}

		if (socket->state.tag != TCP_SOCKET_STATE_BOUND) {
			abort();
		}
		// Great! We'll continue below.
		break;
	}
	case TCP_SOCKET_STATE_BOUND:
		// Great! We'll continue below.
		break;
	case TCP_SOCKET_STATE_LISTENING:
		// We can only update the backlog size.
		break;
	case TCP_SOCKET_STATE_CONNECTING:
	case TCP_SOCKET_STATE_CONNECTED:
	case TCP_SOCKET_STATE_CONNECT_FAILED:
	default:
		errno = EINVAL;
		return -1;
	}

	if (!tcp_method_tcp_socket_set_listen_backlog_size(socket_borrow,
							   backlog, &error)) {
		abort(); // Our own state checks should've prevented this from happening.
	}

	if (socket->state.tag == TCP_SOCKET_STATE_LISTENING) {
		// Updating the backlog is all we had to do.
		return 0;
	}

	network_borrow_network_t network_borrow =
		__wasi_sockets_utils__borrow_network();
	if (!tcp_method_tcp_socket_start_listen(socket_borrow, &error)) {
		errno = __wasi_sockets_utils__map_error(error);
		return -1;
	}

	// Listen has successfully started. Attempt to finish it:
	while (!tcp_method_tcp_socket_finish_listen(socket_borrow, &error)) {
		if (error == NETWORK_ERROR_CODE_WOULD_BLOCK) {
			poll_borrow_pollable_t pollable_borrow =
				poll_borrow_pollable(socket->socket_pollable);
			poll_method_pollable_block(pollable_borrow);
		} else {
			errno = __wasi_sockets_utils__map_error(error);
			return -1;
		}
	}

	// Listen successful.

	socket->state = (tcp_socket_state_t){
		.tag = TCP_SOCKET_STATE_LISTENING,
		.listening = { /* No additional state */ }
	};
	return 0;
}

int udp_listen(udp_socket_t *socket, int backlog)
{
	// UDP doesn't support listen
	errno = EOPNOTSUPP;
	return -1;
}

int listen(int socket, int backlog)
{
	descriptor_table_entry_t *entry;
	if (!descriptor_table_get_ref(socket, &entry)) {
		errno = EBADF;
		return -1;
	}

	if (backlog < 0) {
		// POSIX:
		// > If listen() is called with a backlog argument value that is
		// > less than 0, the function behaves as if it had been called
		// > with a backlog argument value of 0.
		backlog = 0;
	}

	switch (entry->tag) {
	case DESCRIPTOR_TABLE_ENTRY_TCP_SOCKET:
		return tcp_listen(&entry->tcp_socket, backlog);
	case DESCRIPTOR_TABLE_ENTRY_UDP_SOCKET:
		return udp_listen(&entry->udp_socket, backlog);
	default:
		errno = EOPNOTSUPP;
		return -1;
	}
}