Bug#1007872: libc6-dev: getaddrinfo() finds an AF_INET address when hinting AF_UNSPEC, but not when hinting AF_INET

[Robert Martin <rmartin@rpmsoftware.com>]

Package: libc6-dev
Version: 2.33-7
Severity: normal

Dear Maintainer,

Under certain circumstances, when calling getaddrinfo with hints.ai_family = AF_UNSPEC, the first result is an AF_INET address. When calling it with hints.ai_family = AF_INET, however, it returns 251 (No address associated with hostname).

Here is a short program that reproduces the issue:
```c
#include <assert.h>
#include <stdio.h>
#include <string.h>
#include <sys/socket.h>
#include <netdb.h>

int main(int argc, char *argv[]) {
	const char hostname[] = "SomeHostname";
	const char service[] = "1433";

	struct addrinfo hints, *res;
	memset(&hints, 0, sizeof(hints));

	int ret = getaddrinfo(hostname, service, &hints, &res);
	assert(ret == 0);
	assert(res->ai_family == AF_INET);
	freeaddrinfo(res);

	hints.ai_family = AF_INET;
	ret = getaddrinfo(hostname, service, &hints, &res);

	if (ret != 0) {
		printf(gai_strerror(ret));
		printf("\n");
	} else {
		freeaddrinfo(res);
	}
	return ret;
}
```

I have only been able to reproduce the bug when all of the following criteria are met:
- Running in a Docker container on a Windows host
- The hostname is unqualified
- The container's /etc/resolv.conf does not include the correct search option to resolve the hostname
- The Windows host is set up to resolve unqualified names by applying the correct DNS suffix

getaddrinfo() also returns 251 if the AI_ADDRCONFIG flag is set, even though the container has an IPV4 address.

The bug is also present in 2.34-0experimental3.

Symptoms are superficially similar to #854301, but the container is online and passing AI_ADDRCONFIG returns no result.

-- System Information:
Debian Release: bookworm/sid
  APT prefers testing
  APT policy: (500, 'testing')
Architecture: amd64 (x86_64)

Kernel: Linux 5.10.60.1-microsoft-standard-WSL2 (SMP w/12 CPU threads)
Locale: LANG=C, LC_CTYPE=C.UTF-8 (charmap=UTF-8), LANGUAGE not set
Shell: /bin/sh linked to /bin/dash
Init: unable to detect

Versions of packages libc6-dev depends on:
ii  libc-dev-bin    2.33-7
ii  libc6           2.33-7
ii  libcrypt-dev    1:4.4.27-1.1
ii  libnsl-dev      1.3.0-2
ii  linux-libc-dev  5.16.12-1
ii  rpcsvc-proto    1.4.2-4

libc6-dev recommends no packages.

Versions of packages libc6-dev suggests:
pn  glibc-doc     <none>
ii  manpages-dev  5.10-1

-- no debconf information