Viktors Žilinskis
2008-Oct-02 15:00 UTC
SSH connection hangs on shell commands when used through tinc
Hello! I have 3 PCs - Windows, FreeBSD and Ubuntu. FreeBSD runs as a tinc server as it has a real IP. Ubuntu runs as a tinc client as it has a dynamically changing public IP. Windows has not tinc installed yet. Therefore I use Putty ssh client to ssh to FreeBSD machine (as it has real IP) and then from there I ssh to the Ubuntu box using its virtual IP. The connection establishes well, I can ping FreeBSD and Ubuntu virtual IPs in both directions, no problems so far. But when I use any shell commands which have significant text output, the ssh connection just hangs. For example, if I list files in a small direcotry (5-10) it lists them, If i list a bigger directory it hangs. It also hangs on other commands, like top. Interestingly enough, I tried to do that in the opposite direction - connected via ssh to FreeBSD box virtual IP from Ubuntu box, and I could not find a command which could hang the connection. I've tried to use different ssh clients, but this does not help. Though I am not sure, I think there should be something wrong with my tinc setup. Any ideas? Best Regards, -- Viktors ?ilinskis -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.tinc-vpn.org/pipermail/tinc/attachments/20081002/f406ce5b/attachment.htm
Guus Sliepen
2008-Oct-02 16:56 UTC
SSH connection hangs on shell commands when used through tinc
On Thu, Oct 02, 2008 at 06:00:42PM +0300, Viktors ?ilinskis wrote:> [...] The connection > establishes well, I can ping FreeBSD and Ubuntu virtual IPs in both > directions, no problems so far. But when I use any shell commands which have > significant text output, the ssh connection just hangs. For example, if I > list files in a small direcotry (5-10) it lists them, If i list a bigger > directory it hangs. It also hangs on other commands, like top. Interestingly > enough, I tried to do that in the opposite direction - connected via ssh to > FreeBSD box virtual IP from Ubuntu box, and I could not find a command which > could hang the connection. > > I've tried to use different ssh clients, but this does not help. Though I am > not sure, I think there should be something wrong with my tinc setup.It sounds like a MTU problem. Either a router is silently dropping packets that are too large, or it is correctly sending back ICMP Fragmentation Needed packets and a firewall somewhere is blocking them. Some options to work around the problem: - Add "PMTUDiscovery = yes" to your host config files. - Add "PMTU = 1400" to your host config files, or add "ifconfig $INTERFACE mtu 1400" to the tinc-up scripts. - Add "TCPOnly = yes" to your host config files. Of course, the best solution is to fix the offending router/firewall. Let me know if everything fails. -- Met vriendelijke groet / with kind regards, Guus Sliepen <guus at tinc-vpn.org> -------------- next part -------------- A non-text attachment was scrubbed... Name: not available Type: application/pgp-signature Size: 197 bytes Desc: Digital signature Url : http://www.tinc-vpn.org/pipermail/tinc/attachments/20081002/87267c56/attachment.pgp
Viktors Žilinskis
2008-Oct-02 21:54 UTC
SSH connection hangs on shell commands when used through tinc
Hello, Guus! Thank you for your advice! I used two of the options and it seems that fixed the problem This is how a working host file looks now: ########################### *PMTUDiscovery = yes* *TCPOnly = yes* # PMTU = 1400 Compression = 9 Subnet = 10.20.40.2/32 -----BEGIN RSA PUBLIC KEY----- -----END RSA PUBLIC KEY----- ########################### Best Regards, -- Viktors ?ilinskis -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.tinc-vpn.org/pipermail/tinc/attachments/20081003/ac9c241d/attachment.htm