From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ed W Subject: Need help with dialup connection (and syn packets) Date: Sat, 23 Mar 2013 16:33:43 +0000 Message-ID: <514DD967.1080501@wildgooses.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: Sender: netfilter-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: netfilter@vger.kernel.org Hi, I have a dialup connection (yes they still exist) and PPP with demand dial. I have a problem with the exponential backoff sending new SYN packets when creating a new tcp connection. The problem is that the dialup connection takes around 23 seconds to complete (and then hangs up 10 seconds later due to inactivitity), but by then the gaps between SYN packets is very long... Unfortunately most operating systems send an initial SYN, then exponentially backoff with intermittent resends, say after 1 sec, 2 secs, 4 secs, 8 secs, 16 secs, etc. So what we observe is that because the dialup connection takes so long to complete, by then the tcp connection is only trying quite intermittently to connect, eg you might well wait another 8+ seconds before the next syn is resent, quite easily my demand dial connection will hangup before the retransmit is even fired... Does anyone have any suggestions on how I might fake this a little? I effectively desire to simulate buffering syn packets before the PPP connection comes up? Thanks for any off the wall thoughts... Ed W