From mboxrd@z Thu Jan 1 00:00:00 1970 From: walter harms Subject: Re: help needed with debugging tcp/ip over ax25 Date: Sat, 05 Feb 2011 11:28:30 +0100 Message-ID: <4D4D264E.2020707@bfs.de> References: <1296857793.3329.22.camel@tesla.lan> Reply-To: wharms@bfs.de Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1296857793.3329.22.camel@tesla.lan> Sender: linux-hams-owner@vger.kernel.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Guido Trentalancia Cc: linux-hams@vger.kernel.org Am 04.02.2011 23:16, schrieb Guido Trentalancia: > 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. > did you try arp -s ? re, wh