Add the StrictSubnets option.

When this option is enabled, tinc will not accept dynamic updates of Subnets
from other nodes, but will only use Subnets read from local host config files
to build its routing table.

doc/tinc.conf.5.in

@@ -308,11 +308,18 @@ specified in the configuration file.
 When this option is used the priority of the tincd process will be adjusted.
 Increasing the priority may help to reduce latency and packet loss on the VPN.
 
-.It Va TunnelServer Li = yes | no Po no Pc Bq experimental
+.It Va StrictSubnets Li = yes | no Po no Pc Bq experimental
-When this option is enabled tinc will no longer forward information between other tinc daemons,
+When this option is enabled tinc will only use Subnet statements which are
-and will only allow nodes and subnets on the VPN which are present in the
+present in the host config files in the local
 .Pa @sysconfdir@/tinc/ Ns Ar NETNAME Ns Pa /hosts/
 directory.
+
+.It Va TunnelServer Li = yes | no Po no Pc Bq experimental
+When this option is enabled tinc will no longer forward information between other tinc daemons,
+and will only allow connections with nodes for which host config files are present in the local
+.Pa @sysconfdir@/tinc/ Ns Ar NETNAME Ns Pa /hosts/
+directory.
+Setting this options also implicitly sets StrictSubnets.
 .El
 
 .Sh HOST CONFIGURATION FILES

doc/tinc.texi

@@ -928,11 +928,18 @@ specified in the configuration file.
 When this option is used the priority of the tincd process will be adjusted.
 Increasing the priority may help to reduce latency and packet loss on the VPN.
 
+@cindex StrictSubnets
+@item StrictSubnets <yes|no> (no) [experimental]
+When this option is enabled tinc will only use Subnet statements which are
+present in the host config files in the local
+@file{@value{sysconfdir}/tinc/@var{netname}/hosts/} directory.
+
 @cindex TunnelServer
 @item TunnelServer = <yes|no> (no) [experimental]
 When this option is enabled tinc will no longer forward information between other tinc daemons,
-and will only allow nodes and subnets on the VPN which are present in the
+and will only allow connections with nodes for which host config files are present in the local
 @file{@value{sysconfdir}/tinc/@var{netname}/hosts/} directory.
+Setting this options also implicitly sets StrictSubnets.
 
 @end table
 

src/net.c

@@ -68,7 +68,7 @@ static void purge(void) {
 			for(snode = n->subnet_tree->head; snode; snode = snext) {
 				snext = snode->next;
 				s = snode->data;
-				if(!tunnelserver)
+				if(!strictsubnets)
 					send_del_subnet(broadcast, s);
 				subnet_del(n, s);
 			}

src/net_setup.c

@@ -339,7 +339,9 @@ bool setup_myself(void) {
 	if(myself->options & OPTION_TCPONLY)
 		myself->options |= OPTION_INDIRECT;
 
+	get_config_bool(lookup_config(config_tree, "StrictSubnets"), &strictsubnets);
 	get_config_bool(lookup_config(config_tree, "TunnelServer"), &tunnelserver);
+	strictsubnets |= tunnelserver;
 
 	if(get_config_string(lookup_config(config_tree, "Mode"), &mode)) {
 		if(!strcasecmp(mode, "router"))
@@ -485,7 +487,7 @@ bool setup_myself(void) {
 
 	graph();
 
-	if(tunnelserver)
+	if(strictsubnets)
 		load_all_subnets();
 
 	/* Open device */

src/protocol.c

@@ -29,6 +29,7 @@
 #include "xalloc.h"
 
 bool tunnelserver = false;
+bool strictsubnets = false;
 
 /* Jumptable for the request handlers */
 

src/protocol.h

@@ -53,6 +53,7 @@ typedef struct past_request_t {
 } past_request_t;
 
 extern bool tunnelserver;
+extern bool strictsubnets;
 
 /* Maximum size of strings in a request.
  * scanf terminates %2048s with a NUL character,

src/protocol_subnet.c

@@ -112,6 +112,13 @@ bool add_subnet_h(connection_t *c) {
 		return true;
 	}
 
+	/* Ignore if strictsubnets is true, but forward it to others */
+
+	if(strictsubnets) {
+		forward_request(c);
+		return true;
+	}
+
 	/* If everything is correct, add the subnet to the list of the owner */
 
 	*(new = new_subnet()) = s;
@@ -198,6 +205,8 @@ bool del_subnet_h(connection_t *c) {
 	if(!find) {
 		ifdebug(PROTOCOL) logger(LOG_WARNING, "Got %s from %s (%s) for %s which does not appear in his subnet tree",
 				   "DEL_SUBNET", c->name, c->hostname, name);
+		if(strictsubnets)
+			forward_request(c);
 		return true;
 	}
 
@@ -216,6 +225,8 @@ bool del_subnet_h(connection_t *c) {
 	/* Tell the rest */
 
 	forward_request(c);
+	if(strictsubnets)
+		return true;
 
 	/* Finally, delete it. */