r15170@catbus: nickm | 2007-09-19 11:41:50 -0400

 Carry a new evdns function over from libevent: do not rely on compile-time code to set the transaction ID correctly.  This will be important when we finally drop our internal copy of eventdns.c


svn:r11517

src/or/dns.c

@@ -179,11 +179,21 @@ evdns_log_cb(int warn, const char *msg)
   log(severity, LD_EXIT, "eventdns: %s", msg);
 }
 
+/** Helper: generate a good random transaction ID. */
+static uint16_t
+dns_get_transaction_id(void)
+{
+  uint16_t result;
+  crypto_rand((void*)&result, sizeof(result));
+  return result;
+}
+
 /** Initialize the DNS subsystem; called by the OR process. */
 int
 dns_init(void)
 {
   init_cache_map();
+  evdns_set_transaction_id_fn(dns_get_transaction_id);
   if (server_mode(get_options()))
     return configure_nameservers(1);
   return 0;

src/or/eventdns.c

@@ -1034,14 +1034,12 @@ err:
 #undef GET8
 }
 
-/* Try to choose a strong transaction id which isn't already in flight */
-static u16
-transaction_id_pick(void) {
-	for (;;) {
-		const struct request *req = req_head, *started_at;
+static uint16_t
+default_transaction_id_fn(void)
+{
+	u16 trans_id;
 #ifdef DNS_USE_CPU_CLOCK_FOR_ID
 	struct timespec ts;
-		u16 trans_id;
 #ifdef CLOCK_MONOTONIC
 	if (clock_gettime(CLOCK_MONOTONIC, &ts) == -1)
 #else
@@ -1053,13 +1051,11 @@ transaction_id_pick(void) {
 
 #ifdef DNS_USE_GETTIMEOFDAY_FOR_ID
 	struct timeval tv;
-		u16 trans_id;
 	gettimeofday(&tv, NULL);
 	trans_id = tv.tv_usec & 0xffff;
 #endif
 
 #ifdef DNS_USE_OPENSSL_FOR_ID
-		u16 trans_id;
 	if (RAND_pseudo_bytes((u8 *) &trans_id, 2) == -1) {
 		/* in the case that the RAND call fails we back */
 		/* down to using gettimeofday. */
@@ -1071,6 +1067,26 @@ transaction_id_pick(void) {
 		abort();
 	}
 #endif
+	return (unsigned short) trans_id;
+}
+
+static uint16_t (*trans_id_function)(void) = default_transaction_id_fn;
+
+void
+evdns_set_transaction_id_fn(uint16_t (*fn)(void))
+{
+	if (fn)
+		trans_id_function = fn;
+	else
+		trans_id_function = default_transaction_id_fn;
+}
+
+/* Try to choose a strong transaction id which isn't already in flight */
+static u16
+transaction_id_pick(void) {
+	for (;;) {
+		const struct request *req = req_head, *started_at;
+		u16 trans_id = trans_id_function();
 
 		if (trans_id == 0xffff) continue;
 		/* now check to see if that id is already inflight */

src/or/eventdns.h

@@ -281,6 +281,8 @@ void evdns_search_ndots_set(const int ndots);
 typedef void (*evdns_debug_log_fn_type)(int is_warning, const char *msg);
 void evdns_set_log_fn(evdns_debug_log_fn_type fn);
 
+void evdns_set_transaction_id_fn(uint16_t (*fn)(void));
+
 #define DNS_NO_SEARCH 1
 
 /* Structures and functions used to implement a DNS server. */