resolved: add enablers for DNS-SD

Introduce network services loaded from .dnssd files that
can be used for server-side DNS-SD implementation in systemd-resolved.

src/resolve/meson.build

@@ -35,6 +35,8 @@ systemd_resolved_only_sources = files('''
         resolved.c
         resolved-manager.c
         resolved-manager.h
+        resolved-dnssd.c
+        resolved-dnssd.h
         resolved-conf.c
         resolved-conf.h
         resolved-resolv-conf.c
@@ -131,8 +133,14 @@ resolved_gperf_c = custom_target(
         output : 'resolved-gperf.c',
         command : [gperf, '@INPUT@', '--output-file', '@OUTPUT@'])
 
+resolved_dnssd_gperf_c = custom_target(
+        'resolved_dnssd_gperf.c',
+        input : 'resolved-dnssd-gperf.gperf',
+        output : 'resolved-dnssd-gperf.c',
+        command : [gperf, '@INPUT@', '--output-file', '@OUTPUT@'])
+
 systemd_resolved_sources = (basic_dns_sources +
-                            [resolved_gperf_c] +
+                            [resolved_gperf_c, resolved_dnssd_gperf_c] +
                             systemd_resolved_only_sources +
                             dns_type_headers)
 

src/resolve/resolved-conf.c

@@ -22,10 +22,14 @@
 #include "conf-parser.h"
 #include "def.h"
 #include "extract-word.h"
+#include "hexdecoct.h"
 #include "parse-util.h"
 #include "resolved-conf.h"
+#include "resolved-dnssd.h"
+#include "specifier.h"
 #include "string-table.h"
 #include "string-util.h"
+#include "utf8.h"
 
 DEFINE_CONFIG_PARSE_ENUM(config_parse_dns_stub_listener_mode, dns_stub_listener_mode, DnsStubListenerMode, "Failed to parse DNS stub listener mode setting");
 
@@ -228,6 +232,152 @@ int config_parse_search_domains(
         return 0;
 }
 
+int config_parse_dnssd_service_name(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata) {
+        static const Specifier specifier_table[] = {
+                { 'b', specifier_boot_id,         NULL },
+                { 'H', specifier_host_name, NULL },
+                { 'm', specifier_machine_id, NULL },
+                { 'v', specifier_kernel_release,  NULL },
+                {}
+        };
+        DnssdService *s = userdata;
+        _cleanup_free_ char *name = NULL;
+        int r;
+
+        assert(filename);
+        assert(lvalue);
+        assert(rvalue);
+        assert(s);
+
+        if (isempty(rvalue)) {
+                log_syntax(unit, LOG_ERR, filename, line, 0, "Service instance name can't be empty. Ignoring.");
+                return -EINVAL;
+        }
+
+        r = free_and_strdup(&s->name_template, rvalue);
+        if (r < 0)
+                return log_oom();
+
+        r = specifier_printf(s->name_template, specifier_table, NULL, &name);
+        if (r < 0)
+                return log_debug_errno(r, "Failed to replace specifiers: %m");
+
+        if (!dns_service_name_is_valid(name)) {
+                log_syntax(unit, LOG_ERR, filename, line, 0, "Service instance name template renders to invalid name '%s'. Ignoring.", name);
+                return -EINVAL;
+        }
+
+        return 0;
+}
+
+int config_parse_dnssd_service_type(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata) {
+        DnssdService *s = userdata;
+        int r;
+
+        assert(filename);
+        assert(lvalue);
+        assert(rvalue);
+        assert(s);
+
+        if (isempty(rvalue)) {
+                log_syntax(unit, LOG_ERR, filename, line, 0, "Service type can't be empty. Ignoring.");
+                return -EINVAL;
+        }
+
+        if (!dnssd_srv_type_is_valid(rvalue)) {
+                log_syntax(unit, LOG_ERR, filename, line, 0, "Service type is invalid. Ignoring.");
+                return -EINVAL;
+        }
+
+        r = free_and_strdup(&s->type, rvalue);
+        if (r < 0)
+                return log_oom();
+
+        return 0;
+}
+
+int config_parse_dnssd_txt(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata) {
+        DnssdService *s = userdata;
+        DnsTxtItem *last = NULL;
+
+        assert(filename);
+        assert(lvalue);
+        assert(rvalue);
+        assert(s);
+
+        /* TODO: Since RFC6763 allows more than one TXT RR per service
+         *       this s->txt field should be implemented as a list
+         *       of DnsTxtItem lists. */
+        s->txt = dns_txt_item_free_all(s->txt);
+
+        if (isempty(rvalue))
+                return 0;
+
+        for (;;) {
+                _cleanup_free_ char *word = NULL;
+                _cleanup_free_ char *key = NULL;
+                _cleanup_free_ char *value = NULL;
+                _cleanup_free_ void *decoded = NULL;
+                size_t length = 0;
+                DnsTxtItem *i;
+                int r;
+
+                r = extract_first_word(&rvalue, &word, NULL,
+                                       EXTRACT_QUOTES|EXTRACT_CUNESCAPE|EXTRACT_CUNESCAPE_RELAX);
+                if (r == 0)
+                        break;
+                if (r == -ENOMEM)
+                        return log_oom();
+                if (r < 0)
+                        return log_syntax(unit, LOG_ERR, filename, line, r, "Invalid syntax, ignoring: %s", rvalue);
+
+                r = split_pair(word, "=", &key, &value);
+                if (r == -ENOMEM)
+                        return log_oom();
+                if (r == -EINVAL) {
+                        key = word;
+                        word = NULL;
+                }
+
+                if (!ascii_is_valid(key)) {
+                        log_syntax(unit, LOG_ERR, filename, line, 0, "Invalid syntax, ignoring: %s", key);
+                        return -EINVAL;
+                }
+
+                switch (ltype) {
+
+                case DNS_TXT_ITEM_DATA:
+                        if (value) {
+                                r = unbase64mem(value, strlen(value), &decoded, &length);
+                                if (r == -ENOMEM)
+                                        return log_oom();
+                                if (r < 0)
+                                        return log_syntax(unit, LOG_ERR, filename, line, r,
+                                                          "Invalid base64 encoding, ignoring: %s", value);
+                        }
+
+                        r = dnssd_txt_item_new_from_data(key, decoded, length, &i);
+                        if (r < 0)
+                                return log_oom();
+                        break;
+
+                case DNS_TXT_ITEM_TEXT:
+                        r = dnssd_txt_item_new_from_string(key, value, &i);
+                        if (r < 0)
+                                return log_oom();
+                        break;
+
+                default:
+                        assert_not_reached("Unknown type of Txt config");
+                }
+
+                LIST_INSERT_AFTER(items, s->txt, last, i);
+                last = i;
+        }
+
+        return 0;
+}
+
 int manager_parse_config_file(Manager *m) {
         int r;
 

src/resolve/resolved-conf.h

@@ -44,9 +44,14 @@ int manager_parse_dns_server_string_and_warn(Manager *m, DnsServerType type, con
 
 const struct ConfigPerfItem* resolved_gperf_lookup(const char *key, GPERF_LEN_TYPE length);
 
+const struct ConfigPerfItem* resolved_dnssd_gperf_lookup(const char *key, GPERF_LEN_TYPE length);
+
 int config_parse_dns_servers(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
 int config_parse_search_domains(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
 int config_parse_dns_stub_listener_mode(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
+int config_parse_dnssd_service_name(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
+int config_parse_dnssd_service_type(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
+int config_parse_dnssd_txt(const char *unit, const char *filename, unsigned line, const char *section, unsigned section_line, const char *lvalue, int ltype, const char *rvalue, void *data, void *userdata);
 
 const char* dns_stub_listener_mode_to_string(DnsStubListenerMode p) _const_;
 DnsStubListenerMode dns_stub_listener_mode_from_string(const char *s) _pure_;

src/resolve/resolved-dnssd-gperf.gperf

@@ -0,0 +1,24 @@
+%{
+#include <stddef.h>
+#include "conf-parser.h"
+#include "resolved-conf.h"
+#include "resolved-dnssd.h"
+%}
+struct ConfigPerfItem;
+%null_strings
+%language=ANSI-C
+%define slot-name section_and_lvalue
+%define hash-function-name resolved_dnssd_gperf_hash
+%define lookup-function-name resolved_dnssd_gperf_lookup
+%readonly-tables
+%omit-struct-type
+%struct-type
+%includes
+%%
+Service.Name,     config_parse_dnssd_service_name, 0,                 0
+Service.Type,     config_parse_dnssd_service_type, 0,                 0
+Service.Port,     config_parse_ip_port,            0,                 offsetof(DnssdService, port)
+Service.Priority, config_parse_uint16,             0,                 offsetof(DnssdService, priority)
+Service.Weight,   config_parse_uint16,             0,                 offsetof(DnssdService, weight)
+Service.TxtText,  config_parse_dnssd_txt,          DNS_TXT_ITEM_TEXT, 0
+Service.TxtData,  config_parse_dnssd_txt,          DNS_TXT_ITEM_DATA, 0

src/resolve/resolved-dnssd.c

@@ -0,0 +1,245 @@
+/***
+  This file is part of systemd.
+
+  Copyright 2017 Dmitry Rozhkov
+
+  systemd 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.
+
+  systemd 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 systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include "conf-files.h"
+#include "conf-parser.h"
+#include "resolved-dnssd.h"
+#include "resolved-dns-rr.h"
+#include "resolved-manager.h"
+#include "specifier.h"
+#include "strv.h"
+
+const char* const dnssd_service_dirs[] = {
+        "/etc/systemd/dnssd",
+        "/run/systemd/dnssd",
+        "/usr/lib/systemd/dnssd",
+#ifdef HAVE_SPLIT_USR
+        "/lib/systemd/dnssd",
+#endif
+    NULL
+};
+
+DnssdService *dnssd_service_free(DnssdService *service) {
+        if (!service)
+                return NULL;
+
+        if (service->manager)
+                hashmap_remove(service->manager->dnssd_services, service->name);
+
+        dns_resource_record_unref(service->ptr_rr);
+        dns_resource_record_unref(service->srv_rr);
+        dns_resource_record_unref(service->txt_rr);
+
+        free(service->filename);
+        free(service->name);
+        free(service->type);
+        free(service->name_template);
+        dns_txt_item_free_all(service->txt);
+
+        return mfree(service);
+}
+
+static int dnssd_service_load(Manager *manager, const char *filename) {
+        _cleanup_(dnssd_service_freep) DnssdService *service = NULL;
+        char *d;
+        const char *dropin_dirname;
+        int r;
+
+        assert(manager);
+        assert(filename);
+
+        service = new0(DnssdService, 1);
+        if (!service)
+                return log_oom();
+
+        service->filename = strdup(filename);
+        if (!service->filename)
+                return log_oom();
+
+        service->name = strdup(basename(filename));
+        if (!service->name)
+                return log_oom();
+
+        d = endswith(service->name, ".dnssd");
+        if (!d)
+                return -EINVAL;
+
+        assert(streq(d, ".dnssd"));
+
+        *d = '\0';
+
+        dropin_dirname = strjoina(service->name, ".dnssd.d");
+
+        r = config_parse_many(filename, dnssd_service_dirs, dropin_dirname,
+                              "Service\0",
+                              config_item_perf_lookup, resolved_dnssd_gperf_lookup,
+                              false, service);
+        if (r < 0)
+                return r;
+
+        if (!service->name_template) {
+                log_error("%s doesn't define service instance name", service->name);
+                return -EINVAL;
+        }
+
+        if (!service->type) {
+                log_error("%s doesn't define service type", service->name);
+                return -EINVAL;
+        }
+
+        if (!service->txt) {
+                r = dns_txt_item_new_empty(&service->txt);
+                if (r < 0)
+                        return r;
+        }
+
+        r = hashmap_ensure_allocated(&manager->dnssd_services, &string_hash_ops);
+        if (r < 0)
+                return r;
+
+        r = hashmap_put(manager->dnssd_services, service->name, service);
+        if (r < 0)
+                return r;
+
+        service->manager = manager;
+
+        service = NULL;
+
+        return 0;
+}
+
+static int specifier_dnssd_host_name(char specifier, void *data, void *userdata, char **ret) {
+        DnssdService *s  = (DnssdService *) userdata;
+        char *n;
+
+        assert(s);
+        assert(s->manager);
+        assert(s->manager->llmnr_hostname);
+
+        n = strdup(s->manager->llmnr_hostname);
+        if (!n)
+                return -ENOMEM;
+
+        *ret = n;
+        return 0;
+}
+
+int dnssd_render_instance_name(DnssdService *s, char **ret_name) {
+        static const Specifier specifier_table[] = {
+                { 'b', specifier_boot_id,         NULL },
+                { 'H', specifier_dnssd_host_name, NULL },
+                { 'm', specifier_machine_id, NULL },
+                { 'v', specifier_kernel_release,  NULL },
+                {}
+        };
+        _cleanup_free_ char *name = NULL;
+        int r;
+
+        assert(s);
+        assert(s->name_template);
+
+        r = specifier_printf(s->name_template, specifier_table, s, &name);
+        if (r < 0)
+                return log_debug_errno(r, "Failed to replace specifiers: %m");
+
+        if (!dns_service_name_is_valid(name)) {
+                log_debug("Service instance name '%s' is invalid.", name);
+                return -EINVAL;
+        }
+
+        *ret_name = name;
+        name = NULL;
+
+        return 0;
+}
+
+int dnssd_load(Manager *manager) {
+        _cleanup_strv_free_ char **files = NULL;
+        char **f;
+        int r;
+
+        assert(manager);
+
+        if (manager->mdns_support != RESOLVE_SUPPORT_YES)
+                return 0;
+
+        r = conf_files_list_strv(&files, ".dnssd", NULL, 0, dnssd_service_dirs);
+        if (r < 0)
+                return log_error_errno(r, "Failed to enumerate .dnssd files: %m");
+
+        STRV_FOREACH_BACKWARDS(f, files) {
+                r = dnssd_service_load(manager, *f);
+                if (r < 0)
+                        log_warning_errno(r, "Failed to load '%s': %m", *f);;
+        }
+
+        return 0;
+}
+
+int dnssd_txt_item_new_from_string(const char *key, const char *value, DnsTxtItem **ret_item) {
+        size_t length;
+        DnsTxtItem *i;
+
+        length = strlen(key);
+
+        if (!isempty(value))
+                length += strlen(value) + 1; /* length of value plus '=' */
+
+        i = malloc0(offsetof(DnsTxtItem, data) + length + 1); /* for safety reasons we add an extra NUL byte */
+        if (!i)
+                return -ENOMEM;
+
+        memcpy(i->data, key, strlen(key));
+        if (!isempty(value)) {
+                memcpy(i->data + strlen(key), "=", 1);
+                memcpy(i->data + strlen(key) + 1, value, strlen(value));
+        }
+        i->length = length;
+
+        *ret_item = i;
+        i = NULL;
+
+        return 0;
+}
+
+int dnssd_txt_item_new_from_data(const char *key, const void *data, const size_t size, DnsTxtItem **ret_item) {
+        size_t length;
+        DnsTxtItem *i;
+
+        length = strlen(key);
+
+        if (size > 0)
+                length += size + 1; /* size of date plus '=' */
+
+        i = malloc0(offsetof(DnsTxtItem, data) + length + 1); /* for safety reasons we add an extra NUL byte */
+        if (!i)
+                return -ENOMEM;
+
+        memcpy(i->data, key, strlen(key));
+        if (size > 0) {
+                memcpy(i->data + strlen(key), "=", 1);
+                memcpy(i->data + strlen(key) + 1, data, size);
+        }
+        i->length = length;
+
+        *ret_item = i;
+        i = NULL;
+
+        return 0;
+}

src/resolve/resolved-dnssd.h

@@ -0,0 +1,57 @@
+#pragma once
+
+/***
+  This file is part of systemd.
+
+  Copyright 2017 Dmitry Rozhkov
+
+  systemd 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.
+
+  systemd 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 systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+typedef struct DnssdService DnssdService;
+
+typedef struct Manager Manager;
+typedef struct DnsResourceRecord DnsResourceRecord;
+typedef struct DnsTxtItem DnsTxtItem;
+
+enum {
+        DNS_TXT_ITEM_TEXT,
+        DNS_TXT_ITEM_DATA
+};
+
+struct DnssdService {
+        char *filename;
+        char *name;
+        char *name_template;
+        char *type;
+        uint16_t port;
+        uint16_t priority;
+        uint16_t weight;
+        DnsTxtItem *txt;
+
+        DnsResourceRecord *ptr_rr;
+        DnsResourceRecord *srv_rr;
+        DnsResourceRecord *txt_rr;
+
+        Manager *manager;
+};
+
+DnssdService *dnssd_service_free(DnssdService *service);
+
+DEFINE_TRIVIAL_CLEANUP_FUNC(DnssdService*, dnssd_service_free);
+
+int dnssd_render_instance_name(DnssdService *s, char **ret_name);
+int dnssd_load(Manager *manager);
+int dnssd_txt_item_new_from_string(const char *key, const char *value, DnsTxtItem **ret_item);
+int dnssd_txt_item_new_from_data(const char *key, const void *value, const size_t size, DnsTxtItem **ret_item);

src/resolve/resolved-manager.c

@@ -41,6 +41,7 @@
 #include "random-util.h"
 #include "resolved-bus.h"
 #include "resolved-conf.h"
+#include "resolved-dnssd.h"
 #include "resolved-dns-stub.h"
 #include "resolved-etc-hosts.h"
 #include "resolved-llmnr.h"
@@ -621,6 +622,10 @@ int manager_new(Manager **ret) {
         if (r < 0)
                 return r;
 
+        r = dnssd_load(m);
+        if (r < 0)
+                log_warning_errno(r, "Failed to load DNS-SD configuration files: %m");
+
         r = dns_scope_new(m, &m->unicast_scope, NULL, DNS_PROTOCOL_DNS, AF_UNSPEC);
         if (r < 0)
                 return r;
@@ -663,6 +668,7 @@ int manager_start(Manager *m) {
 
 Manager *manager_free(Manager *m) {
         Link *l;
+        DnssdService *s;
 
         if (!m)
                 return NULL;
@@ -719,6 +725,10 @@ Manager *manager_free(Manager *m) {
         free(m->llmnr_hostname);
         free(m->mdns_hostname);
 
+        while ((s = hashmap_first(m->dnssd_services)))
+               dnssd_service_free(s);
+        hashmap_free(m->dnssd_services);
+
         dns_trust_anchor_flush(&m->trust_anchor);
         manager_etc_hosts_flush(m);
 

src/resolve/resolved-manager.h

@@ -102,6 +102,9 @@ struct Manager {
         int mdns_ipv4_fd;
         int mdns_ipv6_fd;
 
+        /* DNS-SD */
+        Hashmap *dnssd_services;
+
         sd_event_source *mdns_ipv4_event_source;
         sd_event_source *mdns_ipv6_event_source;