Report EMSGSIZE when appropriate for sendmsg

src/trusted/desc/nrd_xfer.c

 /*
  * Copyright 2008 The Native Client Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can
  * be found in the LICENSE file.
  */
 
 /*
  * Native Client Resource Descriptor Transfer protocol for trusted code.
  */
 
@@ skipping 340 matching lines @@
   retval = (*((struct NaClDescVtbl const *) channel->base.vtbl)->
             SendMsg)(channel, &kern_msg_hdr, flags);
   NaClLog(4, "SendMsg returned %"NACL_PRIdS"\n", retval);
   if (NaClIsNegErrno(retval)) {
     /*
      * NaClWouldBlock uses TSD (for both the errno-based and
      * GetLastError()-based implementations), so this is threadsafe.
      */
     if (0 != (flags & NACL_DONT_WAIT) && NaClWouldBlock()) {
       retval = -NACL_ABI_EAGAIN;
+    } else if (-NACL_ABI_EMSGSIZE == retval) {
+      /*
+       * Allow the above layer to process when imc_sendmsg calls fail due
+       * to the OS not supporting a large enough buffer.
+       */
+      retval = -NACL_ABI_EMSGSIZE;
     } else {
       /*
        * TODO(bsy): the else case is some mysterious internal error.
        * should we destroy the channel?  Was the failure atomic?  Did
        * it send some partial data?  Linux implementation appears
        * okay.
        *
        * We return EIO and let the caller deal with it.
        */
       retval = -NACL_ABI_EIO;
@@ skipping 395 matching lines @@
   }
   if (NACL_INVALID_HANDLE != sock_pair[1]) {
     (void) NaClClose(sock_pair[1]);
   }
 
   free(d0);
   free(d1);
 
   return retval;
 }