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Comment by anonymousisme | Hacker News Reader

Back in the day (nearly 30 years ago) people would run a user-mode stack to obtain Internet connectivity via a (dial-up) Unix shell account. The program was "slirp" which was named after SLIP/CSLIP, but then upgraded to support PPP once that became a thing.

https://en.wikipedia.org/wiki/Slirp

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I was using SLIRP a few years ago to tunnel traffic through a cheap OpenVZ VPS, (for downloading Linux ISOs). I had to manually patch the TCP window size and recompile the binaries to get decent speed as the original code doesn't support TCP Window Size Scaling. I tried to upstream the patch to Debian but the maintainer wouldn't reply. It worked well enough but now I use wireguard.

Modified SLIRP code is also found in VirtualBox, Qemu, UML and other virtualization software, for sharing the host connection in NAT mode.

SLIP was a problem for us when I worked at an ISP in 1995. Cheapsakes would buy our barebones "shell access only" package and then run SLIP on our shell server. We eventually wrote a cron job to kill their processes when we found them. Sneaky ones just renamed the binary.

Man I miss the old internet when things were more playful and that was the extent of harm being done. Not that I condone cheapskates stealing your bandwidth.

Maybe it's just rosy nostalgia.

Remember when security was pretty much just scanning floppies for viruses before you ran the program?

Oh, believe me, that wasn't the worst. The worst was an undergrad in a university computer lab who harnessed many dozens of workstations to DDoS us off the net when he got into an IRC argument with someone.

Haha, right, my nostalgia blocked off that part of it. That was definitely a thing. IRC BNC:s became mandatory to avoid the risk.

I was that guy. I didn't even know ISPs didn't like it.

I thought that's just how you got into the interwebs without running that obnoxious, buggy faux winsock client.

Heh. I used Netcom and they did not outright ban slirp, but they did have a script running that would renice (lower the priority) of user processes once they reached a certain total cpu time (two minutes). I discovered this feature shortly after they implemented it because my slirp network performance went down. Note that I am referring to cpu time and not run time. Most processes spend most of their time waiting for something, so accumulating two minutes of cpu time under slirp usually took several hours.

My solution was to write a program (I called checkcpu) that would spawn a process (slirp) and periodically check its total cpu usage. When it hit the threshold (110 seconds), it would spawn a child and suspend the parent (seamlessly passing the current run state to the child). It worked great and they either never noticed what I was doing, or they did not care. Over time, the number of suspended parent processes would rise, but it never became a problem.

History likes to repeat itself:

https://github.com/rootless-containers/slirp4netns

Heh, as a middle time between the dial-up days and the WireGuard days, I used to use PPP as a poor-man's VPN. SSH to a host inside the work network and run pppd on both sides. Tada, suddenly my home computer is on the work network, NATted from the jump box.

What a trip back in time. I used this and TIA [1] as a youth.

[1] https://en.wikipedia.org/wiki/The_Internet_Adapter

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