Merge b575927042 into 00f546e25e

So things work correctly even if varlinkctl's output is redirected to a
file.

src/resolve/meson.build

@@ -8,6 +8,7 @@ basic_dns_sources = files(
         'resolved-dns-rr.c',
         'resolved-dns-answer.c',
         'resolved-dns-question.c',
+        'resolved-dns-browse-services.c',
         'resolved-util.c',
         'dns-type.c',
 )

src/resolve/resolved-dns-browse-services.c

@@ -0,0 +1,687 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include "af-list.h"
+#include "event-util.h"
+#include "json-util.h"
+#include "random-util.h"
+#include "resolved-dns-browse-services.h"
+#include "resolved-dns-cache.h"
+#include "resolved-varlink.h"
+
+/* RFC 6762 section 5.2 - The querier should plan to issue a query at 80% of
+ * the record lifetime, and then if no answer is received, at 85%, 90%, and 95%. */
+static usec_t mdns_maintenance_next_time(usec_t until, uint32_t ttl, int ttl_state) {
+        return usec_sub_unsigned(until, (20 - ttl_state * 5) * ttl * USEC_PER_SEC / 100);
+}
+
+/* RFC 6762 section 5.2 - A random variation of 2% of the record TTL should
+ * be added to maintenance queries. */
+static usec_t mdns_maintenance_jitter(uint32_t ttl) {
+        return random_u64_range(100) * 2 * ttl * USEC_PER_SEC / 10000;
+}
+
+#define MDNS_80_PERCENT 80
+#define MDNS_5_PERCENT 5
+
+static void mdns_find_service_from_query(DnsService **service, DnsServiceBrowser *sb, DnsQuery *q) {
+        assert(sb);
+
+        /* Find the service that owns the query. */
+        LIST_FOREACH(dns_services, s, sb->dns_services) {
+                if (s->query == q) {
+                        *service = s;
+                        return;
+                }
+        }
+        *service = NULL;
+}
+
+static void mdns_maintenance_query_complete(DnsQuery *q) {
+        _cleanup_(dns_service_browser_unrefp) DnsServiceBrowser *sb = NULL;
+        _cleanup_(dns_query_freep) DnsQuery *query = q;
+        DnsService *service = NULL;
+        int  r;
+
+        assert(query);
+        assert(query->manager);
+
+        sb = dns_service_browser_ref(hashmap_get(query->manager->dns_service_browsers, query->varlink_request));
+        if (!sb)
+                return;
+
+        if (query->state != DNS_TRANSACTION_SUCCESS) {
+                r = 0;
+                goto finish;
+        }
+
+        r = dns_answer_match_key(query->answer, sb->key, NULL);
+        if (r <= 0)
+                goto finish;
+
+        r = mdns_browser_lookup_cache(sb, query->answer_family);
+
+finish:
+        if (r < 0)
+                log_error_errno(r, "mDNS maintenance query complete failed: %m");
+
+        mdns_find_service_from_query(&service, sb, query);
+        if (service)
+                service->query = NULL;
+}
+
+static int mdns_maintenance_query(sd_event_source *s, uint64_t usec, void *userdata) {
+        DnsService *service = NULL;
+        _cleanup_(dns_query_freep) DnsQuery *q = NULL;
+        int r;
+
+        assert(userdata);
+
+        service = userdata;
+
+        if (service->rr_ttl_state++ == MDNS_TTL_100_PERCENT)
+                return mdns_browser_lookup_cache(service->sb, service->family);
+
+        r = dns_query_new(service->sb->m, &q, service->sb->question_utf8, service->sb->question_idna, NULL, service->sb->ifindex, service->sb->flags);
+        if (r < 0)
+                goto finish;
+
+        q->complete = mdns_maintenance_query_complete;
+        q->varlink_request = sd_varlink_ref(service->sb->link);
+        service->query = TAKE_PTR(q);
+
+        usec_t next_time = mdns_maintenance_next_time(service->until, service->rr->ttl, service->rr_ttl_state);
+
+        /* Schedule next maintenance query for service */
+        r = event_reset_time(
+                service->sb->m->event, &service->schedule_event,
+                CLOCK_BOOTTIME, next_time, 0, mdns_maintenance_query,
+                service, 0, "mdns-next-query-schedule", true);
+        if (r < 0)
+                goto finish;
+
+        r = dns_query_go(service->query);
+        if (r < 0)
+                goto finish;
+
+        return 0;
+
+finish:
+        dns_query_free(service->query);
+        return log_error_errno(r, "Failed mdns maintenance query: %m");
+}
+
+int dns_add_new_service(DnsServiceBrowser *sb, DnsResourceRecord *rr, int owner_family) {
+        _cleanup_(dns_service_unrefp) DnsService *s = NULL;
+        int r;
+
+        assert(sb);
+        assert(rr);
+
+        s = new(DnsService, 1);
+        if (!s)
+                return log_oom();
+
+        usec_t usec = now(CLOCK_BOOTTIME);
+
+        *s = (DnsService) {
+                .n_ref = 1,
+                .sb = dns_service_browser_ref(sb),
+                .rr = dns_resource_record_copy(rr),
+                .family = owner_family,
+                .until = rr->until,
+                .query = NULL,
+                .rr_ttl_state = MDNS_TTL_80_PERCENT,
+        };
+
+        LIST_PREPEND(dns_services, sb->dns_services, s);
+
+        /* Schedule the first cache maintenance query at 80% of the record's TTL.
+         * Subsequent queries issued at 5% increments until 100% of the TTL. RFC 6762 section 5.2.
+         * If service is being added after 80% of the TTL has already elapsed,
+         * schedule the next query at the next 5% increment. */
+        usec_t next_time = 0;
+        while (s->rr_ttl_state <= MDNS_TTL_100_PERCENT) {
+                next_time = mdns_maintenance_next_time(rr->until, rr->ttl, s->rr_ttl_state);
+                if (next_time >= usec)
+                        break;
+                s->rr_ttl_state++;
+        }
+
+        if (next_time < usec) {
+                /* If next_time is still in the past, the service is being added after it has already expired.
+                 * Just schedule a 100% maintenance query */
+                next_time = usec + USEC_PER_SEC;
+                s->rr_ttl_state = MDNS_TTL_100_PERCENT;
+        }
+
+        usec_t jitter = mdns_maintenance_jitter(rr->ttl);
+
+        r = sd_event_add_time(
+                        sb->m->event,
+                        &s->schedule_event,
+                        CLOCK_BOOTTIME,
+                        usec_add(next_time, jitter),
+                        0,
+                        mdns_maintenance_query,
+                        s);
+        if (r < 0)
+                return r;
+
+        TAKE_PTR(s);
+        return 0;
+}
+
+void dns_remove_service(DnsServiceBrowser *sb, DnsService *service) {
+        assert(sb);
+        assert(service);
+
+        LIST_REMOVE(dns_services, sb->dns_services, service);
+        dns_service_free(service);
+}
+
+DnsService *dns_service_free(DnsService *service) {
+        if (!service)
+                return NULL;
+
+        sd_event_source_disable_unref(service->schedule_event);
+
+        if (service->query && DNS_TRANSACTION_IS_LIVE(service->query->state))
+                        dns_query_complete(service->query, DNS_TRANSACTION_ABORTED);
+
+        dns_service_browser_unref(service->sb);
+
+        dns_resource_record_unref(service->rr);
+
+        return mfree(service);
+}
+
+DEFINE_TRIVIAL_REF_UNREF_FUNC(DnsService, dns_service, dns_service_free);
+
+int mdns_service_update(DnsService *service, DnsResourceRecord *rr, usec_t t) {
+        service->until = rr->until;
+        service->rr->ttl = rr->ttl;
+
+        /* Update the 80% TTL maintenance event based on new record received from the network.
+         * RFC 6762 section 5.2  */
+        usec_t next_time = mdns_maintenance_next_time(service->until, service->rr->ttl, MDNS_TTL_80_PERCENT);
+        usec_t jitter = mdns_maintenance_jitter(service->rr->ttl);
+
+        if (service->schedule_event)
+                return sd_event_source_set_time(service->schedule_event, usec_add(next_time, jitter));
+
+        return 0;
+}
+
+bool dns_service_contains(DnsService *services, DnsResourceRecord *rr, int owner_family) {
+        usec_t t = now(CLOCK_BOOTTIME);
+
+        LIST_FOREACH(dns_services, service, services)
+                if (dns_resource_record_equal(rr, service->rr) > 0 && service->family == owner_family) {
+                        if (rr->ttl <= 1)
+                                return true;
+
+                        if (rr->until > service->until)
+                                mdns_service_update(service, rr, t);
+
+                        return true;
+                }
+
+        return false;
+}
+
+void dns_browse_services_purge(Manager *m, int family) {
+        int r = 0;
+
+        /* Called after caches are flused.
+         * Clear local service records and notify varlink client. */
+        if (!(m && m->dns_service_browsers))
+                return;
+
+        DnsServiceBrowser *sb;
+        HASHMAP_FOREACH(sb, m->dns_service_browsers) {
+                r = sd_event_source_set_enabled(sb->schedule_event, SD_EVENT_OFF);
+                if (r < 0)
+                        goto finish;
+
+                if (family == AF_UNSPEC) {
+                        r = mdns_browser_lookup_cache(sb, AF_INET);
+                        if (r < 0)
+                                goto finish;
+                        r = mdns_browser_lookup_cache(sb, AF_INET6);
+                        if (r < 0)
+                                goto finish;
+                        return;
+                }
+
+                r = mdns_browser_lookup_cache(sb, family);
+                if (r < 0)
+                        goto finish;
+        }
+
+finish:
+        if (r < 0)
+                log_error_errno(r, "mdns browse services purge failed: %m");
+        return;
+}
+
+int mdns_manage_services_answer(DnsServiceBrowser *sb, DnsAnswer *answer, int owner_family) {
+        DnsResourceRecord *i;
+        _cleanup_(sd_json_variant_unrefp) sd_json_variant *array = NULL;
+        int r;
+
+        assert(sb);
+
+        /* Check for new service added */
+        DNS_ANSWER_FOREACH(i, answer) {
+                _cleanup_free_ char *name = NULL, *type = NULL, *domain = NULL;
+                _cleanup_(sd_json_variant_unrefp) sd_json_variant *entry = NULL;
+
+                if (dns_service_contains(sb->dns_services, i, owner_family))
+                        continue;
+
+                r = dns_service_split(i->ptr.name, &name, &type, &domain);
+                if (r < 0)
+                        goto finish;
+
+                if (!name) {
+                        type = mfree(type);
+                        domain = mfree(domain);
+                        r = dns_service_split(dns_resource_key_name(i->key), &name, &type, &domain);
+                        if (r < 0)
+                                goto finish;
+                }
+
+                if (!type)
+                        continue;
+
+                r = dns_add_new_service(sb, i, owner_family);
+                if (r < 0)
+                        goto finish;
+
+                log_debug("Add into the list  %s, %s, %s, %s, %d",
+                          strna(name),
+                          strna(type),
+                          strna(domain),
+                          strna(af_to_ipv4_ipv6(owner_family)),
+                          sb->ifindex);
+
+                r = sd_json_buildo(&entry,
+                                        SD_JSON_BUILD_PAIR("add_flag", SD_JSON_BUILD_BOOLEAN(true)),
+                                        SD_JSON_BUILD_PAIR("family", SD_JSON_BUILD_INTEGER(owner_family)),
+                                        SD_JSON_BUILD_PAIR("name", SD_JSON_BUILD_STRING(name?: "")),
+                                        SD_JSON_BUILD_PAIR("type", SD_JSON_BUILD_STRING(type?: "")),
+                                        SD_JSON_BUILD_PAIR("domain", SD_JSON_BUILD_STRING(domain?: "")),
+                                        SD_JSON_BUILD_PAIR("interface", SD_JSON_BUILD_INTEGER(sb->ifindex)));
+                if (r < 0)
+                        goto finish;
+
+                r = sd_json_variant_append_array(&array, entry);
+                if (r < 0)
+                        goto finish;
+        }
+
+        /* Check for services removed */
+        LIST_FOREACH(dns_services, service, sb->dns_services) {
+                _cleanup_free_ char *name = NULL, *type = NULL, *domain = NULL;
+                _cleanup_(sd_json_variant_unrefp) sd_json_variant *entry = NULL;
+
+                if (service->family != owner_family)
+                        continue;
+
+                if (dns_answer_contains(answer, service->rr))
+                        continue;
+
+                r = dns_service_split(service->rr->ptr.name, &name, &type, &domain);
+                if (r < 0)
+                        goto finish;
+
+                if (!name) {
+                        type = mfree(type);
+                        domain = mfree(domain);
+                        r = dns_service_split(dns_resource_key_name(service->rr->key), &name, &type, &domain);
+                        if (r < 0)
+                                goto finish;
+                }
+
+                dns_remove_service(sb, service);
+
+                log_debug("Remove from the list  %s, %s, %s, %s, %d",
+                          strna(name),
+                          strna(type),
+                          strna(domain),
+                          strna(af_to_ipv4_ipv6(owner_family)),
+                          sb->ifindex);
+
+                r = sd_json_buildo(&entry,
+                                        SD_JSON_BUILD_PAIR("add_flag", SD_JSON_BUILD_BOOLEAN(false)),
+                                        SD_JSON_BUILD_PAIR("family", SD_JSON_BUILD_INTEGER(owner_family)),
+                                        SD_JSON_BUILD_PAIR("name", SD_JSON_BUILD_STRING(name?: "")),
+                                        SD_JSON_BUILD_PAIR("type", SD_JSON_BUILD_STRING(type?: "")),
+                                        SD_JSON_BUILD_PAIR("domain", SD_JSON_BUILD_STRING(domain?: "")),
+                                        SD_JSON_BUILD_PAIR("interface", SD_JSON_BUILD_INTEGER(sb->ifindex)));
+                if (r < 0)
+                        goto finish;
+
+                r = sd_json_variant_append_array(&array, entry);
+                if (r < 0)
+                        goto finish;
+        }
+
+        if (!sd_json_variant_is_blank_array(array)) {
+                _cleanup_(sd_json_variant_unrefp) sd_json_variant *vm = NULL;
+
+                r = sd_json_buildo(&vm,
+                                        SD_JSON_BUILD_PAIR("browser_service_data", SD_JSON_BUILD_VARIANT(array)));
+                if (r < 0)
+                        goto finish;
+
+                r = sd_varlink_notify(sb->link, vm);
+                if (r < 0)
+                        goto finish;
+        }
+
+        return 0;
+
+finish:
+        log_error_errno(r, "Failed to process received services: %m");
+        return sd_varlink_error_errno(sb->link, r);
+}
+
+int mdns_browser_lookup_cache(DnsServiceBrowser *sb, int owner_family) {
+        _cleanup_(dns_answer_unrefp) DnsAnswer *lookup_ret_answer = NULL;
+        DnsScope *scope;
+        int r;
+
+        assert(sb);
+        assert(sb->m);
+
+        scope = manager_find_scope_from_protocol(sb->m, sb->ifindex, DNS_PROTOCOL_MDNS, owner_family);
+        if (!scope)
+                return 0;
+
+        dns_cache_prune(&scope->cache);
+
+        r = dns_cache_lookup(
+                        &scope->cache,
+                        sb->key,
+                        sb->flags,
+                        NULL,
+                        &lookup_ret_answer,
+                        NULL,
+                        NULL,
+                        NULL);
+        if (r < 0)
+                return r;
+
+        return mdns_manage_services_answer(sb, lookup_ret_answer, owner_family);
+}
+
+int mdns_notify_browsers_goodbye(DnsScope *scope) {
+        DnsServiceBrowser *sb = NULL;
+        int r;
+
+        if (!scope)
+                return 0;
+
+        HASHMAP_FOREACH(sb, scope->manager->dns_service_browsers) {
+                r = mdns_browser_lookup_cache(sb, scope->family);
+                if (r < 0)
+                        goto finish;
+        }
+
+        return 0;
+
+finish:
+        return r;
+}
+
+int mdns_notify_browsers_unsolicited_updates(Manager *m, DnsAnswer *answer, int owner_family) {
+        DnsServiceBrowser *sb = NULL;
+        int r;
+
+        assert(m);
+
+        if (!answer)
+                return 0;
+
+        if (!m->dns_service_browsers)
+                return 0;
+
+        HASHMAP_FOREACH(sb, m->dns_service_browsers) {
+                r = dns_answer_match_key(answer, sb->key, NULL);
+                if (r < 0)
+                        goto finish;
+                else if (r == 0)
+                        continue;
+
+                r = mdns_browser_lookup_cache(sb, owner_family);
+                if (r < 0)
+                        goto finish;
+        }
+
+        return 0;
+
+finish:
+        return log_error_errno(r, "Failed to notify mDNS service subscribers, %m");
+}
+
+static void mdns_browse_service_query_complete(DnsQuery *q) {
+        _cleanup_(dns_service_browser_unrefp) DnsServiceBrowser *sb = NULL;
+        _cleanup_(dns_query_freep) DnsQuery *query = q;
+        int r;
+
+        assert(query);
+        assert(query->manager);
+
+        if (query->state != DNS_TRANSACTION_SUCCESS)
+                return;
+
+        sb = dns_service_browser_ref(hashmap_get(query->manager->dns_service_browsers, query->varlink_request));
+        if (!sb)
+                return;
+
+        r = dns_answer_match_key(query->answer, sb->key, NULL);
+        if (r < 0)
+                goto finish;
+        else if (r == 0)
+                return;
+
+        r = mdns_browser_lookup_cache(sb, query->answer_family);
+        if (r < 0)
+                goto finish;
+
+        /* When the query is answered from cache, we only get answers for one answer_family
+         * i.e. either ipv4 or ipv6.
+         * We need to perform another cache lookup for the other answer_family */
+        if (query->answer_query_flags == SD_RESOLVED_FROM_CACHE) {
+                r = mdns_browser_lookup_cache(sb, query->answer_family == AF_INET? AF_INET6 : AF_INET);
+                if (r < 0)
+                        goto finish;
+        }
+
+        return;
+finish:
+        log_error_errno(r, "mDNS browse query complete failed, %m");
+}
+
+static int mdns_next_query_schedule(sd_event_source *s, uint64_t usec, void *userdata) {
+        _cleanup_(dns_service_browser_unrefp) DnsServiceBrowser *sb = NULL;
+        _cleanup_(dns_query_freep) DnsQuery *q = NULL;
+        int r;
+
+        assert(userdata);
+
+        sb = dns_service_browser_ref(userdata);
+
+        r = dns_query_new(sb->m, &q, sb->question_utf8, sb->question_idna, NULL, sb->ifindex, sb->flags);
+        if (r < 0)
+                goto finish;
+
+        q->complete = mdns_browse_service_query_complete;
+        q->varlink_request = sd_varlink_ref(sb->link);
+        sd_varlink_set_userdata(sb->link, q);
+
+        r = dns_query_go(q);
+        if (r < 0)
+                goto finish;
+
+        /* RFC6762 5.2
+         * The intervals between successive queries MUST increase by at least a factor of two.
+         * When the interval between queries reaches or exceeds 60 minutes,perform
+         * subsequent queries at a steady-state rate of one query per hour */
+        if (sb->delay == 0) {
+                sb->delay++;
+                /* First query is sent wihtout SD_RESOLVED_NO_CACHE to fetch answers already in cache.
+                 * Set SD_RESOLVED_NO_CACHE to make all subsequent queries go to the network. */
+                sb->flags |= SD_RESOLVED_NO_CACHE;
+        }
+        else
+                sb->delay = sb->delay < 2048 ? sb->delay * 2 : 3600;
+
+        r = event_reset_time_relative(
+                sb->m->event, &sb->schedule_event,
+                CLOCK_BOOTTIME, (sb->delay * USEC_PER_SEC),
+                0, mdns_next_query_schedule,
+                sb, 0, "mdns-next-query-schedule", true);
+        if (r < 0)
+                goto finish;
+
+        TAKE_PTR(q);
+
+        return 0;
+
+finish:
+        return log_error_errno(r, "Failed to schedule mDNS query, %m");
+}
+
+void dns_service_browser_reset(Manager *m) {
+        int r;
+
+        if (!(m && m->dns_service_browsers))
+                return;
+
+        DnsServiceBrowser *sb;
+
+        HASHMAP_FOREACH(sb, m->dns_service_browsers) {
+                sb->delay = 0;
+
+                r = event_reset_time_relative(
+                        sb->m->event, &sb->schedule_event,
+                        CLOCK_BOOTTIME, (sb->delay * USEC_PER_SEC),
+                        0, mdns_next_query_schedule,
+                        sb, 0, "mdns-next-query-schedule", true);
+                if (r < 0)
+                        log_error_errno(r, "Failed to reset mdns service subscriber, %m");
+        }
+
+        return;
+}
+
+int dns_subscribe_browse_service(
+                Manager *m,
+                sd_varlink *link,
+                const char *domain,
+                const char *name,
+                const char *type,
+                int ifindex,
+                uint64_t flags) {
+
+        _cleanup_(dns_service_browser_unrefp) DnsServiceBrowser *sb = NULL;
+        _cleanup_(dns_question_unrefp) DnsQuestion *question_idna = NULL, *question_utf8 = NULL;
+        int r;
+
+        assert(m);
+        assert(link);
+
+        if (ifindex <= 0)
+                return sd_varlink_error_invalid_parameter(link, JSON_VARIANT_STRING_CONST("ifindex"));
+
+        if (isempty(name))
+                name = NULL;
+        else if (!dns_service_name_is_valid(name))
+                return sd_varlink_error_invalid_parameter(link, JSON_VARIANT_STRING_CONST("name"));
+
+        if (isempty(type))
+                type = NULL;
+        else if (!dnssd_srv_type_is_valid(type))
+                return sd_varlink_error_invalid_parameter(link, JSON_VARIANT_STRING_CONST("type"));
+
+        r = dns_name_is_valid(domain);
+        if (r < 0)
+                return r;
+        if (r == 0)
+                return sd_varlink_error_invalid_parameter(link, JSON_VARIANT_STRING_CONST("domain"));
+
+        r = dns_question_new_service_type(&question_utf8, name, type, domain, false, DNS_TYPE_PTR);
+        if (r < 0)
+                return r;
+
+        r = dns_question_new_service_type(&question_idna, name, type, domain, true, DNS_TYPE_PTR);
+        if (r < 0)
+                return r;
+
+        sb = new(DnsServiceBrowser, 1);
+        if (!sb)
+                return log_oom();
+
+        *sb = (DnsServiceBrowser) {
+                .n_ref = 1,
+                .m = m,
+                .link = sd_varlink_ref(link),
+                .question_utf8 = dns_question_ref(question_utf8),
+                .question_idna = dns_question_ref(question_idna),
+                .key = dns_question_first_key(question_utf8),
+                .ifindex = ifindex,
+                .flags = flags,
+        };
+
+        /* Only mDNS continuous querying is currently supported. See RFC 6762 */
+        switch (flags & SD_RESOLVED_PROTOCOLS_ALL) {
+        case SD_RESOLVED_MDNS:
+                r = sd_event_add_time(m->event,
+                                &sb->schedule_event,
+                                CLOCK_BOOTTIME,
+                                usec_add(now(CLOCK_BOOTTIME), (sb->delay * USEC_PER_SEC)),
+                                0,
+                                mdns_next_query_schedule,
+                                sb);
+                if (r < 0)
+                        return r;
+                break;
+        default:
+                return -EINVAL;
+        }
+
+        r = hashmap_ensure_put(&m->dns_service_browsers, NULL, link, sb);
+        if (r < 0)
+                return r;
+
+        TAKE_PTR(sb);
+
+        return 0;
+}
+
+DnsServiceBrowser *dns_service_browser_free(DnsServiceBrowser *sb) {
+        DnsQuery *q;
+
+        if (!sb)
+                return NULL;
+
+        LIST_FOREACH(dns_services, service, sb->dns_services)
+                dns_remove_service(sb, service);
+
+        sd_event_source_disable_unref(sb->schedule_event);
+
+        q = sd_varlink_get_userdata(sb->link);
+        if (q && DNS_TRANSACTION_IS_LIVE(q->state))
+                dns_query_complete(q, DNS_TRANSACTION_ABORTED);
+
+        dns_question_unref(sb->question_idna);
+        dns_question_unref(sb->question_utf8);
+
+        sd_varlink_unref(sb->link);
+
+        return mfree(sb);
+}
+
+DEFINE_TRIVIAL_REF_UNREF_FUNC(DnsServiceBrowser, dns_service_browser, dns_service_browser_free);

src/resolve/resolved-dns-browse-services.h

@@ -0,0 +1,79 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#pragma once
+
+typedef struct DnsServiceBrowser DnsServiceBrowser;
+
+#include "resolved-dns-query.h"
+#include "resolved-manager.h"
+#include "sd-varlink.h"
+
+typedef struct DnsService DnsService;
+
+typedef enum DnsRecordTTLState DnsRecordTTLState;
+
+enum DnsRecordTTLState {
+        MDNS_TTL_80_PERCENT,
+        MDNS_TTL_85_PERCENT,
+        MDNS_TTL_90_PERCENT,
+        MDNS_TTL_95_PERCENT,
+        MDNS_TTL_100_PERCENT
+};
+
+struct DnsService {
+        unsigned n_ref;
+        DnsServiceBrowser *sb;
+        sd_event_source *schedule_event;
+        DnsResourceRecord *rr;
+        int family;
+        usec_t until;
+        DnsRecordTTLState rr_ttl_state;
+        DnsQuery *query;
+        LIST_FIELDS(DnsService, dns_services);
+};
+
+struct DnsServiceBrowser {
+        unsigned n_ref;
+        Manager *m;
+        sd_varlink *link;
+        DnsQuestion *question_idna;
+        DnsQuestion *question_utf8;
+        uint64_t flags;
+        sd_event_source *schedule_event;
+        usec_t delay;
+        DnsResourceKey *key;
+        int ifindex;
+        uint64_t token;
+        LIST_HEAD(DnsService, dns_services);
+};
+
+DnsServiceBrowser *dns_service_browser_free(DnsServiceBrowser *sb);
+void dns_remove_service(DnsServiceBrowser *sb, DnsService *service);
+DnsService *dns_service_free(DnsService *service);
+
+DnsServiceBrowser* dns_service_browser_ref(DnsServiceBrowser *sb);
+DnsServiceBrowser* dns_service_browser_unref(DnsServiceBrowser *sb);
+
+DnsService* dns_service_ref(DnsService *service);
+DnsService* dns_service_unref(DnsService *service);
+
+void dns_browse_services_purge(Manager *m, int family);
+void dns_service_browser_reset(Manager *m);
+
+DEFINE_TRIVIAL_CLEANUP_FUNC(DnsServiceBrowser*, dns_service_browser_unref);
+DEFINE_TRIVIAL_CLEANUP_FUNC(DnsService*, dns_service_unref);
+
+bool dns_service_contains(DnsService *services, DnsResourceRecord *rr, int owner_family);
+int mdns_manage_services_answer(DnsServiceBrowser *sb, DnsAnswer *answer, int owner_family);
+int dns_add_new_service(DnsServiceBrowser *sb, DnsResourceRecord *rr, int owner_family);
+int mdns_service_update(DnsService *service, DnsResourceRecord *rr, usec_t t);
+int mdns_browser_lookup_cache(DnsServiceBrowser *sb, int owner_family);
+int dns_subscribe_browse_service(Manager *m,
+                sd_varlink *link,
+                const char *domain,
+                const char * name,
+                const char * type,
+                int ifindex,
+                uint64_t flags);
+int mdns_notify_browsers_unsolicited_updates(Manager *m, DnsAnswer *answer, int owner_family);
+int mdns_notify_browsers_goodbye(DnsScope *scope);

src/resolve/resolved-dns-cache.c

@@ -1011,6 +1011,7 @@ static int answer_add_clamp_ttl(
                 }
         }
 
+        rr->until = until;
         r = dns_answer_add_extend(answer, rr, ifindex, answer_flags, rrsig);
         if (r < 0)
                 return r;

src/resolve/resolved-dns-question.c

@@ -418,6 +418,66 @@ int dns_question_new_reverse(DnsQuestion **ret, int family, const union in_addr_
         return 0;
 }
 
+int dns_question_new_service_type(
+                DnsQuestion **ret,
+                const char *service,
+                const char *type,
+                const char *domain,
+                bool convert_idna,
+                uint16_t record_type) {
+
+        _cleanup_(dns_resource_key_unrefp) DnsResourceKey *key = NULL;
+        _cleanup_(dns_question_unrefp) DnsQuestion *q = NULL;
+        _cleanup_free_ char *buf = NULL, *joined = NULL;
+        const char *name;
+        int r;
+
+        assert(ret);
+
+        if (record_type == DNS_TYPE_SRV)
+                return -EINVAL;
+
+        if (!domain)
+                return -EINVAL;
+
+        if (type) {
+                if (convert_idna) {
+                        r = dns_name_apply_idna(domain, &buf);
+                        if (r < 0)
+                                return r;
+                        if (r > 0)
+                                domain = buf;
+                }
+
+                r = dns_service_join(service, type, domain, &joined);
+                if (r < 0)
+                        return r;
+
+                name = joined;
+        } else {
+                if (service)
+                        return -EINVAL;
+
+                name = domain;
+        }
+
+        q = dns_question_new(1);
+        if (!q)
+                return -ENOMEM;
+
+        key = dns_resource_key_new(DNS_CLASS_IN, record_type, name);
+        if (!key)
+                return -ENOMEM;
+
+        r = dns_question_add(q, key, 0);
+        if (r < 0)
+                return r;
+
+        *ret = TAKE_PTR(q);
+
+        return 0;
+}
+
 int dns_question_new_service(
                 DnsQuestion **ret,
                 const char *service,

src/resolve/resolved-dns-question.h

@@ -31,6 +31,7 @@ DnsQuestion *dns_question_unref(DnsQuestion *q);
 int dns_question_new_address(DnsQuestion **ret, int family, const char *name, bool convert_idna);
 int dns_question_new_reverse(DnsQuestion **ret, int family, const union in_addr_union *a);
 int dns_question_new_service(DnsQuestion **ret, const char *service, const char *type, const char *domain, bool with_txt, bool convert_idna);
+int dns_question_new_service_type(DnsQuestion **ret, const char *service, const char *type, const char *domain, bool convert_idna, uint16_t record_type);
 
 int dns_question_add_raw(DnsQuestion *q, DnsResourceKey *key, DnsQuestionFlags flags);
 int dns_question_add(DnsQuestion *q, DnsResourceKey *key, DnsQuestionFlags flags);

src/resolve/resolved-dns-rr.c

@@ -398,6 +398,7 @@ DnsResourceRecord* dns_resource_record_new(DnsResourceKey *key) {
                 .n_ref = 1,
                 .key = dns_resource_key_ref(key),
                 .expiry = USEC_INFINITY,
+                .until = USEC_INFINITY,
                 .n_skip_labels_signer = UINT8_MAX,
                 .n_skip_labels_source = UINT8_MAX,
         };
@@ -1704,6 +1705,7 @@ DnsResourceRecord *dns_resource_record_copy(DnsResourceRecord *rr) {
 
         copy->ttl = rr->ttl;
         copy->expiry = rr->expiry;
+        copy->until = rr->until;
         copy->n_skip_labels_signer = rr->n_skip_labels_signer;
         copy->n_skip_labels_source = rr->n_skip_labels_source;
         copy->unparsable = rr->unparsable;

src/resolve/resolved-dns-rr.h

@@ -107,6 +107,8 @@ struct DnsResourceRecord {
         unsigned n_ref;
         uint32_t ttl;
         usec_t expiry; /* RRSIG signature expiry */
+        usec_t until; /* Used to pass until of a record when doing a dns_cache_lookup().
+                       * Needed to schedule cache maintenance queries when browsing for services. */
 
         DnsResourceKey *key;
 

src/resolve/resolved-dns-scope.c

@@ -10,6 +10,7 @@
 #include "hostname-util.h"
 #include "missing_network.h"
 #include "random-util.h"
+#include "resolved-dns-browse-services.h"
 #include "resolved-dnssd.h"
 #include "resolved-dns-scope.h"
 #include "resolved-dns-synthesize.h"
@@ -121,6 +122,9 @@ DnsScope* dns_scope_free(DnsScope *s) {
         dns_cache_flush(&s->cache);
         dns_zone_flush(&s->zone);
 
+        /* Clear records of mDNS service browse subscriber, since cache bas been flushed */
+        dns_browse_services_purge(s->manager, s->family);
+
         LIST_REMOVE(scopes, s->manager->dns_scopes, s);
         return mfree(s);
 }

src/resolve/resolved-link.c

@@ -14,6 +14,7 @@
 #include "mkdir.h"
 #include "netif-util.h"
 #include "parse-util.h"
+#include "resolved-dns-browse-services.h"
 #include "resolved-link.h"
 #include "resolved-llmnr.h"
 #include "resolved-mdns.h"
@@ -166,6 +167,7 @@ void link_allocate_scopes(Link *l) {
                         r = dns_scope_new(l->manager, &l->mdns_ipv4_scope, l, DNS_PROTOCOL_MDNS, AF_INET);
                         if (r < 0)
                                 log_link_warning_errno(l, r, "Failed to allocate mDNS IPv4 scope, ignoring: %m");
+                        dns_service_browser_reset(l->manager);
                 }
         } else
                 l->mdns_ipv4_scope = dns_scope_free(l->mdns_ipv4_scope);
@@ -176,6 +178,7 @@ void link_allocate_scopes(Link *l) {
                         r = dns_scope_new(l->manager, &l->mdns_ipv6_scope, l, DNS_PROTOCOL_MDNS, AF_INET6);
                         if (r < 0)
                                 log_link_warning_errno(l, r, "Failed to allocate mDNS IPv6 scope, ignoring: %m");
+                        dns_service_browser_reset(l->manager);
                 }
         } else
                 l->mdns_ipv6_scope = dns_scope_free(l->mdns_ipv6_scope);

src/resolve/resolved-manager.c

@@ -751,6 +751,7 @@ int manager_start(Manager *m) {
 Manager *manager_free(Manager *m) {
         Link *l;
         DnssdService *s;
+        DnsServiceBrowser *sb;
 
         if (!m)
                 return NULL;
@@ -826,6 +827,10 @@ Manager *manager_free(Manager *m) {
         dns_trust_anchor_flush(&m->trust_anchor);
         manager_etc_hosts_flush(m);
 
+        while ((sb = hashmap_first(m->dns_service_browsers)))
+                dns_service_browser_free(sb);
+        hashmap_free(m->dns_service_browsers);
+
         return mfree(m);
 }
 
@@ -1460,29 +1465,28 @@ bool manager_packet_from_our_transaction(Manager *m, DnsPacket *p) {
         return t->sent && dns_packet_equal(t->sent, p);
 }
 
-DnsScope* manager_find_scope(Manager *m, DnsPacket *p) {
+DnsScope* manager_find_scope_from_protocol(Manager *m, int ifindex, DnsProtocol protocol, int family) {
         Link *l;
 
         assert(m);
-        assert(p);
 
-        l = hashmap_get(m->links, INT_TO_PTR(p->ifindex));
+        l = hashmap_get(m->links, INT_TO_PTR(ifindex));
         if (!l)
                 return NULL;
 
-        switch (p->protocol) {
+        switch (protocol) {
         case DNS_PROTOCOL_LLMNR:
-                if (p->family == AF_INET)
+                if (family == AF_INET)
                         return l->llmnr_ipv4_scope;
-                else if (p->family == AF_INET6)
+                else if (family == AF_INET6)
                         return l->llmnr_ipv6_scope;
 
                 break;
 
         case DNS_PROTOCOL_MDNS:
-                if (p->family == AF_INET)
+                if (family == AF_INET)
                         return l->mdns_ipv4_scope;
-                else if (p->family == AF_INET6)
+                else if (family == AF_INET6)
                         return l->mdns_ipv6_scope;
 
                 break;
@@ -1692,6 +1696,9 @@ void manager_flush_caches(Manager *m, int log_level) {
         LIST_FOREACH(scopes, scope, m->dns_scopes)
                 dns_cache_flush(&scope->cache);
 
+        dns_browse_services_purge(m, AF_UNSPEC); /* Clear records of DNS service browse subscriber, since caches are flushed */
+        dns_service_browser_reset(m);
+
         log_full(log_level, "Flushed all caches.");
 }
 

src/resolve/resolved-manager.h

@@ -16,6 +16,7 @@
 
 typedef struct Manager Manager;
 
+#include "resolved-dns-browse-services.h"
 #include "resolved-dns-query.h"
 #include "resolved-dns-search-domain.h"
 #include "resolved-dns-stream.h"
@@ -165,6 +166,9 @@ struct Manager {
         size_t n_socket_graveyard;
 
         struct sigrtmin18_info sigrtmin18_info;
+
+        /* Map varlink links to DnsServiceBrowser instances. */
+        Hashmap *dns_service_browsers;
 };
 
 /* Manager */
@@ -192,7 +196,13 @@ int manager_next_hostname(Manager *m);
 bool manager_packet_from_local_address(Manager *m, DnsPacket *p);
 bool manager_packet_from_our_transaction(Manager *m, DnsPacket *p);
 
-DnsScope* manager_find_scope(Manager *m, DnsPacket *p);
+DnsScope* manager_find_scope_from_protocol(Manager *m, int ifindex, DnsProtocol protocol, int family);
+
+static inline DnsScope* manager_find_scope(Manager *m, DnsPacket *p) {
+        assert(m);
+        assert(p);
+        return manager_find_scope_from_protocol(m, p->ifindex, p->protocol, p->family);
+}
 
 void manager_verify_all(Manager *m);
 

src/resolve/resolved-mdns.c

@@ -360,6 +360,10 @@ static int mdns_goodbye_callback(sd_event_source *s, uint64_t usec, void *userda
 
         dns_cache_prune(&scope->cache);
 
+        r = mdns_notify_browsers_goodbye(scope);
+        if (r < 0)
+                log_error_errno(r, "mDNS: Failed to notify service subscribers of goodbyes, %m");
+
         if (dns_cache_expiry_in_one_second(&scope->cache, usec)) {
                 r = sd_event_add_time_relative(
                         scope->manager->event,
@@ -381,6 +385,7 @@ static int on_mdns_packet(sd_event_source *s, int fd, uint32_t revents, void *us
         Manager *m = userdata;
         DnsScope *scope;
         int r;
+        bool unsolicited_packet = true;
 
         r = manager_recv(m, fd, DNS_PROTOCOL_MDNS, &p);
         if (r <= 0)
@@ -456,30 +461,6 @@ static int on_mdns_packet(sd_event_source *s, int fd, uint32_t revents, void *us
                         }
                 }
 
-                for (bool match = true; match;) {
-                        match = false;
-                        LIST_FOREACH(transactions_by_scope, t, scope->transactions) {
-                                if (t->state != DNS_TRANSACTION_PENDING)
-                                        continue;
-
-                                r = dns_answer_match_key(p->answer, dns_transaction_key(t), NULL);
-                                if (r <= 0) {
-                                        if (r < 0)
-                                                log_debug_errno(r, "Failed to match resource key, ignoring: %m");
-                                        continue;
-                                }
-
-                                /* This packet matches the transaction, let's pass it on as reply */
-                                dns_transaction_process_reply(t, p, false);
-
-                                /* The dns_transaction_process_reply() -> dns_transaction_complete() ->
-                                 * dns_query_candidate_stop() may free multiple transactions. Hence, restart
-                                 * the loop. */
-                                match = true;
-                                break;
-                        }
-                }
-
                 dns_cache_put(
                         &scope->cache,
                         scope->manager->enable_cache,
@@ -495,6 +476,35 @@ static int on_mdns_packet(sd_event_source *s, int fd, uint32_t revents, void *us
                         &p->sender,
                         scope->manager->stale_retention_usec);
 
+                for (bool match = true; match;) {
+                        match = false;
+                        LIST_FOREACH(transactions_by_scope, t, scope->transactions) {
+                                if (t->state != DNS_TRANSACTION_PENDING)
+                                        continue;
+
+                                r = dns_answer_match_key(p->answer, dns_transaction_key(t), NULL);
+                                if (r <= 0) {
+                                        if (r < 0)
+                                                log_debug_errno(r, "Failed to match resource key, ignoring: %m");
+                                        continue;
+                                }
+
+                                unsolicited_packet = false;
+                                /* This packet matches the transaction, let's pass it on as reply */
+                                dns_transaction_process_reply(t, p, false);
+
+                                /* The dns_transaction_process_reply() -> dns_transaction_complete() ->
+                                 * dns_query_candidate_stop() may free multiple transactions. Hence, restart
+                                 * the loop. */
+                                match = true;
+                                break;
+                        }
+                }
+
+                /* Check incoming packet key matches with active clients if yes update the same */
+                if (unsolicited_packet)
+                        mdns_notify_browsers_unsolicited_updates(m, p->answer, p->family);
+
         } else if (dns_packet_validate_query(p) > 0)  {
                 log_debug("Got mDNS query packet for id %u", DNS_PACKET_ID(p));
 

src/resolve/resolved-varlink.c

@@ -4,6 +4,7 @@
 #include "glyph-util.h"
 #include "in-addr-util.h"
 #include "json-util.h"
+#include "resolved-dns-browse-services.h"
 #include "resolved-dns-synthesize.h"
 #include "resolved-varlink.h"
 #include "socket-netlink.h"
@@ -30,11 +31,26 @@ typedef struct LookupParametersResolveService {
         uint64_t flags;
 } LookupParametersResolveService;
 
+typedef struct LookupParametersMdnsBrowse {
+        char *domainName;
+        char *name;
+        char *type;
+        int ifindex;
+        uint64_t flags;
+} LookupParametersMdnsBrowse;
+
 static void lookup_parameters_destroy(LookupParameters *p) {
         assert(p);
         free(p->name);
 }
 
+static void lookup_parameters_mdns_destroy(LookupParametersMdnsBrowse *p) {
+        assert(p);
+        free(p->domainName);
+        free(p->name);
+        free(p->type);
+}
+
 static int reply_query_state(DnsQuery *q) {
 
         assert(q);
@@ -108,10 +124,18 @@ static int reply_query_state(DnsQuery *q) {
 
 static void vl_on_disconnect(sd_varlink_server *s, sd_varlink *link, void *userdata) {
         DnsQuery *q;
+        Manager *m;
 
         assert(s);
         assert(link);
 
+        m = sd_varlink_server_get_userdata(s);
+        if (!m)
+                return;
+
+        DnsServiceBrowser *sb = hashmap_remove(m->dns_service_browsers, link);
+        dns_service_browser_free(sb);
+
         q = sd_varlink_get_userdata(link);
         if (!q)
                 return;
@@ -1257,6 +1281,43 @@ static int verify_polkit(sd_varlink *link, sd_json_variant *parameters, const ch
                                 &m->polkit_registry);
 }
 
+static int vl_method_start_browse(sd_varlink* link, sd_json_variant* parameters, sd_varlink_method_flags_t flags, void* userdata) {
+        static const sd_json_dispatch_field dispatch_table[] = {
+                { "domainName", SD_JSON_VARIANT_STRING,        sd_json_dispatch_string, offsetof(LookupParametersMdnsBrowse, domainName), SD_JSON_MANDATORY },
+                { "name",       SD_JSON_VARIANT_STRING,        sd_json_dispatch_string, offsetof(LookupParametersMdnsBrowse, name),       0              },
+                { "type",       SD_JSON_VARIANT_STRING,        sd_json_dispatch_string, offsetof(LookupParametersMdnsBrowse, type),       0              },
+                { "ifindex",    _SD_JSON_VARIANT_TYPE_INVALID, sd_json_dispatch_int,    offsetof(LookupParametersMdnsBrowse, ifindex),    SD_JSON_MANDATORY },
+                { "flags",      _SD_JSON_VARIANT_TYPE_INVALID, sd_json_dispatch_uint64, offsetof(LookupParametersMdnsBrowse, flags),      SD_JSON_MANDATORY },
+                {}
+        };
+
+        _cleanup_(lookup_parameters_mdns_destroy) LookupParametersMdnsBrowse p = {};
+        Manager *m;
+        int r = 0;
+
+        assert(link);
+
+        /* if the client didn't set the more flag, it is using us incorrectly */
+        if (!FLAGS_SET(flags, SD_VARLINK_METHOD_MORE))
+                return sd_varlink_error(link, SD_VARLINK_ERROR_EXPECTED_MORE, NULL);
+
+        m = sd_varlink_server_get_userdata(sd_varlink_get_server(link));
+        assert(m);
+
+        r = sd_varlink_dispatch(link, parameters, dispatch_table, &p);
+        if (r < 0)
+                return log_error_errno(r, "vl_method_start_browse json_dispatch fail: %m");
+
+        if (!validate_and_mangle_flags(NULL, &p.flags, 0))
+                return sd_varlink_error_invalid_parameter(link, JSON_VARIANT_STRING_CONST("flags"));
+
+        r = dns_subscribe_browse_service(m, link, p.domainName, p.name, p.type, p.ifindex, p.flags);
+        if (r < 0)
+                return sd_varlink_error_errno(link, r);
+
+        return 1;
+}
+
 static int vl_method_subscribe_query_results(sd_varlink *link, sd_json_variant *parameters, sd_varlink_method_flags_t flags, void *userdata) {
         Manager *m = ASSERT_PTR(sd_varlink_get_userdata(ASSERT_PTR(link)));
         int r;
@@ -1470,7 +1531,8 @@ static int varlink_main_server_init(Manager *m) {
                         "io.systemd.Resolve.ResolveHostname", vl_method_resolve_hostname,
                         "io.systemd.Resolve.ResolveAddress",  vl_method_resolve_address,
                         "io.systemd.Resolve.ResolveService",  vl_method_resolve_service,
-                        "io.systemd.Resolve.ResolveRecord",   vl_method_resolve_record);
+                        "io.systemd.Resolve.ResolveRecord",   vl_method_resolve_record,
+                        "io.systemd.Resolve.StartBrowse", vl_method_start_browse);
         if (r < 0)
                 return log_error_errno(r, "Failed to register varlink methods: %m");
 

src/shared/varlink-io.systemd.Resolve.c

@@ -92,6 +92,15 @@ static SD_VARLINK_DEFINE_STRUCT_TYPE(
                 SD_VARLINK_DEFINE_FIELD(ifindex, SD_VARLINK_INT, SD_VARLINK_NULLABLE),
                 SD_VARLINK_DEFINE_FIELD(name, SD_VARLINK_STRING, 0));
 
+static SD_VARLINK_DEFINE_STRUCT_TYPE(
+                ServiceData,
+                SD_VARLINK_DEFINE_FIELD(add_flag, SD_VARLINK_BOOL, 0),
+                SD_VARLINK_DEFINE_FIELD(family, SD_VARLINK_INT, 0),
+                SD_VARLINK_DEFINE_FIELD(name, SD_VARLINK_STRING, SD_VARLINK_NULLABLE),
+                SD_VARLINK_DEFINE_FIELD(type, SD_VARLINK_STRING, 0),
+                SD_VARLINK_DEFINE_FIELD(domain, SD_VARLINK_STRING, 0),
+                SD_VARLINK_DEFINE_FIELD(interface, SD_VARLINK_INT, 0));
+
 static SD_VARLINK_DEFINE_METHOD(
                 ResolveAddress,
                 SD_VARLINK_DEFINE_INPUT(ifindex, SD_VARLINK_INT, SD_VARLINK_NULLABLE),
@@ -146,6 +155,15 @@ static SD_VARLINK_DEFINE_METHOD(
                 SD_VARLINK_DEFINE_OUTPUT_BY_TYPE(rrs, ResolvedRecord, SD_VARLINK_ARRAY),
                 SD_VARLINK_DEFINE_OUTPUT(flags, SD_VARLINK_INT, 0));
 
+static SD_VARLINK_DEFINE_METHOD(
+                StartBrowse,
+                SD_VARLINK_DEFINE_INPUT(domainName, SD_VARLINK_STRING, 0),
+                SD_VARLINK_DEFINE_INPUT(name, SD_VARLINK_STRING, SD_VARLINK_NULLABLE),
+                SD_VARLINK_DEFINE_INPUT(type, SD_VARLINK_STRING, SD_VARLINK_NULLABLE),
+                SD_VARLINK_DEFINE_INPUT(ifindex, SD_VARLINK_INT, 0),
+                SD_VARLINK_DEFINE_INPUT(flags, SD_VARLINK_INT, 0),
+                SD_VARLINK_DEFINE_OUTPUT_BY_TYPE(browser_service_data, ServiceData, SD_VARLINK_ARRAY));
+
 static SD_VARLINK_DEFINE_ERROR(NoNameServers);
 static SD_VARLINK_DEFINE_ERROR(NoSuchResourceRecord);
 static SD_VARLINK_DEFINE_ERROR(QueryTimedOut);
@@ -182,6 +200,7 @@ SD_VARLINK_DEFINE_INTERFACE(
                 SD_VARLINK_SYMBOL_COMMENT("Resolves a named DNS-SD or unnamed simple SRV service."),
                 &vl_method_ResolveService,
                 &vl_method_ResolveRecord,
+                &vl_method_StartBrowse,
                 &vl_type_ResolvedAddress,
                 &vl_type_ResolvedName,
                 &vl_type_ResolvedService,
@@ -190,6 +209,7 @@ SD_VARLINK_DEFINE_INTERFACE(
                 &vl_type_ResourceKey,
                 &vl_type_ResourceRecord,
                 &vl_type_ResolvedRecord,
+                &vl_type_ServiceData,
                 &vl_error_NoNameServers,
                 &vl_error_NoSuchResourceRecord,
                 &vl_error_QueryTimedOut,

src/varlinkctl/varlinkctl.c

@@ -507,6 +507,7 @@ static int reply_callback(
         if (!arg_quiet)
                 sd_json_variant_dump(parameters, arg_json_format_flags, stdout, NULL);
 
+        fflush(stdout);
         return r;
 }
 

test/TEST-86-RESOLVED-MDNS/Makefile

@@ -0,0 +1,6 @@
+# SPDX-License-Identifier: LGPL-2.1-or-later
+
+all setup run clean clean-again:
+	@TEST_BASE_DIR=../ ./test.sh --$@
+
+.PHONY: all setup run clean clean-again

test/TEST-86-RESOLVED-MDNS/meson.build

@@ -0,0 +1,7 @@
+# SPDX-License-Identifier: LGPL-2.1-or-later
+
+integration_tests += [
+        integration_test_template + {
+                'name' : fs.name(meson.current_source_dir()),
+        },
+]

test/TEST-86-RESOLVED-MDNS/test.sh

@@ -0,0 +1,12 @@
+#!/usr/bin/env bash
+# SPDX-License-Identifier: LGPL-2.1-or-later
+set -e
+
+TEST_DESCRIPTION="Test for systemd-resolved's mDNS functionality"
+IMAGE_NAME="resolved-mdns"
+TEST_NO_NSPAWN=1
+
+# shellcheck source=test/test-functions
+. "${TEST_BASE_DIR:?}/test-functions"
+
+do_test "$@"

test/meson.build

@@ -376,6 +376,7 @@ foreach dirname : [
         'TEST-83-BTRFS',
         'TEST-84-STORAGETM',
         'TEST-85-NETWORK',
+        'TEST-86-RESOLVED-MDNS',
 ]
         subdir(dirname)
 endforeach

test/test-network/systemd-networkd-tests.py

@@ -77,6 +77,7 @@ show_journal = True # When true, show journal on stopping networkd.
 
 active_units = []
 protected_links = {
+    'br0',
     'erspan0',
     'gre0',
     'gretap0',

test/units/TEST-86-RESOLVED-MDNS.service

@@ -0,0 +1,8 @@
+# SPDX-License-Identifier: LGPL-2.1-or-later
+[Unit]
+Description=TEST-86-RESOLVED-MDNS
+
+[Service]
+ExecStartPre=rm -f /failed /testok
+ExecStart=/usr/lib/systemd/tests/testdata/units/%N.sh
+Type=oneshot

test/units/TEST-86-RESOLVED-MDNS.sh

@@ -0,0 +1,247 @@
+#!/usr/bin/env bash
+# SPDX-License-Identifier: LGPL-2.1-or-later
+set -eux
+set -o pipefail
+
+# shellcheck source=test/units/test-control.sh
+. "$(dirname "$0")"/test-control.sh
+
+SERVICE_TYPE_COUNT=10
+SERVICE_COUNT=20
+CONTAINER_ZONE="test-$RANDOM"
+CONTAINER_1="test-mdns-1"
+CONTAINER_2="test-mdns-2"
+
+# Prepare containers
+create_container() {
+    local container="${1:?}"
+    local stype sid svc
+
+    # Prepare container's /etc
+    #
+    # Since we also need the various test suite related dropins from the host's /etc,
+    # we'll overlay our customizations on top of that
+    mkdir -p "/var/lib/machines/$container/etc/systemd/dnssd"
+    # Create 20 test services for each service type (_testServiceX._udp) and number them sequentially,
+    # i.e. create services 0-19 for _testService0._udp, services 20-39 for _testService1._udp, and so on
+    for stype in $(seq 0 $((SERVICE_TYPE_COUNT - 1))); do
+        for sid in $(seq 0 $((SERVICE_COUNT - 1))); do
+            svc=$((stype * SERVICE_COUNT + sid))
+
+            cat >"/var/lib/machines/$container/etc/systemd/dnssd/test-service-$container-$svc.dnssd" <<EOF
+[Service]
+Name=Test Service $svc on %H
+Type=_testService$stype._udp
+Port=24002
+TxtText=DC=Monitor PN=867313 SN=XZ051Z0051
+EOF
+        done
+    done
+
+    # To make things fast, spawn the container with a transient version of what's currently the host's
+    # rootfs, sans a couple of tweaks to make the container unique enough
+    mkdir -p "/run/systemd/system/systemd-nspawn@$container.service.d"
+    cat >"/run/systemd/system/systemd-nspawn@$container.service.d/override.conf" <<EOF
+[Service]
+ExecStart=
+ExecStart=systemd-nspawn --quiet --link-journal=try-guest --keep-unit --machine=%i --boot \
+                         --volatile=yes --directory=/ \
+                         --inaccessible=/etc/machine-id \
+                         --inaccessible=/etc/hostname \
+                         --resolv-conf=replace-stub \
+                         --network-zone=$CONTAINER_ZONE \
+                         --overlay=/etc:/var/lib/machines/$container/etc::/etc
+EOF
+}
+
+check_both() {
+    local service_id="${1:?}"
+    local result_file="${2:?}"
+
+    # We should get 20 services per container, 40 total
+    if [[ "$(wc -l <"$result_file")" -eq 40 ]]; then
+        # Check if the services we got are the correct ones
+        for i in $(seq 0 $((SERVICE_TYPE_COUNT - 1))); do
+            svc=$((service_id * SERVICE_COUNT + i))
+            if ! grep "Test Service $svc on $CONTAINER_1" "$result_file" || \
+               ! grep "Test Service $svc on $CONTAINER_2" "$result_file"; then
+                return 1
+            fi
+        done
+
+        # We got all records and all of them are what we expect
+        return 0
+    fi
+
+    return 1
+}
+
+check_first() {
+    local service_id="${1:?}"
+    local result_file="${2:?}"
+
+    # We should get 20 services per container
+    if [[ "$(wc -l <"$result_file")" -eq 20 ]]; then
+        # Check if the services we got are the correct ones
+        for i in $(seq 0 $((SERVICE_TYPE_COUNT - 1))); do
+            svc=$((service_id * SERVICE_COUNT + i))
+            if ! grep "Test Service $svc on $CONTAINER_1" "$result_file"; then
+                return 1
+            fi
+            # This check assumes the second container is unreachable, so this shouldn't happen
+            if grep "Test Service $svc on $CONTAINER_2" "$result_file"; then
+                echo >&2 "Found a record from an unreachable container"
+                cat "$result_file"
+                exit 1
+            fi
+        done
+
+        # We got all records and all of them are what we expect
+        return 0
+    fi
+
+    return 1
+}
+
+run_and_check_services() {
+    local service_id="${1:?}"
+    local check_func="${2:?}"
+    local unit_name="varlinkctl-$service_id-$SRANDOM.service"
+    local i out_file parameters service_type svc tmp_file
+
+    out_file="$(mktemp)"
+    tmp_file="$(mktemp)"
+    service_type="_testService$service_id._udp"
+    parameters="{ \"domainName\": \"$service_type.local\", \"name\": \"\", \"type\": \"\", \"ifindex\": ${BRIDGE_INDEX:?}, \"flags\": 16785432 }"
+
+    systemd-run --unit="$unit_name" --service-type=exec -p StandardOutput="file:$out_file" \
+        varlinkctl call --more /run/systemd/resolve/io.systemd.Resolve io.systemd.Resolve.StartBrowse "$parameters"
+
+    # shellcheck disable=SC2064
+    # Note: unregister the trap once it's fired, otherwise it'll get propagated to functions that call this
+    #       one, *sigh*
+    trap "trap - RETURN; systemctl stop $unit_name" RETURN
+
+    for _ in {0..14}; do
+        # The response format, for reference (it's JSON-SEQ):
+        #
+        # {
+        #   "browser_service_data": [
+        #     {
+        #       "add_flag": true,
+        #       "family": 10,
+        #       "name": "Test Service 13 on test-mdns-1",
+        #       "type": "_testService0._udp",
+        #       "domain": "local",
+        #       "interface": 3
+        #     },
+        #     ...
+        #   ]
+        # }
+        if [[ -s "$out_file" ]]; then
+            # Extract the service name from each valid record...
+            jq --slurp --raw-output \
+                ".[].browser_service_data[] | select(.add_flag == true and .type == \"$service_type\" and .family == 10).name" "$out_file" | sort | tee "$tmp_file"
+            # ...and compare them with what we expect
+            if "$check_func" "$service_id" "$tmp_file"; then
+                return 0
+            fi
+        fi
+
+        sleep 2
+    done
+
+    cat "$out_file"
+    return 1
+}
+
+testcase_all_sequential() {
+    : "Test each service type (sequentially)"
+    resolvectl flush-caches
+    for id in $(seq 0 $((SERVICE_TYPE_COUNT - 1))); do
+        run_and_check_services "$id" check_both
+    done
+
+    echo testcase_end
+}
+
+testcase_all_parallel() {
+    : "Test each service type (in parallel)"
+    resolvectl flush-caches
+    for id in $(seq 0 $((SERVICE_TYPE_COUNT - 1))); do
+        run_and_check_services "$id" check_both &
+    done
+    wait
+}
+
+testcase_single_service_multiple_times() {
+    : "Test one service type multiple times"
+    resolvectl flush-caches
+    for _ in {0..4}; do
+        run_and_check_services 4 check_both
+    done
+}
+
+testcase_second_unreachable() {
+    : "Test each service type while the second container is unreachable"
+    resolvectl flush-caches
+    systemd-run -M "$CONTAINER_2" --wait --pipe -- networkctl down host0
+    for id in $(seq 0 $((SERVICE_TYPE_COUNT - 1))); do
+        run_and_check_services "$id" check_first
+    done
+
+
+    : "Test each service type after bringing the second container back up again"
+    systemd-run -M "$CONTAINER_2" --wait --pipe -- networkctl up host0
+    systemd-run -M "$CONTAINER_2" --wait --pipe -- \
+        /usr/lib/systemd/systemd-networkd-wait-online --ipv4 --ipv6 --interface=host0 --operational-state=degraded --timeout=30
+    for id in $(seq 0 $((SERVICE_TYPE_COUNT - 1))); do
+        run_and_check_services "$id" check_both
+    done
+}
+
+: "Setup host & containers"
+# Note: create the drop-in intentionally under /etc, so it gets automagically propagated
+#       to the container we create later
+mkdir /etc/systemd/resolved.conf.d/
+cat >/etc/systemd/resolved.conf.d/99-mdns-llmnr.conf <<EOF
+[Resolve]
+MulticastDNS=yes
+LLMNR=yes
+EOF
+
+systemctl unmask systemd-resolved.service systemd-networkd.{service,socket}
+systemctl enable --now systemd-resolved.service systemd-networkd.{socket,service}
+ln -svrf /run/systemd/resolve/stub-resolv.conf /etc/resolv.conf
+
+for container in "$CONTAINER_1" "$CONTAINER_2"; do
+    create_container "$container"
+    systemctl daemon-reload
+    machinectl start "$container"
+    # Wait for the system bus to start...
+    timeout 30s bash -xec "while ! systemd-run -M '$container' --wait --pipe true; do sleep 1; done"
+    # ...and from there wait for the machine bootup to finish. We don't really care if the container
+    # boots up in a degraded state, hence the `:`
+    timeout 30s systemd-run -M "$container" --wait --pipe -- systemctl --wait is-system-running || :
+    # Wait until the veth interface is configured and turn on mDNS and LLMNR
+    systemd-run -M "$container" --wait --pipe -- \
+        /usr/lib/systemd/systemd-networkd-wait-online --ipv4 --ipv6 --interface=host0 --operational-state=degraded --timeout=30
+    systemd-run -M "$container" --wait --pipe -- resolvectl mdns host0 yes
+    systemd-run -M "$container" --wait --pipe -- resolvectl llmnr host0 yes
+    systemd-run -M "$container" --wait --pipe -- networkctl status --no-pager
+    systemd-run -M "$container" --wait --pipe -- resolvectl status --no-pager
+    [[ "$(systemd-run -M "$container" --wait --pipe -- resolvectl mdns host0)" =~ :\ yes$ ]]
+    [[ "$(systemd-run -M "$container" --wait --pipe -- resolvectl llmnr host0)" =~ :\ yes$ ]]
+done
+
+BRIDGE_INDEX="$(<"/sys/class/net/vz-$CONTAINER_ZONE/ifindex")"
+machinectl list
+resolvectl mdns "vz-$CONTAINER_ZONE" on
+resolvectl llmnr "vz-$CONTAINER_ZONE" on
+networkctl status
+resolvectl status
+
+# Run the actual test cases (functions prefixed by testcase_)
+run_testcases
+
+touch /testok