Today's accomplishment: got sufficiently irritated by Go failing self-tests on stock FreeBSD systems that I finally filed a report on the second issue: https://github.com/golang/go/issues/77411
The first issue on stock FreeBSD is https://github.com/golang/go/issues/70702
It's very obvious that approximately nobody runs Go's all.bash on real FreeBSD systems. At best it is "tested" on Go's builder machines, which are clearly non-standard in multiple ways.
My "Go failing selftests for its net package on FreeBSD" issue¹ turns out to be specific to FreeBSD 15. Evidently there's some networking change that is doing something different from what Go is counting on. If I'm energetic, I can peruse FreeBSD changelogs and stuff.
(It's possible all of the failures involve IPv6 / IPv4 interactions.)
I believe I've found the FreeBSD 15 networking change that breaks Go's net package self-tests, and it's an interesting one¹. As described in the release notes²:
Making a connection to INADDR_ANY, i.e., using it as an alias for localhost, is now disabled by default. This functionality can be re-enabled by setting the net.inet.ip.connect_inaddr_wild sysctl to 1.
I can see the point, even though this is a behavior change.
¹ https://cgit.freebsd.org/src/commit/?id=cd240957d7ba
² https://www.freebsd.org/releases/15.0R/relnotes/#network-general
For proper credit (or if you prefer, blame), I learned about 'ssh 0' from a comment @lyda left on my techblog. But now that I've seen it I can't unsee it. What else will accept '0' as a hostname? Feel free to try it today.
(Firefox will, it looks like.)
Everything that can accept human-readable IPv4 addresses in place of hostnames, and that does so by using the conventional C library inet_aton() or inet_pton() functions.
A single (32-bit) number has been an accepted human-readable form from the start, back in the 4.3BSD days. It's a thing that gets regularly rediscovered.
(Bernstein's networking tools use a ip4_scan() function that only supports strict 4-decimal-numbers form. But several of them special case and re-map the string "0" before calling this function. libowfat's scan_ip4() is similar to ip4_scan(). As is ip4_scan() in @ska's libstddjb.)
This and three other accepted formats are explained in all of the #FreeBSD, #OpenBSD, #NetBSD, and Linux GNU libc manual pages. They also explain why 0x00000000 and 0x7F000001 and 0177.1 will work as IPv4 addresses with such programs.
@JdeBP @cks @lyda @ska and it seems as part of the ASR resolver within libc getaddrinfo() will call inet_pton rather than inet_aton — see sockaddr_from_str — this is why e.g. “ssh 0” gives a “no address associated with name” error. This looks like it’s been around for ~14 years, so this hasn’t worked on OpenBSD for a long time.
Of course because it doesn’t special case numeric addresses putting:
localhost 127.0.0.1 0
in /etc/hosts works. But don’t do that.
Chris Siebenmann
JdeBP
David Leadbeater