tinc/src/subnet.c

/*
    subnet.c -- handle subnet lookups and lists
    Copyright (C) 2000-2019 Guus Sliepen <guus@tinc-vpn.org>,
                  2000-2005 Ivo Timmermans

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License along
    with this program; if not, write to the Free Software Foundation, Inc.,
    51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/

#include "system.h"

#include "avl_tree.h"
#include "device.h"
#include "logger.h"
#include "net.h"
#include "netutl.h"
#include "node.h"
#include "process.h"
#include "subnet.h"
#include "utils.h"
#include "xalloc.h"

/* lists type of subnet */

avl_tree_t *subnet_tree;

/* Subnet lookup cache */

static ipv4_t cache_ipv4_address[2];
static subnet_t *cache_ipv4_subnet[2];
static bool cache_ipv4_valid[2];
static int cache_ipv4_slot;

static ipv6_t cache_ipv6_address[2];
static subnet_t *cache_ipv6_subnet[2];
static bool cache_ipv6_valid[2];
static int cache_ipv6_slot;

static mac_t cache_mac_address[2];
static subnet_t *cache_mac_subnet[2];
static bool cache_mac_valid[2];
static int cache_mac_slot;

void subnet_cache_flush(void) {
	cache_ipv4_valid[0] = cache_ipv4_valid[1] = false;
	cache_ipv6_valid[0] = cache_ipv6_valid[1] = false;
	cache_mac_valid[0] = cache_mac_valid[1] = false;
}

/* Subnet comparison */

static int subnet_compare_mac(const subnet_t *a, const subnet_t *b) {
	int result;

	result = memcmp(&a->net.mac.address, &b->net.mac.address, sizeof(mac_t));

	if(result) {
		return result;
	}

	result = a->weight - b->weight;

	if(result || !a->owner || !b->owner) {
		return result;
	}

	return strcmp(a->owner->name, b->owner->name);
}

static int subnet_compare_ipv4(const subnet_t *a, const subnet_t *b) {
	int result;

	result = b->net.ipv4.prefixlength - a->net.ipv4.prefixlength;

	if(result) {
		return result;
	}

	result = memcmp(&a->net.ipv4.address, &b->net.ipv4.address, sizeof(ipv4_t));

	if(result) {
		return result;
	}

	result = a->weight - b->weight;

	if(result || !a->owner || !b->owner) {
		return result;
	}

	return strcmp(a->owner->name, b->owner->name);
}

static int subnet_compare_ipv6(const subnet_t *a, const subnet_t *b) {
	int result;

	result = b->net.ipv6.prefixlength - a->net.ipv6.prefixlength;

	if(result) {
		return result;
	}

	result = memcmp(&a->net.ipv6.address, &b->net.ipv6.address, sizeof(ipv6_t));

	if(result) {
		return result;
	}

	result = a->weight - b->weight;

	if(result || !a->owner || !b->owner) {
		return result;
	}

	return strcmp(a->owner->name, b->owner->name);
}

int subnet_compare(const subnet_t *a, const subnet_t *b) {
	int result;

	result = a->type - b->type;

	if(result) {
		return result;
	}

	switch(a->type) {
	case SUBNET_MAC:
		return subnet_compare_mac(a, b);

	case SUBNET_IPV4:
		return subnet_compare_ipv4(a, b);

	case SUBNET_IPV6:
		return subnet_compare_ipv6(a, b);

	default:
		logger(LOG_ERR, "subnet_compare() was called with unknown subnet type %d, exitting!",
		       a->type);
		exit(0);
	}

	return 0;
}

/* Initialising trees */

void init_subnets(void) {
	subnet_tree = avl_alloc_tree((avl_compare_t) subnet_compare, (avl_action_t) free_subnet);

	subnet_cache_flush();
}

void exit_subnets(void) {
	avl_delete_tree(subnet_tree);
}

avl_tree_t *new_subnet_tree(void) {
	return avl_alloc_tree((avl_compare_t) subnet_compare, NULL);
}

void free_subnet_tree(avl_tree_t *subnet_tree) {
	avl_delete_tree(subnet_tree);
}

/* Allocating and freeing space for subnets */

subnet_t *new_subnet(void) {
	return xmalloc_and_zero(sizeof(subnet_t));
}

void free_subnet(subnet_t *subnet) {
	free(subnet);
}

/* Adding and removing subnets */

void subnet_add(node_t *n, subnet_t *subnet) {
	subnet->owner = n;

	avl_insert(subnet_tree, subnet);
	avl_insert(n->subnet_tree, subnet);

	subnet_cache_flush();
}

void subnet_del(node_t *n, subnet_t *subnet) {
	avl_delete(n->subnet_tree, subnet);
	avl_delete(subnet_tree, subnet);

	subnet_cache_flush();
}

/* Ascii representation of subnets */

bool str2net(subnet_t *subnet, const char *subnetstr) {
	char str[1024];
	strncpy(str, subnetstr, sizeof(str));
	str[sizeof(str) - 1] = 0;
	int consumed;

	int weight = 10;
	char *weight_separator = strchr(str, '#');

	if(weight_separator) {
		char *weight_str = weight_separator + 1;

		if(sscanf(weight_str, "%d%n", &weight, &consumed) < 1) {
			return false;
		}

		if(weight_str[consumed]) {
			return false;
		}

		*weight_separator = 0;
	}

	int prefixlength = -1;
	char *prefixlength_separator = strchr(str, '/');

	if(prefixlength_separator) {
		char *prefixlength_str = prefixlength_separator + 1;

		if(sscanf(prefixlength_str, "%d%n", &prefixlength, &consumed) < 1) {
			return false;
		}

		if(prefixlength_str[consumed]) {
			return false;
		}

		*prefixlength_separator = 0;

		if(prefixlength < 0) {
			return false;
		}
	}

	uint16_t x[8];

	if(sscanf(str, "%hx:%hx:%hx:%hx:%hx:%hx%n", &x[0], &x[1], &x[2], &x[3], &x[4], &x[5], &consumed) >= 6 && !str[consumed]) {
		/*
		   Normally we should check that each part has two digits to prevent ambiguities.
		   However, in old tinc versions net2str() will aggressively return MAC addresses with one-digit parts,
		   so we have to accept them otherwise we would be unable to parse ADD_SUBNET messages.
		*/
		if(prefixlength >= 0) {
			return false;
		}

		subnet->type = SUBNET_MAC;
		subnet->weight = weight;

		for(int i = 0; i < 6; i++) {
			subnet->net.mac.address.x[i] = x[i];
		}

		return true;
	}

	if(sscanf(str, "%hu.%hu.%hu.%hu%n", &x[0], &x[1], &x[2], &x[3], &consumed) >= 4 && !str[consumed]) {
		if(prefixlength == -1) {
			prefixlength = 32;
		}

		if(prefixlength > 32) {
			return false;
		}

		subnet->type = SUBNET_IPV4;
		subnet->net.ipv4.prefixlength = prefixlength;
		subnet->weight = weight;

		for(int i = 0; i < 4; i++) {
			if(x[i] > 255) {
				return false;
			}

			subnet->net.ipv4.address.x[i] = x[i];
		}

		return true;
	}

	/* IPv6 */

	char *last_colon = strrchr(str, ':');

	if(last_colon && sscanf(last_colon, ":%hu.%hu.%hu.%hu%n", &x[0], &x[1], &x[2], &x[3], &consumed) >= 4 && !last_colon[consumed]) {
		/* Dotted quad suffix notation, convert to standard IPv6 notation */
		for(int i = 0; i < 4; i++)
			if(x[i] > 255) {
				return false;
			}

		snprintf(last_colon, sizeof(str) - (last_colon - str), ":%02x%02x:%02x%02x", x[0], x[1], x[2], x[3]);
	}

	char *double_colon = strstr(str, "::");

	if(double_colon) {
		/* Figure out how many zero groups we need to expand */
		int zero_group_count = 8;

		for(const char *cur = str; *cur; cur++)
			if(*cur != ':') {
				zero_group_count--;

				while(cur[1] && cur[1] != ':') {
					cur++;
				}
			}

		if(zero_group_count < 1) {
			return false;
		}

		/* Split the double colon in the middle to make room for zero groups */
		double_colon++;
		memmove(double_colon + (zero_group_count * 2 - 1), double_colon, strlen(double_colon) + 1);

		/* Write zero groups in the resulting gap, overwriting the second colon */
		for(int i = 0; i < zero_group_count; i++) {
			memcpy(&double_colon[i * 2], "0:", 2);
		}

		/* Remove any leading or trailing colons */
		if(str[0] == ':') {
			memmove(&str[0], &str[1], strlen(&str[1]) + 1);
		}

		if(str[strlen(str) - 1] == ':') {
			str[strlen(str) - 1] = 0;
		}
	}

	if(sscanf(str, "%hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx%n",
	                &x[0], &x[1], &x[2], &x[3], &x[4], &x[5], &x[6], &x[7], &consumed) >= 8 && !str[consumed]) {
		if(prefixlength == -1) {
			prefixlength = 128;
		}

		if(prefixlength > 128) {
			return false;
		}

		subnet->type = SUBNET_IPV6;
		subnet->net.ipv6.prefixlength = prefixlength;
		subnet->weight = weight;

		for(int i = 0; i < 8; i++) {
			subnet->net.ipv6.address.x[i] = htons(x[i]);
		}

		return true;
	}

	return false;
}

bool net2str(char *netstr, int len, const subnet_t *subnet) {
	if(!netstr || !subnet) {
		logger(LOG_ERR, "net2str() was called with netstr=%p, subnet=%p!", (void *)netstr, (void *)subnet);
		return false;
	}

	switch(subnet->type) {
	case SUBNET_MAC:
		snprintf(netstr, len, "%x:%x:%x:%x:%x:%x#%d",
		         subnet->net.mac.address.x[0],
		         subnet->net.mac.address.x[1],
		         subnet->net.mac.address.x[2],
		         subnet->net.mac.address.x[3],
		         subnet->net.mac.address.x[4],
		         subnet->net.mac.address.x[5],
		         subnet->weight);
		break;

	case SUBNET_IPV4:
		snprintf(netstr, len, "%u.%u.%u.%u/%d#%d",
		         subnet->net.ipv4.address.x[0],
		         subnet->net.ipv4.address.x[1],
		         subnet->net.ipv4.address.x[2],
		         subnet->net.ipv4.address.x[3],
		         subnet->net.ipv4.prefixlength,
		         subnet->weight);
		break;

	case SUBNET_IPV6:
		snprintf(netstr, len, "%x:%x:%x:%x:%x:%x:%x:%x/%d#%d",
		         ntohs(subnet->net.ipv6.address.x[0]),
		         ntohs(subnet->net.ipv6.address.x[1]),
		         ntohs(subnet->net.ipv6.address.x[2]),
		         ntohs(subnet->net.ipv6.address.x[3]),
		         ntohs(subnet->net.ipv6.address.x[4]),
		         ntohs(subnet->net.ipv6.address.x[5]),
		         ntohs(subnet->net.ipv6.address.x[6]),
		         ntohs(subnet->net.ipv6.address.x[7]),
		         subnet->net.ipv6.prefixlength,
		         subnet->weight);
		break;

	default:
		logger(LOG_ERR,
		       "net2str() was called with unknown subnet type %d, exiting!",
		       subnet->type);
		exit(0);
	}

	return true;
}

/* Subnet lookup routines */

subnet_t *lookup_subnet(const node_t *owner, const subnet_t *subnet) {
	return avl_search(owner->subnet_tree, subnet);
}

subnet_t *lookup_subnet_mac(const node_t *owner, const mac_t *address) {
	subnet_t *p, *r = NULL;
	avl_node_t *n;
	int i;

	// Check if this address is cached

	for(i = 0; i < 2; i++) {
		if(!cache_mac_valid[i]) {
			continue;
		}

		if(owner && cache_mac_subnet[i] && cache_mac_subnet[i]->owner != owner) {
			continue;
		}

		if(!memcmp(address, &cache_mac_address[i], sizeof(*address))) {
			return cache_mac_subnet[i];
		}
	}

	// Search all subnets for a matching one

	for(n = owner ? owner->subnet_tree->head : subnet_tree->head; n; n = n->next) {
		p = n->data;

		if(!p || p->type != SUBNET_MAC) {
			continue;
		}

		if(!memcmp(address, &p->net.mac.address, sizeof(*address))) {
			r = p;

			if(p->owner->status.reachable) {
				break;
			}
		}
	}

	// Cache the result

	cache_mac_slot = !cache_mac_slot;
	memcpy(&cache_mac_address[cache_mac_slot], address, sizeof(*address));
	cache_mac_subnet[cache_mac_slot] = r;
	cache_mac_valid[cache_mac_slot] = true;

	return r;
}

subnet_t *lookup_subnet_ipv4(const ipv4_t *address) {
	subnet_t *p, *r = NULL;
	avl_node_t *n;
	int i;

	// Check if this address is cached

	for(i = 0; i < 2; i++) {
		if(!cache_ipv4_valid[i]) {
			continue;
		}

		if(!memcmp(address, &cache_ipv4_address[i], sizeof(*address))) {
			return cache_ipv4_subnet[i];
		}
	}

	// Search all subnets for a matching one

	for(n = subnet_tree->head; n; n = n->next) {
		p = n->data;

		if(!p || p->type != SUBNET_IPV4) {
			continue;
		}

		if(!maskcmp(address, &p->net.ipv4.address, p->net.ipv4.prefixlength)) {
			r = p;

			if(p->owner->status.reachable) {
				break;
			}
		}
	}

	// Cache the result

	cache_ipv4_slot = !cache_ipv4_slot;
	memcpy(&cache_ipv4_address[cache_ipv4_slot], address, sizeof(*address));
	cache_ipv4_subnet[cache_ipv4_slot] = r;
	cache_ipv4_valid[cache_ipv4_slot] = true;

	return r;
}

subnet_t *lookup_subnet_ipv6(const ipv6_t *address) {
	subnet_t *p, *r = NULL;
	avl_node_t *n;
	int i;

	// Check if this address is cached

	for(i = 0; i < 2; i++) {
		if(!cache_ipv6_valid[i]) {
			continue;
		}

		if(!memcmp(address, &cache_ipv6_address[i], sizeof(*address))) {
			return cache_ipv6_subnet[i];
		}
	}

	// Search all subnets for a matching one

	for(n = subnet_tree->head; n; n = n->next) {
		p = n->data;

		if(!p || p->type != SUBNET_IPV6) {
			continue;
		}

		if(!maskcmp(address, &p->net.ipv6.address, p->net.ipv6.prefixlength)) {
			r = p;

			if(p->owner->status.reachable) {
				break;
			}
		}
	}

	// Cache the result

	cache_ipv6_slot = !cache_ipv6_slot;
	memcpy(&cache_ipv6_address[cache_ipv6_slot], address, sizeof(*address));
	cache_ipv6_subnet[cache_ipv6_slot] = r;
	cache_ipv6_valid[cache_ipv6_slot] = true;

	return r;
}

void subnet_update(node_t *owner, subnet_t *subnet, bool up) {
	avl_node_t *node;
	int i;
	char *envp[10] = {NULL};
	char netstr[MAXNETSTR];
	char *name, *address, *port;
	char empty[] = "";

	// Prepare environment variables to be passed to the script

	xasprintf(&envp[0], "NETNAME=%s", netname ? netname : "");
	xasprintf(&envp[1], "DEVICE=%s", device ? device : "");
	xasprintf(&envp[2], "INTERFACE=%s", iface ? iface : "");
	xasprintf(&envp[3], "NODE=%s", owner->name);
	xasprintf(&envp[4], "NAME=%s", myself->name);

	if(owner != myself) {
		sockaddr2str(&owner->address, &address, &port);
		// 5 and 6 are reserved for SUBNET and WEIGHT
		xasprintf(&envp[7], "REMOTEADDRESS=%s", address);
		xasprintf(&envp[8], "REMOTEPORT=%s", port);
		free(port);
		free(address);
	}

	name = up ? "subnet-up" : "subnet-down";

	if(!subnet) {
		for(node = owner->subnet_tree->head; node; node = node->next) {
			subnet = node->data;

			if(!net2str(netstr, sizeof(netstr), subnet)) {
				continue;
			}

			// Strip the weight from the subnet, and put it in its own environment variable
			char *weight = strchr(netstr, '#');

			if(weight) {
				*weight++ = 0;
			} else {
				weight = empty;
			}

			// Prepare the SUBNET and WEIGHT variables
			free(envp[5]);
			free(envp[6]);

			xasprintf(&envp[5], "SUBNET=%s", netstr);
			xasprintf(&envp[6], "WEIGHT=%s", weight);

			execute_script(name, envp);
		}
	} else {
		if(net2str(netstr, sizeof(netstr), subnet)) {
			// Strip the weight from the subnet, and put it in its own environment variable
			char *weight = strchr(netstr, '#');

			if(weight) {
				*weight++ = 0;
			} else {
				weight = empty;
			}

			// Prepare the SUBNET and WEIGHT variables
			xasprintf(&envp[5], "SUBNET=%s", netstr);
			xasprintf(&envp[6], "WEIGHT=%s", weight);

			execute_script(name, envp);
		}
	}

	for(i = 0; i < 9; i++) {
		free(envp[i]);
	}
}

void dump_subnets(void) {
	char netstr[MAXNETSTR];
	subnet_t *subnet;
	avl_node_t *node;

	logger(LOG_DEBUG, "Subnet list:");

	for(node = subnet_tree->head; node; node = node->next) {
		subnet = node->data;

		if(!net2str(netstr, sizeof(netstr), subnet)) {
			continue;
		}

		logger(LOG_DEBUG, " %s owner %s", netstr, subnet->owner->name);
	}

	logger(LOG_DEBUG, "End of subnet list.");
}