r8608@Kushana: nickm | 2006-08-27 16:57:47 -0400

Make it possible to change nameserver options while Tor is running.


svn:r8255

doc/TODO

@@ -100,7 +100,8 @@ N   . Improve memory usage on tight-memory machines.
         reload.
       o Fail when we have no configured nameservers!
       o Make it the default on platforms where it works.
-      - Make resolv.conf (or local equivalent) get checked on reload,
+      - Document SearchDomains, ResolvConf options
+      o Make resolv.conf (or local equivalent) get checked on reload,
         settable while running, etc.
       - Add ipv6 support; make API closer to getaddrinfo().  (i.e., allow a
         single AAAA/A query, return cname as well)

src/or/config.c

@@ -802,8 +802,13 @@ options_act(or_options_t *old_options)
           inform_testing_reachability();
       }
       cpuworkers_rotate();
-      dnsworkers_rotate();
+      dns_reset();
     }
+#ifdef USE_EVENTDNS
+    else {
+      dns_reset();
+    }
+#endif
   }
 
   /* Check if we need to parse and add the EntryNodes config option. */
@@ -2555,6 +2560,7 @@ options_transition_affects_workers(or_options_t *old_options,
   if (!opt_streq(old_options->DataDirectory, new_options->DataDirectory) ||
       old_options->NumCpus != new_options->NumCpus ||
       old_options->ORPort != new_options->ORPort ||
+      old_options->SearchDomains != new_options->SearchDomains ||
       old_options->SafeLogging != new_options->SafeLogging ||
       !config_lines_eq(old_options->Logs, new_options->Logs))
     return 1;

src/or/dns.c

@@ -101,20 +101,28 @@ static void dns_found_answer(const char *address, uint32_t addr, char outcome,
 static void send_resolved_cell(edge_connection_t *conn, uint8_t answer_type);
 static int launch_resolve(edge_connection_t *exitconn);
 #ifndef USE_EVENTDNS
+static void dnsworkers_rotate(void);
 static int dnsworker_main(void *data);
 static int spawn_dnsworker(void);
 static int spawn_enough_dnsworkers(void);
 #else
-static int configure_nameservers(void);
+static int configure_nameservers(int force);
 #endif
 #ifdef DEBUG_DNS_CACHE
 static void _assert_cache_ok(void);
 #define assert_cache_ok() _assert_cache_ok()
 #else
-#define assert_cache_ok() do {} while(0)
+#define assert_cache_ok() do {} while (0)
 #endif
 static void assert_resolve_ok(cached_resolve_t *resolve);
 
+#ifdef USE_EVENTDNS
+/* DOCDOC */
+static int nameservers_configured = 0;
+static char *resolv_conf_fname = NULL;
+static time_t resolv_conf_mtime = 0;
+#endif
+
 /** Hash table of cached_resolve objects. */
 static HT_HEAD(cache_map, cached_resolve_t) cache_root;
 
@@ -164,14 +172,37 @@ int
 dns_init(void)
 {
   init_cache_map();
-  dnsworkers_rotate();
 #ifdef USE_EVENTDNS
   if (server_mode(get_options()))
-    return configure_nameservers();
+    return configure_nameservers(1);
+#else
+  dnsworkers_rotate();
 #endif
   return 0;
 }
 
+/* DOCDOC */
+void
+dns_reset(void)
+{
+#ifdef USE_EVENTDNS
+  or_options_t *options = get_options();
+  if (! server_mode(options)) {
+    eventdns_clear_nameservers_and_suspend();
+    eventdns_search_clear();
+    nameservers_configured = 0;
+    tor_free(resolv_conf_fname);
+    resolv_conf_mtime = 0;
+  } else {
+    if (configure_nameservers(0) < 0)
+      /* XXXX */
+      return;
+  }
+#else
+  dnsworkers_rotate();
+#endif
+}
+
 uint32_t
 dns_clip_ttl(uint32_t ttl)
 {
@@ -910,7 +941,7 @@ connection_dns_process_inbuf(connection_t *conn)
 /** Close and re-open all idle dnsworkers; schedule busy ones to be closed
  * and re-opened once they're no longer busy.
  **/
-void
+static void
 dnsworkers_rotate(void)
 {
   connection_t *dnsconn;
@@ -1162,10 +1193,6 @@ eventdns_err_is_transient(int err)
       return 0;
   }
 }
-void
-dnsworkers_rotate(void)
-{
-}
 int
 connection_dns_finished_flushing(connection_t *conn)
 {
@@ -1187,26 +1214,37 @@ connection_dns_reached_eof(connection_t *conn)
   tor_assert(0);
   return 0;
 }
-static int nameservers_configured = 0;
 
 /* DOCDOC */
 static int
-configure_nameservers(void)
+configure_nameservers(int force)
 {
   or_options_t *options;
   const char *conf_fname;
   struct stat st;
-  if (nameservers_configured)
-    return 0;
   options = get_options();
-  eventdns_set_log_fn(eventdns_log_cb);
-
   conf_fname = options->ResolvConf;
 #ifndef MS_WINDOWS
-  if (!conf_fname) conf_fname = "/etc/resolv.conf";
+  if (!conf_fname)
+    conf_fname = "/etc/resolv.conf";
 #endif
 
+  eventdns_set_log_fn(eventdns_log_cb);
   if (conf_fname) {
+    if (stat(conf_fname, &st)) {
+      log_warn(LD_EXIT, "Unable to stat resolver configuration in '%s'",
+               conf_fname);
+      return -1;
+    }
+    if (!force && resolv_conf_fname && !strcmp(conf_fname,resolv_conf_fname)
+        && st.st_mtime == resolv_conf_mtime) {
+      log_info(LD_EXIT, "No change to '%s'", conf_fname);
+      return 0;
+    }
+    if (nameservers_configured) {
+      eventdns_search_clear();
+      eventdns_clear_nameservers_and_suspend();
+    }
     log_info(LD_EXIT, "Parsing resolver configuration in '%s'", conf_fname);
     if (eventdns_resolv_conf_parse(DNS_OPTIONS_ALL, conf_fname))
       return -1;
@@ -1214,9 +1252,18 @@ configure_nameservers(void)
       log_warn(LD_EXIT, "Unable to find any nameservers in '%s'.", conf_fname);
       return -1;
     }
+    tor_free(resolv_conf_fname);
+    resolv_conf_fname = tor_strdup(resolv_conf_fname);
+    resolv_conf_mtime = st.st_mtime;
+    if (nameservers_configured)
+      eventdns_resume();
   }
 #ifdef MS_WINDOWS
   else {
+    if (nameservers_configured) {
+      eventdns_search_clear();
+      eventdns_clear_nameservers_and_suspend();
+    }
     if (eventdns_config_windows_nameservers())
       return -1;
     if (eventdns_count_nameservers() == 0) {
@@ -1225,6 +1272,10 @@ configure_nameservers(void)
                "ResolvConf file in your torrc?");
       return -1;
     }
+    if (nameservers_configured)
+      eventdns_resume();
+    tor_free(resolv_conf_fname);
+    resolv_conf_mtime = 0;
   }
 #endif
 
@@ -1275,7 +1326,7 @@ launch_resolve(edge_connection_t *exitconn)
   int r;
   int options = get_options()->SearchDomains ? 0 : DNS_QUERY_NO_SEARCH;
   if (!nameservers_configured)
-    if (configure_nameservers() < 0)
+    if (configure_nameservers(1) < 0)
       return -1;
   log_info(LD_EXIT, "Launching eventdns request for %s",
            escaped_safe_str(exitconn->_base.address));
@@ -1338,3 +1389,4 @@ _assert_cache_ok(void)
                              _compare_cached_resolves_by_expiry);
 }
 #endif
+

src/or/eventdns.c

@@ -553,7 +553,7 @@ nameserver_failed(struct nameserver *const ns, const char *msg) {
 	global_good_nameservers--;
 	assert(global_good_nameservers >= 0);
 	if (global_good_nameservers == 0) {
-		log("All nameservers have failed");
+		log(1,"All nameservers have failed");
 	}
 
 	ns->state = 0;
@@ -561,8 +561,8 @@ nameserver_failed(struct nameserver *const ns, const char *msg) {
 
 	evtimer_set(&ns->timeout_event, nameserver_prod_callback, ns);
 	if (evtimer_add(&ns->timeout_event, (struct timeval *) &global_nameserver_timeouts[0]) < 0) {
-          log("Error from libevent when adding timer event for %s",
-              debug_ntoa(ns->address));
+		log(1,"Error from libevent when adding timer event for %s",
+		    debug_ntoa(ns->address));
           // ???? Do more?
         }
 
@@ -910,7 +910,7 @@ reply_parse(u8 *packet, int length) {
 			}
                         // XXXX do something sane with malformed A answers.
 			addrcount = datalength >> 2;  // each IP address is 4 bytes
-			addrtocopy = MIN(MAX_ADDRS - reply.data.a.addrcount, addrcount);
+			addrtocopy = MIN(MAX_ADDRS - reply.data.a.addrcount, (unsigned)addrcount);
 			ttl_r = MIN(ttl_r, ttl);
 			// we only bother with the first four addresses.
 			if (j + 4*addrtocopy > length) return -1;
@@ -1390,7 +1390,6 @@ eventdns_clear_nameservers_and_suspend(void)
 	return 0;
 }
 
-
 // exported function
 int
 eventdns_resume(void)

src/or/main.c

@@ -1081,7 +1081,7 @@ do_hup(void)
     /* Restart cpuworker and dnsworker processes, so they get up-to-date
      * configuration options. */
     cpuworkers_rotate();
-    dnsworkers_rotate();
+    dns_reset();
 #if 0
     /* Write out a fresh descriptor, but leave old one on failure. */
     router_rebuild_descriptor(1);

src/or/or.h

@@ -710,7 +710,6 @@ typedef struct edge_connection_t {
                        * circuit? */
   int deliver_window; /**< How many more relay cells can end at me? */
 
-
   /** Nickname of planned exit node -- used with .exit support. */
   char *chosen_exit_name;
 
@@ -2133,7 +2132,7 @@ uint32_t dns_clip_ttl(uint32_t ttl);
 int connection_dns_finished_flushing(connection_t *conn);
 int connection_dns_reached_eof(connection_t *conn);
 int connection_dns_process_inbuf(connection_t *conn);
-void dnsworkers_rotate(void);
+void dns_reset(void);
 void connection_dns_remove(edge_connection_t *conn);
 void assert_connection_edge_not_dns_pending(edge_connection_t *conn);
 void assert_all_pending_dns_resolves_ok(void);