busybox/networking/udhcp/dhcprelay.c

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/* 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.
*
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* DHCP Relay for 'DHCPv4 Configuration of IPSec Tunnel Mode' support
* Copyright (C) 2002 Mario Strasser <mast@gmx.net>,
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* Zuercher Hochschule Winterthur,
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* Netbeat AG
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* Upstream has GPL v2 or later
*/
#include "common.h"
#include "options.h"
/* constants */
#define SERVER_PORT 67
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#define SELECT_TIMEOUT 5 /* select timeout in sec. */
#define MAX_LIFETIME 2*60 /* lifetime of an xid entry in sec. */
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/* This list holds information about clients. The xid_* functions manipulate this list. */
struct xid_item {
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unsigned timestamp;
int client;
uint32_t xid;
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struct sockaddr_in ip;
struct xid_item *next;
};
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#define dhcprelay_xid_list (*(struct xid_item*)&bb_common_bufsiz1)
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static struct xid_item *xid_add(uint32_t xid, struct sockaddr_in *ip, int client)
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{
struct xid_item *item;
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/* create new xid entry */
item = xmalloc(sizeof(struct xid_item));
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/* add xid entry */
item->ip = *ip;
item->xid = xid;
item->client = client;
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item->timestamp = monotonic_sec();
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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;
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unsigned current_time = monotonic_sec();
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while (item != NULL) {
if ((current_time - item->timestamp) > MAX_LIFETIME) {
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last->next = item->next;
free(item);
item = last->next;
} else {
last = item;
item = item->next;
}
}
}
static struct xid_item *xid_find(uint32_t xid)
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{
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)
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{
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 dhcpMessage *p)
{
uint8_t *op;
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/* 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)
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{
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char *s, **client_dev;
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int i, cn;
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/* copy list */
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dev_list = xstrdup(dev_list);
/* get number of items, replace ',' with NULs */
s = dev_list;
cn = 1;
while (*s) {
if (*s == ',') {
*s = '\0';
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cn++;
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}
s++;
}
*client_number = cn;
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/* create vector of pointers */
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client_dev = xzalloc(cn * sizeof(*client_dev));
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client_dev[0] = dev_list;
i = 1;
while (i != cn) {
client_dev[i] = client_dev[i - 1] + strlen(client_dev[i - 1]) + 1;
i++;
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}
return client_dev;
}
/* Creates listen sockets (in fds) and returns numerically max fd. */
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static int init_sockets(char **client, int num_clients,
char *server, int *fds)
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{
int i, n;
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/* talk to real server on bootps */
fds[0] = listen_socket(/*INADDR_ANY,*/ SERVER_PORT, server);
n = fds[0];
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for (i = 1; i < num_clients; i++) {
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/* listen for clients on bootps */
fds[i] = listen_socket(/*INADDR_ANY,*/ SERVER_PORT, client[i-1]);
if (fds[i] > n)
n = fds[i];
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}
return n;
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}
/**
* pass_on() - forwards dhcp packets from client to server
* p - packet to send
* client - number of the client
*/
static void pass_on(struct dhcpMessage *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) */
res = sendto(fds[0], p, packet_len, 0, (struct sockaddr*)server_addr,
sizeof(struct sockaddr_in));
if (res != packet_len) {
bb_perror_msg("pass_on");
return;
}
}
/**
* pass_back() - forwards dhcp packets from server to client
* p - packet to send
*/
static void pass_back(struct dhcpMessage *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);
res = sendto(fds[item->client], p, packet_len, 0, (struct sockaddr*)(&item->ip),
sizeof(item->ip));
if (res != packet_len) {
bb_perror_msg("pass_back");
return;
}
/* remove xid entry */
xid_del(p->xid);
}
static void dhcprelay_loop(int *fds, int num_sockets, int max_socket, char **clients,
struct sockaddr_in *server_addr, uint32_t gw_ip) ATTRIBUTE_NORETURN;
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static void dhcprelay_loop(int *fds, int num_sockets, int max_socket, char **clients,
struct sockaddr_in *server_addr, uint32_t gw_ip)
{
struct dhcpMessage dhcp_msg;
fd_set rfds;
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size_t packlen;
socklen_t addr_size;
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struct sockaddr_in client_addr;
struct timeval tv;
int i;
while (1) {
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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_packet(&dhcp_msg, fds[0]);
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if (packlen > 0) {
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pass_back(&dhcp_msg, packlen, fds);
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}
}
for (i = 1; i < num_sockets; i++) {
/* clients */
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;
if (read_interface(clients[i-1], NULL, &dhcp_msg.giaddr, NULL))
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dhcp_msg.giaddr = gw_ip;
pass_on(&dhcp_msg, packlen, i, fds, &client_addr, server_addr);
}
}
xid_expire();
}
}
int dhcprelay_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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int dhcprelay_main(int argc, char **argv)
{
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int num_sockets, max_socket;
int *fds;
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uint32_t gw_ip;
char **clients;
struct sockaddr_in server_addr;
server_addr.sin_family = AF_INET;
server_addr.sin_port = htons(SERVER_PORT);
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if (argc == 4) {
if (!inet_aton(argv[3], &server_addr.sin_addr))
bb_perror_msg_and_die("didn't grok server");
} else if (argc == 3) {
server_addr.sin_addr.s_addr = htonl(INADDR_BROADCAST);
} else {
bb_show_usage();
}
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clients = get_client_devices(argv[1], &num_sockets);
num_sockets++; /* for server socket at fds[0] */
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fds = xmalloc(num_sockets * sizeof(fds[0]));
max_socket = init_sockets(clients, num_sockets, argv[2], fds);
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if (read_interface(argv[2], NULL, &gw_ip, NULL))
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return 1;
/* doesn't return */
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dhcprelay_loop(fds, num_sockets, max_socket, clients, &server_addr, gw_ip);
/* return 0; - not reached */
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}