keeping connections up while moving from wired to wireless

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keeping connections up while moving from wired to wireless

Postby openbrian » 2010-02-22 19:33

Hi, Perhaps someone can help me out here and point me in the right direction.

I run several ssh tunnels, sshfs mounted filesystems, and occasionally a VPN (from work to home). Starting from a wired connection (dhcp) in a docking station, i want to be able to join a wireless network (dhcp), pick up my laptop and move around my office building, say to a meeting room for a demonstration, and then return to my desk and dock my laptop. And all this time, i want my open connections to stay open.

(For bonus points... i'd also like to join a cell network (evdo, gprs, gsm), drive home, automatically join my wireless network, and drop the vpn connection.)

I see there are others[1] who want this too.

[1] https://bugzilla.gnome.org/show_bug.cgi?id=540995

Just to be clear, i'm not interested in bonding in the sense of fault tolerant networks. And i'm not interested in bridging networks to give access to virtual machines. Also i'm not really interested in forwarding traffic from eth0 to wlan0.

I'm not sure if bridging, bonding, tun/tap, or some other mechanism is required. But i'm pretty sure when you run netstat -nt, all the Local Addresses must have the same IP address, one that isn't on the wired or wired networks (e.g. 192.168.223.220).

On bridging: Seems like it would be easy to bring up each interface and join them to a bridge. Give the bridge itself and IP address. But i'm not sure if packets would be routed correctly. ebtables may help here.

On bonding: Also it seems that bonding eth0 and wlan0 isn't correct because each network may have a different network address.

On tun/tap: A tap0 interface seems to make sense if there was a process to listen on this interface and send packets back out eth0 or wlan0. But i don't know if such a thing exists.

I don't know how or if Wicd / Network Manager are involved. Looks like Network Manager has planned support for bridge and bond interfaces[2] and "multiple active devices" [3].

[2] http://live.gnome.org/NetworkManager/ReleaseProcess
[3] http://live.gnome.org/NetworkManagerToDo

Do i need to wait for IPv6 or Mobile IP (rfc 3344)?

http://en.wikipedia.org/wiki/Mobile_IP

Reference pages:
http://wiki.debian.org/BridgeNetworkConnections
http://www.linuxfoundation.org/collabor ... ing/bridge
http://brainstorm.ubuntu.com/idea/10534/

thanks,
Brian
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Re: keeping connections up while moving from wired to wireless

Postby Coax » 2010-02-23 16:29

When you set up an ssh connection, that will keep on working as long as both machines keep the same IP.

I've even replaced firewalls on networks while being able to keep an ssh shell open through them.
However, when you swap onto wifi or some mobile phone network, your IP changes, and your ssh connections will be gone. That's just how TCP/IP works.

What you COULD try, is to use openvpn or some sort of ipsec VPN to always have a VPN to your machines. (or tunnel everything through one)
That way, you would be able to regain the same IP, no matter which way you connect. However, I'm not sure how an ssh connection will react when such a virtual interface goes down...

Anyway, good luck. :-)
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Re: keeping connections up while moving from wired to wireless

Postby openbrian » 2010-02-23 18:21

The Strongswan (IPsec VPN) page mentions "Dynamical IP address and interface update with IKEv2 MOBIKE (RFC 4555)". I'm gonna look into that. But i feel that just means it will re-establish the vpn connection. All open connections over it will be dropped.
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Re: keeping connections up while moving from wired to wireless

Postby Coax » 2010-02-25 11:44

openbrian wrote:The Strongswan (IPsec VPN) page mentions "Dynamical IP address and interface update with IKEv2 MOBIKE (RFC 4555)". I'm gonna look into that. But i feel that just means it will re-establish the vpn connection. All open connections over it will be dropped.

Could be.

I'd give openvpn a try, as I think the gnome network manager supports that...
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