BUG/MEDIUM: dns/server: fix incomatibility between SRV resolution and server state file

Server state file has no indication that a server is currently managed
by a DNS SRV resolution.
And thus, both feature (DNS SRV resolution and server state), when used
together, does not provide the expected behavior: a smooth experience...

This patch introduce the "SRV record name" in the server state file and
loads and applies it if found and wherever required.

This patch applies to haproxy-dev branch only. For backport, a specific patch
is provided for 1.8.

doc/management.txt

@@ -2130,6 +2130,7 @@ show servers state [<backend>]
                                   configuration.
      srv_fqdn:                    Server FQDN.
      srv_port:                    Server port.
+     srvrecord:                   DNS SRV record associated to this SRV.
 
 show sess
   Dump all known sessions. Avoid doing this on slow connections as this can

include/types/server.h

@@ -126,10 +126,11 @@ enum srv_initaddr {
     "bk_f_forced_id "             \
     "srv_f_forced_id "            \
     "srv_fqdn "                   \
-    "srv_port"
+    "srv_port "                   \
+    "srvrecord"
 
-#define SRV_STATE_FILE_MAX_FIELDS 19
+#define SRV_STATE_FILE_MAX_FIELDS 20
-#define SRV_STATE_FILE_NB_FIELDS_VERSION_1 18
+#define SRV_STATE_FILE_NB_FIELDS_VERSION_1 19
 #define SRV_STATE_LINE_MAXLEN 512
 
 /* server flags -- 32 bits */

src/proxy.c

@@ -1429,6 +1429,7 @@ static int dump_servers_state(struct stream_interface *si, struct buffer *buf)
 	char srv_addr[INET6_ADDRSTRLEN + 1];
 	time_t srv_time_since_last_change;
 	int bk_f_forced_id, srv_f_forced_id;
+	char *srvrecord;
 
 	/* we don't want to report any state if the backend is not enabled on this process */
 	if (px->bind_proc && !(px->bind_proc & pid_bit))
@@ -1458,18 +1459,23 @@ static int dump_servers_state(struct stream_interface *si, struct buffer *buf)
 		bk_f_forced_id = px->options & PR_O_FORCED_ID ? 1 : 0;
 		srv_f_forced_id = srv->flags & SRV_F_FORCED_ID ? 1 : 0;
 
+		srvrecord = NULL;
+		if (srv->srvrq && srv->srvrq->name)
+			srvrecord = srv->srvrq->name;
+
 		chunk_appendf(buf,
 				"%d %s "
 				"%d %s %s "
 				"%d %d %d %d %ld "
 				"%d %d %d %d %d "
-				"%d %d %s %u"
+				"%d %d %s %u %s"
 				"\n",
 				px->uuid, px->id,
 				srv->puid, srv->id, srv_addr,
 				srv->cur_state, srv->cur_admin, srv->uweight, srv->iweight, (long int)srv_time_since_last_change,
 				srv->check.status, srv->check.result, srv->check.health, srv->check.state, srv->agent.state,
-				bk_f_forced_id, srv_f_forced_id, srv->hostname ? srv->hostname : "-", srv->svc_port);
+				bk_f_forced_id, srv_f_forced_id, srv->hostname ? srv->hostname : "-", srv->svc_port,
+				srvrecord ? srvrecord : "-");
 		if (ci_putchk(si_ic(si), &trash) == -1) {
 			si_applet_cant_put(si);
 			return 0;

src/server.c

@@ -2758,6 +2758,7 @@ static void srv_update_state(struct server *srv, int version, char **params)
 	const char *fqdn;
 	const char *port_str;
 	unsigned int port;
+	char *srvrecord;
 
 	fqdn = NULL;
 	port = 0;
@@ -2781,6 +2782,7 @@ static void srv_update_state(struct server *srv, int version, char **params)
 			 * srv_f_forced_id:      params[12]
 			 * srv_fqdn:             params[13]
 			 * srv_port:             params[14]
+			 * srvrecord:            params[15]
 			 */
 
 			/* validating srv_op_state */
@@ -2913,6 +2915,13 @@ static void srv_update_state(struct server *srv, int version, char **params)
 				}
 			}
 
+			/* SRV record
+			 * NOTE: in HAProxy, SRV records must start with an underscore '_'
+			 */
+			srvrecord = params[15];
+			if (srvrecord && *srvrecord != '_')
+				srvrecord = NULL;
+
 			/* don't apply anything if one error has been detected */
 			if (msg->data)
 				goto out;
@@ -3045,6 +3054,48 @@ static void srv_update_state(struct server *srv, int version, char **params)
 					}
 				}
 			}
+			/* If all the conditions below are validated, this means
+			 * we're evaluating a server managed by SRV resolution
+			 */
+			else if (fqdn && !srv->hostname && srvrecord) {
+				int res;
+
+				/* we can't apply previous state if SRV record has changed */
+				if (srv->srvrq && strcmp(srv->srvrq->name, srvrecord) != 0) {
+					chunk_appendf(msg, ", SRV record mismatch between configuration ('%s') and state file ('%s) for server '%s'. Previous state not applied", srv->srvrq->name, srvrecord, srv->id);
+					HA_SPIN_UNLOCK(SERVER_LOCK, &srv->lock);
+					goto out;
+				}
+
+				/* create or find a SRV resolution for this srv record */
+				if (srv->srvrq == NULL && (srv->srvrq = find_srvrq_by_name(srvrecord, srv->proxy)) == NULL)
+					srv->srvrq = new_dns_srvrq(srv, srvrecord);
+				if (srv->srvrq == NULL) {
+					chunk_appendf(msg, ", can't create or find SRV resolution '%s' for server '%s'", srvrecord, srv->id);
+					HA_SPIN_UNLOCK(SERVER_LOCK, &srv->lock);
+					goto out;
+				}
+
+				/* prepare DNS resolution for this server */
+				res = srv_prepare_for_resolution(srv, fqdn);
+				if (res == -1) {
+					chunk_appendf(msg, ", can't allocate memory for DNS resolution for server '%s'", srv->id);
+					HA_SPIN_UNLOCK(SERVER_LOCK, &srv->lock);
+					goto out;
+				}
+
+				/* configure check.port accordingly */
+				if ((srv->check.state & CHK_ST_CONFIGURED) &&
+				    !(srv->flags & SRV_F_CHECKPORT))
+					srv->check.port = port;
+
+				/* Unset SRV_F_MAPPORTS for SRV records.
+				 * SRV_F_MAPPORTS is unfortunately set by parse_server()
+				 * because no ports are provided in the configuration file.
+				 * This is because HAProxy will use the port found into the SRV record.
+				 */
+				srv->flags &= ~SRV_F_MAPPORTS;
+			}
 
 			if (port_str)
 				srv->svc_port = port;
@@ -3301,6 +3352,7 @@ void apply_server_state(void)
 							 * srv_f_forced_id:      params[16] => srv_params[12]
 							 * srv_fqdn:             params[17] => srv_params[13]
 							 * srv_port:             params[18] => srv_params[14]
+							 * srvrecord:            params[19] => srv_params[15]
 							 */
 							if (arg >= 4) {
 								srv_params[srv_arg] = cur;