tinc-vpn.org Git - tinc/blob - src/autoconnect.c

   1 /*
   2     autoconnect.c -- automatic connection establishment
   3     Copyright (C) 2017 Guus Sliepen <guus@tinc-vpn.org>
   4
   5     This program is free software; you can redistribute it and/or modify
   6     it under the terms of the GNU General Public License as published by
   7     the Free Software Foundation; either version 2 of the License, or
   8     (at your option) any later version.
   9
  10     This program is distributed in the hope that it will be useful,
  11     but WITHOUT ANY WARRANTY; without even the implied warranty of
  12     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13     GNU General Public License for more details.
  14
  15     You should have received a copy of the GNU General Public License along
  16     with this program; if not, write to the Free Software Foundation, Inc.,
  17     51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  18 */
  19
  20 #include "system.h"
  21
  22 #include "connection.h"
  23 #include "crypto.h"
  24 #include "logger.h"
  25 #include "node.h"
  26 #include "xalloc.h"
  27
  28 static void make_new_connection() {
  29         /* Select a random node we haven't connected to yet. */
  30         uint32_t count = 0;
  31
  32         for splay_each(node_t, n, &node_tree) {
  33                 if(n == myself || n->connection || !(n->status.has_address || n->status.reachable)) {
  34                         continue;
  35                 }
  36
  37                 count++;
  38         }
  39
  40         if(!count) {
  41                 return;
  42         }
  43
  44         uint32_t r = prng(count);
  45
  46         for splay_each(node_t, n, &node_tree) {
  47                 if(n == myself || n->connection || !(n->status.has_address || n->status.reachable)) {
  48                         continue;
  49                 }
  50
  51                 if(r) {
  52                         --r;
  53                         continue;
  54                 }
  55
  56                 bool found = false;
  57
  58                 for list_each(outgoing_t, outgoing, &outgoing_list) {
  59                         if(outgoing->node == n) {
  60                                 found = true;
  61                                 break;
  62                         }
  63                 }
  64
  65                 if(!found) {
  66                         logger(DEBUG_CONNECTIONS, LOG_INFO, "Autoconnecting to %s", n->name);
  67                         outgoing_t *outgoing = xzalloc(sizeof(*outgoing));
  68                         outgoing->node = n;
  69                         list_insert_tail(&outgoing_list, outgoing);
  70                         setup_outgoing_connection(outgoing, false);
  71                 }
  72
  73                 break;
  74         }
  75 }
  76
  77 static void connect_to_unreachable() {
  78         /* Select a random known node. The rationale is that if there are many
  79          * reachable nodes, and only a few unreachable nodes, we don't want all
  80          * reachable nodes to try to connect to the unreachable ones at the
  81          * same time. This way, we back off automatically. Conversely, if there
  82          * are only a few reachable nodes, and many unreachable ones, we're
  83          * going to try harder to connect to them. */
  84
  85         uint32_t r = prng(node_tree.count);
  86
  87         for splay_each(node_t, n, &node_tree) {
  88                 if(r--) {
  89                         continue;
  90                 }
  91
  92                 /* Is it unreachable and do we know an address for it? If not, return. */
  93                 if(n == myself || n->connection || n->status.reachable || !n->status.has_address) {
  94                         return;
  95                 }
  96
  97                 /* Are we already trying to make an outgoing connection to it? If so, return. */
  98                 for list_each(outgoing_t, outgoing, &outgoing_list) {
  99                         if(outgoing->node == n) {
 100                                 return;
 101                         }
 102                 }
 103
 104                 logger(DEBUG_CONNECTIONS, LOG_INFO, "Autoconnecting to %s", n->name);
 105                 outgoing_t *outgoing = xzalloc(sizeof(*outgoing));
 106                 outgoing->node = n;
 107                 list_insert_tail(&outgoing_list, outgoing);
 108                 setup_outgoing_connection(outgoing, false);
 109
 110                 return;
 111         }
 112 }
 113
 114 static void drop_superfluous_outgoing_connection() {
 115         /* Choose a random outgoing connection to a node that has at least one other connection. */
 116         uint32_t count = 0;
 117
 118         for list_each(connection_t, c, &connection_list) {
 119                 if(!c->edge || !c->outgoing || !c->node || c->node->edge_tree.count < 2) {
 120                         continue;
 121                 }
 122
 123                 count++;
 124         }
 125
 126         if(!count) {
 127                 return;
 128         }
 129
 130         uint32_t r = prng(count);
 131
 132         for list_each(connection_t, c, &connection_list) {
 133                 if(!c->edge || !c->outgoing || !c->node || c->node->edge_tree.count < 2) {
 134                         continue;
 135                 }
 136
 137                 if(r--) {
 138                         continue;
 139                 }
 140
 141                 logger(DEBUG_CONNECTIONS, LOG_INFO, "Autodisconnecting from %s", c->name);
 142                 list_delete(&outgoing_list, c->outgoing);
 143                 c->outgoing = NULL;
 144                 terminate_connection(c, c->edge);
 145                 break;
 146         }
 147 }
 148
 149 static void drop_superfluous_pending_connections() {
 150         for list_each(outgoing_t, o, &outgoing_list) {
 151                 /* Only look for connections that are waiting to be retried later. */
 152                 bool found = false;
 153
 154                 for list_each(connection_t, c, &connection_list) {
 155                         if(c->outgoing == o) {
 156                                 found = true;
 157                                 break;
 158                         }
 159                 }
 160
 161                 if(found) {
 162                         continue;
 163                 }
 164
 165                 logger(DEBUG_CONNECTIONS, LOG_INFO, "Cancelled outgoing connection to %s", o->node->name);
 166                 list_delete_node(&outgoing_list, node);
 167         }
 168 }
 169
 170 void do_autoconnect() {
 171         /* Count number of active connections. */
 172         uint32_t nc = 0;
 173
 174         for list_each(connection_t, c, &connection_list) {
 175                 if(c->edge) {
 176                         nc++;
 177                 }
 178         }
 179
 180         /* Less than 3 connections? Eagerly try to make a new one. */
 181         if(nc < 3) {
 182                 make_new_connection();
 183                 return;
 184         }
 185
 186         /* More than 3 connections? See if we can get rid of a superfluous one. */
 187         if(nc > 3) {
 188                 drop_superfluous_outgoing_connection();
 189         }
 190
 191         /* Drop pending outgoing connections from the outgoing list. */
 192         drop_superfluous_pending_connections();
 193
 194         /* Check if there are unreachable nodes that we should try to connect to. */
 195         connect_to_unreachable();
 196 }