On Mon, 19 Jan 2026, Paul Ripke wrote:
Do we check for underscores somewhere in name resolution?
Yes.
I know that RFC 1035 disallows them from hostnames...
That's it.
I had a quick browse of our code and nothing obvious stood out.
I think:
src/lib/libc/net/gethnamaddr.c:
gethostbyname() > gethostbyname_r() -> gethostbyname_internal() ->
nsdispatch() -> _dns_gethtbyname() -> getanswer() ->
name_ok = res_hnok / maybe_ok()
This works--see resolv.conf(5):
# echo 'options no-check-names' >> /etc/resolv.conf
-RVP