compat/recvmsg.c

   1 /*****************************************************************************
   2  * recvmsg.c: POSIX recvmsg() replacement
   3  *****************************************************************************
   4  * Copyright © 2017 VLC authors and VideoLAN
   5  * Copyright © 2016 Rémi Denis-Courmont
   6  *
   7  * Authors: Rémi Denis-Courmont
   8  *          Dennis Hamester <dhamester@jusst.de>
   9  *
  10  * This program is free software; you can redistribute it and/or modify it
  11  * under the terms of the GNU Lesser General Public License as published by
  12  * the Free Software Foundation; either version 2.1 of the License, or
  13  * (at your option) any later version.
  14  *
  15  * This program is distributed in the hope that it will be useful,
  16  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  17  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  18  * GNU Lesser General Public License for more details.
  19  *
  20  * You should have received a copy of the GNU Lesser General Public License
  21  * along with this program; if not, write to the Free Software Foundation,
  22  * Inc., 51 Franklin Street, Fifth Floor, Boston MA 02110-1301, USA.
  23  *****************************************************************************/
  24
  25 #ifdef HAVE_CONFIG_H
  26 # include <config.h>
  27 #endif
  28
  29 #ifdef _WIN32
  30 # include <errno.h>
  31 # include <stdlib.h>
  32 # include <winsock2.h>
  33
  34 ssize_t recvmsg(int fd, struct msghdr *msg, int flags)
  35 {
  36     if (msg->msg_controllen != 0)
  37     {
  38         errno = ENOSYS;
  39         return -1;
  40     }
  41
  42     if (msg->msg_iovlen > IOV_MAX)
  43     {
  44         errno = EINVAL;
  45         return -1;
  46     }
  47
  48     WSABUF *buf = malloc(msg->msg_iovlen * sizeof (*buf));
  49     if (buf == NULL)
  50         return -1;
  51
  52     for (unsigned i = 0; i < msg->msg_iovlen; i++)
  53     {
  54         buf[i].len = msg->msg_iov[i].iov_len;
  55         buf[i].buf = msg->msg_iov[i].iov_base;
  56     }
  57
  58     DWORD dwFlags = flags;
  59     INT fromlen = msg->msg_namelen;
  60     DWORD rcvd;
  61     int ret;
  62     if (fromlen)
  63         ret = WSARecvFrom(fd, buf, msg->msg_iovlen, &rcvd, &dwFlags,
  64                           msg->msg_name, &fromlen, NULL, NULL);
  65     else
  66         ret = WSARecv(fd, buf, msg->msg_iovlen, &rcvd, &dwFlags,
  67                       NULL, NULL);
  68     free(buf);
  69
  70     if (ret == 0)
  71     {
  72         msg->msg_namelen = fromlen;
  73         msg->msg_flags = dwFlags;
  74         return rcvd;
  75     }
  76
  77     switch (WSAGetLastError())
  78     {
  79         case WSAEWOULDBLOCK:
  80             errno = EAGAIN;
  81             break;
  82     }
  83     return -1;
  84 }
  85
  86 #elif defined __native_client__
  87 #include <errno.h>
  88 #include <limits.h>
  89 #include <stdlib.h>
  90 #include <string.h>
  91 #ifdef HAVE_SYS_SOCKET_H
  92 #include <sys/socket.h>
  93 #endif
  94 #ifdef HAVE_SYS_UIO_H
  95 #include <sys/uio.h>
  96 #endif
  97
  98 ssize_t recvmsg(int fd, struct msghdr *msg, int flags)
  99 {
 100     if (msg->msg_controllen != 0)
 101     {
 102         errno = ENOSYS;
 103         return -1;
 104     }
 105
 106     if ((msg->msg_iovlen <= 0) || (msg->msg_iovlen > IOV_MAX))
 107     {
 108         errno = EMSGSIZE;
 109         return -1;
 110     }
 111
 112     size_t full_size = 0;
 113     for (int i = 0; i < msg->msg_iovlen; ++i)
 114         full_size += msg->msg_iov[i].iov_len;
 115
 116     if (full_size > SSIZE_MAX) {
 117         errno = EINVAL;
 118         return -1;
 119     }
 120
 121     /**
 122      * We always allocate here, because whether recv/recvfrom allow NULL message
 123      * or not is unspecified.
 124      */
 125     char *data = malloc(full_size ? full_size : 1);
 126     if (!data) {
 127         errno = ENOMEM;
 128         return -1;
 129     }
 130
 131     ssize_t res;
 132     if (msg->msg_name)
 133         res = recvfrom(fd, data, full_size, flags, msg->msg_name, &msg->msg_namelen);
 134     else
 135         res = recv(fd, data, full_size, flags);
 136
 137     if (res > 0) {
 138         size_t left;
 139         if ((size_t)res <= full_size) {
 140             left = res;
 141             msg->msg_flags = 0;
 142         }
 143         else {
 144             left = full_size;
 145             msg->msg_flags = MSG_TRUNC;
 146         }
 147
 148         const char *src = data;
 149         for (int i = 0; (i < msg->msg_iovlen) && (left > 0); ++i)
 150         {
 151             size_t to_copy = msg->msg_iov[i].iov_len;
 152             if (to_copy > left)
 153                 to_copy = left;
 154
 155             memcpy(msg->msg_iov[i].iov_base, src, to_copy);
 156             src += to_copy;
 157             left -= to_copy;
 158         }
 159     }
 160
 161     free(data);
 162     return res;
 163 }
 164
 165 #else
 166 #error recvmsg not implemented on your platform!
 167 #endif