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

[Roman Arutyunyan]

On Wed, Jun 15, 2022 at 02:27:27PM +0400, Sergey Kandaurov wrote:
> 
> > 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.

I agree.  Although ngx_conf_set_flag_slot() treats its argument as
case-insensitive, "listen" directive handler provides a number of
case-sensitive examples.

--
Roman Arutyunyan