ObjFW  Artifact [0702a801d8]

Artifact 0702a801d8f651516ea6e303f07d51f58398f8f8455bf1439c3c198400b8418e:

• File src/OFDDPSocket.m — part of check-in [41535b41da] at 2022-11-01 22:18:34 on branch trunk — Implement OFDDPSocket using SOCK_RAW on macOS

  This required quite some reverse engineering, as it is all completely
  undocumented.

  Receiving worked pretty much as expected: Do a readv() and get the raw
  DDP packet including headers, then parse the headers ourselves to get
  the source and fill out an OFSocketAddress.

  But sending was tricky and required reading through kernel sources.
  writev() does not work on a raw DDP socket and always fails with
  EDESTADDRREQ, even if the destination address is provided as part of the
  raw DDP packet. Meanwhile, sendmsg() always creates a DDP packet for us,
  even in raw mode, and prepends the data with what it believes to be the
  DDP protocol type (the protocol parameter passed to socket()). After
  reading through the kernel source for some time to find a way to disable
  this behavior, I found that you can set DDP_HDRINCL in ATPROTO_NONE to
  provide your entire header to sendmsg() instead to work around this,
  making it behave like you would expect from a writev() to a raw socket.

  The only missing part now is to return a proper address a socket was
  bound to, as currently it just leaves network and node at 0 and only
  fills the port. This probably just requires some more reading of kernel
  sources. (user: js, size: 5781) [annotate] [blame] [check-ins using]

/*
 * Copyright (c) 2008-2022 Jonathan Schleifer <js@nil.im>
 *
 * All rights reserved.
 *
 * This file is part of ObjFW. It may be distributed under the terms of the
 * Q Public License 1.0, which can be found in the file LICENSE.QPL included in
 * the packaging of this file.
 *
 * Alternatively, it may be distributed under the terms of the GNU General
 * Public License, either version 2 or 3, which can be found in the file
 * LICENSE.GPLv2 or LICENSE.GPLv3 respectively included in the packaging of this
 * file.
 */

#include "config.h"

#include <errno.h>

#ifdef HAVE_FCNTL_H
# include <fcntl.h>
#endif

#import "OFDDPSocket.h"
#import "OFSocket.h"
#import "OFSocket+Private.h"

#import "OFAlreadyConnectedException.h"
#import "OFBindDDPSocketFailedException.h"
#import "OFNotOpenException.h"
#import "OFReadFailedException.h"
#import "OFWriteFailedException.h"

#ifdef OF_HAVE_NETAT_APPLETALK_H
# include <netat/ddp.h>
#endif

@implementation OFDDPSocket
@dynamic delegate;

- (OFSocketAddress)bindToNetwork: (uint16_t)network
			    node: (uint8_t)node
			    port: (uint8_t)port
{
#ifdef OF_MACOS
	const int one = 1;
#endif
	OFSocketAddress address;
#if SOCK_CLOEXEC == 0 && defined(HAVE_FCNTL_H) && defined(FD_CLOEXEC)
	int flags;
#endif

	if (_socket != OFInvalidSocketHandle)
		@throw [OFAlreadyConnectedException exceptionWithSocket: self];

	address = OFSocketAddressMakeAppleTalk(network, node, port);

#ifdef OF_MACOS
	if ((_socket = socket(address.sockaddr.at.sat_family,
	    SOCK_RAW | SOCK_CLOEXEC, 0)) == OFInvalidSocketHandle)
#else
	if ((_socket = socket(address.sockaddr.at.sat_family,
	    SOCK_DGRAM | SOCK_CLOEXEC, 0)) == OFInvalidSocketHandle)
#endif
		@throw [OFBindDDPSocketFailedException
		    exceptionWithNetwork: network
				    node: node
				    port: port
				  socket: self
				   errNo: OFSocketErrNo()];

	_canBlock = true;

#if SOCK_CLOEXEC == 0 && defined(HAVE_FCNTL_H) && defined(FD_CLOEXEC)
	if ((flags = fcntl(_socket, F_GETFD, 0)) != -1)
		fcntl(_socket, F_SETFD, flags | FD_CLOEXEC);
#endif

	if (bind(_socket, (struct sockaddr *)&address.sockaddr,
	    address.length) != 0) {
		int errNo = OFSocketErrNo();

		closesocket(_socket);
		_socket = OFInvalidSocketHandle;

		@throw [OFBindDDPSocketFailedException
		    exceptionWithNetwork: network
				    node: node
				    port: port
				  socket: self
				   errNo: errNo];
	}

	memset(&address, 0, sizeof(address));
	address.family = OFSocketAddressFamilyAppleTalk;
	address.length = (socklen_t)sizeof(address.sockaddr);

	if (OFGetSockName(_socket, (struct sockaddr *)&address.sockaddr,
	    &address.length) != 0) {
		int errNo = OFSocketErrNo();

		closesocket(_socket);
		_socket = OFInvalidSocketHandle;

		@throw [OFBindDDPSocketFailedException
		    exceptionWithNetwork: network
				    node: node
				    port: port
				  socket: self
				   errNo: errNo];
	}

	if (address.sockaddr.at.sat_family != AF_APPLETALK) {
		closesocket(_socket);
		_socket = OFInvalidSocketHandle;

		@throw [OFBindDDPSocketFailedException
		    exceptionWithNetwork: network
				    node: node
				    port: port
				  socket: self
				   errNo: EAFNOSUPPORT];
	}

#ifdef OF_MACOS
	if (setsockopt(_socket, ATPROTO_NONE, DDP_HDRINCL, &one,
	    sizeof(one)) != 0)
		@throw [OFBindDDPSocketFailedException
		    exceptionWithNetwork: network
				    node: node
				    port: port
				  socket: self
				   errNo: OFSocketErrNo()];
#endif

	return address;
}

#ifdef OF_MACOS
- (size_t)receiveIntoBuffer: (void *)buffer
		     length: (size_t)length
		     sender: (OFSocketAddress *)sender
{
	ssize_t ret;
	at_ddp_t header;
	struct iovec iov[2] = {
		{ &header, offsetof(at_ddp_t, type) },
		{ buffer, length }
	};

	if (_socket == OFInvalidSocketHandle)
		@throw [OFNotOpenException exceptionWithObject: self];

	if ((ret = readv(_socket, iov, 2)) < 0)
		@throw [OFReadFailedException
		    exceptionWithObject: self
			requestedLength: length
				  errNo: OFSocketErrNo()];

	*sender = OFSocketAddressMakeAppleTalk(
	    header.src_net[0] << 8 | header.src_net[1], header.src_node,
	    header.src_socket);

	ret -= offsetof(at_ddp_t, type);
	if (ret < 0)
		return 0;

	return ret;
}

- (void)sendBuffer: (const void *)buffer
	    length: (size_t)length
	  receiver: (const OFSocketAddress *)receiver
{
	at_ddp_t header = { 0 };
	struct iovec iov[2] = {
		{ &header, offsetof(at_ddp_t, type) },
		{ (void *)buffer, length }
	};
	struct msghdr msg = {
		.msg_name = (struct sockaddr *)&receiver->sockaddr,
		.msg_namelen = receiver->length,
		.msg_iov = iov,
		.msg_iovlen = 2
	};
	size_t packetLength = length + offsetof(at_ddp_t, type);
	uint16_t net;
	ssize_t bytesWritten;

	if (_socket == OFInvalidSocketHandle)
		@throw [OFNotOpenException exceptionWithObject: self];

	if (packetLength > DDP_DATAGRAM_SIZE)
		@throw [OFWriteFailedException exceptionWithObject: self
						   requestedLength: length
						      bytesWritten: 0
							     errNo: EMSGSIZE];

	net = OFSocketAddressAppleTalkNetwork(receiver);

	header.length_H = (packetLength >> 8) & 3;
	header.length_L = packetLength & 0xFF;
	header.dst_net[0] = net >> 8;
	header.dst_net[1] = net & 0xFF;
	header.dst_node = OFSocketAddressAppleTalkNode(receiver);
	header.dst_socket = OFSocketAddressAppleTalkPort(receiver);

	if ((bytesWritten = sendmsg(_socket, &msg, 0)) < 0)
		@throw [OFWriteFailedException
		    exceptionWithObject: self
			requestedLength: length
			   bytesWritten: 0
				  errNo: OFSocketErrNo()];

	if ((size_t)bytesWritten != packetLength) {
		bytesWritten -= offsetof(at_ddp_t, type);

		if (bytesWritten < 0)
			bytesWritten = 0;

		@throw [OFWriteFailedException exceptionWithObject: self
						   requestedLength: length
						      bytesWritten: bytesWritten
							     errNo: 0];
	}
}
#endif
@end