Show HN: How did your computer reach my server?

Re:Show HN: How did your computer reach my server? by globular-toast on Tuesday December 05, 2023 @12:51PM (#38534377)

Interesting, I didn't know traceroute used UDP by default. Just did some testing with the best traceroute tool, mtr[0], and using the -u flag for UDP seemed to give the worst results. -t for TCP seemed OK. I never thought about the difference between how TCP and ICMP packets are handled.

[0] https://bitwizard.nl/mtr/

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Re:Show HN: How did your computer reach my server? by nullindividual on Tuesday December 05, 2023 @12:56PM (#38534468)

Yep! UDP/3343 by default.

You can use the -P flag to set the protocol (TCP, UDP, ICMP Other, GRE) and -p to set the port number, if applicable.

Microsoft should have stuck to the BSD traceroute. I don't know why they "invented" tracert.exe (which I believe is _based_ on BSD traceroute, like most of those early network tools in Windows). I wonder if this was a Winsock (or STREAMS[0]!) limitation.

[0] https://web.archive.org/web/20151229084950/http://www.kuro5h...

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Re:Show HN: How did your computer reach my server? by dfox on Tuesday December 05, 2023 @02:18PM (#38535628)

I assume that tracert using ICMP is not that much an WinSock limitation but limitation of the underlying NT security architecture without suid binaries, which was worked around with ICMP-only non-privileged “raw sockets”. But that is mostly an educated guess.

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Re:Show HN: How did your computer reach my server? by nullindividual on Tuesday December 05, 2023 @02:26PM (#38535721)

This is a limitation that dates back to NT 3.1 where SOCK_RAW was callable by standard User accounts. Only starting with Windows 2000 [0] does creating a RAW socket require local administrator rights.

[0] https://learn.microsoft.com/en-us/windows/win32/winsock/tcp-...

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