[PATCH 1 of 2] The "ipv4=" parameter of the "resolver" directive

[Maxim Dounin]

Hello!

On Tue, Jun 28, 2022 at 08:25:35PM +0400, Sergey Kandaurov wrote:

> # HG changeset patch
> # User Ruslan Ermilov <ru at nginx.com>
> # Date 1645589317 -10800
> #      Wed Feb 23 07:08:37 2022 +0300
> # Node ID 04e314eb6b4d20a48c5d7bab0609e1b03b51b406
> # Parent  fecd73db563fb64108f7669eca419badb2aba633
> The "ipv4=" parameter of the "resolver" directive.
> 
> When set to "off", only IPv6 addresses will be resolved, and no
> A queries are ever sent (ticket #2196).
> 
> diff -r fecd73db563f -r 04e314eb6b4d src/core/ngx_resolver.c
> --- a/src/core/ngx_resolver.c	Tue Jun 21 17:25:37 2022 +0300
> +++ b/src/core/ngx_resolver.c	Wed Feb 23 07:08:37 2022 +0300
> @@ -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) {
> @@ -273,6 +292,14 @@ ngx_resolver_create(ngx_conf_t *cf, ngx_
>          }
>      }
>  
> +#if (NGX_HAVE_INET6)
> +    if (r->ipv4 + r->ipv6 == 0) {
> +        ngx_conf_log_error(NGX_LOG_EMERG, cf, 0,
> +                           "\"ipv4\" and \"ipv6\" cannot both be \"off\"");
> +        return NULL;
> +    }
> +#endif
> +
>      if (n && r->connections.nelts == 0) {
>          ngx_conf_log_error(NGX_LOG_EMERG, cf, 0, "no name servers defined");
>          return NULL;
> @@ -836,7 +863,7 @@ ngx_resolve_name_locked(ngx_resolver_t *
>          r->last_connection = 0;
>      }
>  
> -    rn->naddrs = (u_short) -1;
> +    rn->naddrs = r->ipv4 ? (u_short) -1 : 0;
>      rn->tcp = 0;
>  #if (NGX_HAVE_INET6)
>      rn->naddrs6 = r->ipv6 ? (u_short) -1 : 0;
> @@ -1263,7 +1290,7 @@ ngx_resolver_send_query(ngx_resolver_t *
>          rec->log.action = "resolving";
>      }
>  
> -    if (rn->naddrs == (u_short) -1) {
> +    if (rn->query && rn->naddrs == (u_short) -1) {
>          rc = rn->tcp ? ngx_resolver_send_tcp_query(r, rec, rn->query, rn->qlen)
>                       : ngx_resolver_send_udp_query(r, rec, rn->query, rn->qlen);
>  
> @@ -1765,10 +1792,13 @@ ngx_resolver_process_response(ngx_resolv
>               q = ngx_queue_next(q))
>          {
>              rn = ngx_queue_data(q, ngx_resolver_node_t, queue);
> -            qident = (rn->query[0] << 8) + rn->query[1];
> -
> -            if (qident == ident) {
> -                goto dns_error_name;
> +
> +            if (rn->query) {
> +                qident = (rn->query[0] << 8) + rn->query[1];
> +
> +                if (qident == ident) {
> +                    goto dns_error_name;
> +                }
>              }
>  
>  #if (NGX_HAVE_INET6)
> @@ -3645,7 +3675,7 @@ ngx_resolver_create_name_query(ngx_resol
>      len = sizeof(ngx_resolver_hdr_t) + nlen + sizeof(ngx_resolver_qs_t);
>  
>  #if (NGX_HAVE_INET6)
> -    p = ngx_resolver_alloc(r, r->ipv6 ? len * 2 : len);
> +    p = ngx_resolver_alloc(r, len * (r->ipv4 + r->ipv6));
>  #else
>      p = ngx_resolver_alloc(r, len);
>  #endif
> @@ -3654,23 +3684,28 @@ ngx_resolver_create_name_query(ngx_resol
>      }
>  
>      rn->qlen = (u_short) len;
> -    rn->query = p;
> +
> +    if (r->ipv4) {
> +        rn->query = p;
> +    }
>  
>  #if (NGX_HAVE_INET6)
>      if (r->ipv6) {
> -        rn->query6 = p + len;
> +        rn->query6 = r->ipv4 ? (p + len) : p;
>      }
>  #endif
>  
>      query = (ngx_resolver_hdr_t *) p;
>  
> -    ident = ngx_random();
> -
> -    ngx_log_debug2(NGX_LOG_DEBUG_CORE, r->log, 0,
> -                   "resolve: \"%V\" A %i", name, ident & 0xffff);
> -
> -    query->ident_hi = (u_char) ((ident >> 8) & 0xff);
> -    query->ident_lo = (u_char) (ident & 0xff);
> +    if (r->ipv4) {
> +        ident = ngx_random();
> +
> +        ngx_log_debug2(NGX_LOG_DEBUG_CORE, r->log, 0,
> +                       "resolve: \"%V\" A %i", name, ident & 0xffff);
> +
> +        query->ident_hi = (u_char) ((ident >> 8) & 0xff);
> +        query->ident_lo = (u_char) (ident & 0xff);
> +    }
>  
>      /* recursion query */
>      query->flags_hi = 1; query->flags_lo = 0;
> @@ -3731,7 +3766,9 @@ ngx_resolver_create_name_query(ngx_resol
>  
>      p = rn->query6;
>  
> -    ngx_memcpy(p, rn->query, rn->qlen);
> +    if (r->ipv4) {
> +        ngx_memcpy(p, rn->query, rn->qlen);
> +    }
>  
>      query = (ngx_resolver_hdr_t *) p;
>  
> diff -r fecd73db563f -r 04e314eb6b4d src/core/ngx_resolver.h
> --- a/src/core/ngx_resolver.h	Tue Jun 21 17:25:37 2022 +0300
> +++ b/src/core/ngx_resolver.h	Wed Feb 23 07:08:37 2022 +0300
> @@ -175,8 +175,10 @@ struct ngx_resolver_s {
>      ngx_queue_t               srv_expire_queue;
>      ngx_queue_t               addr_expire_queue;
>  
> +    unsigned                  ipv4:1;
> +
>  #if (NGX_HAVE_INET6)
> -    ngx_uint_t                ipv6;                 /* unsigned  ipv6:1; */
> +    unsigned                  ipv6:1;
>      ngx_rbtree_t              addr6_rbtree;
>      ngx_rbtree_node_t         addr6_sentinel;
>      ngx_queue_t               addr6_resend_queue;

Looks good.

-- 
Maxim Dounin
http://mdounin.ru/