mdw@git.distorted.org.uk Git - mLib/blob - sys/fdpass.c

   1 /* -*-c-*-
   2  *
   3  * File descriptor passing
   4  *
   5  * (c) 2003 Straylight/Edgeware
   6  */
   7
   8 /*----- Licensing notice --------------------------------------------------*
   9  *
  10  * This file is part of the mLib utilities library.
  11  *
  12  * mLib is free software; you can redistribute it and/or modify
  13  * it under the terms of the GNU Library General Public License as
  14  * published by the Free Software Foundation; either version 2 of the
  15  * License, or (at your option) any later version.
  16  *
  17  * mLib is distributed in the hope that it will be useful,
  18  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  20  * GNU Library General Public License for more details.
  21  *
  22  * You should have received a copy of the GNU Library General Public
  23  * License along with mLib; if not, write to the Free
  24  * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
  25  * MA 02111-1307, USA.
  26  */
  27
  28 /*----- Header files ------------------------------------------------------*/
  29
  30 #include "config.h"
  31
  32 #include <errno.h>
  33 #include <stdio.h>
  34 #include <stdlib.h>
  35 #include <string.h>
  36
  37 #include <sys/types.h>
  38 #include <sys/time.h>
  39 #include <unistd.h>
  40 #include <sys/socket.h>
  41 #include <sys/uio.h>
  42 #include <sys/un.h>
  43
  44 #include "fdpass.h"
  45 #include "macros.h"
  46
  47 /*----- Main code ---------------------------------------------------------*/
  48
  49 /* --- @fdpass_send@ --- *
  50  *
  51  * Arguments:   @int sock@ = socket to send over
  52  *              @int fd@ = file descriptor to send
  53  *              @const void *p@ = pointer to data to send
  54  *              @size_t sz@ = size of buffer to send
  55  *
  56  * Returns:     On error, @-1@, otherwise number of bytes transferred from
  57  *              @p@.
  58  *
  59  * Use:         Sends a copy of file descriptor @fd@ to the other end of
  60  *              @sock@.
  61  */
  62
  63 ssize_t fdpass_send(int sock, int fd, const void *p, size_t sz)
  64 {
  65   struct iovec iov;
  66   struct msghdr msg;
  67 #ifndef HAVE_MSG_ACCRIGHTS
  68   char buf[CMSG_SPACE(sizeof(fd))];
  69   struct cmsghdr *cmsg;
  70 #endif
  71
  72   iov.iov_base = UNCONST(void, p);
  73   iov.iov_len = sz;
  74   msg.msg_name = 0;
  75   msg.msg_namelen = 0;
  76   msg.msg_iov = &iov;
  77   msg.msg_iovlen = 1;
  78 #ifdef HAVE_MSG_ACCRIGHTS
  79   msg.msg_accrights = &fd;
  80   msg.msg_accrightslen = sizeof(fd);
  81 #else
  82   msg.msg_flags = 0;
  83   msg.msg_control = buf;
  84   msg.msg_controllen = sizeof(buf);
  85   cmsg = CMSG_FIRSTHDR(&msg);
  86   cmsg->cmsg_len = CMSG_LEN(sizeof(fd));
  87   cmsg->cmsg_level = SOL_SOCKET;
  88   cmsg->cmsg_type = SCM_RIGHTS;
  89   memcpy(CMSG_DATA(cmsg), &fd, sizeof(fd));
  90 #endif
  91   return (sendmsg(sock, &msg, 0));
  92 }
  93
  94 /* --- @fdpass_recv@ --- *
  95  *
  96  * Arguments:   @int sock@ = socket to send over
  97  *              @int *fd@ = where to put received descriptor
  98  *              @void *p@ = pointer to where to put data
  99  *              @size_t sz@ = size of buffer
 100  *
 101  * Returns:     On error, @-1@, otherwise number of bytes transferred.
 102  *
 103  * Use:         Receives a file descriptor.  If the call succeeds, and there
 104  *              was a file descriptor, then @fd@ won't be @-1@ on exit;
 105  *              otherwise it will.  At most one descriptor will be collected.
 106  */
 107
 108 /* Qemu 2.8.1 clobbers 12 bytes beyond the end of the control-message
 109  * buffer.  This is fixed in 2.12, but I'll bodge it for the sake of Debian
 110  * stable.
 111  */
 112 #define QEMU_SCRATCHSZ 16
 113
 114 ssize_t fdpass_recv(int sock, int *fd, void *p, size_t sz)
 115 {
 116   struct iovec iov;
 117   struct msghdr msg;
 118   ssize_t rc;
 119 #ifndef HAVE_MSG_ACCRIGHTS
 120   char buf[CMSG_SPACE(sizeof(fd)) + QEMU_SCRATCHSZ];
 121   struct cmsghdr *cmsg;
 122   int fdtmp;
 123 #endif
 124
 125   *fd = -1;
 126   iov.iov_base = p;
 127   iov.iov_len = sz;
 128   msg.msg_name = 0;
 129   msg.msg_namelen = 0;
 130   msg.msg_iov = &iov;
 131   msg.msg_iovlen = 1;
 132 #ifdef HAVE_MSG_ACCRIGHTS
 133   msg.msg_accrights = fd;
 134   msg.msg_accrightslen = sizeof(*fd);
 135 #else
 136   msg.msg_flags = 0;
 137   msg.msg_control = buf;
 138   msg.msg_controllen = sizeof(buf) - QEMU_SCRATCHSZ;
 139 #endif
 140   if ((rc = recvmsg(sock, &msg, 0)) < 0)
 141     return (rc);
 142 #ifdef HAVE_MSG_ACCRIGHTS
 143   if (msg.msg_accrightslen < sizeof(*fd))
 144     *fd = -1;
 145 #else
 146   for (cmsg = CMSG_FIRSTHDR(&msg); cmsg; cmsg = CMSG_NXTHDR(&msg, cmsg)) {
 147     if (cmsg->cmsg_level == SOL_SOCKET &&
 148         cmsg->cmsg_type == SCM_RIGHTS &&
 149         cmsg->cmsg_len >= CMSG_LEN(sizeof(*fd))) {
 150       memcpy(&fdtmp, CMSG_DATA(cmsg), sizeof(fdtmp));
 151       if (*fd == -1)
 152         *fd = fdtmp;
 153       else
 154         close(fdtmp);
 155     }
 156   }
 157 #endif
 158   return (rc);
 159 }
 160
 161 #undef QEMU_SCRATCHSZ
 162
 163 /*----- That's all, folks -------------------------------------------------*/