--- /dev/null
+/***
+ This file is part of avahi.
+
+ avahi is free software; you can redistribute it and/or modify it
+ under the terms of the GNU Lesser General Public License as
+ published by the Free Software Foundation; either version 2.1 of the
+ License, or (at your option) any later version.
+
+ avahi is distributed in the hope that it will be useful, but WITHOUT
+ ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
+ or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General
+ Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with avahi; if not, write to the Free Software
+ Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
+ USA.
+***/
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <stdlib.h>
+
+#include <avahi/timeval.h>
+#include <avahi/malloc.h>
+
+#include "query-sched.h"
+#include <avahi/log.h>
+
+#define AVAHI_QUERY_HISTORY_MSEC 100
+#define AVAHI_QUERY_DEFER_MSEC 100
+
+typedef struct AvahiQueryJob AvahiQueryJob;
+typedef struct AvahiKnownAnswer AvahiKnownAnswer;
+
+struct AvahiQueryJob {
+ unsigned id;
+ int n_posted;
+
+ AvahiQueryScheduler *scheduler;
+ AvahiTimeEvent *time_event;
+
+ int done;
+ struct timeval delivery;
+
+ AvahiKey *key;
+
+ /* Jobs are stored in a simple linked list. It might turn out in
+ * the future that this list grows too long and we must switch to
+ * some other kind of data structure. This needs further
+ * investigation. I expect the list to be very short (< 20
+ * entries) most of the time, but this might be a wrong
+ * assumption, especially on setups where traffic reflection is
+ * involved. */
+
+ AVAHI_LLIST_FIELDS(AvahiQueryJob, jobs);
+};
+
+struct AvahiKnownAnswer {
+ AvahiQueryScheduler *scheduler;
+ AvahiRecord *record;
+
+ AVAHI_LLIST_FIELDS(AvahiKnownAnswer, known_answer);
+};
+
+struct AvahiQueryScheduler {
+ AvahiInterface *interface;
+ AvahiTimeEventQueue *time_event_queue;
+
+ unsigned next_id;
+
+ AVAHI_LLIST_HEAD(AvahiQueryJob, jobs);
+ AVAHI_LLIST_HEAD(AvahiQueryJob, history);
+ AVAHI_LLIST_HEAD(AvahiKnownAnswer, known_answers);
+};
+
+static AvahiQueryJob* job_new(AvahiQueryScheduler *s, AvahiKey *key, int done) {
+ AvahiQueryJob *qj;
+
+ assert(s);
+ assert(key);
+
+ if (!(qj = avahi_new(AvahiQueryJob, 1))) {
+ avahi_log_error(__FILE__": Out of memory");
+ return NULL;
+ }
+
+ qj->scheduler = s;
+ qj->key = avahi_key_ref(key);
+ qj->time_event = NULL;
+ qj->n_posted = 1;
+ qj->id = s->next_id++;
+
+ if ((qj->done = done))
+ AVAHI_LLIST_PREPEND(AvahiQueryJob, jobs, s->history, qj);
+ else
+ AVAHI_LLIST_PREPEND(AvahiQueryJob, jobs, s->jobs, qj);
+
+ return qj;
+}
+
+static void job_free(AvahiQueryScheduler *s, AvahiQueryJob *qj) {
+ assert(s);
+ assert(qj);
+
+ if (qj->time_event)
+ avahi_time_event_free(qj->time_event);
+
+ if (qj->done)
+ AVAHI_LLIST_REMOVE(AvahiQueryJob, jobs, s->history, qj);
+ else
+ AVAHI_LLIST_REMOVE(AvahiQueryJob, jobs, s->jobs, qj);
+
+ avahi_key_unref(qj->key);
+ avahi_free(qj);
+}
+
+static void elapse_callback(AvahiTimeEvent *e, void* data);
+
+static void job_set_elapse_time(AvahiQueryScheduler *s, AvahiQueryJob *qj, unsigned msec, unsigned jitter) {
+ struct timeval tv;
+
+ assert(s);
+ assert(qj);
+
+ avahi_elapse_time(&tv, msec, jitter);
+
+ if (qj->time_event)
+ avahi_time_event_update(qj->time_event, &tv);
+ else
+ qj->time_event = avahi_time_event_new(s->time_event_queue, &tv, elapse_callback, qj);
+}
+
+static void job_mark_done(AvahiQueryScheduler *s, AvahiQueryJob *qj) {
+ assert(s);
+ assert(qj);
+
+ assert(!qj->done);
+
+ AVAHI_LLIST_REMOVE(AvahiQueryJob, jobs, s->jobs, qj);
+ AVAHI_LLIST_PREPEND(AvahiQueryJob, jobs, s->history, qj);
+
+ qj->done = 1;
+
+ job_set_elapse_time(s, qj, AVAHI_QUERY_HISTORY_MSEC, 0);
+ gettimeofday(&qj->delivery, NULL);
+}
+
+AvahiQueryScheduler *avahi_query_scheduler_new(AvahiInterface *i) {
+ AvahiQueryScheduler *s;
+ assert(i);
+
+ if (!(s = avahi_new(AvahiQueryScheduler, 1))) {
+ avahi_log_error(__FILE__": Out of memory");
+ return NULL; /* OOM */
+ }
+
+ s->interface = i;
+ s->time_event_queue = i->monitor->server->time_event_queue;
+ s->next_id = 0;
+
+ AVAHI_LLIST_HEAD_INIT(AvahiQueryJob, s->jobs);
+ AVAHI_LLIST_HEAD_INIT(AvahiQueryJob, s->history);
+ AVAHI_LLIST_HEAD_INIT(AvahiKnownAnswer, s->known_answers);
+
+ return s;
+}
+
+void avahi_query_scheduler_free(AvahiQueryScheduler *s) {
+ assert(s);
+
+ assert(!s->known_answers);
+ avahi_query_scheduler_clear(s);
+ avahi_free(s);
+}
+
+void avahi_query_scheduler_clear(AvahiQueryScheduler *s) {
+ assert(s);
+
+ while (s->jobs)
+ job_free(s, s->jobs);
+ while (s->history)
+ job_free(s, s->history);
+}
+
+static void* known_answer_walk_callback(AvahiCache *c, AvahiKey *pattern, AvahiCacheEntry *e, void* userdata) {
+ AvahiQueryScheduler *s = userdata;
+ AvahiKnownAnswer *ka;
+
+ assert(c);
+ assert(pattern);
+ assert(e);
+ assert(s);
+
+ if (avahi_cache_entry_half_ttl(c, e))
+ return NULL;
+
+ if (!(ka = avahi_new0(AvahiKnownAnswer, 1))) {
+ avahi_log_error(__FILE__": Out of memory");
+ return NULL;
+ }
+
+ ka->scheduler = s;
+ ka->record = avahi_record_ref(e->record);
+
+ AVAHI_LLIST_PREPEND(AvahiKnownAnswer, known_answer, s->known_answers, ka);
+ return NULL;
+}
+
+static int packet_add_query_job(AvahiQueryScheduler *s, AvahiDnsPacket *p, AvahiQueryJob *qj) {
+ assert(s);
+ assert(p);
+ assert(qj);
+
+ if (!avahi_dns_packet_append_key(p, qj->key, 0))
+ return 0;
+
+ /* Add all matching known answers to the list */
+ avahi_cache_walk(s->interface->cache, qj->key, known_answer_walk_callback, s);
+
+ job_mark_done(s, qj);
+
+ return 1;
+}
+
+static void append_known_answers_and_send(AvahiQueryScheduler *s, AvahiDnsPacket *p) {
+ AvahiKnownAnswer *ka;
+ unsigned n;
+ assert(s);
+ assert(p);
+
+ n = 0;
+
+ while ((ka = s->known_answers)) {
+ int too_large = 0;
+
+ while (!avahi_dns_packet_append_record(p, ka->record, 0, 0)) {
+
+ if (avahi_dns_packet_is_empty(p)) {
+ /* The record is too large to fit into one packet, so
+ there's no point in sending it. Better is letting
+ the owner of the record send it as a response. This
+ has the advantage of a cache refresh. */
+
+ too_large = 1;
+ break;
+ }
+
+ avahi_dns_packet_set_field(p, AVAHI_DNS_FIELD_FLAGS, avahi_dns_packet_get_field(p, AVAHI_DNS_FIELD_FLAGS) | AVAHI_DNS_FLAG_TC);
+ avahi_dns_packet_set_field(p, AVAHI_DNS_FIELD_ANCOUNT, n);
+ avahi_interface_send_packet(s->interface, p);
+ avahi_dns_packet_free(p);
+
+ p = avahi_dns_packet_new_query(s->interface->hardware->mtu);
+ n = 0;
+ }
+
+ AVAHI_LLIST_REMOVE(AvahiKnownAnswer, known_answer, s->known_answers, ka);
+ avahi_record_unref(ka->record);
+ avahi_free(ka);
+
+ if (!too_large)
+ n++;
+ }
+
+ avahi_dns_packet_set_field(p, AVAHI_DNS_FIELD_ANCOUNT, n);
+ avahi_interface_send_packet(s->interface, p);
+ avahi_dns_packet_free(p);
+}
+
+static void elapse_callback(AVAHI_GCC_UNUSED AvahiTimeEvent *e, void* data) {
+ AvahiQueryJob *qj = data;
+ AvahiQueryScheduler *s;
+ AvahiDnsPacket *p;
+ unsigned n;
+ int b;
+
+ assert(qj);
+ s = qj->scheduler;
+
+ if (qj->done) {
+ /* Lets remove it from the history */
+ job_free(s, qj);
+ return;
+ }
+
+ assert(!s->known_answers);
+
+ if (!(p = avahi_dns_packet_new_query(s->interface->hardware->mtu)))
+ return; /* OOM */
+
+ b = packet_add_query_job(s, p, qj);
+ assert(b); /* An query must always fit in */
+ n = 1;
+
+ /* Try to fill up packet with more queries, if available */
+ while (s->jobs) {
+
+ if (!packet_add_query_job(s, p, s->jobs))
+ break;
+
+ n++;
+ }
+
+ avahi_dns_packet_set_field(p, AVAHI_DNS_FIELD_QDCOUNT, n);
+
+ /* Now add known answers */
+ append_known_answers_and_send(s, p);
+}
+
+static AvahiQueryJob* find_scheduled_job(AvahiQueryScheduler *s, AvahiKey *key) {
+ AvahiQueryJob *qj;
+
+ assert(s);
+ assert(key);
+
+ for (qj = s->jobs; qj; qj = qj->jobs_next) {
+ assert(!qj->done);
+
+ if (avahi_key_equal(qj->key, key))
+ return qj;
+ }
+
+ return NULL;
+}
+
+static AvahiQueryJob* find_history_job(AvahiQueryScheduler *s, AvahiKey *key) {
+ AvahiQueryJob *qj;
+
+ assert(s);
+ assert(key);
+
+ for (qj = s->history; qj; qj = qj->jobs_next) {
+ assert(qj->done);
+
+ if (avahi_key_equal(qj->key, key)) {
+ /* Check whether this entry is outdated */
+
+ if (avahi_age(&qj->delivery) > AVAHI_QUERY_HISTORY_MSEC*1000) {
+ /* it is outdated, so let's remove it */
+ job_free(s, qj);
+ return NULL;
+ }
+
+ return qj;
+ }
+ }
+
+ return NULL;
+}
+
+int avahi_query_scheduler_post(AvahiQueryScheduler *s, AvahiKey *key, int immediately, unsigned *ret_id) {
+ struct timeval tv;
+ AvahiQueryJob *qj;
+
+ assert(s);
+ assert(key);
+
+ if ((qj = find_history_job(s, key)))
+ return 0;
+
+ avahi_elapse_time(&tv, immediately ? 0 : AVAHI_QUERY_DEFER_MSEC, 0);
+
+ if ((qj = find_scheduled_job(s, key))) {
+ /* Duplicate questions suppression */
+
+ if (avahi_timeval_compare(&tv, &qj->delivery) < 0) {
+ /* If the new entry should be scheduled earlier,
+ * update the old entry */
+ qj->delivery = tv;
+ avahi_time_event_update(qj->time_event, &qj->delivery);
+ }
+
+ qj->n_posted++;
+
+ } else {
+
+ if (!(qj = job_new(s, key, 0)))
+ return 0; /* OOM */
+
+ qj->delivery = tv;
+ qj->time_event = avahi_time_event_new(s->time_event_queue, &qj->delivery, elapse_callback, qj);
+ }
+
+ if (ret_id)
+ *ret_id = qj->id;
+
+ return 1;
+}
+
+void avahi_query_scheduler_incoming(AvahiQueryScheduler *s, AvahiKey *key) {
+ AvahiQueryJob *qj;
+
+ assert(s);
+ assert(key);
+
+ /* This function is called whenever an incoming query was
+ * received. We drop scheduled queries that match. The keyword is
+ * "DUPLICATE QUESTION SUPPRESION". */
+
+ if ((qj = find_scheduled_job(s, key))) {
+ job_mark_done(s, qj);
+ return;
+ }
+
+ /* Look if there's a history job for this key. If there is, just
+ * update the elapse time */
+ if (!(qj = find_history_job(s, key)))
+ if (!(qj = job_new(s, key, 1)))
+ return; /* OOM */
+
+ gettimeofday(&qj->delivery, NULL);
+ job_set_elapse_time(s, qj, AVAHI_QUERY_HISTORY_MSEC, 0);
+}
+
+int avahi_query_scheduler_withdraw_by_id(AvahiQueryScheduler *s, unsigned id) {
+ AvahiQueryJob *qj;
+
+ assert(s);
+
+ /* Very short lived queries can withdraw an already scheduled item
+ * from the queue using this function, simply by passing the id
+ * returned by avahi_query_scheduler_post(). */
+
+ for (qj = s->jobs; qj; qj = qj->jobs_next) {
+ assert(!qj->done);
+
+ if (qj->id == id) {
+ /* Entry found */
+
+ assert(qj->n_posted >= 1);
+
+ if (--qj->n_posted <= 0) {
+
+ /* We withdraw this job only if the calling object was
+ * the only remaining poster. (Usually this is the
+ * case since there should exist only one querier per
+ * key, but there are exceptions, notably reflected
+ * traffic.) */
+
+ job_free(s, qj);
+ return 1;
+ }
+ }
+ }
+
+ return 0;
+}