Add comments to source code

2025-09-02 15:45:25 +00:00 · 2000-07-18 18:51:40 +00:00
parent 0ade7651fc
commit 5e804988e9
2 changed files with 192 additions and 74 deletions
--- a/bin/dig/dig.c
+++ b/bin/dig/dig.c
@@ -15,7 +15,7 @@
 * SOFTWARE.
 */

-/* $Id: dig.c,v 1.69 2000/07/18 01:28:15 mws Exp $ */
+/* $Id: dig.c,v 1.70 2000/07/18 18:51:38 mws Exp $ */

 #include <config.h>
 #include <stdlib.h>
@@ -173,6 +173,9 @@ show_usage(void) {
 , stderr);
 }				

+/*
+ * Callback from dighost.c to print the received message.
+ */
 void
 received(int bytes, int frmsize, char *frm, dig_query_t *query) {
 	isc_uint64_t diff;
@@ -208,6 +211,10 @@ received(int bytes, int frmsize, char *frm, dig_query_t *query) {
 	}
 }

+/*
+ * Callback from dighost.c to print that it is trying a server.
+ * Not used in dig.
+ */
 void
 trying(int frmsize, char *frm, dig_lookup_t *lookup) {
 	UNUSED(frmsize);
@@ -215,6 +222,9 @@ trying(int frmsize, char *frm, dig_lookup_t *lookup) {
 	UNUSED(lookup);
 }

+/*
+ * Internal print routine used to print short form replies.
+ */
 static isc_result_t
 say_message(dns_rdata_t *rdata, dig_query_t *query, isc_buffer_t *buf) {
 	isc_result_t result;
@@ -244,6 +254,9 @@ say_message(dns_rdata_t *rdata, dig_query_t *query, isc_buffer_t *buf) {
 	return (ISC_R_SUCCESS);
 }

+/*
+ * short_form message print handler.  Calls above say_message()
+ */
 static isc_result_t
 short_answer(dns_message_t *msg, dns_messagetextflag_t flags,
 	     isc_buffer_t *buf, dig_query_t *query)
@@ -293,7 +306,9 @@ short_answer(dns_message_t *msg, dns_messagetextflag_t flags,
 	return (ISC_R_SUCCESS);
 }

-
+/*
+ * Callback from dighost.c to print the reply from a server
+ */
 isc_result_t
 printmessage(dig_query_t *query, dns_message_t *msg, isc_boolean_t headers) {
 	isc_boolean_t did_flag = ISC_FALSE;
@@ -478,6 +493,9 @@ printmessage(dig_query_t *query, dns_message_t *msg, isc_boolean_t headers) {
 	return (result);
 }

+/*
+ * print the greeting message when the program first starts up.
+ */
 static void
 printgreeting(int argc, char **argv) {
 	int i = 1;
@@ -534,7 +552,7 @@ reorder_args(int argc, char *argv[]) {
 /*
 * We're not using isc_commandline_parse() here since the command line
 * syntax of dig is quite a bit different from that which can be described
- * that routine.  There is a portability issue here.
+ * that routine.
 */
 static void
 parse_args(isc_boolean_t is_batchfile, int argc, char **argv) {
@@ -969,6 +987,11 @@ parse_args(isc_boolean_t is_batchfile, int argc, char **argv) {
 	}
 }

+/*
+ * Callback from dighost.c to allow program-specific shutdown code.  Here,
+ * Here, we're possibly reading from a batch file, then shutting down for
+ * real if there's nothing in the batch file to read.
+ */
 void
 dighost_shutdown(void) {
 	char batchline[MXNAME];
--- a/bin/dig/dighost.c
+++ b/bin/dig/dighost.c
@@ -15,7 +15,7 @@
 * SOFTWARE.
 */

-/* $Id: dighost.c,v 1.90 2000/07/18 01:28:16 mws Exp $ */
+/* $Id: dighost.c,v 1.91 2000/07/18 18:51:40 mws Exp $ */

 /*
 * Notice to programmers:  Do not use this code as an example of how to
@@ -128,6 +128,12 @@ dig_lookup_t *current_lookup = NULL;
 static void
 cancel_lookup(dig_lookup_t *lookup);

+static void
+recv_done(isc_task_t *task, isc_event_t *event);
+
+static void
+connect_timeout(isc_task_t *task, isc_event_t *event);
+
 static int
 count_dots(char *string) {
 	char *s;
@@ -170,15 +176,6 @@ fatal(const char *format, ...) {
 	fprintf(stderr, "\n");
 	if (exitcode == 0)
 		exitcode = 8;
-#ifdef NEVER
-	dighost_shutdown();
-	free_lists(exitcode);
-	if (mctx != NULL) {
-		if (isc_mem_debugging)
-			isc_mem_stats(mctx, stderr);
-		isc_mem_destroy(&mctx);
-	}
-#endif
 	exit(exitcode);
 }

@@ -202,6 +199,11 @@ check_result(isc_result_t result, const char *msg) {
 	}
 }

+/*
+ * Create a server structure, which is part of the lookup structure.
+ * This is little more than a linked list of servers to query in hopes
+ * of finding the answer the user is looking for
+ */
 dig_server_t *
 make_server(const char *servname) {
 	dig_server_t *srv;
@@ -217,6 +219,10 @@ make_server(const char *servname) {
 	return (srv);
 }

+/* 
+ * Produce a cloned server list.  The dest list must have already had
+ * ISC_LIST_INIT applied.
+ */
 void
 clone_server_list(dig_serverlist_t src, 
 		  dig_serverlist_t *dest)
@@ -232,6 +238,12 @@ clone_server_list(dig_serverlist_t src,
 	}
 }

+/*
+ * Create an empty lookup structure, which holds all the information needed
+ * to get an answer to a user's question.  This structure contains two
+ * linked lists: the server list (servers to query) and the query list
+ * (outstanding queries which have been made to the listed servers).
+ */
 dig_lookup_t *
 make_empty_lookup(void) {
 	dig_lookup_t *looknew;
@@ -284,6 +296,9 @@ make_empty_lookup(void) {
 }

 /*
+ * Clone a lookup, perhaps copying the server list.  This does not clone
+ * the query list, since it will be regenerated by the setup_lookup()
+ * function, nor does it queue up the new lookup for processing.
 * Caution: If you don't clone the servers, you MUST clone the server
 * list seperately from somewhere else, or construct it by hand.
 */
@@ -326,6 +341,14 @@ clone_lookup(dig_lookup_t *lookold, isc_boolean_t servers) {
 	return (looknew);
 }

+/*
+ * Requeue a lookup for further processing, perhaps copying the server
+ * list.  The new lookup structure is returned to the caller, and is
+ * queued for processing.  If servers are not cloned in the requeue, they
+ * must be added before allowing the current event to complete, since the
+ * completion of the event may result in the next entry on the lookup
+ * queue getting run.
+ */
 dig_lookup_t *
 requeue_lookup(dig_lookup_t *lookold, isc_boolean_t servers) {
 	dig_lookup_t *looknew;
@@ -349,6 +372,10 @@ requeue_lookup(dig_lookup_t *lookold, isc_boolean_t servers) {
 	return (looknew);
 }	

+/*
+ * Setup the system as a whole, reading key information and resolv.conf
+ * settings.
+ */
 void
 setup_system(void) {
 	char rcinput[MXNAME];
@@ -542,6 +569,9 @@ setup_system(void) {
 	}
 }
 	
+/*
+ * Setup the ISC and DNS libraries for use by the system.
+ */
 void
 setup_libs(void) {
 	isc_result_t result;
@@ -601,6 +631,10 @@ setup_libs(void) {
 	check_result(result, "isc_mutex_init");
 }

+/*
+ * Add EDNS0 option record to a message.  Currently, the only supported
+ * option is UDP buffer size.
+ */
 static void
 add_opt(dns_message_t *msg, isc_uint16_t udpsize) {
 	dns_rdataset_t *rdataset = NULL;
@@ -631,6 +665,10 @@ add_opt(dns_message_t *msg, isc_uint16_t udpsize) {
 	check_result(result, "dns_message_setopt");
 }

+/*
+ * Add a question section to a message, asking for the specified name, 
+ * type, and class.
+ */
 static void
 add_question(dns_message_t *message, dns_name_t *name,
 	     dns_rdataclass_t rdclass, dns_rdatatype_t rdtype)
@@ -648,7 +686,12 @@ add_question(dns_message_t *message, dns_name_t *name,
 }

 /*
- * We're done iff all the counts are zero and the lookup list is empty
+ * Check if we're done with all the queued lookups, which is true iff
+ * all sockets, sends, and recvs are accounted for (counters == 0),
+ * and the lookup list is empty.
+ * If we are done, pass control back out to dighost_shutdown() (which is
+ * part of dig.c, host.c, or nslookup.c) to either shutdown the system as
+ * a whole or reseed the lookup list.
 */
 static void
 check_if_done(void) {
@@ -696,6 +739,11 @@ clear_query(dig_query_t *query) {
 	isc_mem_free(mctx, query);
 }
 	
+/*
+ * Try and clear out a lookup if we're done with it.  Return ISC_TRUE if
+ * the lookup was successfully cleared.  If ISC_TRUE is returned, the
+ * lookup pointer has been invalidated.
+ */
 static isc_boolean_t
 try_clear_lookup(dig_lookup_t *lookup) {
 	dig_server_t *s;
@@ -751,7 +799,8 @@ try_clear_lookup(dig_lookup_t *lookup) {
 /*
 * If we can, start the next lookup in the queue running.
 * This assumes that the lookup on the head of the queue hasn't been
- * started yet.
+ * started yet.  It also moves the lookup from the head of the queue
+ * off, setting the current_lookup pointer pointing to it.
 */
 void
 start_lookup(void) {
@@ -782,9 +831,8 @@ start_lookup(void) {
 }

 /*
- * WARNING: The following routine may invalidate the lookup pointer.
- * Never depend on being able to reference lookup or query pointers on the
- * current lookup after calling this.
+ * If we can, clear the current lookup and start the next one running.
+ * This calls try_clear_lookup, so may invalidate the lookup pointer.
 */
 static void
 check_next_lookup(dig_lookup_t *lookup) {
@@ -810,6 +858,12 @@ check_next_lookup(dig_lookup_t *lookup) {
 	}
 }

+/*
+ * Create and queue a new lookup as a followup to the current lookup,
+ * based on the supplied message and section.  This is used in trace and
+ * name server search modes to start a new lookup using servers from
+ * NS records in a reply.
+ */
 static void
 followup_lookup(dns_message_t *msg, dig_query_t *query,
 		dns_section_t section) {
@@ -920,6 +974,10 @@ followup_lookup(dns_message_t *msg, dig_query_t *query,
 		followup_lookup(msg, query, DNS_SECTION_AUTHORITY);
 }

+/*
+ * Create and queue a new lookup using the next origin from the origin
+ * list, read in setup_system().
+ */
 static void
 next_origin(dns_message_t *msg, dig_query_t *query) {
 	dig_lookup_t *lookup;
@@ -944,7 +1002,10 @@ next_origin(dns_message_t *msg, dig_query_t *query) {
 	lookup->origin = ISC_LIST_NEXT(query->lookup->origin, link);
 }

-
+/*
+ * Insert an SOA record into the sendmessage in a lookup.  Used for
+ * creating IXFR queries.
+ */
 static void
 insert_soa(dig_lookup_t *lookup) {
 	isc_result_t result;
@@ -1006,6 +1067,12 @@ insert_soa(dig_lookup_t *lookup) {
 	dns_message_addname(lookup->sendmsg, soaname, DNS_SECTION_AUTHORITY);
 }

+/*
+ * Setup the supplied lookup structure, making it ready to start sending
+ * queries to servers.  Create and initialize the message to be sent as
+ * well as the query structures and buffer space for the replies.  If the
+ * server list is empty, clone it from the system default list.
+ */
 void
 setup_lookup(dig_lookup_t *lookup) {
 	isc_result_t result, res2;
@@ -1235,6 +1302,13 @@ setup_lookup(dig_lookup_t *lookup) {
 	}
 }	

+/*
+ * Event handler for send completion.  Track send counter, and clear out
+ * the query if the send was canceled.
+ * XXXMWS Possible race condition!  When the send gets canceled, doesn't the
+ * recv also, so it will also be trying to clear out the query?
+ * Not really sure that this should touch the query at all.
+ */
 static void
 send_done(isc_task_t *task, isc_event_t *event) {
 	isc_socketevent_t *sevent = NULL;
@@ -1267,6 +1341,11 @@ send_done(isc_task_t *task, isc_event_t *event) {
 	UNLOCK_LOOKUP;
 }

+/*
+ * Cancel a lookup, sending isc_socket_cancel() requests to all outstanding
+ * IO sockets.  The cancel handlers should take care of cleaning up the
+ * query and lookup structures
+ */
 void
 cancel_lookup(dig_lookup_t *lookup) {
 	dig_query_t *query = NULL;
@@ -1288,12 +1367,11 @@ cancel_lookup(dig_lookup_t *lookup) {
 	lookup->retries = 0;
 }

-static void
-recv_done(isc_task_t *task, isc_event_t *event);
-
-static void
-connect_timeout(isc_task_t *task, isc_event_t *event);
-
+/*
+ * Send a UDP packet to the remote nameserver, possible starting the
+ * recv action as well.  Also make sure that the timer is running and
+ * is properly reset.
+ */
 static void
 send_udp(dig_lookup_t *lookup, isc_boolean_t make_recv) {
 	dig_query_t *query;
@@ -1366,7 +1444,9 @@ send_udp(dig_lookup_t *lookup, isc_boolean_t make_recv) {
 }

 /*
- * connect_timeout is used for both UDP recieves and TCP connects.
+ * IO timeout handler, used for both connect and recv timeouts.  If
+ * retries are still allowed, either resend the UDP packet or queue a
+ * new TCP lookup.  Otherwise, cancel the lookup.
 */
 static void
 connect_timeout(isc_task_t *task, isc_event_t *event) {
@@ -1400,6 +1480,10 @@ connect_timeout(isc_task_t *task, isc_event_t *event) {
 	UNLOCK_LOOKUP;
 }

+/*
+ * Event handler for the TCP recv which gets the length header of TCP
+ * packets.  Start the next recv of length bytes.
+ */
 static void
 tcp_length_done(isc_task_t *task, isc_event_t *event) { 
 	isc_socketevent_t *sevent;
@@ -1481,6 +1565,10 @@ tcp_length_done(isc_task_t *task, isc_event_t *event) {
 	UNLOCK_LOOKUP;
 }

+/*
+ * For transfers that involve multiple recvs (XFR's in particular),
+ * launch the next recv.
+ */
 static void
 launch_next_query(dig_query_t *query, isc_boolean_t include_question) {
 	isc_result_t result;
@@ -1521,7 +1609,7 @@ launch_next_query(dig_query_t *query, isc_boolean_t include_question) {
 	recvcount++;
 	debug("recvcount=%d",recvcount);
 	if (!query->first_soa_rcvd) {
-		debug("sending a request");
+		debug("sending a request in launch_next_query");
 		result = isc_time_now(&query->time_sent);
 		check_result(result, "isc_time_now");
 		result = isc_socket_sendv(query->sock, &query->sendlist,
@@ -1531,10 +1619,17 @@ launch_next_query(dig_query_t *query, isc_boolean_t include_question) {
 		debug("sendcount=%d", sendcount);
 	}
 	query->waiting_connect = ISC_FALSE;
+#if 0
 	check_next_lookup(query->lookup);
+#endif
 	return;
 }
 	
+/*
+ * Event handler for TCP connect complete.  Make sure the connection was
+ * successful, then pass into launch_next_query to actually send the
+ * question.
+ */
 static void
 connect_done(isc_task_t *task, isc_event_t *event) {
 	isc_result_t result;
@@ -1593,32 +1688,11 @@ connect_done(isc_task_t *task, isc_event_t *event) {
 	UNLOCK_LOOKUP;
 }

-
-#if 0
-static isc_boolean_t
-msg_contains_soa(dns_message_t *msg, dig_query_t *query) {
-	isc_result_t result;
-	dns_name_t *name=NULL;
-	
-	debug("msg_contains_soa()");
-	
-	result = dns_message_findname(msg, DNS_SECTION_ANSWER,
-				      query->lookup->name, dns_rdatatype_soa,
-				      0, &name, NULL);
-	if (result == ISC_R_SUCCESS) {
-		debug("found SOA", stderr);
-		return (ISC_TRUE);
-	} else {
-		debug("didn't find SOA, result=%d:%s",
-		      result, dns_result_totext(result));
-		return (ISC_FALSE);
-	}
-	
-}
-#endif
-
 /*
- * Returns true if we should call cancel_lookup().  This is a hack.
+ * Check if the ongoing XFR needs more data before it's complete, using
+ * the semantics of IXFR and AXFR protocols.  Much of the complexity of
+ * this routine comes from determining when an IXFR is complete.
+ * ISC_TRUE means more data is on the way, and the recv has been issued.
 */
 static isc_boolean_t
 check_for_more_data(dig_query_t *query, dns_message_t *msg,
@@ -1649,9 +1723,6 @@ check_for_more_data(dig_query_t *query, dns_message_t *msg,
 		query->working = ISC_FALSE;
 		return (ISC_TRUE);
 	}
-#ifdef NEVER
-	check_result(result, "dns_message_firstname");
-#endif
 	do {
 		dns_name_t *name = NULL;
 		dns_message_currentname(msg, DNS_SECTION_ANSWER,
@@ -1773,6 +1844,10 @@ check_for_more_data(dig_query_t *query, dns_message_t *msg,
 	return (ISC_FALSE);
 }

+/*
+ * Event handler for recv complete.  Perform whatever actions are necessary,
+ * based on the specifics of the user's request.
+ */
 static void
 recv_done(isc_task_t *task, isc_event_t *event) {
 	isc_socketevent_t *sevent = NULL;
@@ -2040,6 +2115,11 @@ recv_done(isc_task_t *task, isc_event_t *event) {
 	      isc_result_totext(sevent->result));
 }

+/*
+ * Turn a name into an address, using system-supplied routines.  This is
+ * used in looking up server names, etc... and needs to use system-supplied
+ * routines, since they may be using a non-DNS system for these lookups.
+ */
 void
 get_address(char *host, in_port_t port, isc_sockaddr_t *sockaddr) {
 	struct in_addr in4;
@@ -2081,6 +2161,9 @@ get_address(char *host, in_port_t port, isc_sockaddr_t *sockaddr) {
 	}
 }

+/*
+ * Initiate a TCP lookup, starting all of the queries running
+ */
 static void
 do_lookup_tcp(dig_lookup_t *lookup) {
 	dig_query_t *query;
@@ -2133,6 +2216,9 @@ do_lookup_tcp(dig_lookup_t *lookup) {
 	}
 }

+/*
+ * Initiate a UDP lookup, starting all of the queries running
+ */
 static void
 do_lookup_udp(dig_lookup_t *lookup) {
 	dig_query_t *query;
@@ -2170,6 +2256,9 @@ do_lookup_udp(dig_lookup_t *lookup) {
 	send_udp(lookup, ISC_TRUE);
 }

+/*
+ * Initiate either a TCP or UDP lookup
+ */
 void
 do_lookup(dig_lookup_t *lookup) {

@@ -2182,6 +2271,9 @@ do_lookup(dig_lookup_t *lookup) {
 		do_lookup_udp(lookup);
 }

+/*
+ * Start everything in action upon task startup.
+ */
 void
 onrun_callback(isc_task_t *task, isc_event_t *event) {
 	UNUSED(task);
@@ -2192,7 +2284,8 @@ onrun_callback(isc_task_t *task, isc_event_t *event) {
 }

 /*
- * This will be used in the SIGINT handler, and perhaps other places.
+ * Make everything on the lookup queue go away.  Mainly used by the
+ * SIGINT handler.
 */
 void
 cancel_all(void) {
@@ -2231,14 +2324,30 @@ cancel_all(void) {
 	UNLOCK_LOOKUP;
 }

-static void
-xfree_lists(void) {
+/*
+ * Destroy all of the libs we are using, and get everything ready for a 
+ * clean shutdown.
+ */
+void
+destroy_libs(void) {
 	void *ptr;
 	dig_server_t *s;
 	dig_searchlist_t *o;

-	debug("xfree_lists()");
-
+	debug("destroy_libs()");
+	if (global_task != NULL) {
+		debug("freeing task");
+		isc_task_detach(&global_task);
+	}
+	/*
+	 * The taskmgr_destroy() call blocks until all events are cleared
+	 * from the task.
+	 */
+	if (taskmgr != NULL) {
+		debug("Freeing taskmgr");
+		isc_taskmgr_destroy(&taskmgr);
+        }
+	LOCK_LOOKUP;
 	REQUIRE(sockcount == 0);
 	REQUIRE(recvcount == 0);
 	REQUIRE(sendcount == 0);
@@ -2296,21 +2405,7 @@ xfree_lists(void) {
 		debug("detach from entropy");
 		isc_entropy_detach(&entp);
 	}
-}

-void
-destroy_libs(void) {
-	debug("destroy_libs()");
-	if (global_task != NULL) {
-		debug("freeing task");
-		isc_task_detach(&global_task);
-	}
-	if (taskmgr != NULL) {
-		debug("Freeing taskmgr");
-		isc_taskmgr_destroy(&taskmgr);
-        }
-	LOCK_LOOKUP;
-	xfree_lists();
 	isc_mutex_destroy(&lookup_lock);
 	if (isc_mem_debugging)
 		isc_mem_stats(mctx, stderr);