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/* serverpacket.c
*
* Construct and send DHCP server packets
*
* Russ Dill <Russ.Dill@asu.edu> 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 <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <string.h>
#include <time.h>
#include "serverpacket.h"
#include "dhcpd.h"
#include "options.h"
#include "common.h"
/* send a packet to giaddr using the kernel ip stack */
static int send_packet_to_relay(struct dhcpMessage *payload)
{
DEBUG(LOG_INFO, "Forwarding packet to relay");
return kernel_packet(payload, server_config.server, SERVER_PORT,
payload->giaddr, SERVER_PORT);
}
/* send a packet to a specific arp address and ip address by creating our own ip packet */
static int send_packet_to_client(struct dhcpMessage *payload, int force_broadcast)
{
uint8_t *chaddr;
uint32_t ciaddr;
if (force_broadcast) {
DEBUG(LOG_INFO, "broadcasting packet to client (NAK)");
ciaddr = INADDR_BROADCAST;
chaddr = MAC_BCAST_ADDR;
} else if (payload->ciaddr) {
DEBUG(LOG_INFO, "unicasting packet to client ciaddr");
ciaddr = payload->ciaddr;
chaddr = payload->chaddr;
} else if (ntohs(payload->flags) & BROADCAST_FLAG) {
DEBUG(LOG_INFO, "broadcasting packet to client (requested)");
ciaddr = INADDR_BROADCAST;
chaddr = MAC_BCAST_ADDR;
} else {
DEBUG(LOG_INFO, "unicasting packet to client yiaddr");
ciaddr = payload->yiaddr;
chaddr = payload->chaddr;
}
return raw_packet(payload, server_config.server, SERVER_PORT,
ciaddr, CLIENT_PORT, chaddr, server_config.ifindex);
}
/* send a dhcp packet, if force broadcast is set, the packet will be broadcast to the client */
static int send_packet(struct dhcpMessage *payload, int force_broadcast)
{
int ret;
if (payload->giaddr)
ret = send_packet_to_relay(payload);
else ret = send_packet_to_client(payload, force_broadcast);
return ret;
}
static void init_packet(struct dhcpMessage *packet, struct dhcpMessage *oldpacket, char type)
{
init_header(packet, type);
packet->xid = oldpacket->xid;
memcpy(packet->chaddr, oldpacket->chaddr, 16);
packet->flags = oldpacket->flags;
packet->giaddr = oldpacket->giaddr;
packet->ciaddr = oldpacket->ciaddr;
add_simple_option(packet->options, DHCP_SERVER_ID, server_config.server);
}
/* add in the bootp options */
static void add_bootp_options(struct dhcpMessage *packet)
{
packet->siaddr = server_config.siaddr;
if (server_config.sname)
strncpy(packet->sname, server_config.sname, sizeof(packet->sname) - 1);
if (server_config.boot_file)
strncpy(packet->file, server_config.boot_file, sizeof(packet->file) - 1);
}
/* send a DHCP OFFER to a DHCP DISCOVER */
int sendOffer(struct dhcpMessage *oldpacket)
{
struct dhcpMessage packet;
struct dhcpOfferedAddr *lease = NULL;
uint32_t req_align, lease_time_align = server_config.lease;
uint8_t *req, *lease_time;
struct option_set *curr;
struct in_addr addr;
init_packet(&packet, oldpacket, DHCPOFFER);
/* ADDME: if static, short circuit */
/* the client is in our lease/offered table */
if ((lease = find_lease_by_chaddr(oldpacket->chaddr))) {
if (!lease_expired(lease))
lease_time_align = lease->expires - time(0);
packet.yiaddr = lease->yiaddr;
/* Or the client has a requested ip */
} else if ((req = get_option(oldpacket, DHCP_REQUESTED_IP)) &&
/* Don't look here (ugly hackish thing to do) */
memcpy(&req_align, req, 4) &&
/* and the ip is in the lease range */
ntohl(req_align) >= ntohl(server_config.start) &&
ntohl(req_align) <= ntohl(server_config.end) &&
/* and its not already taken/offered */ /* ADDME: check that its not a static lease */
((!(lease = find_lease_by_yiaddr(req_align)) ||
/* or its taken, but expired */ /* ADDME: or maybe in here */
lease_expired(lease)))) {
packet.yiaddr = req_align; /* FIXME: oh my, is there a host using this IP? */
/* otherwise, find a free IP */ /*ADDME: is it a static lease? */
} else {
packet.yiaddr = find_address(0);
/* try for an expired lease */
if (!packet.yiaddr) packet.yiaddr = find_address(1);
}
if(!packet.yiaddr) {
LOG(LOG_WARNING, "no IP addresses to give -- OFFER abandoned");
return -1;
}
if (!add_lease(packet.chaddr, packet.yiaddr, server_config.offer_time)) {
LOG(LOG_WARNING, "lease pool is full -- OFFER abandoned");
return -1;
}
if ((lease_time = get_option(oldpacket, DHCP_LEASE_TIME))) {
memcpy(&lease_time_align, lease_time, 4);
lease_time_align = ntohl(lease_time_align);
if (lease_time_align > server_config.lease)
lease_time_align = server_config.lease;
}
/* Make sure we aren't just using the lease time from the previous offer */
if (lease_time_align < server_config.min_lease)
lease_time_align = server_config.lease;
/* ADDME: end of short circuit */
add_simple_option(packet.options, DHCP_LEASE_TIME, htonl(lease_time_align));
curr = server_config.options;
while (curr) {
if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
add_option_string(packet.options, curr->data);
curr = curr->next;
}
add_bootp_options(&packet);
addr.s_addr = packet.yiaddr;
LOG(LOG_INFO, "sending OFFER of %s", inet_ntoa(addr));
return send_packet(&packet, 0);
}
int sendNAK(struct dhcpMessage *oldpacket)
{
struct dhcpMessage packet;
init_packet(&packet, oldpacket, DHCPNAK);
DEBUG(LOG_INFO, "sending NAK");
return send_packet(&packet, 1);
}
int sendACK(struct dhcpMessage *oldpacket, uint32_t yiaddr)
{
struct dhcpMessage packet;
struct option_set *curr;
uint8_t *lease_time;
uint32_t lease_time_align = server_config.lease;
struct in_addr addr;
init_packet(&packet, oldpacket, DHCPACK);
packet.yiaddr = yiaddr;
if ((lease_time = get_option(oldpacket, DHCP_LEASE_TIME))) {
memcpy(&lease_time_align, lease_time, 4);
lease_time_align = ntohl(lease_time_align);
if (lease_time_align > server_config.lease)
lease_time_align = server_config.lease;
else if (lease_time_align < server_config.min_lease)
lease_time_align = server_config.lease;
}
add_simple_option(packet.options, DHCP_LEASE_TIME, htonl(lease_time_align));
curr = server_config.options;
while (curr) {
if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
add_option_string(packet.options, curr->data);
curr = curr->next;
}
add_bootp_options(&packet);
addr.s_addr = packet.yiaddr;
LOG(LOG_INFO, "sending ACK to %s", inet_ntoa(addr));
if (send_packet(&packet, 0) < 0)
return -1;
add_lease(packet.chaddr, packet.yiaddr, lease_time_align);
return 0;
}
int send_inform(struct dhcpMessage *oldpacket)
{
struct dhcpMessage packet;
struct option_set *curr;
init_packet(&packet, oldpacket, DHCPACK);
curr = server_config.options;
while (curr) {
if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
add_option_string(packet.options, curr->data);
curr = curr->next;
}
add_bootp_options(&packet);
return send_packet(&packet, 0);
}
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