bin/58834: whois(1) spuriously fails with exit status 65=EHOSTUNREACH on v4-only hosts

[campbell+netbsd%mumble.net@localhost]

>Number:         58834
>Category:       bin
>Synopsis:       whois(1) spuriously fails with exit status 65=EHOSTUNREACH on v4-only hosts
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    bin-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Nov 19 22:10:00 +0000 2024
>Originator:     Taylor R Campbell
>Release:        current, 10, 9, ...
>Organization:
The NetBSDv6 Whoisdation
>Environment:
>Description:
On certain inputs, when run on hosts without IPv6 connectivity, whois(1) will successfully query WHOIS information, print it to stdout, and then exit with status 65=EHOSTUNREACH instead of status 0 as expected.

Example:

$ whois 4.2.2.1 >/dev/null; echo $?
65

This happens because the variable `error', which is used to record the last errno value in a loop over getaddrinfo(3) results in the event that they all fail in order to print an error message, is reused for recursive whois results and the final return value later on:

    199 	for (s = -1, ai = res; ai != NULL; ai = ai->ai_next) {
    200 		s = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
    201 		if (s < 0) {
    202 			error = errno;
    203 			reason = "socket";
    204 			continue;
    205 		}
...
    214 	}
    215 	freeaddrinfo(res);
    216 	if (s < 0) {
    217 		if (reason) {
    218 			errno = error;
    219 			warn("%s: %s", server, reason);
    220 		} else
    221 			warnx("Unknown error in connection attempt");
    222 		return (1);
    223 	}
...             /* NOTE: error is not reset to zero here */
    284 	if (nhost != NULL) {
    285 		error = whois(query, nhost, port, 0);
    286 		free(nhost);
    287 	}
    288 
    289 	return (error);

https://nxr.netbsd.org/xref/src/usr.bin/whois/whois.c?r=1.38#199
>How-To-Repeat:
1. set up a host with no IPv6 connectivity but DNS answers that have AAAA records for WHOIS servers
2. run a whois(1) with an input whose WHOIS server has AAAA records, e.g. an IP address for which whois.arin.net will be queried
3. examine the process's exit status
>Fix:
reset local variable `error' to zero at line 224 in whois.c rev. 1.38