networking/udhcp/dhcprelay.c - busybox - Git at Google

 /* vi: set sw=4 ts=4: */
 /* Port to Busybox Copyright (C) 2006 Jesse Dutton <jessedutton@gmail.com>
  *
  * Licensed under GPL v2, see file LICENSE in this tarball for details.
  *
  * DHCP Relay for 'DHCPv4 Configuration of IPSec Tunnel Mode' support
  * Copyright (C) 2002 Mario Strasser <mast@gmx.net>,
  *                   Zuercher Hochschule Winterthur,
  *                   Netbeat AG
  * Upstream has GPL v2 or later
  */

 #include "common.h"
 #include "options.h"

 #define SERVER_PORT      67
 #define SELECT_TIMEOUT    5 /* select timeout in sec. */
 #define MAX_LIFETIME   2*60 /* lifetime of an xid entry in sec. */

 /* This list holds information about clients. The xid_* functions manipulate this list. */
 struct xid_item {
 	unsigned timestamp;
 	int client;
 	uint32_t xid;
 	struct sockaddr_in ip;
 	struct xid_item *next;
 };

 #define dhcprelay_xid_list (*(struct xid_item*)&bb_common_bufsiz1)

 static struct xid_item *xid_add(uint32_t xid, struct sockaddr_in *ip, int client)
 {
 	struct xid_item *item;

 	/* create new xid entry */
 	item = xmalloc(sizeof(struct xid_item));

 	/* add xid entry */
 	item->ip = *ip;
 	item->xid = xid;
 	item->client = client;
 	item->timestamp = monotonic_sec();
 	item->next = dhcprelay_xid_list.next;
 	dhcprelay_xid_list.next = item;

 	return item;
 }

 static void xid_expire(void)
 {
 	struct xid_item *item = dhcprelay_xid_list.next;
 	struct xid_item *last = &dhcprelay_xid_list;
 	unsigned current_time = monotonic_sec();

 	while (item != NULL) {
 		if ((current_time - item->timestamp) > MAX_LIFETIME) {
 			last->next = item->next;
 			free(item);
 			item = last->next;
 		} else {
 			last = item;
 			item = item->next;
 		}
 	}
 }

 static struct xid_item *xid_find(uint32_t xid)
 {
 	struct xid_item *item = dhcprelay_xid_list.next;
 	while (item != NULL) {
 		if (item->xid == xid) {
 			return item;
 		}
 		item = item->next;
 	}
 	return NULL;
 }

 static void xid_del(uint32_t xid)
 {
 	struct xid_item *item = dhcprelay_xid_list.next;
 	struct xid_item *last = &dhcprelay_xid_list;
 	while (item != NULL) {
 		if (item->xid == xid) {
 			last->next = item->next;
 			free(item);
 			item = last->next;
 		} else {
 			last = item;
 			item = item->next;
 		}
 	}
 }

 /**
  * get_dhcp_packet_type - gets the message type of a dhcp packet
  * p - pointer to the dhcp packet
  * returns the message type on success, -1 otherwise
  */
 static int get_dhcp_packet_type(struct dhcp_packet *p)
 {
 	uint8_t *op;

 	/* it must be either a BOOTREQUEST or a BOOTREPLY */
 	if (p->op != BOOTREQUEST && p->op != BOOTREPLY)
 		return -1;
 	/* get message type option */
 	op = get_option(p, DHCP_MESSAGE_TYPE);
 	if (op != NULL)
 		return op[0];
 	return -1;
 }

 /**
  * get_client_devices - parses the devices list
  * dev_list - comma separated list of devices
  * returns array
  */
 static char **get_client_devices(char *dev_list, int *client_number)
 {
 	char *s, **client_dev;
 	int i, cn;

 	/* copy list */
 	dev_list = xstrdup(dev_list);

 	/* get number of items, replace ',' with NULs */
 	s = dev_list;
 	cn = 1;
 	while (*s) {
 		if (*s == ',') {
 			*s = '\0';
 			cn++;
 		}
 		s++;
 	}
 	*client_number = cn;

 	/* create vector of pointers */
 	client_dev = xzalloc(cn * sizeof(*client_dev));
 	client_dev[0] = dev_list;
 	i = 1;
 	while (i != cn) {
 		client_dev[i] = client_dev[i - 1] + strlen(client_dev[i - 1]) + 1;
 		i++;
 	}
 	return client_dev;
 }


 /* Creates listen sockets (in fds) bound to client and server ifaces,
  * and returns numerically max fd.
  */
 static int init_sockets(char **client_ifaces, int num_clients,
 			char *server_iface, int *fds)
 {
 	int i, n;

 	/* talk to real server on bootps */
 	fds[0] = udhcp_listen_socket(/*INADDR_ANY,*/ SERVER_PORT, server_iface);
 	n = fds[0];

 	for (i = 1; i < num_clients; i++) {
 		/* listen for clients on bootps */
 		fds[i] = udhcp_listen_socket(/*INADDR_ANY,*/ SERVER_PORT, client_ifaces[i-1]);
 		if (fds[i] > n)
 			n = fds[i];
 	}
 	return n;
 }


 /**
  * pass_to_server() - forwards dhcp packets from client to server
  * p - packet to send
  * client - number of the client
  */
 static void pass_to_server(struct dhcp_packet *p, int packet_len, int client, int *fds,
 			struct sockaddr_in *client_addr, struct sockaddr_in *server_addr)
 {
 	int res, type;
 	struct xid_item *item;

 	/* check packet_type */
 	type = get_dhcp_packet_type(p);
 	if (type != DHCPDISCOVER && type != DHCPREQUEST
 	 && type != DHCPDECLINE && type != DHCPRELEASE
 	 && type != DHCPINFORM
 	) {
 		return;
 	}

 	/* create new xid entry */
 	item = xid_add(p->xid, client_addr, client);

 	/* forward request to LAN (server) */
 	errno = 0;
 	res = sendto(fds[0], p, packet_len, 0, (struct sockaddr*)server_addr,
 			sizeof(struct sockaddr_in));
 	if (res != packet_len) {
 		bb_perror_msg("sendto");
 	}
 }

 /**
  * pass_to_client() - forwards dhcp packets from server to client
  * p - packet to send
  */
 static void pass_to_client(struct dhcp_packet *p, int packet_len, int *fds)
 {
 	int res, type;
 	struct xid_item *item;

 	/* check xid */
 	item = xid_find(p->xid);
 	if (!item) {
 		return;
 	}

 	/* check packet type */
 	type = get_dhcp_packet_type(p);
 	if (type != DHCPOFFER && type != DHCPACK && type != DHCPNAK) {
 		return;
 	}

 	if (item->ip.sin_addr.s_addr == htonl(INADDR_ANY))
 		item->ip.sin_addr.s_addr = htonl(INADDR_BROADCAST);
 	errno = 0;
 	res = sendto(fds[item->client], p, packet_len, 0, (struct sockaddr*) &(item->ip),
 			sizeof(item->ip));
 	if (res != packet_len) {
 		bb_perror_msg("sendto");
 		return;
 	}

 	/* remove xid entry */
 	xid_del(p->xid);
 }

 int dhcprelay_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 int dhcprelay_main(int argc, char **argv)
 {
 	struct dhcp_packet dhcp_msg;
 	struct sockaddr_in server_addr;
 	struct sockaddr_in client_addr;
 	fd_set rfds;
 	char **client_ifaces;
 	int *fds;
 	int num_sockets, max_socket;
 	uint32_t our_nip;

 	server_addr.sin_family = AF_INET;
 	server_addr.sin_port = htons(SERVER_PORT);

 	/* dhcprelay client_iface1,client_iface2,... server_iface [server_IP] */
 	if (argc == 4) {
 		if (!inet_aton(argv[3], &server_addr.sin_addr))
 			bb_perror_msg_and_die("bad server IP");
 	} else if (argc == 3) {
 		server_addr.sin_addr.s_addr = htonl(INADDR_BROADCAST);
 	} else {
 		bb_show_usage();
 	}

 	/* Produce list of client ifaces */
 	client_ifaces = get_client_devices(argv[1], &num_sockets);

 	num_sockets++; /* for server socket at fds[0] */
 	fds = xmalloc(num_sockets * sizeof(fds[0]));

 	/* Create sockets and bind one to every iface */
 	max_socket = init_sockets(client_ifaces, num_sockets, argv[2], fds);

 	/* Get our IP on server_iface */
 	if (udhcp_read_interface(argv[2], NULL, &our_nip, NULL))
 		return 1;

 	/* Main loop */
 	while (1) {
 //reinit stuff from time to time? go back to get_client_devices
 //every N minutes?
 		struct timeval tv;
 		size_t packlen;
 		socklen_t addr_size;
 		int i;

 		FD_ZERO(&rfds);
 		for (i = 0; i < num_sockets; i++)
 			FD_SET(fds[i], &rfds);
 		tv.tv_sec = SELECT_TIMEOUT;
 		tv.tv_usec = 0;
 		if (select(max_socket + 1, &rfds, NULL, NULL, &tv) > 0) {
 			/* server */
 			if (FD_ISSET(fds[0], &rfds)) {
 				packlen = udhcp_recv_kernel_packet(&dhcp_msg, fds[0]);
 				if (packlen > 0) {
 					pass_to_client(&dhcp_msg, packlen, fds);
 				}
 			}
 			/* clients */
 			for (i = 1; i < num_sockets; i++) {
 				if (!FD_ISSET(fds[i], &rfds))
 					continue;
 				addr_size = sizeof(struct sockaddr_in);
 				packlen = recvfrom(fds[i], &dhcp_msg, sizeof(dhcp_msg), 0,
 						(struct sockaddr *)(&client_addr), &addr_size);
 				if (packlen <= 0)
 					continue;

 				/* Get our IP on corresponding client_iface */
 //why? what if server can't route such IP?
 				if (udhcp_read_interface(client_ifaces[i-1], NULL, &dhcp_msg.gateway_nip, NULL)) {
 					/* Fall back to our server_iface's IP */
 //this makes more sense!
 					dhcp_msg.gateway_nip = our_nip;
 				}
 //maybe set dhcp_msg.flags |= BROADCAST_FLAG too?
 				pass_to_server(&dhcp_msg, packlen, i, fds, &client_addr, &server_addr);
 			}
 		}
 		xid_expire();
 	} /* while (1) */

 	/* return 0; - not reached */
 }
	/* vi: set sw=4 ts=4: */
	/* Port to Busybox Copyright (C) 2006 Jesse Dutton <jessedutton@gmail.com>
	*
	* Licensed under GPL v2, see file LICENSE in this tarball for details.
	*
	* DHCP Relay for 'DHCPv4 Configuration of IPSec Tunnel Mode' support
	* Copyright (C) 2002 Mario Strasser <mast@gmx.net>,
	* Zuercher Hochschule Winterthur,
	* Netbeat AG
	* Upstream has GPL v2 or later
	*/

	#include "common.h"
	#include "options.h"

	#define SERVER_PORT 67
	#define SELECT_TIMEOUT 5 /* select timeout in sec. */
	#define MAX_LIFETIME 260 / lifetime of an xid entry in sec. */

	/* This list holds information about clients. The xid_* functions manipulate this list. */
	struct xid_item {
	unsigned timestamp;
	int client;
	uint32_t xid;
	struct sockaddr_in ip;
	struct xid_item *next;
	};

	#define dhcprelay_xid_list ((struct xid_item)&bb_common_bufsiz1)

	static struct xid_item xid_add(uint32_t xid, struct sockaddr_in ip, int client)
	{
	struct xid_item *item;

	/* create new xid entry */
	item = xmalloc(sizeof(struct xid_item));

	/* add xid entry */
	item->ip = *ip;
	item->xid = xid;
	item->client = client;
	item->timestamp = monotonic_sec();
	item->next = dhcprelay_xid_list.next;
	dhcprelay_xid_list.next = item;

	return item;
	}

	static void xid_expire(void)
	{
	struct xid_item *item = dhcprelay_xid_list.next;
	struct xid_item *last = &dhcprelay_xid_list;
	unsigned current_time = monotonic_sec();

	while (item != NULL) {
	if ((current_time - item->timestamp) > MAX_LIFETIME) {
	last->next = item->next;
	free(item);
	item = last->next;
	} else {
	last = item;
	item = item->next;
	}
	}
	}

	static struct xid_item *xid_find(uint32_t xid)
	{
	struct xid_item *item = dhcprelay_xid_list.next;
	while (item != NULL) {
	if (item->xid == xid) {
	return item;
	}
	item = item->next;
	}
	return NULL;
	}

	static void xid_del(uint32_t xid)
	{
	struct xid_item *item = dhcprelay_xid_list.next;
	struct xid_item *last = &dhcprelay_xid_list;
	while (item != NULL) {
	if (item->xid == xid) {
	last->next = item->next;
	free(item);
	item = last->next;
	} else {
	last = item;
	item = item->next;
	}
	}
	}

	/**
	* get_dhcp_packet_type - gets the message type of a dhcp packet
	* p - pointer to the dhcp packet
	* returns the message type on success, -1 otherwise
	*/
	static int get_dhcp_packet_type(struct dhcp_packet *p)
	{
	uint8_t *op;

	/* it must be either a BOOTREQUEST or a BOOTREPLY */
	if (p->op != BOOTREQUEST && p->op != BOOTREPLY)
	return -1;
	/* get message type option */
	op = get_option(p, DHCP_MESSAGE_TYPE);
	if (op != NULL)
	return op[0];
	return -1;
	}

	/**
	* get_client_devices - parses the devices list
	* dev_list - comma separated list of devices
	* returns array
	*/
	static char *get_client_devices(char dev_list, int *client_number)
	{
	char s, *client_dev;
	int i, cn;

	/* copy list */
	dev_list = xstrdup(dev_list);

	/* get number of items, replace ',' with NULs */
	s = dev_list;
	cn = 1;
	while (*s) {
	if (*s == ',') {
	*s = '\0';
	cn++;
	}
	s++;
	}
	*client_number = cn;

	/* create vector of pointers */
	client_dev = xzalloc(cn * sizeof(*client_dev));
	client_dev[0] = dev_list;
	i = 1;
	while (i != cn) {
	client_dev[i] = client_dev[i - 1] + strlen(client_dev[i - 1]) + 1;
	i++;
	}
	return client_dev;
	}


	/* Creates listen sockets (in fds) bound to client and server ifaces,
	* and returns numerically max fd.
	*/
	static int init_sockets(char **client_ifaces, int num_clients,
	char server_iface, int fds)
	{
	int i, n;

	/* talk to real server on bootps */
	fds[0] = udhcp_listen_socket(/INADDR_ANY,/ SERVER_PORT, server_iface);
	n = fds[0];

	for (i = 1; i < num_clients; i++) {
	/* listen for clients on bootps */
	fds[i] = udhcp_listen_socket(/INADDR_ANY,/ SERVER_PORT, client_ifaces[i-1]);
	if (fds[i] > n)
	n = fds[i];
	}
	return n;
	}


	/**
	* pass_to_server() - forwards dhcp packets from client to server
	* p - packet to send
	* client - number of the client
	*/
	static void pass_to_server(struct dhcp_packet p, int packet_len, int client, int fds,
	struct sockaddr_in client_addr, struct sockaddr_in server_addr)
	{
	int res, type;
	struct xid_item *item;

	/* check packet_type */
	type = get_dhcp_packet_type(p);
	if (type != DHCPDISCOVER && type != DHCPREQUEST
	&& type != DHCPDECLINE && type != DHCPRELEASE
	&& type != DHCPINFORM
	) {
	return;
	}

	/* create new xid entry */
	item = xid_add(p->xid, client_addr, client);

	/* forward request to LAN (server) */
	errno = 0;
	res = sendto(fds[0], p, packet_len, 0, (struct sockaddr*)server_addr,
	sizeof(struct sockaddr_in));
	if (res != packet_len) {
	bb_perror_msg("sendto");
	}
	}

	/**
	* pass_to_client() - forwards dhcp packets from server to client
	* p - packet to send
	*/
	static void pass_to_client(struct dhcp_packet p, int packet_len, int fds)
	{
	int res, type;
	struct xid_item *item;

	/* check xid */
	item = xid_find(p->xid);
	if (!item) {
	return;
	}

	/* check packet type */
	type = get_dhcp_packet_type(p);
	if (type != DHCPOFFER && type != DHCPACK && type != DHCPNAK) {
	return;
	}

	if (item->ip.sin_addr.s_addr == htonl(INADDR_ANY))
	item->ip.sin_addr.s_addr = htonl(INADDR_BROADCAST);
	errno = 0;
	res = sendto(fds[item->client], p, packet_len, 0, (struct sockaddr*) &(item->ip),
	sizeof(item->ip));
	if (res != packet_len) {
	bb_perror_msg("sendto");
	return;
	}

	/* remove xid entry */
	xid_del(p->xid);
	}

	int dhcprelay_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
	int dhcprelay_main(int argc, char **argv)
	{
	struct dhcp_packet dhcp_msg;
	struct sockaddr_in server_addr;
	struct sockaddr_in client_addr;
	fd_set rfds;
	char **client_ifaces;
	int *fds;
	int num_sockets, max_socket;
	uint32_t our_nip;

	server_addr.sin_family = AF_INET;
	server_addr.sin_port = htons(SERVER_PORT);

	/* dhcprelay client_iface1,client_iface2,... server_iface [server_IP] */
	if (argc == 4) {
	if (!inet_aton(argv[3], &server_addr.sin_addr))
	bb_perror_msg_and_die("bad server IP");
	} else if (argc == 3) {
	server_addr.sin_addr.s_addr = htonl(INADDR_BROADCAST);
	} else {
	bb_show_usage();
	}

	/* Produce list of client ifaces */
	client_ifaces = get_client_devices(argv[1], &num_sockets);

	num_sockets++; /* for server socket at fds[0] */
	fds = xmalloc(num_sockets * sizeof(fds[0]));

	/* Create sockets and bind one to every iface */
	max_socket = init_sockets(client_ifaces, num_sockets, argv[2], fds);

	/* Get our IP on server_iface */
	if (udhcp_read_interface(argv[2], NULL, &our_nip, NULL))
	return 1;

	/* Main loop */
	while (1) {
	//reinit stuff from time to time? go back to get_client_devices
	//every N minutes?
	struct timeval tv;
	size_t packlen;
	socklen_t addr_size;
	int i;

	FD_ZERO(&rfds);
	for (i = 0; i < num_sockets; i++)
	FD_SET(fds[i], &rfds);
	tv.tv_sec = SELECT_TIMEOUT;
	tv.tv_usec = 0;
	if (select(max_socket + 1, &rfds, NULL, NULL, &tv) > 0) {
	/* server */
	if (FD_ISSET(fds[0], &rfds)) {
	packlen = udhcp_recv_kernel_packet(&dhcp_msg, fds[0]);
	if (packlen > 0) {
	pass_to_client(&dhcp_msg, packlen, fds);
	}
	}
	/* clients */
	for (i = 1; i < num_sockets; i++) {
	if (!FD_ISSET(fds[i], &rfds))
	continue;
	addr_size = sizeof(struct sockaddr_in);
	packlen = recvfrom(fds[i], &dhcp_msg, sizeof(dhcp_msg), 0,
	(struct sockaddr *)(&client_addr), &addr_size);
	if (packlen <= 0)
	continue;

	/* Get our IP on corresponding client_iface */
	//why? what if server can't route such IP?
	if (udhcp_read_interface(client_ifaces[i-1], NULL, &dhcp_msg.gateway_nip, NULL)) {
	/* Fall back to our server_iface's IP */
	//this makes more sense!
	dhcp_msg.gateway_nip = our_nip;
	}
	//maybe set dhcp_msg.flags \|= BROADCAST_FLAG too?
	pass_to_server(&dhcp_msg, packlen, i, fds, &client_addr, &server_addr);
	}
	}
	xid_expire();
	} /* while (1) */

	/* return 0; - not reached */
	}