text: /* $OpenBSD: monitor_fdpass.c,v 1.21 2016/02/29 20:22:36 jca Exp $ */
  /*
   * Copyright 2001 Niels Provos <provos@citi.umich.edu>
   * All rights reserved.
   *
   * 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 AUTHOR ``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 AUTHOR 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 <sys/uio.h>
  
  #include <errno.h>
  #include <poll.h>
  #include <string.h>
  #include <stdarg.h>
  
  #include "log.h"
  #include "monitor_fdpass.h"
  
  int
  mm_send_fd(int sock, int fd)
  {
  	struct msghdr msg;
  	union {
  		struct cmsghdr hdr;
  		char buf[CMSG_SPACE(sizeof(int))];
  	} cmsgbuf;
  	struct cmsghdr *cmsg;
  	struct iovec vec;
  	char ch = '\0';
  	ssize_t n;
  	struct pollfd pfd;
  
  	memset(&msg, 0, sizeof(msg));
  	memset(&cmsgbuf, 0, sizeof(cmsgbuf));
  	msg.msg_control = (caddr_t)&cmsgbuf.buf;
  	msg.msg_controllen = sizeof(cmsgbuf.buf);
  	cmsg = CMSG_FIRSTHDR(&msg);
  	cmsg->cmsg_len = CMSG_LEN(sizeof(int));
  	cmsg->cmsg_level = SOL_SOCKET;
  	cmsg->cmsg_type = SCM_RIGHTS;
  	*(int *)CMSG_DATA(cmsg) = fd;
  
  	vec.iov_base = &ch;
  	vec.iov_len = 1;
  	msg.msg_iov = &vec;
  	msg.msg_iovlen = 1;
  
  	pfd.fd = sock;
  	pfd.events = POLLOUT;
  	while ((n = sendmsg(sock, &msg, 0)) == -1 &&
  	    (errno == EAGAIN || errno == EINTR)) {
  		debug3("%s: sendmsg(%d): %s", __func__, fd, strerror(errno));
  		(void)poll(&pfd, 1, -1);
  	}
  	if (n == -1) {
  		error("%s: sendmsg(%d): %s", __func__, fd,
  		    strerror(errno));
  		return -1;
  	}
  
  	if (n != 1) {
  		error("%s: sendmsg: expected sent 1 got %zd", __func__, n);
  		return -1;
  	}
  	return 0;
  }
  
  int
  mm_receive_fd(int sock)
  {
  	struct msghdr msg;
  	union {
  		struct cmsghdr hdr;
  		char buf[CMSG_SPACE(sizeof(int))];
  	} cmsgbuf;
  	struct cmsghdr *cmsg;
  	struct iovec vec;
  	ssize_t n;
  	char ch;
  	int fd;
  	struct pollfd pfd;
  
  	memset(&msg, 0, sizeof(msg));
  	memset(&cmsgbuf, 0, sizeof(cmsgbuf));
  	vec.iov_base = &ch;
  	vec.iov_len = 1;
  	msg.msg_iov = &vec;
  	msg.msg_iovlen = 1;
  	msg.msg_control = &cmsgbuf.buf;
  	msg.msg_controllen = sizeof(cmsgbuf.buf);
  
  	pfd.fd = sock;
  	pfd.events = POLLIN;
  	while ((n = recvmsg(sock, &msg, 0)) == -1 &&
  	    (errno == EAGAIN || errno == EINTR)) {
  		debug3("%s: recvmsg: %s", __func__, strerror(errno));
  		(void)poll(&pfd, 1, -1);
  	}
  	if (n == -1) {
  		error("%s: recvmsg: %s", __func__, strerror(errno));
  		return -1;
  	}
  
  	if (n != 1) {
  		error("%s: recvmsg: expected received 1 got %zd", __func__, n);
  		return -1;
  	}
  
  	cmsg = CMSG_FIRSTHDR(&msg);
  	if (cmsg == NULL) {
  		error("%s: no message header", __func__);
  		return -1;
  	}
  
  	if (cmsg->cmsg_type != SCM_RIGHTS) {
  		error("%s: expected type %d got %d", __func__,
  		    SCM_RIGHTS, cmsg->cmsg_type);
  		return -1;
  	}
  	fd = (*(int *)CMSG_DATA(cmsg));
  	return fd;
  }
  