tinc/src/route.c

/*
    route.c -- routing
    Copyright (C) 2000-2003 Ivo Timmermans <ivo@o2w.nl>,
                  2000-2003 Guus Sliepen <guus@sliepen.eu.org>

    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., 675 Mass Ave, Cambridge, MA 02139, USA.

    $Id: route.c,v 1.1.2.63 2003/07/31 13:18:34 guus Exp $
*/

#include "system.h"

#ifdef HAVE_NET_ETHERNET_H
#include <net/ethernet.h>
#endif
#ifdef HAVE_NET_IF_ARP_H
#include <net/if_arp.h>
#endif
#ifdef HAVE_NETINET_IP_ICMP_H
#include <netinet/ip_icmp.h>
#endif
#ifdef HAVE_NETINET_ICMP6_H
#include <netinet/icmp6.h>
#endif
#ifdef HAVE_NETINET_IF_ETHER_H
#include <netinet/if_ether.h>
#endif

#include "avl_tree.h"
#include "connection.h"
#include "device.h"
#include "ethernet.h"
#include "ipv4.h"
#include "ipv6.h"
#include "logger.h"
#include "net.h"
#include "protocol.h"
#include "route.h"
#include "subnet.h"
#include "utils.h"

rmode_t routing_mode = RMODE_ROUTER;
bool priorityinheritance = false;
int macexpire = 600;
bool overwrite_mac = false;
mac_t mymac = {{0xFE, 0xFD, 0, 0, 0, 0}};

/* RFC 1071 */

static uint16_t inet_checksum(void *data, int len, uint16_t prevsum)
{
	uint16_t *p = data;
	uint32_t checksum = prevsum ^ 0xFFFF;

	while(len >= 2) {
		checksum += *p++;
		len -= 2;
	}
	
	if(len)
		checksum += *(unsigned char *)p;

	while(checksum >> 16)
		checksum = (checksum & 0xFFFF) + (checksum >> 16);

	return ~checksum;
}

static bool ratelimit(void) {
	static time_t lasttime = 0;
	
	if(lasttime == now)
		return true;

	lasttime = now;
	return false;
}
	
static void learn_mac(mac_t *address)
{
	subnet_t *subnet;
	avl_node_t *node;
	connection_t *c;

	cp();

	subnet = lookup_subnet_mac(address);

	/* If we don't know this MAC address yet, store it */

	if(!subnet || subnet->owner != myself) {
		ifdebug(TRAFFIC) logger(LOG_INFO, _("Learned new MAC address %hx:%hx:%hx:%hx:%hx:%hx"),
				   address->x[0], address->x[1], address->x[2], address->x[3],
				   address->x[4], address->x[5]);

		subnet = new_subnet();
		subnet->type = SUBNET_MAC;
		memcpy(&subnet->net.mac.address, address, sizeof(mac_t));
		subnet_add(myself, subnet);

		/* And tell all other tinc daemons it's our MAC */

		for(node = connection_tree->head; node; node = node->next) {
			c = (connection_t *) node->data;
			if(c->status.active)
				send_add_subnet(c, subnet);
		}
	}

	subnet->net.mac.lastseen = now;
}

void age_mac(void)
{
	subnet_t *s;
	connection_t *c;
	avl_node_t *node, *next, *node2;

	cp();

	for(node = myself->subnet_tree->head; node; node = next) {
		next = node->next;
		s = (subnet_t *) node->data;
		if(s->type == SUBNET_MAC && s->net.mac.lastseen && s->net.mac.lastseen + macexpire < now) {
			ifdebug(TRAFFIC) logger(LOG_INFO, _("MAC address %hx:%hx:%hx:%hx:%hx:%hx expired"),
					   s->net.mac.address.x[0], s->net.mac.address.x[1],
					   s->net.mac.address.x[2], s->net.mac.address.x[3],
					   s->net.mac.address.x[4], s->net.mac.address.x[5]);

			for(node2 = connection_tree->head; node2; node2 = node2->next) {
				c = (connection_t *) node2->data;
				if(c->status.active)
					send_del_subnet(c, s);
			}

			subnet_del(myself, s);
		}
	}
}

static node_t *route_mac(vpn_packet_t *packet)
{
	subnet_t *subnet;

	cp();

	/* Learn source address */

	learn_mac((mac_t *)(&packet->data[6]));

	/* Lookup destination address */

	subnet = lookup_subnet_mac((mac_t *)(&packet->data[0]));

	if(subnet)
		return subnet->owner;
	else
		return NULL;
}

/* RFC 792 */

static void route_ipv4_unreachable(vpn_packet_t *packet, uint8_t code)
{
	struct ip *hdr;
	struct icmp *icmp;
	
	struct in_addr ip_src;
	struct in_addr ip_dst;
	uint32_t oldlen;

	if(ratelimit())
		return;
	
	cp();

	hdr = (struct ip *)(packet->data + 14);
	icmp = (struct icmp *)(packet->data + 14 + 20);

	/* Remember original source and destination */
		
	memcpy(&ip_src, &hdr->ip_src, 4);
	memcpy(&ip_dst, &hdr->ip_dst, 4);
	oldlen = packet->len - 14;
	
	if(oldlen >= IP_MSS - sizeof(*hdr) - sizeof(*icmp))
		oldlen = IP_MSS - sizeof(*hdr) - sizeof(*icmp);
	
	/* Copy first part of original contents to ICMP message */
	
	memmove(&icmp->icmp_ip, hdr, oldlen);

	/* Fill in IPv4 header */
	
	hdr->ip_v = 4;
	hdr->ip_hl = sizeof(*hdr) / 4;
	hdr->ip_tos = 0;
	hdr->ip_len = htons(20 + 8 + oldlen);
	hdr->ip_id = 0;
	hdr->ip_off = 0;
	hdr->ip_ttl = 255;
	hdr->ip_p = IPPROTO_ICMP;
	hdr->ip_sum = 0;
	memcpy(&hdr->ip_src, &ip_dst, 4);
	memcpy(&hdr->ip_dst, &ip_src, 4);

	hdr->ip_sum = inet_checksum(hdr, 20, ~0);
	
	/* Fill in ICMP header */
	
	icmp->icmp_type = ICMP_DEST_UNREACH;
	icmp->icmp_code = code;
	icmp->icmp_cksum = 0;
	
	icmp->icmp_cksum = inet_checksum(icmp, 8 + oldlen, ~0);
	
	packet->len = 14 + 20 + 8 + oldlen;
	
	write_packet(packet);
}

static node_t *route_ipv4(vpn_packet_t *packet)
{
	subnet_t *subnet;

	cp();

	if(priorityinheritance)
		packet->priority = packet->data[15];

	subnet = lookup_subnet_ipv4((ipv4_t *) & packet->data[30]);

	if(!subnet) {
		ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: unknown IPv4 destination address %d.%d.%d.%d"),
				   packet->data[30], packet->data[31], packet->data[32],
				   packet->data[33]);

		route_ipv4_unreachable(packet, ICMP_NET_UNKNOWN);
		return NULL;
	}
	
	if(!subnet->owner->status.reachable)
		route_ipv4_unreachable(packet, ICMP_NET_UNREACH);

	return subnet->owner;
}

/* RFC 2463 */

static void route_ipv6_unreachable(vpn_packet_t *packet, uint8_t code)
{
	struct ip6_hdr *hdr;
	struct icmp6_hdr *icmp;
	uint16_t checksum;	

	struct {
		struct in6_addr ip6_src;	/* source address */
		struct in6_addr ip6_dst;	/* destination address */
		uint32_t length;
		uint32_t next;
	} pseudo;

	if(ratelimit())
		return;
	
	cp();

	hdr = (struct ip6_hdr *)(packet->data + 14);
	icmp = (struct icmp6_hdr *)(packet->data + 14 + sizeof(*hdr));

	/* Remember original source and destination */
		
	memcpy(&pseudo.ip6_src, &hdr->ip6_dst, 16);
	memcpy(&pseudo.ip6_dst, &hdr->ip6_src, 16);
	pseudo.length = ntohs(hdr->ip6_plen) + sizeof(*hdr);
	
	if(pseudo.length >= IP_MSS - sizeof(*hdr) - sizeof(*icmp))
		pseudo.length = IP_MSS - sizeof(*hdr) - sizeof(*icmp);
	
	/* Copy first part of original contents to ICMP message */
	
	memmove(((char *)icmp) + sizeof(*icmp), hdr, pseudo.length);

	/* Fill in IPv6 header */
	
	hdr->ip6_flow = htonl(0x60000000UL);
	hdr->ip6_plen = htons(sizeof(*icmp) + pseudo.length);
	hdr->ip6_nxt = IPPROTO_ICMPV6;
	hdr->ip6_hlim = 255;
	memcpy(&hdr->ip6_dst, &pseudo.ip6_dst, 16);
	memcpy(&hdr->ip6_src, &pseudo.ip6_src, 16);

	/* Fill in ICMP header */
	
	icmp->icmp6_type = ICMP6_DST_UNREACH;
	icmp->icmp6_code = code;
	icmp->icmp6_cksum = 0;

	/* Create pseudo header */
		
	pseudo.length = htonl(sizeof(*icmp) + pseudo.length);
	pseudo.next = htonl(IPPROTO_ICMPV6);

	/* Generate checksum */
	
	checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
	checksum = inet_checksum(icmp, ntohl(pseudo.length), checksum);

	icmp->icmp6_cksum = checksum;
	
	packet->len = 14 + sizeof(*hdr) + ntohl(pseudo.length);
	
	write_packet(packet);
}

static node_t *route_ipv6(vpn_packet_t *packet)
{
	subnet_t *subnet;

	cp();

	subnet = lookup_subnet_ipv6((ipv6_t *) & packet->data[38]);

	if(!subnet) {
		ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: unknown IPv6 destination address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx"),
				   ntohs(*(uint16_t *) & packet->data[38]),
				   ntohs(*(uint16_t *) & packet->data[40]),
				   ntohs(*(uint16_t *) & packet->data[42]),
				   ntohs(*(uint16_t *) & packet->data[44]),
				   ntohs(*(uint16_t *) & packet->data[46]),
				   ntohs(*(uint16_t *) & packet->data[48]),
				   ntohs(*(uint16_t *) & packet->data[50]),
				   ntohs(*(uint16_t *) & packet->data[52]));
		route_ipv6_unreachable(packet, ICMP6_DST_UNREACH_ADDR);

		return NULL;
	}

	if(!subnet->owner->status.reachable)
		route_ipv6_unreachable(packet, ICMP6_DST_UNREACH_NOROUTE);
	
	return subnet->owner;
}

/* RFC 2461 */

static void route_neighborsol(vpn_packet_t *packet)
{
	struct ip6_hdr *hdr;
	struct nd_neighbor_solicit *ns;
	struct nd_opt_hdr *opt;
	subnet_t *subnet;
	uint16_t checksum;

	struct {
		struct in6_addr ip6_src;	/* source address */
		struct in6_addr ip6_dst;	/* destination address */
		uint32_t length;
		uint32_t next;
	} pseudo;

	cp();

	hdr = (struct ip6_hdr *)(packet->data + 14);
	ns = (struct nd_neighbor_solicit *)(packet->data + 14 + sizeof(*hdr));
	opt = (struct nd_opt_hdr *)(packet->data + 14 + sizeof(*hdr) + sizeof(*ns));

	/* First, snatch the source address from the neighbor solicitation packet */

	if(overwrite_mac)
		memcpy(mymac.x, packet->data + 6, 6);

	/* Check if this is a valid neighbor solicitation request */

	if(ns->nd_ns_hdr.icmp6_type != ND_NEIGHBOR_SOLICIT ||
	   opt->nd_opt_type != ND_OPT_SOURCE_LINKADDR) {
		ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: received unknown type neighbor solicitation request"));
		return;
	}

	/* Create pseudo header */

	memcpy(&pseudo.ip6_src, &hdr->ip6_src, 16);
	memcpy(&pseudo.ip6_dst, &hdr->ip6_dst, 16);
	pseudo.length = htonl(sizeof(*ns) + sizeof(*opt) + 6);
	pseudo.next = htonl(IPPROTO_ICMPV6);

	/* Generate checksum */

	checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
	checksum = inet_checksum(ns, sizeof(*ns) + 8, checksum);

	if(checksum) {
		ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: checksum error for neighbor solicitation request"));
		return;
	}

	/* Check if the IPv6 address exists on the VPN */

	subnet = lookup_subnet_ipv6((ipv6_t *) & ns->nd_ns_target);

	if(!subnet) {
		ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: neighbor solicitation request for unknown address %hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx"),
				   ntohs(((uint16_t *) & ns->nd_ns_target)[0]),
				   ntohs(((uint16_t *) & ns->nd_ns_target)[1]),
				   ntohs(((uint16_t *) & ns->nd_ns_target)[2]),
				   ntohs(((uint16_t *) & ns->nd_ns_target)[3]),
				   ntohs(((uint16_t *) & ns->nd_ns_target)[4]),
				   ntohs(((uint16_t *) & ns->nd_ns_target)[5]),
				   ntohs(((uint16_t *) & ns->nd_ns_target)[6]),
				   ntohs(((uint16_t *) & ns->nd_ns_target)[7]));

		return;
	}

	/* Check if it is for our own subnet */

	if(subnet->owner == myself)
		return;					/* silently ignore */

	/* Create neighbor advertation reply */

	memcpy(packet->data, packet->data + ETHER_ADDR_LEN, ETHER_ADDR_LEN);	/* copy destination address */
	packet->data[ETHER_ADDR_LEN * 2 - 1] ^= 0xFF;	/* mangle source address so it looks like it's not from us */

	memcpy(&hdr->ip6_dst, &hdr->ip6_src, 16);	/* swap destination and source protocol address */
	memcpy(&hdr->ip6_src, &ns->nd_ns_target, 16);	/* ... */

	memcpy((char *) opt + sizeof(*opt), packet->data + ETHER_ADDR_LEN, 6);	/* add fake source hard addr */

	ns->nd_ns_hdr.icmp6_cksum = 0;
	ns->nd_ns_hdr.icmp6_type = ND_NEIGHBOR_ADVERT;
	ns->nd_ns_hdr.icmp6_dataun.icmp6_un_data8[0] = 0x40;	/* Set solicited flag */
	ns->nd_ns_hdr.icmp6_dataun.icmp6_un_data8[1] =
		ns->nd_ns_hdr.icmp6_dataun.icmp6_un_data8[2] =
		ns->nd_ns_hdr.icmp6_dataun.icmp6_un_data8[3] = 0;
	opt->nd_opt_type = ND_OPT_TARGET_LINKADDR;

	/* Create pseudo header */

	memcpy(&pseudo.ip6_src, &hdr->ip6_src, 16);
	memcpy(&pseudo.ip6_dst, &hdr->ip6_dst, 16);
	pseudo.length = htonl(sizeof(*ns) + sizeof(*opt) + 6);
	pseudo.next = htonl(IPPROTO_ICMPV6);

	/* Generate checksum */

	checksum = inet_checksum(&pseudo, sizeof(pseudo), ~0);
	checksum = inet_checksum(ns, sizeof(*ns) + 8, checksum);

	ns->nd_ns_hdr.icmp6_cksum = checksum;

	write_packet(packet);
}

/* RFC 826 */

static void route_arp(vpn_packet_t *packet)
{
	struct ether_arp *arp;
	subnet_t *subnet;
	uint8_t ipbuf[4];

	cp();

	/* First, snatch the source address from the ARP packet */

	if(overwrite_mac)
		memcpy(mymac.x, packet->data + 6, 6);

	/* This routine generates replies to ARP requests.
	   You don't need to set NOARP flag on the interface anymore (which is broken on FreeBSD).
	   Most of the code here is taken from choparp.c by Takamichi Tateoka (tree@mma.club.uec.ac.jp)
	 */

	arp = (struct ether_arp *)(packet->data + 14);

	/* Check if this is a valid ARP request */

	if(ntohs(arp->arp_hrd) != ARPHRD_ETHER || ntohs(arp->arp_pro) != ETHERTYPE_IP ||
	   arp->arp_hln != ETHER_ADDR_LEN || arp->arp_pln != 4 || ntohs(arp->arp_op) != ARPOP_REQUEST) {
		ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: received unknown type ARP request"));
		return;
	}

	/* Check if the IPv4 address exists on the VPN */

	subnet = lookup_subnet_ipv4((ipv4_t *) arp->arp_tpa);

	if(!subnet) {
		ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: ARP request for unknown address %d.%d.%d.%d"),
				   arp->arp_tpa[0], arp->arp_tpa[1], arp->arp_tpa[2],
				   arp->arp_tpa[3]);
		return;
	}

	/* Check if it is for our own subnet */

	if(subnet->owner == myself)
		return;					/* silently ignore */

	memcpy(packet->data, packet->data + ETHER_ADDR_LEN, ETHER_ADDR_LEN);	/* copy destination address */
	packet->data[ETHER_ADDR_LEN * 2 - 1] ^= 0xFF;	/* mangle source address so it looks like it's not from us */

	memcpy(ipbuf, arp->arp_tpa, 4);	/* save protocol addr */
	memcpy(arp->arp_tpa, arp->arp_spa, 4);	/* swap destination and source protocol address */
	memcpy(arp->arp_spa, ipbuf, 4);	/* ... */

	memcpy(arp->arp_tha, arp->arp_sha, 10);	/* set target hard/proto addr */
	memcpy(arp->arp_sha, packet->data + ETHER_ADDR_LEN, ETHER_ADDR_LEN);	/* add fake source hard addr */
	arp->arp_op = htons(ARPOP_REPLY);

	write_packet(packet);
}

void route_outgoing(vpn_packet_t *packet)
{
	uint16_t type;
	node_t *n = NULL;

	cp();

	/* FIXME: multicast? */

	switch (routing_mode) {
		case RMODE_ROUTER:
			type = ntohs(*((uint16_t *)(&packet->data[12])));
			switch (type) {
				case 0x0800:
					n = route_ipv4(packet);
					break;

				case 0x86DD:
					if(packet->data[20] == IPPROTO_ICMPV6 && packet->data[54] == ND_NEIGHBOR_SOLICIT) {
						route_neighborsol(packet);
						return;
					}
					n = route_ipv6(packet);
					break;

				case 0x0806:
					route_arp(packet);
					return;

				default:
					ifdebug(TRAFFIC) logger(LOG_WARNING, _("Cannot route packet: unknown type %hx"), type);
					return;
			}
			if(n)
				send_packet(n, packet);
			break;

		case RMODE_SWITCH:
			n = route_mac(packet);
			if(n)
				send_packet(n, packet);
			else
				broadcast_packet(myself, packet);
			break;

		case RMODE_HUB:
			broadcast_packet(myself, packet);
			break;
	}
}

void route_incoming(node_t *source, vpn_packet_t *packet)
{
	switch (routing_mode) {
		case RMODE_ROUTER:
			{
				node_t *n = NULL;
				uint16_t type;

				type = ntohs(*((uint16_t *)(&packet->data[12])));
				switch (type) {
					case 0x0800:
						n = route_ipv4(packet);
						break;

					case 0x86DD:
						n = route_ipv6(packet);
						break;

					default:
						n = myself;
						break;
				}

				if(n) {
					if(n == myself) {
						if(overwrite_mac)
							memcpy(packet->data, mymac.x, 6);
						write_packet(packet);
					} else
						send_packet(n, packet);
				}
			}
			break;

		case RMODE_SWITCH:
			{
				subnet_t *subnet;

				subnet = lookup_subnet_mac((mac_t *)(&packet->data[0]));

				if(subnet) {
					if(subnet->owner == myself)
						write_packet(packet);
					else
						send_packet(subnet->owner, packet);
				} else {
					broadcast_packet(source, packet);
					write_packet(packet);
				}
			}
			break;

		case RMODE_HUB:
			broadcast_packet(source, packet);	/* Spread it on */
			write_packet(packet);
			break;
	}
}