From ed3155acf722a5c75ff1eabfe026c81768647691 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Petr=20Men=C5=A1=C3=ADk?= <pemensik@redhat.com>
Date: Wed, 19 Nov 2025 19:11:42 +0100
Subject: [PATCH] Return notfound when lookup for the unhandled AF is tried

Changes return code for mdns4_minimal and mdns6_minimal, when request is
done for the other address family. It behaves like that host is never
found. That makes plugin to not continue to dns lookup only for single
address family.

It expects user would have return on not found. Just like is suggested
in README.me

/etc/nsswitch is expected to have:
hosts: files mdns4_minimal [NOTFOUND=return] dns

This change will stop resolving all AF_INET6 on mdns4_minimal.

Because there is no configration file used for minimal variants, it does
not have any way to return previous behaviour. It is expected new
behaviour would be considered better by everyone.

Fixes #100
---
 src/nss.c | 37 ++++++++++++++++++-------------------
 1 file changed, 18 insertions(+), 19 deletions(-)

diff --git a/src/nss.c b/src/nss.c
index bbdb726..55b1c03 100644
--- a/src/nss.c
+++ b/src/nss.c
@@ -36,6 +36,12 @@ SPDX-License-Identifier: LGPL-2.1-or-later
 #include "util.h"
 #include "nss.h"
 
+#ifdef NSS_IPV4_ONLY
+#define WANT_AF AF_INET
+#elif NSS_IPV6_ONLY
+#define WANT_AF AF_INET6
+#endif
+
 static avahi_resolve_result_t do_avahi_resolve_name(int af, const char* name,
                                                     userdata_t* userdata) {
     bool ipv4_found = false;
@@ -89,30 +95,25 @@ enum nss_status _nss_mdns_gethostbyname_impl(const char* name, int af,
     FILE* mdns_allow_file = NULL;
     use_name_result_t result;
 
-#ifdef NSS_IPV4_ONLY
+#ifdef WANT_AF
     if (af == AF_UNSPEC) {
-        af = AF_INET;
+        af = WANT_AF;
     }
-#endif
 
-#ifdef NSS_IPV6_ONLY
-    if (af == AF_UNSPEC) {
-        af = AF_INET6;
+    if (af != WANT_AF)
+    {
+        *errnop = EINVAL;
+        *h_errnop = NO_RECOVERY;
+        return NSS_STATUS_NOTFOUND;
     }
-#endif
-
-#ifdef NSS_IPV4_ONLY
-    if (af != AF_INET)
-#elif NSS_IPV6_ONLY
-    if (af != AF_INET6)
 #else
     if (af != AF_INET && af != AF_INET6 && af != AF_UNSPEC)
-#endif
     {
         *errnop = EINVAL;
         *h_errnop = NO_RECOVERY;
         return NSS_STATUS_UNAVAIL;
     }
+#endif
 
     u->count = 0;
 
@@ -191,8 +192,8 @@ enum nss_status _nss_mdns_gethostbyname3_r(const char* name, int af,
     // The interfaces for gethostbyname3_r and below do not actually support
     // returning results for more than one address family
     if (af == AF_UNSPEC) {
-#ifdef NSS_IPV6_ONLY
-        af = AF_INET6;
+#ifdef WANT_AF
+        af = WANT_AF;
 #else
         af = AF_INET;
 #endif
@@ -238,10 +239,8 @@ enum nss_status _nss_mdns_gethostbyaddr_r(const void* addr, int len, int af,
         af == AF_INET ? sizeof(ipv4_address_t) : sizeof(ipv6_address_t);
 
     if (len < (int)address_length ||
-#ifdef NSS_IPV4_ONLY
-        af != AF_INET
-#elif NSS_IPV6_ONLY
-        af != AF_INET6
+#ifdef WANT_AF
+        af != WANT_AF
 #else
         (af != AF_INET && af != AF_INET6)
 #endif