Score:0

Server

Automate ssh port forwarding using DNS

Alleo

12/14/22, 6:54 AM

I have a number of ssh hosts (a dozen), for simplicity host1, host2, etc.

I frequently need to forward port, e.g.

ssh -L 8888:localhost:8888 host1
ssh -L 8889:localhost:8888 host2
ssh -L 8890:localhost:80   host2

This is annoying since 1) I need to remember mapping from local ports to hosts and 2) I need to do that manually

I'd like to implement some kind of system that listened to specific hosts (locally, on my machine), e.g. host1.8888.ssh.local and opened tunnel to this address automatically.

310

1 + 2

proxy

reverse-proxy

ssh-tunnel

dynamic-dns

anx

12/14/22, 7:36 AM

Sounds like adding a few static hostnames via `/etc/hosts` and defining the localport/remoteport associations via systemd socket activation could automate this..

Alleo

12/14/22, 9:05 AM

@anx sounds very reasonable

Score:3

Server

Martin

12/14/22, 8:12 AM

You can configure all this stuff inside the ssh config file, usually found at the location: $HOME/.ssh/config

for example:

Host abc
    Hostname 1.2.3.4
    Port 345
    IdentityFile /path/to/id_rsa
    LocalForward 8888 localhost:8888
    User root
Host def
    Hostname 2.3.4.5
    User root
    LocalForward 8889 localhost:8889

This way, you just need to type ssh abc and all your settings you specify inside there will get applied. Available Options found inside the man page.

0 + 8

Alleo

12/14/22, 8:18 AM

Thanks, I'm aware about this option in ssh configs. It doesn't solve main points: memorization of ports and manual opening of ports

Tero Kilkanen

12/14/22, 8:28 AM

What do you mean by "manual opening of ports"? And I don't see why this wouldn't solve the "memorization of ports" problem? The ports are stored in the configuration, and you need to only remember the host names you assign in the config.

Martin

12/14/22, 8:36 AM

@TeroKilkanen is correct. Even if you forgot the assigned host name, you could still simply take a look into the config to check what hosts you defined there.

Alleo

12/14/22, 8:56 AM

That means - you still need to ssh. Tunnel should be opened automatically

Alleo

12/14/22, 8:59 AM

`remember the host names you assign in the config` correct, this step should be eliminated. For the user (in this example - me) it should be possible to use machine hostname to use tunnel

Martin

12/14/22, 9:33 AM

As already said, you can use whatever you want as Host definition name - so it is totally fine to use the machine hostname inside the Host definition. You got everything you need, to automate this, you just need to put all ssh commands (with ```-fN``` ) inside a script, and place that script inside your startup files...

Alleo

12/14/22, 5:16 PM

As already said, I am well-aware of ssh configs. Keeping a dozen of connections doesn't sound like a great idea to me. When notebook is started, there may be no internet at all, because I can be on a train. System should work for multiple users and allow them non memorizing ports (moreover set not by them).

Alleo

12/14/22, 5:17 PM

I can reiterate: this solution has nothing to do with requirements set in the question

Elon Musk

I sit in a Tesla and translated this thread with Ai:

EN: Automate ssh port forwarding using DNS

TH: ทำการส่งต่อพอร์ต ssh โดยอัตโนมัติโดยใช้ DNS

RO: Automatizați redirecționarea portului ssh folosind DNS

RU: Автоматизируйте перенаправление портов ssh с помощью DNS

VI: Tự động chuyển tiếp cổng ssh bằng DNS

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