[TS-1073] no_dns_just_forward_to_parent configuration parameter is ignored/not used.

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.0.2
• Fix Version/s: 3.1.2
• Component/s: DNS

Environment

Ubuntu 10.0, Fedora 14

• Assignee: Leif Hedstrom
• Reporter: Kevin Giles
• Created: 06/Jan/12 12:28
• Updated: 10/Jun/12 01:35
• Resolved: 25/Jan/12 16:21

Description

I have two instances of trafficserver configured, one instance is configured to use the second instance as a parent proxy using the following parameters from the records.config:

CONFIG proxy.config.http.no_dns_just_forward_to_parent INT 1

CONFIG proxy.config.http.parent_proxy_routing_enable INT 1

The parent config looks like this:
dest_domain=. parent="parent:8080" round_robin=false

The no_dns_just_forward_to_parent is not used in the code and as a result dns lookups are being performed in the child instance.

The following code changes seem to fix this:

proxy/http/HttpSM.cc
@@ -6406,11 +6405,20 @@
t_state.dns_info.lookup_success = true;
call_transact_and_set_next_state(NULL);
break;
} else if (t_state.parent_result.r == PARENT_UNDEFINED && t_state.dns_info.lookup_success)

{ // Already set, and we don't have a parent proxy to lookup ink_assert(t_state.host_db_info.ip()); Debug("dns", "[HttpTransact::HandleRequest] Skipping DNS lookup, provided by plugin"); call_transact_and_set_next_state(NULL); break; + }

else if (t_state.dns_info.looking_up == HttpTransact::ORIGIN_SERVER &&
+ t_state.http_config_param->no_dns_forward_to_parent){
+
+ if(t_state.cop_test_page)

{ + t_state.host_db_info.ip() =t_state.state_machine->ua_session->get_netvc()->get_local_ip(); + }

+
+ t_state.dns_info.lookup_success = true;
+ call_transact_and_set_next_state(NULL);
+ break;
}

HTTP_SM_SET_DEFAULT_HANDLER(&HttpSM::state_hostdb_lookup);

to avoid reverse ns lookups
/proxy/http/HttpTransact.cc
@@ -1650,7 +1651,8 @@
} else if (s->dns_info.lookup_name[0] <= '9' &&
s->dns_info.lookup_name[0] >= '0' &&
//(s->state_machine->authAdapter.needs_rev_dns() ||

• ( host_rule_in_CacheControlTable() || s->parent_params->ParentTable->hostMatch)) {
  + ( host_rule_in_CacheControlTable() || s->parent_params->ParentTable->hostMatch) &&
  + !s->http_config_param->no_dns_forward_to_parent) {
  // note, broken logic: ACC fudges the OR stmt to always be true,
  // 'AuthHttpAdapter' should do the rev-dns if needed, not here .
  TRANSACT_RETURN(REVERSE_DNS_LOOKUP, HttpTransact::StartAccessControl);

I would like to have these changes applied to the repository if they look ok.

I also created an empty resolv.conf and pointed ats to the empty file:
CONFIG proxy.config.dns.resolv_conf STRING /usr/local/etc/trafficserver/resolv.conf

When these changes are applied the child instance no longer attempts to perform dns lookups for the
http requests that it receives. If they are not applied and the dns lookup it slow or unreliable on the
child then the http requests are blocked by the dns lookup within the child trafficserver instance.