Re: [Bacnet-developers] [Update] Activating BVLC code

[<tom...@sw...>]

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On Sun, Jan 13, 2008 at 12:12:20PM +0000, tom...@sw... wrote:
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> Hello,
> 
> call me crazy, but I'm giving a try at the (as far as I can see not yet
> fully functional) BVLC code [...]

Whois works now with "forwarded broadcast" answers. Wohoo! :-)

The only issue I found was in bvlc.c. The BVLC header is a bit longer
for this kind of messages (10 bytes instead of four, to accomodate the
original MAC address). Note that I haven't a version of Annex J, so I'm
working off what Wireshark tells me.

The tentative fix is more or less like so (but bear in mind that I might
just partially know what I'm doing):

=========================================================
- --- a/src/bvlc.c
+++ b/src/bvlc.c
@@ -936,12 +936,27 @@ uint16_t bvlc_receive(
             /*  if this was received via Broadcast, don't broadcast it
 *  */

             /* FIXME:  how do I know if I received a unicast or broadcast? */
+           npdu_len -= 6; /* FIXME very ugly */
             if (!bvlc_broadcast_address_same(&sin)) {
                 dest.sin_addr.s_addr = htonl(bip_get_broadcast_addr());
                 dest.sin_port == htons(bip_get_port());
                 bvlc_send_mpdu(&dest, &npdu[4], npdu_len);
             }
             bvlc_fdt_forward_npdu(&sin, &npdu[4], npdu_len);
+           /* FIXME we might want to do something with tne MAC provided
+               in the BVLC header
+           */
+            if (npdu_len < max_npdu) {
+                /* shift the buffer to return a valid PDU */
+               for (i = 0; i < npdu_len; i++) {
+                 npdu[i] = npdu[i + 10];
+               }
+           } else {
+             /* ignore packets that are too large */
+             /* clients should check my max-apdu first */
+             npdu_len = 0;
+           }
+
             break;
         case BVLC_REGISTER_FOREIGN_DEVICE:
             /* Upon receipt of a BVLL Register-Foreign-Device message, a BBMD
=========================================================

All in all I'm impressed by your code quality. For a part of the code which
is not really supposed to be ready, it is really near to working status.

Thanks and regards
- -- tomás
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