Applying DNS TTL patch from #368.

I've restructured/cleaned up the original patch by thomas.other a bit.

src/DNS_Mgr.cc

@@ -63,6 +63,7 @@ public:
 protected:
 	char* host;	// if non-nil, this is a host request
 	uint32 addr;
+	uint32 ttl;
 	int request_pending;
 };
 
@@ -82,8 +83,8 @@ int DNS_Mgr_Request::MakeRequest(nb_dns_info* nb_dns)
 
 class DNS_Mapping {
 public:
-	DNS_Mapping(const char* host, struct hostent* h);
+	DNS_Mapping(const char* host, struct hostent* h, uint32 ttl);
-	DNS_Mapping(uint32 addr, struct hostent* h);
+	DNS_Mapping(uint32 addr, struct hostent* h, uint32 ttl);
 	DNS_Mapping(FILE* f);
 
 	int NoMapping() const		{ return no_mapping; }
@@ -108,6 +109,9 @@ public:
 	int Failed() const		{ return failed; }
 	int Valid() const		{ return ! failed; }
 
+	bool Expired() const
+		{ return current_time() > (creation_time + req_ttl); }
+
 protected:
 	friend class DNS_Mgr;
 
@@ -119,6 +123,7 @@ protected:
 
 	char* req_host;
 	uint32 req_addr;
+	uint32 req_ttl;
 
 	int num_names;
 	char** names;
@@ -146,21 +151,23 @@ static TableVal* empty_addr_set()
 	return new TableVal(s);
 	}
 
-DNS_Mapping::DNS_Mapping(const char* host, struct hostent* h)
+DNS_Mapping::DNS_Mapping(const char* host, struct hostent* h, uint32 ttl)
 	{
 	Init(h);
 	req_host = copy_string(host);
 	req_addr = 0;
+	req_ttl = ttl;
 
 	if ( names && ! names[0] )
 		names[0] = copy_string(host);
 	}
 
-DNS_Mapping::DNS_Mapping(uint32 addr, struct hostent* h)
+DNS_Mapping::DNS_Mapping(uint32 addr, struct hostent* h, uint32 ttl)
 	{
 	Init(h);
 	req_addr = addr;
 	req_host = 0;
+	req_ttl = ttl;
 	}
 
 DNS_Mapping::DNS_Mapping(FILE* f)
@@ -663,6 +670,7 @@ Val* DNS_Mgr::BuildMappingVal(DNS_Mapping* dm)
 void DNS_Mgr::AddResult(DNS_Mgr_Request* dr, struct nb_dns_result* r)
 	{
 	struct hostent* h = (r && r->host_errno == 0) ? r->hostent : 0;
+	u_int32_t ttl = r->ttl;
 
 	DNS_Mapping* new_dm;
 	DNS_Mapping* prev_dm;
@@ -670,7 +678,7 @@ void DNS_Mgr::AddResult(DNS_Mgr_Request* dr, struct nb_dns_result* r)
 
 	if ( dr->ReqHost() )
 		{
-		new_dm = new DNS_Mapping(dr->ReqHost(), h);
+		new_dm = new DNS_Mapping(dr->ReqHost(), h, ttl);
 		prev_dm = host_mappings.Insert(dr->ReqHost(), new_dm);
 
 		if ( new_dm->Failed() && prev_dm && prev_dm->Valid() )
@@ -683,7 +691,7 @@ void DNS_Mgr::AddResult(DNS_Mgr_Request* dr, struct nb_dns_result* r)
 		}
 	else
 		{
-		new_dm = new DNS_Mapping(dr->ReqAddr(), h);
+		new_dm = new DNS_Mapping(dr->ReqAddr(), h, ttl);
 		uint32 tmp_addr = dr->ReqAddr();
 		HashKey k(&tmp_addr, 1);
 		prev_dm = addr_mappings.Insert(&k, new_dm);
@@ -833,9 +841,16 @@ const char* DNS_Mgr::LookupAddrInCache(dns_mgr_addr_type addr)
 	{
 	HashKey h(&addr, 1);
 	DNS_Mapping* d = dns_mgr->addr_mappings.Lookup(&h);
+
 	if ( ! d )
 		return 0;
 
+	if ( d->Expired() )
+		{
+		dns_mgr->addr_mappings.Remove(&h);
+		return 0;
+		}
+
 	// The escapes in the following strings are to avoid having it
 	// interpreted as a trigraph sequence.
 	return d->names ? d->names[0] : "<\?\?\?>";
@@ -844,9 +859,17 @@ const char* DNS_Mgr::LookupAddrInCache(dns_mgr_addr_type addr)
 TableVal* DNS_Mgr::LookupNameInCache(string name)
 	{
 	DNS_Mapping* d = dns_mgr->host_mappings.Lookup(name.c_str());
+
 	if ( ! d || ! d->names )
 		return 0;
 
+	if ( d->Expired() )
+		{
+		HashKey h(name.c_str());
+		dns_mgr->host_mappings.Remove(&h);
+		return 0;
+		}
+
 	return d->AddrsSet();
 	}
 

src/nb_dns.c

@@ -438,6 +438,7 @@ nb_dns_activity(struct nb_dns_info *nd, struct nb_dns_result *nr, char *errstr)
 	register char **ap, **hap;
 	register u_int16_t id;
 	register const u_char *rdata;
+	register u_int32_t rttl;
 	register struct hostent *he;
 	register size_t rdlen;
 	ns_msg handle;
@@ -557,6 +558,7 @@ nb_dns_activity(struct nb_dns_info *nd, struct nb_dns_result *nr, char *errstr)
 
 		rdata = ns_rr_rdata(rr);
 		rdlen = ns_rr_rdlen(rr);
+		rttl = ns_rr_ttl(rr);
 		switch (atype) {
 
 		case T_A:
@@ -603,10 +605,12 @@ nb_dns_activity(struct nb_dns_info *nd, struct nb_dns_result *nr, char *errstr)
 
 			/* "Find first satisfactory answer" */
 			nr->hostent = he;
+			nr->ttl = rttl;
 			return (1);
 		}
 	}
 
 	nr->hostent = he;
+	nr->ttl = rttl;
 	return (1);
 }

src/nb_dns.h

@@ -11,6 +11,7 @@ struct nb_dns_result {
 	void *cookie;
 	int host_errno;
 	struct hostent *hostent;
+	uint32_t ttl;
 };
 
 typedef unsigned int nb_uint32_t;