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 "logger.h"
  24 #include "node.h"
  25 #include "xalloc.h"
  26
  27 static void make_new_connection() {
  28         /* Select a random node we haven't connected to yet. */
  29         int count = 0;
  30
  31         for splay_each(node_t, n, node_tree) {
  32                 if(n == myself || n->connection || !(n->status.has_address || n->status.reachable)) {
  33                         continue;
  34                 }
  35
  36                 count++;
  37         }
  38
  39         if(!count) {
  40                 return;
  41         }
  42
  43         int r = rand() % count;
  44
  45         for splay_each(node_t, n, node_tree) {
  46                 if(n == myself || n->connection || !(n->status.has_address || n->status.reachable)) {
  47                         continue;
  48                 }
  49
  50                 if(r--) {
  51                         continue;
  52                 }
  53
  54                 bool found = false;
  55
  56                 for list_each(outgoing_t, outgoing, outgoing_list) {
  57                         if(outgoing->node == n) {
  58                                 found = true;
  59                                 break;
  60                         }
  61                 }
  62
  63                 if(!found) {
  64                         logger(DEBUG_CONNECTIONS, LOG_INFO, "Autoconnecting to %s", n->name);
  65                         outgoing_t *outgoing = xzalloc(sizeof(*outgoing));
  66                         outgoing->node = n;
  67                         list_insert_tail(outgoing_list, outgoing);
  68                         setup_outgoing_connection(outgoing, false);
  69                 }
  70
  71                 break;
  72         }
  73 }
  74
  75 static void connect_to_unreachable() {
  76         /* Select a random known node. The rationale is that if there are many
  77          * reachable nodes, and only a few unreachable nodes, we don't want all
  78          * reachable nodes to try to connect to the unreachable ones at the
  79          * same time. This way, we back off automatically. Conversely, if there
  80          * are only a few reachable nodes, and many unreachable ones, we're
  81          * going to try harder to connect to them. */
  82
  83         int r = rand() % node_tree->count;
  84
  85         for splay_each(node_t, n, node_tree) {
  86                 if(r--) {
  87                         continue;
  88                 }
  89
  90                 /* Is it unreachable and do we know an address for it? If not, return. */
  91                 if(n == myself || n->connection || n->status.reachable || !n->status.has_address) {
  92                         return;
  93                 }
  94
  95                 /* Are we already trying to make an outgoing connection to it? If so, return. */
  96                 for list_each(outgoing_t, outgoing, outgoing_list) {
  97                         if(outgoing->node == n) {
  98                                 return;
  99                         }
 100                 }
 101
 102                 logger(DEBUG_CONNECTIONS, LOG_INFO, "Autoconnecting to %s", n->name);
 103                 outgoing_t *outgoing = xzalloc(sizeof(*outgoing));
 104                 outgoing->node = n;
 105                 list_insert_tail(outgoing_list, outgoing);
 106                 setup_outgoing_connection(outgoing, false);
 107
 108                 return;
 109         }
 110 }
 111
 112 static void drop_superfluous_outgoing_connection() {
 113         /* Choose a random outgoing connection to a node that has at least one other connection. */
 114         int count = 0;
 115
 116         for list_each(connection_t, c, connection_list) {
 117                 if(!c->edge || !c->outgoing || !c->node || c->node->edge_tree->count < 2) {
 118                         continue;
 119                 }
 120
 121                 count++;
 122         }
 123
 124         if(!count) {
 125                 return;
 126         }
 127
 128         int r = rand() % count;
 129
 130         for list_each(connection_t, c, connection_list) {
 131                 if(!c->edge || !c->outgoing || !c->node || c->node->edge_tree->count < 2) {
 132                         continue;
 133                 }
 134
 135                 if(r--) {
 136                         continue;
 137                 }
 138
 139                 logger(DEBUG_CONNECTIONS, LOG_INFO, "Autodisconnecting from %s", c->name);
 140                 list_delete(outgoing_list, c->outgoing);
 141                 c->outgoing = NULL;
 142                 terminate_connection(c, c->edge);
 143                 break;
 144         }
 145 }
 146
 147 static void drop_superfluous_pending_connections() {
 148         for list_each(outgoing_t, o, outgoing_list) {
 149                 /* Only look for connections that are waiting to be retried later. */
 150                 bool found = false;
 151
 152                 for list_each(connection_t, c, connection_list) {
 153                         if(c->outgoing == o) {
 154                                 found = true;
 155                                 break;
 156                         }
 157                 }
 158
 159                 if(found) {
 160                         continue;
 161                 }
 162
 163                 logger(DEBUG_CONNECTIONS, LOG_INFO, "Cancelled outgoing connection to %s", o->node->name);
 164                 list_delete_node(outgoing_list, node);
 165         }
 166 }
 167
 168 void do_autoconnect() {
 169         /* Count number of active connections. */
 170         int nc = 0;
 171
 172         for list_each(connection_t, c, connection_list) {
 173                 if(c->edge) {
 174                         nc++;
 175                 }
 176         }
 177
 178         /* Less than 3 connections? Eagerly try to make a new one. */
 179         if(nc < 3) {
 180                 make_new_connection();
 181                 return;
 182         }
 183
 184         /* More than 3 connections? See if we can get rid of a superfluous one. */
 185         if(nc > 3) {
 186                 drop_superfluous_outgoing_connection();
 187         }
 188
 189         /* Drop pending outgoing connections from the outgoing list. */
 190         drop_superfluous_pending_connections();
 191
 192         /* Check if there are unreachable nodes that we should try to connect to. */
 193         connect_to_unreachable();
 194 }