> >> >> > >> >># iptables -t mangle -I PREROUTING -i eth2 -s 192.168.0.168 -j SADDR > >> >>--to-source 10.0.19.2 > >> > > >> One question this throws up... how do you know the address is > >> 192.168.0.168? > > > >Actually, I dont know that! It is only an example to show the different > >IP-ranges. Excuse my improper representation. > > The question is more of a technical one-- if you do not know the > source address the client will be using, how can you reliably > mangle the address? I modified the udhcpd from the busybox - have a look in the attached file. To handle the different cases i wrote a shell script - also attached.
Attachment:
dhcpd.sh
Description: application/shellscript
/* dhcpd.c
*
* udhcp Server
* Copyright (C) 1999 Matthew Ramsay <matthewr@xxxxxxxxxxxxxx>
* Chris Trew <ctrew@xxxxxxxxxxxxxx>
*
* Rewrite by Russ Dill <Russ.Dill@xxxxxxx> July 2001
*
* 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.
*/
#include <fcntl.h>
#include <string.h>
#include <stdlib.h>
#include <sys/wait.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <unistd.h>
#include <signal.h>
#include <errno.h>
#include <sys/ioctl.h>
#include <time.h>
#include <sys/time.h>
#include <netpacket/packet.h>
#include "dhcpd.h"
#include "arpping.h"
#include "socket.h"
#include "options.h"
#include "files.h"
#include "serverpacket.h"
#include "common.h"
#include "signalpipe.h"
/* globals */
struct dhcpOfferedAddr *leases;
struct server_config_t server_config;
#ifdef COMBINED_BINARY
int udhcpd_main(int argc, char *argv[])
#else
int main(int argc, char *argv[])
#endif
{
fd_set rfds;
fd_set thefds;
struct timeval tv;
int bytes, retval;
struct dhcpMessage packet;
uint8_t *state;
uint8_t *server_id, *requested;
uint32_t server_id_align, requested_align;
unsigned long timeout_end;
struct option_set *option;
struct dhcpOfferedAddr *lease;
int max_sock = 0;
unsigned long num_ips;
char buffer[100];
char *pname;
int i;
int lastindex = 0;
memset(&server_config, 0, sizeof(struct server_config_t));
read_config(argc < 2 ? DHCPD_CONF_FILE : argv[1]);
/* Start the log, sanitize fd's, and write a pid file */
start_log_and_pid("udhcpd", server_config.pidfile);
if ((option = find_option(server_config.options, DHCP_LEASE_TIME))) {
memcpy(&server_config.lease, option->data + 2, 4);
server_config.lease = ntohl(server_config.lease);
}
else server_config.lease = LEASE_TIME;
/* Sanity check */
server_config.end = ntohl(server_config.start);
server_config.end = htonl(server_config.end + (server_config.max_leases - 1) * server_config.offset);
num_ips = (ntohl(server_config.end) - ntohl(server_config.start)) / server_config.offset + 1;
if (server_config.max_leases > num_ips) {
LOG(LOG_ERR, "max_leases value (%lu) not sane, "
"setting to %lu instead",
server_config.max_leases, num_ips);
server_config.max_leases = num_ips;
}
leases = xcalloc(server_config.max_leases, sizeof(struct dhcpOfferedAddr));
read_leases(server_config.lease_file);
server_config.numofinterfaces = 0;
pname = strtok(server_config.interfaces, " ");
while (pname) {
server_config.ifname[server_config.numofinterfaces] = pname;
server_config.fds[server_config.numofinterfaces] = -1;
server_config.arpfds[server_config.numofinterfaces] = -1;
if (read_interface(server_config.ifname[server_config.numofinterfaces],
&server_config.ifindex[server_config.numofinterfaces],
&server_config.server[server_config.numofinterfaces],
server_config.arp[server_config.numofinterfaces]) < 0)
return 1;
server_config.numofinterfaces++;
pname = strtok(0, " ");
}
server_config.currentinterface = 0;
/* #ifndef UDHCP_DEBUG */
background(server_config.pidfile); /* hold lock during fork. */
/* #endif */
FD_ZERO(&thefds);
FD_ZERO(&rfds);
/* Setup the signal pipe */
udhcp_sp_setup();
timeout_end = time(0) + server_config.auto_time;
while(1) { /* loop until universe collapses */
for (i = 0; i < server_config.numofinterfaces; i++) {
if (server_config.fds[i] < 0)
if ((server_config.fds[i] = listen_socket(INADDR_ANY, SERVER_PORT,
server_config.ifname[i])) < 0) {
LOG(LOG_ERR, "FATAL: couldn't create server socket, %m");
return 2;
}
if (server_config.ippnp) {
if (server_config.arpfds[i] < 0) {
if ((server_config.arpfds[i] =
arp_socket(server_config.ifname[i], server_config.ifindex[i])) < 0) {
LOG(LOG_ERR, "FATAL: couldn't create arp socket, %m");
return 2;
}
}
}
max_sock = udhcp_sp_fd_set(&thefds, server_config.fds[i]);
if (server_config.ippnp) {
max_sock = udhcp_sp_fd_set(&thefds, server_config.arpfds[i]);
}
}
if (server_config.auto_time) {
tv.tv_sec = timeout_end - time(0);
tv.tv_usec = 0;
}
memcpy(&rfds, &thefds, sizeof(fd_set));
if (!server_config.auto_time || tv.tv_sec > 0) {
retval = select(max_sock + 1, &rfds, NULL, NULL,
server_config.auto_time ? &tv : NULL);
} else retval = 0; /* If we already timed out, fall through */
if (retval == 0) {
write_leases();
timeout_end = time(0) + server_config.auto_time;
continue;
} else if (retval < 0 && errno != EINTR) {
DEBUG(LOG_INFO, "error on select");
continue;
}
switch (udhcp_sp_read(&rfds)) {
case SIGUSR1:
LOG(LOG_INFO, "Received a SIGUSR1");
write_leases();
/* why not just reset the timeout, eh */
timeout_end = time(0) + server_config.auto_time;
continue;
case SIGTERM:
LOG(LOG_INFO, "Received a SIGTERM");
write_leases();
return 0;
case 0: break; /* no signal */
default: continue; /* signal or error (probably EINTR) */
}
for (i = lastindex; i < (server_config.numofinterfaces * 2); i++) {
if (FD_ISSET(server_config.fds[i % server_config.numofinterfaces], &rfds)) {
server_config.currentinterface = i % server_config.numofinterfaces;
lastindex = server_config.currentinterface + 1;
break;
}
if (server_config.ippnp) {
if (FD_ISSET(server_config.arpfds[i % server_config.numofinterfaces], &rfds)) {
server_config.currentinterface = i % server_config.numofinterfaces;
lastindex = server_config.currentinterface + 1;
break;
}
}
}
if (server_config.ippnp) {
if (FD_ISSET(server_config.arpfds[server_config.currentinterface], &rfds)) {
unsigned char buf[1024];
struct sockaddr_ll sll;
int sll_len = sizeof(sll);
int n;
n = recvfrom(server_config.arpfds[server_config.currentinterface],
buf, sizeof(buf), MSG_DONTWAIT, (struct sockaddr*)&sll, &sll_len);
if (n < 0) {
DEBUG(LOG_INFO, "error receiving arp");
}
else {
DEBUG(LOG_INFO, "received arp on %s %d", server_config.ifname[server_config.currentinterface], n);
handleArpPacket(buf);
}
}
}
if (FD_ISSET(server_config.fds[server_config.currentinterface], &rfds)) {
if ((bytes = get_packet(&packet, server_config.fds[server_config.currentinterface])) < 0) {
if (bytes == -1 && errno != EINTR) {
DEBUG(LOG_INFO, "error on read, %m, reopening socket");
close(server_config.fds[server_config.currentinterface]);
max_sock = udhcp_sp_fd_unset(&thefds, server_config.fds[i]);
server_config.fds[server_config.currentinterface] = -1;
}
continue;
}
}
else
continue;
if ((state = get_option(&packet, DHCP_MESSAGE_TYPE)) == NULL) {
DEBUG(LOG_ERR, "couldn't get option from packet, ignoring");
continue;
}
/* ADDME: look for a static lease */
lease = find_lease_by_chaddr(packet.chaddr);
if (lease && lease->ippnpaddr) { /* The computer with this mac was seen with fixed ip address before */
char buf[256];
sprintf(buf, "ippnpremove %02X:%02X:%02X:%02X:%02X:%02X %d.%d.%d.%d %s",
lease->chaddr[0], lease->chaddr[1], lease->chaddr[2],
lease->chaddr[3], lease->chaddr[4], lease->chaddr[5],
(lease->yiaddr) & 0xff, (lease->yiaddr >> 8) & 0xff,
(lease->yiaddr >> 16) & 0xff, (lease->yiaddr >> 24) & 0xff,
lease->ifname);
system(buf);
}
switch (state[0]) {
case DHCPDISCOVER:
DEBUG(LOG_INFO,"received DISCOVER");
sprintf(buffer, "dhcpd.sh discover %02X:%02X:%02X:%02X:%02X:%02X %s",
packet.chaddr[0], packet.chaddr[1], packet.chaddr[2],
packet.chaddr[3], packet.chaddr[4], packet.chaddr[5], server_config.ifname[server_config.currentinterface]);
if (WEXITSTATUS(system(buffer)) == 0) {
if (sendOffer(&packet) < 0) {
LOG(LOG_ERR, "send OFFER failed");
}
}
break;
case DHCPREQUEST:
DEBUG(LOG_INFO, "received REQUEST");
requested = get_option(&packet, DHCP_REQUESTED_IP);
server_id = get_option(&packet, DHCP_SERVER_ID);
if (requested) memcpy(&requested_align, requested, 4);
if (server_id) memcpy(&server_id_align, server_id, 4);
if (lease) { /*ADDME: or static lease */
sprintf(buffer, "dhcpd.sh dhcprequest %02X:%02X:%02X:%02X:%02X:%02X %d.%d.%d.%d %s",
packet.chaddr[0], packet.chaddr[1], packet.chaddr[2],
packet.chaddr[3], packet.chaddr[4], packet.chaddr[5],
lease->yiaddr & 0xff, (lease->yiaddr >> 8) & 0xff,
(lease->yiaddr >> 16) & 0xff, (lease->yiaddr >> 24) & 0xff,
server_config.ifname[server_config.currentinterface]);
if (server_id) {
/* SELECTING State */
DEBUG(LOG_INFO, "server_id = %08x", ntohl(server_id_align));
if (server_id_align == server_config.server[server_config.currentinterface] && requested &&
requested_align == lease->yiaddr) {
if (WEXITSTATUS(system(buffer)) == 0)
sendACK(&packet, lease->yiaddr);
}
} else {
if (requested) {
/* INIT-REBOOT State */
if (lease->yiaddr == requested_align) {
if (WEXITSTATUS(system(buffer)) == 0)
sendACK(&packet, lease->yiaddr);
}
else sendNAK(&packet);
} else {
/* RENEWING or REBINDING State */
if (lease->yiaddr == packet.ciaddr) {
if (WEXITSTATUS(system(buffer)) == 0)
sendACK(&packet, lease->yiaddr);
}
else {
/* don't know what to do!!!! */
sendNAK(&packet);
}
}
}
/* what to do if we have no record of the client */
} else if (server_id) {
/* SELECTING State */
} else if (requested) {
/* INIT-REBOOT State */
if ((lease = find_lease_by_yiaddr(requested_align))) {
if (lease_expired(lease)) {
/* probably best if we drop this lease */
memset(lease->chaddr, 0, 16);
/* make some contention for this address */
} else sendNAK(&packet);
} else if (requested_align < server_config.start ||
requested_align > server_config.end ||
((requested_align - server_config.start) % server_config.start) == 1) {
sendNAK(&packet);
} /* else remain silent */
} else {
/* RENEWING or REBINDING State */
}
break;
case DHCPDECLINE:
DEBUG(LOG_INFO,"received DECLINE");
if (lease) {
memset(lease->chaddr, 0, 16);
lease->expires = time(0) + server_config.decline_time;
}
break;
case DHCPRELEASE:
DEBUG(LOG_INFO,"received RELEASE");
if (lease) {
sprintf(buffer, "dhcpd.sh release %02X:%02X:%02X:%02X:%02X:%02X %d.%d.%d.%d %s",
packet.chaddr[0], packet.chaddr[1], packet.chaddr[2],
packet.chaddr[3], packet.chaddr[4], packet.chaddr[5],
lease->yiaddr & 0xff, (lease->yiaddr >> 8) & 0xff,
(lease->yiaddr >> 16) & 0xff, (lease->yiaddr >> 24) & 0xff,
server_config.ifname[server_config.currentinterface]);
system(buffer);
lease->expires = time(0);
}
break;
case DHCPINFORM:
DEBUG(LOG_INFO,"received INFORM");
if (lease) {
sprintf(buffer, "dhcpd.sh inform %02X:%02X:%02X:%02X:%02X:%02X %d.%d.%d.%d %s",
packet.chaddr[0], packet.chaddr[1], packet.chaddr[2],
packet.chaddr[3], packet.chaddr[4], packet.chaddr[5],
lease->yiaddr & 0xff, (lease->yiaddr >> 8) & 0xff,
(lease->yiaddr >> 16) & 0xff, (lease->yiaddr >> 24) & 0xff,
server_config.ifname[server_config.currentinterface]);
system(buffer);
send_inform(&packet, lease->yiaddr);
}
break;
default:
LOG(LOG_WARNING, "unsupported DHCP message (%02x) -- ignoring", state[0]);
}
}
return 0;
}
