/*
    net_packet.c -- Handles in- and outgoing VPN packets
    Copyright (C) 1998-2002 Ivo Timmermans <ivo@o2w.nl>,
                  2000-2002 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: net_packet.c,v 1.1.2.27 2003/04/18 21:18:36 guus Exp $
*/

#include "config.h"

#include <errno.h>
#include <fcntl.h>
#include <netdb.h>
#include <netinet/in.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include <sys/time.h>
#include <sys/types.h>
#include <syslog.h>
#include <unistd.h>
#include <sys/ioctl.h>
/* SunOS really wants sys/socket.h BEFORE net/if.h,
   and FreeBSD wants these lines below the rest. */
#include <arpa/inet.h>
#include <sys/socket.h>
#include <net/if.h>
#ifdef HAVE_NETINET_IN_SYSTM_H
#include <netinet/in_systm.h>
#endif
#ifdef HAVE_NETINET_IP_H
#include <netinet/ip.h>
#endif
#ifdef HAVE_NETINET_TCP_H
#include <netinet/tcp.h>
#endif

#include <openssl/rand.h>
#include <openssl/evp.h>
#include <openssl/pem.h>
#include <openssl/hmac.h>

#include <zlib.h>

#include <utils.h>
#include <xalloc.h>
#include <avl_tree.h>
#include <list.h>

#include "conf.h"
#include "connection.h"
#include "meta.h"
#include "net.h"
#include "netutl.h"
#include "process.h"
#include "protocol.h"
#include "subnet.h"
#include "graph.h"
#include "process.h"
#include "route.h"
#include "device.h"
#include "event.h"

#include "system.h"

int keylifetime = 0;
int keyexpires = 0;
EVP_CIPHER_CTX packet_ctx;

#define MAX_SEQNO 1073741824

/* VPN packet I/O */

void receive_udppacket(node_t *n, vpn_packet_t *inpkt)
{
	vpn_packet_t pkt1, pkt2;
	vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
	int nextpkt = 0;
	vpn_packet_t *outpkt = pkt[0];
	int outlen, outpad;
	long int complen = MTU + 12;
	char hmac[EVP_MAX_MD_SIZE];
	int i;

	cp();

	/* Check the message authentication code */

	if(myself->digest && myself->maclength) {
		inpkt->len -= myself->maclength;
		HMAC(myself->digest, myself->key, myself->keylength,
			 (char *) &inpkt->seqno, inpkt->len, hmac, NULL);

		if(memcmp(hmac, (char *) &inpkt->seqno + inpkt->len, myself->maclength)) {
			if(debug_lvl >= DEBUG_TRAFFIC)
				syslog(LOG_DEBUG, _("Got unauthenticated packet from %s (%s)"),
					   n->name, n->hostname);
			return;
		}
	}

	/* Decrypt the packet */

	if(myself->cipher) {
		outpkt = pkt[nextpkt++];

		EVP_DecryptInit_ex(&packet_ctx, myself->cipher, NULL, myself->key,
						myself->key + myself->cipher->key_len);
		EVP_DecryptUpdate(&packet_ctx, (char *) &outpkt->seqno, &outlen,
						  (char *) &inpkt->seqno, inpkt->len);
		EVP_DecryptFinal_ex(&packet_ctx, (char *) &outpkt->seqno + outlen, &outpad);
		
		outpkt->len = outlen + outpad;
		inpkt = outpkt;
	}

	/* Check the sequence number */

	inpkt->len -= sizeof(inpkt->seqno);
	inpkt->seqno = ntohl(inpkt->seqno);

	if(inpkt->seqno != n->received_seqno + 1) {
		if(inpkt->seqno >= n->received_seqno + sizeof(n->late) * 8) {
			if(debug_lvl >= DEBUG_TRAFFIC)
				syslog(LOG_WARNING, _("Lost %d packets from %s (%s)"),
					   inpkt->seqno - n->received_seqno - 1, n->name, n->hostname);
			
			memset(n->late, 0, sizeof(n->late));
		} else if (inpkt->seqno <= n->received_seqno) {
			if(inpkt->seqno <= n->received_seqno - sizeof(n->late) * 8 || !(n->late[(inpkt->seqno / 8) % sizeof(n->late)] & (1 << inpkt->seqno % 8))) {
				syslog(LOG_WARNING, _("Got late or replayed packet from %s (%s), seqno %d, last received %d"),
					   n->name, n->hostname, inpkt->seqno, n->received_seqno, n->late[(inpkt->seqno / 8) % sizeof(n->late)]);
			} else
				for(i = n->received_seqno + 1; i < inpkt->seqno; i++)
					n->late[(inpkt->seqno / 8) % sizeof(n->late)] |= 1 << i % 8;
		}
	}
	
	n->received_seqno = inpkt->seqno;
	n->late[(n->received_seqno / 8) % sizeof(n->late)] &= ~(1 << n->received_seqno % 8);
			
	if(n->received_seqno > MAX_SEQNO)
		keyexpires = 0;

	/* Decompress the packet */

	if(myself->compression) {
		outpkt = pkt[nextpkt++];

		if(uncompress(outpkt->data, &complen, inpkt->data, inpkt->len) != Z_OK) {
			syslog(LOG_ERR, _("Error while uncompressing packet from %s (%s)"),
				   n->name, n->hostname);
			return;
		}

		outpkt->len = complen;
		inpkt = outpkt;
	}

	receive_packet(n, inpkt);
}

void receive_tcppacket(connection_t *c, char *buffer, int len)
{
	vpn_packet_t outpkt;

	cp();

	outpkt.len = len;
	memcpy(outpkt.data, buffer, len);

	receive_packet(c->node, &outpkt);
}

void receive_packet(node_t *n, vpn_packet_t *packet)
{
	cp();

	if(debug_lvl >= DEBUG_TRAFFIC)
		syslog(LOG_DEBUG, _("Received packet of %d bytes from %s (%s)"),
			   packet->len, n->name, n->hostname);

	route_incoming(n, packet);
}

void send_udppacket(node_t *n, vpn_packet_t *inpkt)
{
	vpn_packet_t pkt1, pkt2;
	vpn_packet_t *pkt[] = { &pkt1, &pkt2, &pkt1, &pkt2 };
	int nextpkt = 0;
	vpn_packet_t *outpkt;
	int origlen;
	int outlen, outpad;
	long int complen = MTU + 12;
	vpn_packet_t *copy;
	static int priority = 0;
	int origpriority;
	int sock;

	cp();

	/* Make sure we have a valid key */

	if(!n->status.validkey) {
		if(debug_lvl >= DEBUG_TRAFFIC)
			syslog(LOG_INFO,
				   _("No valid key known yet for %s (%s), queueing packet"),
				   n->name, n->hostname);

		/* Since packet is on the stack of handle_tap_input(), we have to make a copy of it first. */

		copy = xmalloc(sizeof(vpn_packet_t));
		memcpy(copy, inpkt, sizeof(vpn_packet_t));

		list_insert_tail(n->queue, copy);

		if(n->queue->count > MAXQUEUELENGTH)
			list_delete_head(n->queue);

		if(!n->status.waitingforkey)
			send_req_key(n->nexthop->connection, myself, n);

		n->status.waitingforkey = 1;

		return;
	}

	origlen = inpkt->len;
	origpriority = inpkt->priority;

	/* Compress the packet */

	if(n->compression) {
		outpkt = pkt[nextpkt++];

		if(compress2
		   (outpkt->data, &complen, inpkt->data, inpkt->len,
			n->compression) != Z_OK) {
			syslog(LOG_ERR, _("Error while compressing packet to %s (%s)"),
				   n->name, n->hostname);
			return;
		}

		outpkt->len = complen;
		inpkt = outpkt;
	}

	/* Add sequence number */

	inpkt->seqno = htonl(++(n->sent_seqno));
	inpkt->len += sizeof(inpkt->seqno);

	/* Encrypt the packet */

	if(n->cipher) {
		outpkt = pkt[nextpkt++];

		EVP_EncryptInit_ex(&packet_ctx, n->cipher, NULL, n->key, n->key + n->cipher->key_len);
		EVP_EncryptUpdate(&packet_ctx, (char *) &outpkt->seqno, &outlen,
						  (char *) &inpkt->seqno, inpkt->len);
		EVP_EncryptFinal_ex(&packet_ctx, (char *) &outpkt->seqno + outlen, &outpad);

		outpkt->len = outlen + outpad;
		inpkt = outpkt;
	}

	/* Add the message authentication code */

	if(n->digest && n->maclength) {
		HMAC(n->digest, n->key, n->keylength, (char *) &inpkt->seqno,
			 inpkt->len, (char *) &inpkt->seqno + inpkt->len, &outlen);
		inpkt->len += n->maclength;
	}

	/* Determine which socket we have to use */

	for(sock = 0; sock < listen_sockets; sock++)
		if(n->address.sa.sa_family == listen_socket[sock].sa.sa.sa_family)
			break;

	if(sock >= listen_sockets)
		sock = 0;				/* If none is available, just use the first and hope for the best. */

	/* Send the packet */

#if defined(SOL_IP) && defined(IP_TOS)
	if(priorityinheritance && origpriority != priority
	   && listen_socket[sock].sa.sa.sa_family == AF_INET) {
		priority = origpriority;
		if(debug_lvl >= DEBUG_TRAFFIC)
			syslog(LOG_DEBUG, _("Setting outgoing packet priority to %d"),
				   priority);
		if(setsockopt(listen_socket[sock].udp, SOL_IP, IP_TOS, &priority, sizeof(priority)))	/* SO_PRIORITY doesn't seem to work */
			syslog(LOG_ERR, _("System call `%s' failed: %s"), "setsockopt",
				   strerror(errno));
	}
#endif

	if((sendto(listen_socket[sock].udp, (char *) &inpkt->seqno, inpkt->len, 0, &(n->address.sa), SALEN(n->address.sa))) < 0) {
		syslog(LOG_ERR, _("Error sending packet to %s (%s): %s"), n->name,
			   n->hostname, strerror(errno));
		return;
	}

	inpkt->len = origlen;
}

/*
  send a packet to the given vpn ip.
*/
void send_packet(node_t *n, vpn_packet_t *packet)
{
	node_t *via;

	cp();

	if(debug_lvl >= DEBUG_TRAFFIC)
		syslog(LOG_ERR, _("Sending packet of %d bytes to %s (%s)"),
			   packet->len, n->name, n->hostname);

	if(n == myself) {
		if(debug_lvl >= DEBUG_TRAFFIC)
			syslog(LOG_NOTICE, _("Packet is looping back to us!"));

		return;
	}

	if(!n->status.reachable) {
		if(debug_lvl >= DEBUG_TRAFFIC)
			syslog(LOG_INFO, _("Node %s (%s) is not reachable"),
				   n->name, n->hostname);

		return;
	}

	via = (n->via == myself) ? n->nexthop : n->via;

	if(via != n && debug_lvl >= DEBUG_TRAFFIC)
		syslog(LOG_ERR, _("Sending packet to %s via %s (%s)"),
			   n->name, via->name, n->via->hostname);

	if((myself->options | via->options) & OPTION_TCPONLY) {
		if(send_tcppacket(via->connection, packet))
			terminate_connection(via->connection, 1);
	} else
		send_udppacket(via, packet);
}

/* Broadcast a packet using the minimum spanning tree */

void broadcast_packet(node_t *from, vpn_packet_t *packet)
{
	avl_node_t *node;
	connection_t *c;

	cp();

	if(debug_lvl >= DEBUG_TRAFFIC)
		syslog(LOG_INFO, _("Broadcasting packet of %d bytes from %s (%s)"),
			   packet->len, from->name, from->hostname);

	for(node = connection_tree->head; node; node = node->next) {
		c = (connection_t *) node->data;

		if(c->status.active && c->status.mst && c != from->nexthop->connection)
			send_packet(c->node, packet);
	}
}

void flush_queue(node_t *n)
{
	list_node_t *node, *next;

	cp();

	if(debug_lvl >= DEBUG_TRAFFIC)
		syslog(LOG_INFO, _("Flushing queue for %s (%s)"), n->name, n->hostname);

	for(node = n->queue->head; node; node = next) {
		next = node->next;
		send_udppacket(n, (vpn_packet_t *) node->data);
		list_delete_node(n->queue, node);
	}
}

void handle_incoming_vpn_data(int sock)
{
	vpn_packet_t pkt;
	int x, l = sizeof(x);
	char *hostname;
	sockaddr_t from;
	socklen_t fromlen = sizeof(from);
	node_t *n;

	cp();

	if(getsockopt(sock, SOL_SOCKET, SO_ERROR, &x, &l) < 0) {
		syslog(LOG_ERR, _("This is a bug: %s:%d: %d:%s"),
			   __FILE__, __LINE__, sock, strerror(errno));
		cp_trace();
		exit(1);
	}

	if(x) {
		syslog(LOG_ERR, _("Incoming data socket error: %s"), strerror(x));
		return;
	}

	pkt.len = recvfrom(sock, (char *) &pkt.seqno, MAXSIZE, 0, &from.sa, &fromlen);

	if(pkt.len <= 0) {
		syslog(LOG_ERR, _("Receiving packet failed: %s"), strerror(errno));
		return;
	}

	sockaddrunmap(&from);		/* Some braindead IPv6 implementations do stupid things. */

	n = lookup_node_udp(&from);

	if(!n) {
		hostname = sockaddr2hostname(&from);
		syslog(LOG_WARNING, _("Received UDP packet from unknown source %s"),
			   hostname);
		free(hostname);
		return;
	}

	if(n->connection)
		n->connection->last_ping_time = now;

	receive_udppacket(n, &pkt);
}