glibc/sysdeps/mach/hurd/recvmsg.c

/* Copyright (C) 2001-2023 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public License as
   published by the Free Software Foundation; either version 2.1 of the
   License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; see the file COPYING.LIB.  If
   not, see <https://www.gnu.org/licenses/>.  */

#include <errno.h>
#include <string.h>
#include <sys/socket.h>

#include <hurd.h>
#include <hurd/fd.h>
#include <hurd/socket.h>
#include <sysdep-cancel.h>

/* Receive a message as described by MESSAGE from socket FD.
   Returns the number of bytes read or -1 for errors.  */
ssize_t
__libc_recvmsg (int fd, struct msghdr *message, int flags)
{
  error_t err;
  addr_port_t aport;
  char *data = NULL;
  mach_msg_type_number_t len = 0;
  mach_port_t *ports, *newports = NULL;
  mach_msg_type_number_t nports = 0;
  struct cmsghdr *cmsg;
  char *cdata = NULL;
  mach_msg_type_number_t clen = 0;
  size_t amount;
  char *buf;
  int nfds, *opened_fds = NULL;
  int i, ii, j;
  int newfds;
  int cancel_oldtype;

  error_t reauthenticate (mach_port_t port, mach_port_t *result)
    {
      error_t err;
      mach_port_t ref;
      ref = __mach_reply_port ();
      int cancel_oldtype;

      cancel_oldtype = LIBC_CANCEL_ASYNC();
      do
	err = __io_reauthenticate (port, ref, MACH_MSG_TYPE_MAKE_SEND);
      while (err == EINTR);
      if (!err)
	do
	  err = __USEPORT_CANCEL (AUTH, __auth_user_authenticate (port,
					  ref, MACH_MSG_TYPE_MAKE_SEND,
					  result));
	while (err == EINTR);
      LIBC_CANCEL_RESET (cancel_oldtype);

      __mach_port_destroy (__mach_task_self (), ref);
      return err;
    }

  /* Find the total number of bytes to be read.  */
  amount = 0;
  for (i = 0; i < message->msg_iovlen; i++)
    {
      amount += message->msg_iov[i].iov_len;

      /* As an optimization, we set the initial values of DATA and LEN
         from the first non-empty iovec.  This kicks-in in the case
         where the whole packet fits into that iovec buffer.  */
      if (data == NULL && message->msg_iov[i].iov_len > 0)
	{
	  data = message->msg_iov[i].iov_base;
	  len = message->msg_iov[i].iov_len;
	}
    }

  buf = data;
  cancel_oldtype = LIBC_CANCEL_ASYNC();
  err = HURD_DPORT_USE_CANCEL (fd, __socket_recv (port, &aport,
						  flags, &data, &len,
						  &ports, &nports,
						  &cdata, &clen,
						  &message->msg_flags, amount));
  LIBC_CANCEL_RESET (cancel_oldtype);
  if (err)
    return __hurd_sockfail (fd, flags, err);

  if (message->msg_name != NULL && aport != MACH_PORT_NULL)
    {
      char *buf = message->msg_name;
      mach_msg_type_number_t buflen = message->msg_namelen;
      int type;

      cancel_oldtype = LIBC_CANCEL_ASYNC();
      err = __socket_whatis_address (aport, &type, &buf, &buflen);
      LIBC_CANCEL_RESET (cancel_oldtype);

      if (err == EOPNOTSUPP)
	/* If the protocol server can't tell us the address, just return a
	   zero-length one.  */
	{
	  buf = message->msg_name;
	  buflen = 0;
	  err = 0;
	}

      if (err)
	{
	  __mach_port_deallocate (__mach_task_self (), aport);
	  return __hurd_sockfail (fd, flags, err);
	}

      if (message->msg_namelen > buflen)
	message->msg_namelen = buflen;

      if (buf != message->msg_name)
	{
	  memcpy (message->msg_name, buf, message->msg_namelen);
	  __vm_deallocate (__mach_task_self (), (vm_address_t) buf, buflen);
	}

      if (buflen > 0)
	((struct sockaddr *) message->msg_name)->sa_family = type;
    }
  else if (message->msg_name != NULL)
    message->msg_namelen = 0;

  if (MACH_PORT_VALID (aport))
    __mach_port_deallocate (__mach_task_self (), aport);

  if (buf == data)
    buf += len;
  else
    {
      /* Copy the data into MSG.  */
      if (len > amount)
	message->msg_flags |= MSG_TRUNC;
      else
	amount = len;

      buf = data;
      for (i = 0; i < message->msg_iovlen; i++)
	{
#define min(a, b)	((a) > (b) ? (b) : (a))
	  size_t copy = min (message->msg_iov[i].iov_len, amount);

	  memcpy (message->msg_iov[i].iov_base, buf, copy);

	  buf += copy;
	  amount -= copy;
	  if (len == 0)
	    break;
	}

      __vm_deallocate (__mach_task_self (), (vm_address_t) data, len);
    }

  /* Copy the control message into MSG.  */
  if (clen > message->msg_controllen)
    message->msg_flags |= MSG_CTRUNC;
  else
    message->msg_controllen = clen;
  memcpy (message->msg_control, cdata, message->msg_controllen);

  if (nports > 0)
    {
      newports = __alloca (nports * sizeof (mach_port_t));
      opened_fds = __alloca (nports * sizeof (int));
    }

  /* This counts how many ports we processed completely.  */
  i = 0;
  /* This counts how many new fds we create.  */
  newfds = 0;

  for (cmsg = CMSG_FIRSTHDR (message);
       cmsg;
       cmsg = CMSG_NXTHDR (message, cmsg))
  {
    if (cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type == SCM_RIGHTS)
      {
	/* SCM_RIGHTS support.  */
	/* The fd's flags are passed in the control data.  */
	int *fds = (int *) CMSG_DATA (cmsg);
	nfds = (cmsg->cmsg_len - CMSG_ALIGN (sizeof (struct cmsghdr)))
	       / sizeof (int);

	for (j = 0; j < nfds; j++)
	  {
	    int fd_flags = (flags & MSG_CMSG_CLOEXEC) ? O_CLOEXEC : 0;
	    err = reauthenticate (ports[i], &newports[newfds]);
	    if (err)
	      goto cleanup;
	    fds[j] = opened_fds[newfds] = _hurd_intern_fd (newports[newfds],
							   fds[j] | fd_flags,
							   0);
	    if (fds[j] == -1)
	      {
		err = errno;
		__mach_port_deallocate (__mach_task_self (), newports[newfds]);
		goto cleanup;
	      }
	    i++;
	    newfds++;
	  }
      }
  }

  for (i = 0; i < nports; i++)
    __mach_port_deallocate (mach_task_self (), ports[i]);

  __vm_deallocate (__mach_task_self (), (vm_address_t) cdata, clen);

  return (buf - data);

cleanup:
  /* Clean up all the file descriptors from port 0 to i-1.  */
  if (nports > 0)
    {
      ii = 0;
      newfds = 0;
      for (cmsg = CMSG_FIRSTHDR (message);
	   cmsg;
	   cmsg = CMSG_NXTHDR (message, cmsg))
	{
	  if (cmsg->cmsg_level == SOL_SOCKET && cmsg->cmsg_type == SCM_RIGHTS)
	    {
	      nfds = (cmsg->cmsg_len - CMSG_ALIGN (sizeof (struct cmsghdr)))
		     / sizeof (int);
	      for (j = 0; j < nfds && ii < i; j++, ii++, newfds++)
	      {
		_hurd_fd_close (_hurd_fd_get (opened_fds[newfds]));
		__mach_port_deallocate (__mach_task_self (), newports[newfds]);
		__mach_port_deallocate (__mach_task_self (), ports[ii]);
	      }
	    }
	}
    }

  __vm_deallocate (__mach_task_self (), (vm_address_t) cdata, clen);
  return __hurd_fail (err);
}

weak_alias (__libc_recvmsg, recvmsg)
weak_alias (__libc_recvmsg, __recvmsg)