resolved: add ResolveService() bus call for resolving SRV and DNS-SD services

This also adds client-side support for this to systemd-resolve-host.

Note that the ResolveService() API can deal both with DNS-SD service
(consisting of service name, type and domain), as well as classic SRV
services (consisting just of a type and a domain), all exposed in the
same call.

This patch also reworks CNAME handling in order to reuse it between
hostname, RR and service lookups.

In contrast to Avahi and Bonjour, this new API will actually reolve the
A/AAAA RRs the SRV RRs point to in one go (unless this is explicitly
disabled). This normally comes for free, as these RRs are sent along
the SRV responses anyway, hence let's make use of that. This makes the
API considerably easier to use, as a single ResolveService() invocation
will return all necessary data to pick a server and connect() to it.

Note that this only implements the DNS-SD resolving step, it does not
implement DNS-SD browsing, as that makes sense primarily on mDNS, due to
its continuous nature.

1 files changed, 306 insertions, 36 deletions

diff --git a/src/resolve-host/resolve-host.c b/src/resolve-host/resolve-host.c
index eb4e646846..2c17ad6ede 100644
--- a/src/resolve-host/resolve-host.c
+++ b/src/resolve-host/resolve-host.c
@@ -28,6 +28,7 @@
 #include "alloc-util.h"
 #include "bus-error.h"
 #include "bus-util.h"
+#include "escape.h"
 #include "in-addr-util.h"
 #include "parse-util.h"
 #include "resolved-def.h"
@@ -41,6 +42,7 @@ static int arg_type = 0;
 static uint16_t arg_class = 0;
 static bool arg_legend = true;
 static uint64_t arg_flags = 0;
+static bool arg_resolve_service = false;
 
 static void print_source(uint64_t flags, usec_t rtt) {
         char rtt_str[FORMAT_TIMESTAMP_MAX];
@@ -102,10 +104,8 @@ static int resolve_host(sd_bus *bus, const char *name) {
         ts = now(CLOCK_MONOTONIC);
 
         r = sd_bus_call(bus, req, DNS_CALL_TIMEOUT_USEC, &error, &reply);
-        if (r < 0) {
-                log_error("%s: resolve call failed: %s", name, bus_error_message(&error, r));
-                return r;
-        }
+        if (r < 0)
+                return log_error_errno(r, "%s: resolve call failed: %s", name, bus_error_message(&error, r));
 
         ts = now(CLOCK_MONOTONIC) - ts;
 
@@ -114,10 +114,10 @@ static int resolve_host(sd_bus *bus, const char *name) {
                 return bus_log_parse_error(r);
 
         while ((r = sd_bus_message_enter_container(reply, 'r', "iiay")) > 0) {
-                const void *a;
-                size_t sz;
                 _cleanup_free_ char *pretty = NULL;
                 int ifindex, family;
+                const void *a;
+                size_t sz;
 
                 assert_cc(sizeof(int) == sizeof(int32_t));
 
@@ -140,7 +140,7 @@ static int resolve_host(sd_bus *bus, const char *name) {
 
                 if (sz != FAMILY_ADDRESS_SIZE(family)) {
                         log_error("%s: systemd-resolved returned address of invalid size %zu for family %s", name, sz, af_to_name(family) ?: "unknown");
-                        continue;
+                        return -EINVAL;
                 }
 
                 ifname[0] = 0;
@@ -437,6 +437,207 @@ static int resolve_record(sd_bus *bus, const char *name) {
         return 0;
 }
 
+static int resolve_service(sd_bus *bus, const char *name, const char *type, const char *domain) {
+        const char *canonical_name, *canonical_type, *canonical_domain;
+        _cleanup_bus_message_unref_ sd_bus_message *req = NULL, *reply = NULL;
+        _cleanup_bus_error_free_ sd_bus_error error = SD_BUS_ERROR_NULL;
+        char ifname[IF_NAMESIZE] = "";
+        size_t indent, sz;
+        uint64_t flags;
+        const char *p;
+        unsigned c;
+        usec_t ts;
+        int r;
+
+        assert(bus);
+        assert(domain);
+
+        if (isempty(name))
+                name = NULL;
+        if (isempty(type))
+                type = NULL;
+
+        if (arg_ifindex > 0 && !if_indextoname(arg_ifindex, ifname))
+                return log_error_errno(errno, "Failed to resolve interface name for index %i: %m", arg_ifindex);
+
+        if (name)
+                log_debug("Resolving service \"%s\" of type %s in %s (family %s, interface %s).", name, type, domain, af_to_name(arg_family) ?: "*", isempty(ifname) ? "*" : ifname);
+        else if (type)
+                log_debug("Resolving service type %s of %s (family %s, interface %s).", type, domain, af_to_name(arg_family) ?: "*", isempty(ifname) ? "*" : ifname);
+        else
+                log_debug("Resolving service type %s (family %s, interface %s).", domain, af_to_name(arg_family) ?: "*", isempty(ifname) ? "*" : ifname);
+
+        r = sd_bus_message_new_method_call(
+                        bus,
+                        &req,
+                        "org.freedesktop.resolve1",
+                        "/org/freedesktop/resolve1",
+                        "org.freedesktop.resolve1.Manager",
+                        "ResolveService");
+        if (r < 0)
+                return bus_log_create_error(r);
+
+        r = sd_bus_message_append(req, "isssit", arg_ifindex, name, type, domain, arg_family, arg_flags);
+        if (r < 0)
+                return bus_log_create_error(r);
+
+        ts = now(CLOCK_MONOTONIC);
+
+        r = sd_bus_call(bus, req, DNS_CALL_TIMEOUT_USEC, &error, &reply);
+        if (r < 0)
+                return log_error_errno(r, "Resolve call failed: %s", bus_error_message(&error, r));
+
+        ts = now(CLOCK_MONOTONIC) - ts;
+
+        r = sd_bus_message_enter_container(reply, 'a', "(qqqsa(iiay)s)");
+        if (r < 0)
+                return bus_log_parse_error(r);
+
+        indent =
+                (name ? strlen(name) + 1 : 0) +
+                (type ? strlen(type) + 1 : 0) +
+                strlen(domain) + 2;
+
+        c = 0;
+        while ((r = sd_bus_message_enter_container(reply, 'r', "qqqsa(iiay)s")) > 0) {
+                uint16_t priority, weight, port;
+                const char *hostname, *canonical;
+
+                r = sd_bus_message_read(reply, "qqqs", &priority, &weight, &port, &hostname);
+                if (r < 0)
+                        return bus_log_parse_error(r);
+
+                if (name)
+                        printf("%*s%s", (int) strlen(name), c == 0 ? name : "", c == 0 ? "/" : " ");
+                if (type)
+                        printf("%*s%s", (int) strlen(type), c == 0 ? type : "", c == 0 ? "/" : " ");
+
+                printf("%*s%s %s:%u [priority=%u, weight=%u]\n",
+                       (int) strlen(domain), c == 0 ? domain : "",
+                       c == 0 ? ":" : " ",
+                       hostname, port,
+                       priority, weight);
+
+                r = sd_bus_message_enter_container(reply, 'a', "(iiay)");
+                if (r < 0)
+                        return bus_log_parse_error(r);
+
+                while ((r = sd_bus_message_enter_container(reply, 'r', "iiay")) > 0) {
+                        _cleanup_free_ char *pretty = NULL;
+                        int ifindex, family;
+                        const void *a;
+
+                        assert_cc(sizeof(int) == sizeof(int32_t));
+
+                        r = sd_bus_message_read(reply, "ii", &ifindex, &family);
+                        if (r < 0)
+                                return bus_log_parse_error(r);
+
+                        r = sd_bus_message_read_array(reply, 'y', &a, &sz);
+                        if (r < 0)
+                                return bus_log_parse_error(r);
+
+                        r = sd_bus_message_exit_container(reply);
+                        if (r < 0)
+                                return bus_log_parse_error(r);
+
+                        if (!IN_SET(family, AF_INET, AF_INET6)) {
+                                log_debug("%s: skipping entry with family %d (%s)", name, family, af_to_name(family) ?: "unknown");
+                                continue;
+                        }
+
+                        if (sz != FAMILY_ADDRESS_SIZE(family)) {
+                                log_error("%s: systemd-resolved returned address of invalid size %zu for family %s", name, sz, af_to_name(family) ?: "unknown");
+                                return -EINVAL;
+                        }
+
+                        ifname[0] = 0;
+                        if (ifindex > 0 && !if_indextoname(ifindex, ifname))
+                                log_warning_errno(errno, "Failed to resolve interface name for index %i: %m", ifindex);
+
+                        r = in_addr_to_string(family, a, &pretty);
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to print address for %s: %m", name);
+
+                        printf("%*s%s%s%s\n", (int) indent, "", pretty, isempty(ifname) ? "" : "%s", ifname);
+                }
+                if (r < 0)
+                        return bus_log_parse_error(r);
+
+                r = sd_bus_message_exit_container(reply);
+                if (r < 0)
+                        return bus_log_parse_error(r);
+
+                r = sd_bus_message_read(reply, "s", &canonical);
+                if (r < 0)
+                        return bus_log_parse_error(r);
+
+                if (!streq(hostname, canonical))
+                        printf("%*s(%s)\n", (int) indent, "", canonical);
+
+                r = sd_bus_message_exit_container(reply);
+                if (r < 0)
+                        return bus_log_parse_error(r);
+
+                c++;
+        }
+        if (r < 0)
+                return bus_log_parse_error(r);
+
+        r = sd_bus_message_exit_container(reply);
+        if (r < 0)
+                return bus_log_parse_error(r);
+
+        r = sd_bus_message_enter_container(reply, 'a', "ay");
+        if (r < 0)
+                return bus_log_parse_error(r);
+
+        c = 0;
+        while ((r = sd_bus_message_read_array(reply, 'y', (const void**) &p, &sz)) > 0) {
+                _cleanup_free_ char *escaped = NULL;
+
+                escaped = cescape_length(p, sz);
+                if (!escaped)
+                        return log_oom();
+
+                printf("%*s%s\n", (int) indent, "", escaped);
+                c++;
+        }
+        if (r < 0)
+                return bus_log_parse_error(r);
+
+        r = sd_bus_message_exit_container(reply);
+        if (r < 0)
+                return bus_log_parse_error(r);
+
+        r = sd_bus_message_read(reply, "ssst", &canonical_name, &canonical_type, &canonical_domain, &flags);
+        if (r < 0)
+                return bus_log_parse_error(r);
+
+        if (isempty(canonical_name))
+                canonical_name = NULL;
+        if (isempty(canonical_type))
+                canonical_type = NULL;
+
+        if (!streq_ptr(name, canonical_name) ||
+            !streq_ptr(type, canonical_type) ||
+            !streq_ptr(domain, canonical_domain)) {
+
+                printf("%*s(", (int) indent, "");
+
+                if (canonical_name)
+                        printf("%s/", canonical_name);
+                if (canonical_type)
+                        printf("%s/", canonical_type);
+
+                printf("%s)\n", canonical_domain);
+        }
+
+        print_source(flags, ts);
+
+        return 0;
+}
+
 static void help_dns_types(void) {
         int i;
         const char *t;
@@ -464,33 +665,46 @@ static void help_dns_classes(void) {
 }
 
 static void help(void) {
-        printf("%s [OPTIONS...]\n\n"
-               "Resolve IPv4 or IPv6 addresses.\n\n"
-               "  -h --help               Show this help\n"
-               "     --version            Show package version\n"
-               "  -4                      Resolve IPv4 addresses\n"
-               "  -6                      Resolve IPv6 addresses\n"
-               "  -i INTERFACE            Look on interface\n"
-               "  -p --protocol=PROTOCOL  Look via protocol\n"
-               "  -t --type=TYPE          Query RR with DNS type\n"
-               "  -c --class=CLASS        Query RR with DNS class\n"
-               "     --legend[=BOOL]      Do [not] print column headers\n"
-               , program_invocation_short_name);
+        printf("%s [OPTIONS...] NAME...\n"
+               "%s [OPTIONS...] --service [[NAME] TYPE] DOMAIN\n\n"
+               "Resolve domain names, IPv4 or IPv6 addresses, resource records, and services.\n\n"
+               "  -h --help                 Show this help\n"
+               "     --version              Show package version\n"
+               "  -4                        Resolve IPv4 addresses\n"
+               "  -6                        Resolve IPv6 addresses\n"
+               "  -i INTERFACE              Look on interface\n"
+               "  -p --protocol=PROTOCOL    Look via protocol\n"
+               "  -t --type=TYPE            Query RR with DNS type\n"
+               "  -c --class=CLASS          Query RR with DNS class\n"
+               "     --service              Resolve service (SRV)\n"
+               "     --service-address=BOOL Do [not] resolve address for services\n"
+               "     --service-txt=BOOL     Do [not] resolve TXT records for services\n"
+               "     --cname=BOOL           Do [not] follow CNAME redirects\n"
+               "     --legend=BOOL          Do [not] print column headers\n"
+               , program_invocation_short_name, program_invocation_short_name);
 }
 
 static int parse_argv(int argc, char *argv[]) {
         enum {
                 ARG_VERSION = 0x100,
                 ARG_LEGEND,
+                ARG_SERVICE,
+                ARG_CNAME,
+                ARG_SERVICE_ADDRESS,
+                ARG_SERVICE_TXT,
         };
 
         static const struct option options[] = {
-                { "help",      no_argument,       NULL, 'h'           },
-                { "version",   no_argument,       NULL, ARG_VERSION   },
-                { "type",      required_argument, NULL, 't'           },
-                { "class",     required_argument, NULL, 'c'           },
-                { "legend",    optional_argument, NULL, ARG_LEGEND    },
-                { "protocol",  required_argument, NULL, 'p'           },
+                { "help",            no_argument,       NULL, 'h'                 },
+                { "version",         no_argument,       NULL, ARG_VERSION         },
+                { "type",            required_argument, NULL, 't'                 },
+                { "class",           required_argument, NULL, 'c'                 },
+                { "legend",          required_argument, NULL, ARG_LEGEND          },
+                { "protocol",        required_argument, NULL, 'p'                 },
+                { "cname",           required_argument, NULL, ARG_CNAME           },
+                { "service",         no_argument,       NULL, ARG_SERVICE         },
+                { "service-address", required_argument, NULL, ARG_SERVICE_ADDRESS },
+                { "service-txt",     required_argument, NULL, ARG_SERVICE_TXT     },
                 {}
         };
 
@@ -563,16 +777,11 @@ static int parse_argv(int argc, char *argv[]) {
                         break;
 
                 case ARG_LEGEND:
-                        if (optarg) {
-                                r = parse_boolean(optarg);
-                                if (r < 0) {
-                                        log_error("Failed to parse --legend= argument");
-                                        return r;
-                                }
-
-                                arg_legend = !!r;
-                        } else
-                                arg_legend = false;
+                        r = parse_boolean(optarg);
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to parse --legend= argument");
+
+                        arg_legend = r;
                         break;
 
                 case 'p':
@@ -591,6 +800,40 @@ static int parse_argv(int argc, char *argv[]) {
 
                         break;
 
+                case ARG_SERVICE:
+                        arg_resolve_service = true;
+                        break;
+
+                case ARG_CNAME:
+                        r = parse_boolean(optarg);
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to parse --cname= argument.");
+                        if (r == 0)
+                                arg_flags |= SD_RESOLVED_NO_CNAME;
+                        else
+                                arg_flags &= ~SD_RESOLVED_NO_CNAME;
+                        break;
+
+                case ARG_SERVICE_ADDRESS:
+                        r = parse_boolean(optarg);
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to parse --service-address= argument.");
+                        if (r == 0)
+                                arg_flags |= SD_RESOLVED_NO_ADDRESS;
+                        else
+                                arg_flags &= ~SD_RESOLVED_NO_ADDRESS;
+                        break;
+
+                case ARG_SERVICE_TXT:
+                        r = parse_boolean(optarg);
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to parse --service-txt= argument.");
+                        if (r == 0)
+                                arg_flags |= SD_RESOLVED_NO_TXT;
+                        else
+                                arg_flags &= ~SD_RESOLVED_NO_TXT;
+                        break;
+
                 case '?':
                         return -EINVAL;
 
@@ -599,7 +842,12 @@ static int parse_argv(int argc, char *argv[]) {
                 }
 
         if (arg_type == 0 && arg_class != 0) {
-                log_error("--class= may only be used in conjunction with --type=");
+                log_error("--class= may only be used in conjunction with --type=.");
+                return -EINVAL;
+        }
+
+        if (arg_type != 0 && arg_resolve_service) {
+                log_error("--service and --type= may not be combined.");
                 return -EINVAL;
         }
 
@@ -632,6 +880,28 @@ int main(int argc, char **argv) {
                 goto finish;
         }
 
+        if (arg_resolve_service) {
+
+                if (argc < optind + 1) {
+                        log_error("Domain specification required.");
+                        r = -EINVAL;
+                        goto finish;
+
+                } else if (argc == optind + 1)
+                        r = resolve_service(bus, NULL, NULL, argv[optind]);
+                else if (argc == optind + 2)
+                        r = resolve_service(bus, NULL, argv[optind], argv[optind+1]);
+                else if (argc == optind + 3)
+                        r = resolve_service(bus, argv[optind], argv[optind+1], argv[optind+2]);
+                else {
+                        log_error("Too many arguments");
+                        r = -EINVAL;
+                        goto finish;
+                }
+
+                goto finish;
+        }
+
         while (argv[optind]) {
                 int family, ifindex, k;
                 union in_addr_union a;