Comment 4 for bug 1916541

I did some more investigation, and did not find an explanation, but I am writing it here to maybe save somebody else some effort.

Postfix uses normal(?) `getservbyname(service, protocol)` in the file src/smtp/smtp_connect.c line 363:

        if ((sp = getservbyname(service, protocol)) == 0)
            msg_fatal("unknown service: %s/%s", service, protocol);

and I see this message in the log.

On the other hand, a simple program that performs `chroot("/var/spool/postfix")` and calls `getservbyname()` _works correctly_ on hirsute (C code in attachment):

crosser@pccross:~/src$ sudo ./getsrvname
[sudo] password for crosser:
s_name="smtp", s_port=25, s_proto="tcp"

Note though that in such form the the program does not try to use NSS, it just opens `/etc/services` directly. While postfix's `smtp` goes through nsswitch, as can be seen in the strace log from my previous attachment.