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                         continue;
  53                 }
  54
  55                 bool found = false;
  56
  57                 for list_each(outgoing_t, outgoing, &outgoing_list) {
  58                         if(outgoing->node == n) {
  59                                 found = true;
  60                                 break;
  61                         }
  62                 }
  63
  64                 if(!found) {
  65                         logger(DEBUG_CONNECTIONS, LOG_INFO, "Autoconnecting to %s", n->name);
  66                         outgoing_t *outgoing = xzalloc(sizeof(*outgoing));
  67                         outgoing->node = n;
  68                         list_insert_tail(&outgoing_list, outgoing);
  69                         setup_outgoing_connection(outgoing, false);
  70                 }
  71
  72                 break;
  73         }
  74 }
  75
  76 static void connect_to_unreachable() {
  77         /* Select a random known node. The rationale is that if there are many
  78          * reachable nodes, and only a few unreachable nodes, we don't want all
  79          * reachable nodes to try to connect to the unreachable ones at the
  80          * same time. This way, we back off automatically. Conversely, if there
  81          * are only a few reachable nodes, and many unreachable ones, we're
  82          * going to try harder to connect to them. */
  83
  84         uint32_t r = prng(node_tree.count);
  85
  86         for splay_each(node_t, n, &node_tree) {
  87                 if(r--) {
  88                         continue;
  89                 }
  90
  91                 /* Is it unreachable and do we know an address for it? If not, return. */
  92                 if(n == myself || n->connection || n->status.reachable || !n->status.has_address) {
  93                         return;
  94                 }
  95
  96                 /* Are we already trying to make an outgoing connection to it? If so, return. */
  97                 for list_each(outgoing_t, outgoing, &outgoing_list) {
  98                         if(outgoing->node == n) {
  99                                 return;
 100                         }
 101                 }
 102
 103                 logger(DEBUG_CONNECTIONS, LOG_INFO, "Autoconnecting to %s", n->name);
 104                 outgoing_t *outgoing = xzalloc(sizeof(*outgoing));
 105                 outgoing->node = n;
 106                 list_insert_tail(&outgoing_list, outgoing);
 107                 setup_outgoing_connection(outgoing, false);
 108
 109                 return;
 110         }
 111 }
 112
 113 static void drop_superfluous_outgoing_connection() {
 114         /* Choose a random outgoing connection to a node that has at least one other connection. */
 115         uint32_t count = 0;
 116
 117         for list_each(connection_t, c, &connection_list) {
 118                 if(!c->edge || !c->outgoing || !c->node || c->node->edge_tree.count < 2) {
 119                         continue;
 120                 }
 121
 122                 count++;
 123         }
 124
 125         if(!count) {
 126                 return;
 127         }
 128
 129         uint32_t r = prng(count);
 130
 131         for list_each(connection_t, c, &connection_list) {
 132                 if(!c->edge || !c->outgoing || !c->node || c->node->edge_tree.count < 2) {
 133                         continue;
 134                 }
 135
 136                 if(r--) {
 137                         continue;
 138                 }
 139
 140                 logger(DEBUG_CONNECTIONS, LOG_INFO, "Autodisconnecting from %s", c->name);
 141                 list_delete(&outgoing_list, c->outgoing);
 142                 c->outgoing = NULL;
 143                 terminate_connection(c, c->edge);
 144                 break;
 145         }
 146 }
 147
 148 static void drop_superfluous_pending_connections() {
 149         for list_each(outgoing_t, o, &outgoing_list) {
 150                 /* Only look for connections that are waiting to be retried later. */
 151                 bool found = false;
 152
 153                 for list_each(connection_t, c, &connection_list) {
 154                         if(c->outgoing == o) {
 155                                 found = true;
 156                                 break;
 157                         }
 158                 }
 159
 160                 if(found) {
 161                         continue;
 162                 }
 163
 164                 logger(DEBUG_CONNECTIONS, LOG_INFO, "Cancelled outgoing connection to %s", o->node->name);
 165                 list_delete_node(&outgoing_list, node);
 166         }
 167 }
 168
 169 void do_autoconnect() {
 170         /* Count number of active connections. */
 171         uint32_t nc = 0;
 172
 173         for list_each(connection_t, c, &connection_list) {
 174                 if(c->edge) {
 175                         nc++;
 176                 }
 177         }
 178
 179         /* Less than 3 connections? Eagerly try to make a new one. */
 180         if(nc < 3) {
 181                 make_new_connection();
 182                 return;
 183         }
 184
 185         /* More than 3 connections? See if we can get rid of a superfluous one. */
 186         if(nc > 3) {
 187                 drop_superfluous_outgoing_connection();
 188         }
 189
 190         /* Drop pending outgoing connections from the outgoing list. */
 191         drop_superfluous_pending_connections();
 192
 193         /* Check if there are unreachable nodes that we should try to connect to. */
 194         connect_to_unreachable();
 195 }