proto_common.c

/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2009-2010 The FreeBSD Foundation
 * Copyright (c) 2011 Pawel Jakub Dawidek <[email protected]>
 * All rights reserved.
 *
 * This software was developed by Pawel Jakub Dawidek under sponsorship from
 * the FreeBSD Foundation.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHORS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHORS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/types.h>
#include <sys/socket.h>

#include <errno.h>
#include <fcntl.h>
#include <stdbool.h>
#include <stdlib.h>
#include <strings.h>
#include <unistd.h>

#include "pjdlog.h"
#include "proto_impl.h"

/* Maximum size of packet we want to use when sending data. */
#ifndef MAX_SEND_SIZE
#define	MAX_SEND_SIZE	32768
#endif

static bool
blocking_socket(int sock)
{
	int flags;

	flags = fcntl(sock, F_GETFL);
	PJDLOG_ASSERT(flags >= 0);
	return ((flags & O_NONBLOCK) == 0);
}

static int
proto_descriptor_send(int sock, int fd)
{
	unsigned char ctrl[CMSG_SPACE(sizeof(fd))];
	struct msghdr msg;
	struct cmsghdr *cmsg;

	PJDLOG_ASSERT(sock >= 0);
	PJDLOG_ASSERT(fd >= 0);

	bzero(&msg, sizeof(msg));
	bzero(&ctrl, sizeof(ctrl));

	msg.msg_iov = NULL;
	msg.msg_iovlen = 0;
	msg.msg_control = ctrl;
	msg.msg_controllen = sizeof(ctrl);

	cmsg = CMSG_FIRSTHDR(&msg);
	cmsg->cmsg_level = SOL_SOCKET;
	cmsg->cmsg_type = SCM_RIGHTS;
	cmsg->cmsg_len = CMSG_LEN(sizeof(fd));
	bcopy(&fd, CMSG_DATA(cmsg), sizeof(fd));

	if (sendmsg(sock, &msg, 0) == -1)
		return (errno);

	return (0);
}

int
proto_common_send(int sock, const unsigned char *data, size_t size, int fd)
{
	ssize_t done;
	size_t sendsize;
	int errcount = 0;

	PJDLOG_ASSERT(sock >= 0);

	if (data == NULL) {
		/* The caller is just trying to decide about direction. */

		PJDLOG_ASSERT(size == 0);

		if (shutdown(sock, SHUT_RD) == -1)
			return (errno);
		return (0);
	}

	PJDLOG_ASSERT(data != NULL);
	PJDLOG_ASSERT(size > 0);

	do {
		sendsize = size < MAX_SEND_SIZE ? size : MAX_SEND_SIZE;
		done = send(sock, data, sendsize, MSG_NOSIGNAL);
		if (done == 0) {
			return (ENOTCONN);
		} else if (done == -1) {
			if (errno == EINTR)
				continue;
			if (errno == ENOBUFS) {
				/*
				 * If there are no buffers we retry.
				 * After each try we increase delay before the
				 * next one and we give up after fifteen times.
				 * This gives 11s of total wait time.
				 */
				if (errcount == 15) {
					pjdlog_warning("Getting ENOBUFS errors for 11s on send(), giving up.");
				} else {
					if (errcount == 0)
						pjdlog_warning("Got ENOBUFS error on send(), retrying for a bit.");
					errcount++;
					usleep(100000 * errcount);
					continue;
				}
			}
			/*
			 * If this is blocking socket and we got EAGAIN, this
			 * means the request timed out. Translate errno to
			 * ETIMEDOUT, to give administrator a hint to
			 * eventually increase timeout.
			 */
			if (errno == EAGAIN && blocking_socket(sock))
				errno = ETIMEDOUT;
			return (errno);
		}
		data += done;
		size -= done;
	} while (size > 0);
	if (errcount > 0) {
		pjdlog_info("Data sent successfully after %d ENOBUFS error%s.",
		    errcount, errcount == 1 ? "" : "s");
	}

	if (fd == -1)
		return (0);
	return (proto_descriptor_send(sock, fd));
}

static int
proto_descriptor_recv(int sock, int *fdp)
{
	unsigned char ctrl[CMSG_SPACE(sizeof(*fdp))];
	struct msghdr msg;
	struct cmsghdr *cmsg;

	PJDLOG_ASSERT(sock >= 0);
	PJDLOG_ASSERT(fdp != NULL);

	bzero(&msg, sizeof(msg));
	bzero(&ctrl, sizeof(ctrl));

	msg.msg_iov = NULL;
	msg.msg_iovlen = 0;
	msg.msg_control = ctrl;
	msg.msg_controllen = sizeof(ctrl);

	if (recvmsg(sock, &msg, 0) == -1)
		return (errno);

	cmsg = CMSG_FIRSTHDR(&msg);
	if (cmsg == NULL || cmsg->cmsg_level != SOL_SOCKET ||
	    cmsg->cmsg_type != SCM_RIGHTS) {
		return (EINVAL);
	}
	bcopy(CMSG_DATA(cmsg), fdp, sizeof(*fdp));

	return (0);
}

int
proto_common_recv(int sock, unsigned char *data, size_t size, int *fdp)
{
	ssize_t done;

	PJDLOG_ASSERT(sock >= 0);

	if (data == NULL) {
		/* The caller is just trying to decide about direction. */

		PJDLOG_ASSERT(size == 0);

		if (shutdown(sock, SHUT_WR) == -1)
			return (errno);
		return (0);
	}

	PJDLOG_ASSERT(data != NULL);
	PJDLOG_ASSERT(size > 0);

	do {
		done = recv(sock, data, size, MSG_WAITALL);
	} while (done == -1 && errno == EINTR);
	if (done == 0) {
		return (ENOTCONN);
	} else if (done == -1) {
		/*
		 * If this is blocking socket and we got EAGAIN, this
		 * means the request timed out. Translate errno to
		 * ETIMEDOUT, to give administrator a hint to
		 * eventually increase timeout.
		 */
		if (errno == EAGAIN && blocking_socket(sock))
			errno = ETIMEDOUT;
		return (errno);
	}
	if (fdp == NULL)
		return (0);
	return (proto_descriptor_recv(sock, fdp));
}