Add support for DNS in Address=

```
[Network]
Address=syslog.company.fi:514

```

Author: ssahani

src/netlog/netlog-conf.c

@@ -1,9 +1,13 @@
 /* SPDX-License-Identifier: LGPL-2.1-or-later */
 
+#include <resolv.h>
+
+#include "conf-parser.h"
 #include "def.h"
 #include "in-addr-util.h"
 #include "netlog-conf.h"
-#include "conf-parser.h"
+#include "parse-util.h"
+#include "sd-resolve.h"
 #include "string-util.h"
 
 int config_parse_netlog_remote_address(const char *unit,
@@ -17,6 +21,7 @@ int config_parse_netlog_remote_address(const char *unit,
                                        void *data,
                                        void *userdata) {
         Manager *m = userdata;
+        char *e;
         int r;
 
         assert(filename);
@@ -27,6 +32,43 @@ int config_parse_netlog_remote_address(const char *unit,
 
         r = socket_address_parse(&m->address, rvalue);
         if (r < 0) {
+                struct addrinfo hints = {
+                        .ai_flags = AI_NUMERICSERV|AI_ADDRCONFIG,
+                        .ai_socktype = SOCK_DGRAM,
+                        .ai_family = socket_ipv6_is_supported() ? AF_UNSPEC : AF_INET,
+                };
+               uint32_t u;
+
+                e = strchr(rvalue, ':');
+                if (e) {
+                        r = safe_atou(e+1, &u);
+                        if (r < 0)
+                                return r;
+
+                        if (u <= 0 || u > 0xFFFF)
+                                return -EINVAL;
+
+                        m->port = u;
+                        m->server_name = strndupa(rvalue, e-rvalue);
+                        if (!m->server_name)
+                                return log_oom();
+
+                        log_debug("Remote server='%s' port: '%u'...", m->server_name, u);
+
+                        /* Tell the resolver to reread /etc/resolv.conf, in
+                         * case it changed. */
+                        res_init();
+
+                        log_debug("Resolving %s...", m->server_name);
+
+                        r = sd_resolve_getaddrinfo(m->resolve, &m->resolve_query, m->server_name, NULL, &hints, manager_resolve_handler, m);
+                        if (r < 0)
+                                return log_error_errno(r, "Failed to create resolver: %m");
+
+                        m->resolving = true;
+                        return 0;
+                }
+
                 log_syntax(unit, LOG_WARNING, filename, line, -r, "Failed to parse '%s=%s', ignoring.", lvalue, rvalue);
                 return 0;
         }

src/netlog/netlog-manager.c

@@ -426,6 +426,9 @@ int manager_connect(Manager *m) {
 
         assert(m);
 
+        if (m->resolving)
+                return 0;
+
         manager_disconnect(m);
 
         log_debug("Connecting network ...");
@@ -469,6 +472,8 @@ void manager_disconnect(Manager *m) {
 
         log_debug("Disconnecting network ...");
 
+        m->resolve_query = sd_resolve_query_unref(m->resolve_query);
+
         close_journal_input(m);
 
         manager_close_network_socket(m);
@@ -481,6 +486,59 @@ void manager_disconnect(Manager *m) {
         sd_notifyf(false, "STATUS=Idle.");
 }
 
+int manager_resolve_handler(sd_resolve_query *q, int ret, const struct addrinfo *ai, void *userdata) {
+        Manager *m = userdata;
+
+        assert(q);
+        assert(m);
+        assert(m->server_name);
+
+        log_debug("Resolve %s: %s", m->server_name, gai_strerror(ret));
+
+        m->resolve_query = sd_resolve_query_unref(m->resolve_query);
+
+        if (ret != 0) {
+                log_debug("Failed to resolve %s: %s", m->server_name, gai_strerror(ret));
+
+                /* Try next host */
+                return manager_connect(m);
+        }
+
+        for (; ai; ai = ai->ai_next) {
+                _cleanup_free_ char *pretty = NULL;
+
+                assert(ai->ai_addr);
+                assert(ai->ai_addrlen >= offsetof(struct sockaddr, sa_data));
+
+                if (!IN_SET(ai->ai_addr->sa_family, AF_INET, AF_INET6)) {
+                        log_warning("Unsuitable address protocol for %s", m->server_name);
+                        continue;
+                }
+
+                m->socklen = ai->ai_addrlen;
+                memcpy(&m->address.sockaddr, (const union sockaddr_union*) ai->ai_addr, ai->ai_addrlen);
+
+                if (ai->ai_addr->sa_family == AF_INET6)
+                        m->address.sockaddr.in6.sin6_port = htobe16((uint16_t) m->port);
+                else
+                        m->address.sockaddr.in.sin_port = htobe16((uint16_t) m->port);
+
+                sockaddr_pretty(&m->address.sockaddr.sa, m->socklen, true, true, &pretty);
+                m->resolving = false;
+
+                log_debug("Resolved address %s for %s.", pretty, m->server_name);
+        }
+
+        if (!IN_SET(m->address.sockaddr.sa.sa_family, AF_INET, AF_INET6)) {
+                log_error("Failed to find suitable address for host %s.", m->server_name);
+
+                /* Try next host */
+                return manager_connect(m);
+        }
+
+        return manager_connect(m);
+}
+
 static int manager_network_event_handler(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
         Manager *m = userdata;
         bool connected, online;
@@ -551,6 +609,8 @@ void manager_free(Manager *m) {
         free(m->dir);
         free(m->namespace);
 
+        sd_resolve_unref(m->resolve);
+
         sd_event_source_unref(m->network_event_source);
         sd_network_monitor_unref(m->network_monitor);
 
@@ -586,7 +646,7 @@ int manager_new(const char *state_file, const char *cursor, Manager **ret) {
                 },
             };
 
-        socket_address_parse(&m->address, "239.0.0.1:6000");
+        (void) socket_address_parse(&m->address, "239.0.0.1:6000");
 
         if (!m->state_file)
                 return log_oom();
@@ -607,6 +667,14 @@ int manager_new(const char *state_file, const char *cursor, Manager **ret) {
 
         sd_event_set_watchdog(m->event, true);
 
+        r = sd_resolve_default(&m->resolve);
+        if (r < 0)
+                return r;
+
+        r = sd_resolve_attach_event(m->resolve, m->event, 0);
+        if (r < 0)
+                return r;
+
         r = manager_network_monitor_listen(m);
         if (r < 0)
                 return r;

src/netlog/netlog-manager.h

@@ -7,6 +7,7 @@
 #include "netlog-dtls.h"
 #include "netlog-tls.h"
 #include "sd-network.h"
+#include "sd-resolve.h"
 #include "socket-util.h"
 #include "ratelimit.h"
 
@@ -31,7 +32,9 @@ typedef enum SysLogTransmissionLogFormat {
 typedef struct Manager Manager;
 
 struct Manager {
+        sd_resolve *resolve;
         sd_event *event;
+
         sd_event_source *event_journal_input;
         uint64_t timeout;
         usec_t retry_interval;
@@ -48,10 +51,19 @@ struct Manager {
 
         RateLimit ratelimit;
 
+        /* peer */
+        sd_resolve_query *resolve_query;
+        sd_event_source *event_receive;
+        sd_event_source *event_timeout;
+
         int socket;
 
         /* Multicast UDP address */
         SocketAddress address;
+        socklen_t socklen;
+        uint32_t port;
+
+        char *server_name;
 
         /* journal  */
         int journal_watch_fd;
@@ -79,6 +91,7 @@ struct Manager {
         bool keep_alive;
         bool no_delay;
         bool connected;
+        bool resolving;
 
         unsigned keep_alive_cnt;
 
@@ -101,6 +114,8 @@ void manager_close_network_socket(Manager *m);
 int manager_open_network_socket(Manager *m);
 int manager_network_connect_socket(Manager *m);
 
+int manager_resolve_handler(sd_resolve_query *q, int ret, const struct addrinfo *ai, void *userdata);
+
 int manager_push_to_network(Manager *m,
                             int severity,
                             int facility,