Fix read_write() changes for TCP timeout.

I misread the man page for socket(7) and TCP timeouts.

A timeout generates a -1 return and EAGAIN errno, NOT a short read.

Short reads are legit, and aborting when they are seen creates
hard-to-reproduce errors.

src/util.c

@@ -770,7 +770,7 @@ int retry_send(ssize_t rc)
    rw = 2 -> write once
    rw = 3 -> read once
 
-   "once" fail if all the data doesn't arrive/go in a single read/write.
+   "once" fails on EAGAIN, as this a timeout.
    This indicates a timeout of a TCP socket.
 */
 int read_write(int fd, unsigned char *packet, int size, int rw)
@@ -779,7 +779,6 @@ int read_write(int fd, unsigned char *packet, int size, int rw)
   
   for (done = 0; done < size; done += n)
     {
-      do { 
       if (rw & 1)
 	n = read(fd, &packet[done], (size_t)(size - done));
       else
@@ -788,19 +787,25 @@ int read_write(int fd, unsigned char *packet, int size, int rw)
       if (n == 0)
 	return 0;
 
-	if (n == -1 && errno == EINTR)
+      if (n == -1)
+	{
+	  n = 0; /* don't mess with counter when we loop. */
+
+	  if (errno == EINTR || errno == ENOMEM || errno == ENOBUFS)
 	    continue;
 
+	  if (errno == EAGAIN || errno == EWOULDBLOCK)
+	    {
 	      /* "once" variant */
-	if ((rw & 2) && n != size)
+	      if (rw & 2)
 		return 0;
 
-      } while (n == -1 && (errno == EINTR || errno == ENOMEM || errno == ENOBUFS ||
-			   errno == EAGAIN || errno == EWOULDBLOCK));
+	      continue;
+	    }
 
-      if (n == -1)
 	  return 0;
 	}
+    }
           
   return 1;
 }