feat: allow disabling search option in resolv.conf (#3609)

Also disable it in the test to avoid occassional DNS query timeout.

apisix/core/utils.lua

@@ -88,6 +88,8 @@ local function dns_parse(domain)
     if dns_resolvers ~= current_inited_resolvers then
         local local_conf = config_local.local_conf()
         local valid = table.try_read_attr(local_conf, "apisix", "dns_resolver_valid")
+        local enable_resolv_search_opt = table.try_read_attr(local_conf, "apisix",
+                                                             "enable_resolv_search_opt")
 
         local opts = {
             ipv6 = true,
@@ -97,6 +99,11 @@ local function dns_parse(domain)
             order = {"last", "A", "AAAA", "CNAME"}, -- avoid querying SRV (we don't support it yet)
             validTtl = valid,
         }
+
+        if not enable_resolv_search_opt then
+            opts.search = {}
+        end
+
         local ok, err = dns_client.init(opts)
         if not ok then
             return nil, "failed to init the dns client: " .. err

conf/config-default.yaml

@@ -110,6 +110,7 @@ apisix:
   #  - 8.8.8.8
   # dns_resolver_valid: 30        # if given, override the TTL of the valid records. The unit is second.
   resolver_timeout: 5             # resolver timeout
+  enable_resolv_search_opt: true  # enable search option in resolv.conf
   ssl:
     enable: true
     enable_http2: true

t/APISIX.pm

@@ -93,6 +93,7 @@ apisix:
     tcp:
       - 9100
   admin_key: null
+  enable_resolv_search_opt: false
 _EOC_
 
 my $etcd_enable_auth = $ENV{"ETCD_ENABLE_AUTH"} || "false";

t/core/utils.t

@@ -271,6 +271,10 @@ ip_info: {"address":"127.0.0.1","class":1,"name":"test.com","ttl":315360000,"typ
 
 
 === TEST 8: search host with '.org' suffix
+--- yaml_config
+apisix:
+  node_listen: 1984
+  enable_resolv_search_opt: true
 --- config
     location /t {
         content_by_lua_block {
@@ -289,3 +293,27 @@ GET /t
 .+"name":"apisix\.apache\.org".+
 --- no_error_log
 [error]
+
+
+
+=== TEST 9: disable search option
+--- yaml_config
+apisix:
+  node_listen: 1984
+  enable_resolv_search_opt: false
+--- config
+    location /t {
+        content_by_lua_block {
+            local core = require("apisix.core")
+            local ip_info, err = core.utils.dns_parse("apisix")
+            if not ip_info then
+                core.log.error("failed to parse domain: ", host, ", error: ",err)
+                return
+            end
+            ngx.say("ip_info: ", require("toolkit.json").encode(ip_info))
+        }
+    }
+--- request
+GET /t
+--- error_log
+error: failed to query the DNS server