Em Wed, Jun 20, 2007 at 10:55:39AM +0100, Gerrit Renker escreveu: > [DCCP]: Fix Reset/Sync-Flood Bug > > This updates sequence number checking with regard to RFC 4340, 7.5.4. > Missing in the code was an exception for sequence-invalid Reset packets, > which get a Sync acknowledging GSR, instead of (as usual) P.seqno. > > This can lead to an oscillating ping-pong flood of Reset packets. > > In fact, it has been observed on the wire as follows: > > 1. client establishes connection to server; > 2. before server can write to client, client crashes without notifying > the server (NB: now no longer possible due to ABORT function); > 3. server sends DCCP-Data packet (has no ackno); > 4. client generates Reset "No Connection", seqno=0, increments seqno; > 5. server replies with Sync, using ackno = P.seqno; > 6. client generates Reset "No Connection" with seqno = ackno + 1; > 7. goto (5). > > The difference is that now in (5) the server uses GSR. This causes the > Reset sent by the client in (6) to become sequence-valid, so that in (7) > the vicious circle is broken; the Reset is then enqueued and causes the > socket to enter TIMEWAIT state. Well spotted! I wonder if Step 6 in the RFC pseudocode changed from what was in the draft I used... 8) - Arnaldo - To unsubscribe from this list: send the line "unsubscribe dccp" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
