Show HN: ip2unix – Turn IP sockets into Unix domain sockets | Hacker News Reader

Show HN: ip2unix – Turn IP sockets into Unix domain sockets

github.com

94 pointsaszlig23 comments

This is very clever. Last time i ran benchmarks (several years ago), UNIX domain sockets were twice as fast as IP sockets so that's another reason to use them.

Isn't a TCP socket fastpathed on loopback ranges anyway?

There was a patch[1] a few years ago, but apparently it didn't make it into mainline. At least looking in net/ipv4/tcp.c I haven't found any traces related to that.

However, I could have sworn that I've seen a similar patch in recent years, but either my memories are serving me wrong or I simply can't find it anymore.

Nevertheless, I didn't benchmark whether this is the case, nor was performance the main goal for writing ip2unix. So if performance is a concern, maybe benchmark with your specific workload?

https://www.spinics.net/lists/netdev/msg210741.html

Interesting. Thanks

I do not see an advantage over socat, which can listen on _TCP_-sockets (among 20 other „socket“ inputs) and forward them into unix-sockets. Please tell me? :-/

You don't have to firewall the superfluous open IP socket any more.

From the documentation, it seems this utility uses LD_PRELOAD to change IP socket calls into Unix socket calls; which seems useful if you want to do namespaced and access controlled process to process communication with programs that don't already know how to use unix sockets.

socat as a TCP to unix socket proxy is doing a different job.

As others have mentioned, socat acts more like a router between different socket types/protocols but it doesn't change the behaviour of the program in question.

So for example if you have a service listening to TCP port 1234, you could do something like this:

socat UNIX-LISTEN:foo.sock TCP:localhost:1234

Now the service will still listen to port 1234 and you now have another socket that redirects to the other. This not only comes with a bit of overhead, but port 1234 is still reachable.

While using packet filtering on that port might lower the attack surface a bit, this won't prevent other (possibly compromised) services/users on the system to access port 1234.

Sure you could also filter based on uid, but IMHO it's better if that port isn't accessible in the first place.

Very nice!

// "LD_PRELOAD" should've been in the submission title to avoid the "socat" questions

Thanks a lot for the suggestion. While I can't change the title here on HN, the README now mentions LD_PRELOAD in the first paragraph and I also added a small FAQ[1] section about socat.

[1]: https://github.com/nixcloud/ip2unix/tree/d7d297ed68cdadc65dc...

This is really cool. I run a lot of different services on my home server and don't trust them to the internet. Everything is accessed via a reverse proxy with authentication that I trust.

While listening on localhost is some level of security it still means that lateral movement is possible if one of the services is compromised. It also means that if I give give someone else a user account or similarly run any less trusted code then they can access all of the services without authentication.

I'm going to look into this an apply this so that these services aren't accessible by other users.

very interesting. A docker integration would be fun too (something like "docker run -p /tmp/socket:8080 ...") :)

I'm not very familiar with Docker, but wouldn't something like "docker run some_image ip2unix -r /tmp/socket:8080 ..." work?

You could but it means: - you need to add ip2unix in your images, which is not always convenient - you still need to expose the socket outside the container (which is doable with volumes, but permissions can be a mess, especially if you use user namespaces)

So how do I access a unix socket in my browser? Be nice if "unix://file/path.html" worked.

You could map different ports to specific socket file names and use a dummy address, eg. like this:

ip2unix -r out,addr=127.1.1.1,path=foo-%p.sock firefox --new-instance

Whenever you then head over to something like http://127.1.1.1:9000/, the browser will try to connect to foo-9000.sock.

Do any programs get confused when they call getsockname() and the result is an AF_UNIX they weren't expecting?

If programs call getsockname() the result is not a sockaddr_un, but instead sockaddr_in(6) is used from the original call to bind(). If the socket was implicitly bound, a random[1] address is generated.

Things are a bit trickier if it gets to getpeername(), since we want to have somewhat stable addresses. This is done by querying SO_PEERCRED and encoding[2] the pid for IPv4 or pid, uid and gid for IPv6 into the address.

In summary: Programs shouldn't get confused, but if they do, it's certainly a bug in ip2unix. Feel free to open an issue :-)

[1]: https://github.com/nixcloud/ip2unix/blob/d7d297ed68cdadc65dc...

[2]: https://github.com/nixcloud/ip2unix/blob/d7d297ed68cdadc65dc...

This is kinda awesome... Only request is a ptrace version, that will work on all binaries.

https://github.com/nixcloud/ip2unix/commit/00dddf228a70ad230...

That's what I had in mind someday™. Unfortunately, this has to wait for version 4.x maybe :-/

Now that's cool. Functional and simple to use.

is there a benefit over socat?

It is faster because socat creates additional copies/context switches when forwarding data. This tool changes the bind syscall so it becomes a unix socket in the first place.

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