# HG changeset patch
# User Thibault Charbonnier <thibaultcha@fastmail.com>
# Date 1481847421 28800
#      Thu Dec 15 16:17:01 2016 -0800
# Node ID 8bf038fe006fd8ae253d6b41fc6cf109a8912d3e
# Parent  a3dc657f4e9530623683e6b85bd7492662e4dc47
Resolver: ignore ipv6=off resolver option when no ipv6 support

Makes the resolver directive more robust: we only error out when ipv6
resolution is desired but not supported (ipv6=on).

use case 1: some configurations are sometimes re-used between builds with and
without ipv6 support. This patch avoids the need to remove the "ipv6=off" flag.

use case 2: currently, some tools rely on the --with-ipv6 configure option from
"nginx -V" to determine if ipv6 resolution should be disabled in some cases.
With this option disappearing in Nginx 1.11.5, this patch would allow such tools
to assume "ipv6=off" to be safe regardless of ipv6 support in the current
build.

diff --git a/src/core/ngx_resolver.c b/src/core/ngx_resolver.c
index dade1846..5a3f0aa4 100644
--- a/src/core/ngx_resolver.c
+++ b/src/core/ngx_resolver.c
@@ -426,14 +426,22 @@ ngx_resolver_create(ngx_conf_t *cf, ngx_str_t *names, ngx_uint_t n)
             continue;
         }
 
-#if (NGX_HAVE_INET6)
         if (ngx_strncmp(names[i].data, "ipv6=", 5) == 0) {
 
             if (ngx_strcmp(&names[i].data[5], "on") == 0) {
+#if (NGX_HAVE_INET6)
                 r->ipv6 = 1;
+#else
+                ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
+                                   "no ipv6 support but \"%V\" in resolver",
+                                   &names[i]);
+                return NULL;
+#endif
 
             } else if (ngx_strcmp(&names[i].data[5], "off") == 0) {
+#if (NGX_HAVE_INET6)
                 r->ipv6 = 0;
+#endif
 
             } else {
                 ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
@@ -443,7 +451,6 @@ ngx_resolver_create(ngx_conf_t *cf, ngx_str_t *names, ngx_uint_t n)
 
             continue;
         }
-#endif
 
 #if !(NGX_WIN32)
         if (ngx_strncmp(names[i].data, "local=", 6) == 0) {
