[PATCH] Add ipv4=off option in resolver like ipv6=off (ticket #1330)

[Sergey Kandaurov]

> On 23 Feb 2022, at 08:09, Ruslan Ermilov <ru at nginx.com> wrote:
> 
> On Wed, Feb 16, 2022 at 03:30:55PM +0300, Ruslan Ermilov wrote:
>> Hi Lukas,
>> 
>> On Wed, Jan 19, 2022 at 07:47:44PM +0100, Lukas Lihotzki via nginx-devel wrote:
>>> # HG changeset patch
>>> # User Lukas Lihotzki <lukas at lihotzki.de>
>>> # Date 1642618053 -3600
>>> #      Wed Jan 19 19:47:33 2022 +0100
>>> # Node ID e9f06dc2d6a4a1aa61c15009b84ceedcaf5983b2
>>> # Parent  aeab41dfd2606dd36cabbf01f1472726e27e8aea
>>> Add ipv4=off option in resolver like ipv6=off (ticket #1330).
>>> 
>>> IPv6-only hosts (ticket #1330) and upstreams with IPv6 bind address
>>> (ticket #1535) need to disable resolving to IPv4 addresses.
>>> 
>>> Ticket #1330 mentions ipv4=off is the proper fix.
>> 
>> There's a number of problems in your patch.  Please try this
>> one instead:
>> 
>> # HG changeset patch
>> # User Ruslan Ermilov <ru at nginx.com>
>> # Date 1644873563 -10800
>> #      Tue Feb 15 00:19:23 2022 +0300
>> # Node ID 5d2cb60a78dd32a10a0010ccff39974fd7605867
>> # Parent  1add55d236522616ce34ffaa4dc697a76d3d41a4
>> The "ipv4=" parameter of the "resolver" directive (ticket #2196).
>> 
>> When set to "off", only IPv6 addresses will be resolved, and no
>> A queries are ever sent.
>> 
>> diff --git a/src/core/ngx_resolver.c b/src/core/ngx_resolver.c
>> --- a/src/core/ngx_resolver.c
>> +++ b/src/core/ngx_resolver.c
>> @@ -157,6 +157,8 @@ ngx_resolver_create(ngx_conf_t *cf, ngx_
>>     cln->handler = ngx_resolver_cleanup;
>>     cln->data = r;
>> 
>> +    r->ipv4 = 1;
>> +
>>     ngx_rbtree_init(&r->name_rbtree, &r->name_sentinel,
>>                     ngx_resolver_rbtree_insert_value);
>> 
>> @@ -225,6 +227,23 @@ ngx_resolver_create(ngx_conf_t *cf, ngx_
>>         }
>> 
>> #if (NGX_HAVE_INET6)
>> +        if (ngx_strncmp(names[i].data, "ipv4=", 5) == 0) {
>> +
>> +            if (ngx_strcmp(&names[i].data[5], "on") == 0) {
>> +                r->ipv4 = 1;
>> +
>> +            } else if (ngx_strcmp(&names[i].data[5], "off") == 0) {
>> +                r->ipv4 = 0;
>> +
>> +            } else {
>> +                ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
>> +                                   "invalid parameter: %V", &names[i]);
>> +                return NULL;
>> +            }
>> +
>> +            continue;
>> +        }
>> +
>>         if (ngx_strncmp(names[i].data, "ipv6=", 5) == 0) {
>> 
>>             if (ngx_strcmp(&names[i].data[5], "on") == 0) {
> 
> Addon to the patch:
> 
> diff --git a/src/core/ngx_resolver.c b/src/core/ngx_resolver.c
> --- a/src/core/ngx_resolver.c
> +++ b/src/core/ngx_resolver.c
> @@ -229,10 +229,12 @@ ngx_resolver_create(ngx_conf_t *cf, ngx_
> #if (NGX_HAVE_INET6)
>         if (ngx_strncmp(names[i].data, "ipv4=", 5) == 0) {
> 
> -            if (ngx_strcmp(&names[i].data[5], "on") == 0) {
> +            if (ngx_strcasecmp(&names[i].data[5], (u_char *) "on") == 0) {
>                 r->ipv4 = 1;
> 
> -            } else if (ngx_strcmp(&names[i].data[5], "off") == 0) {
> +            } else if (ngx_strcasecmp(&names[i].data[5], (u_char *) "off")
> +                       == 0)
> +            {
>                 r->ipv4 = 0;
> 
>             } else {
> @@ -246,10 +248,12 @@ ngx_resolver_create(ngx_conf_t *cf, ngx_
> 
>         if (ngx_strncmp(names[i].data, "ipv6=", 5) == 0) {
> 
> -            if (ngx_strcmp(&names[i].data[5], "on") == 0) {
> +            if (ngx_strcasecmp(&names[i].data[5], (u_char *) "on") == 0) {
>                 r->ipv6 = 1;
> 
> -            } else if (ngx_strcmp(&names[i].data[5], "off") == 0) {
> +            } else if (ngx_strcasecmp(&names[i].data[5], (u_char *) "off")
> +                       == 0)
> +            {
>                 r->ipv6 = 0;
> 
>             } else {
> 

I don't see the reasons to make the parameter value case-insensitive.
Existing parameters in ngx_http_core_module.c take it case-sensitive.
Otherwise, looks good to me.

[..]

-- 
Sergey Kandaurov