From mboxrd@z Thu Jan 1 00:00:00 1970 From: Guido Trentalancia Subject: help needed with debugging tcp/ip over ax25 Date: Fri, 04 Feb 2011 23:16:33 +0100 Message-ID: <1296857793.3329.22.camel@tesla.lan> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: Sender: linux-hams-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" To: linux-hams@vger.kernel.org Hello everybody ! I am experiencing problems when trying to run TCP/IP over AX.25 on Linux. I have two hosts 44.134.241.1 and 44.134.241.21, both of them are using Linux. The kiss interfaces are up and running and the ax25 interfaces have been configured. The first machine is running a few servers, for example conversd on port 3600. After a fresh reboot, the first machine is responding correctly to any TCP/IP connection, for example telnet 44.134.241.1 3600 (from the second machine) works correctly and leads to a connection and a successful telnet session. However, after a while (kissattach is killed, the ax25 interface is brought down and then kissattach and the ax25 interface are restarted again on the first machine), the TCP/IP connection does not work anymore. In other words I can no longer telnet from the second machine to the first one. The packets are still there, as shown in the logs below. Output from tcpdump -i ax0 on the first machine: 19:51:46.932089 IP 44.134.241.21.43675 > iz6rdb.ampr.org.convers: Flags [S], seq 2030721846, win 1024, options [mss 256,sackOK,TS val 149718 ecr 0,nop,wscale 6], length 0 19:51:46.932089 IP 44.134.241.21.43675 > iz6rdb.ampr.org.convers: Flags [S], seq 2030721846, win 1024, options [mss 256,sackOK,TS val 149718 ecr 0,nop,wscale 6], length 0 Output from tcpdump -i ax0 on the second machine: 19:51:46.386898 IP 44.134.241.21.43675 > iz6rdb.ampr.org.trap-daemon: Flags [S], seq 2030721846, win 1024, options [mss 256,sackOK,TS val 149718 ecr 0,nop,wscale 6], length 0 19:51:49.388715 IP 44.134.241.21.43675 > iz6rdb.ampr.org.trap-daemon: Flags [S], seq 2030721846, win 1024, options [mss 256,sackOK,TS val 152720 ecr 0,nop,wscale 6], length 0 The output from axlisten -a (on both machines) also shows that packets are getting transmitted and received correctly. But unfortunately, the first machine is not responding anymore ! Similar things can be said about ping or other TCP/IP connections (such as ssh). It shouldn't be an iptables issue (as bringing iptables down does not improve things and in any case, everything is working fine just after a reboot). However, it could be an arp issue because when the connection is working, on the first machine (the one which runs the servers that do not respond) I have the following line in arp: 44.134.241.21 ax25 IZ6RDB-7 C ax0 while, when the connection is not working, that line does not appear anymore in arp. The following lines are also missing from the tcpdump output when the server is not replying: 20:19:35.011128 arp who-has 44.134.241.21 tell iz6rdb.ampr.org 20:19:35.934448 arp reply 44.134.241.21 is-at IZ6RDB-7 20:19:35.934448 arp reply 44.134.241.21 is-at IZ6RDB-7 Any help would be greatly appreciated. 73, Guido IZ6RDB