busybox/networking/udhcp/serverpacket.c

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/* vi: set sw=4 ts=4: */
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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 "common.h"
#include "dhcpc.h"
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#include "dhcpd.h"
#include "options.h"
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/* send a packet to giaddr using the kernel ip stack */
static int send_packet_to_relay(struct dhcpMessage *payload)
{
DEBUG("Forwarding packet to relay");
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return udhcp_send_kernel_packet(payload, server_config.server, SERVER_PORT,
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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)
{
const uint8_t *chaddr;
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uint32_t ciaddr;
if (force_broadcast) {
DEBUG("broadcasting packet to client (NAK)");
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ciaddr = INADDR_BROADCAST;
chaddr = MAC_BCAST_ADDR;
} else if (payload->ciaddr) {
DEBUG("unicasting packet to client ciaddr");
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ciaddr = payload->ciaddr;
chaddr = payload->chaddr;
} else if (payload->flags & htons(BROADCAST_FLAG)) {
DEBUG("broadcasting packet to client (requested)");
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ciaddr = INADDR_BROADCAST;
chaddr = MAC_BCAST_ADDR;
} else {
DEBUG("unicasting packet to client yiaddr");
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ciaddr = payload->yiaddr;
chaddr = payload->chaddr;
}
return udhcp_send_raw_packet(payload,
/*src*/ server_config.server, SERVER_PORT,
/*dst*/ ciaddr, CLIENT_PORT, chaddr,
server_config.ifindex);
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}
/* 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)
{
if (payload->giaddr)
return send_packet_to_relay(payload);
return send_packet_to_client(payload, force_broadcast);
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}
static void init_packet(struct dhcpMessage *packet, struct dhcpMessage *oldpacket, char type)
{
udhcp_init_header(packet, type);
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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((char*)packet->sname, server_config.sname, sizeof(packet->sname) - 1);
if (server_config.boot_file)
strncpy((char*)packet->file, server_config.boot_file, sizeof(packet->file) - 1);
}
/* send a DHCP OFFER to a DHCP DISCOVER */
int FAST_FUNC send_offer(struct dhcpMessage *oldpacket)
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{
struct dhcpMessage packet;
struct dhcpOfferedAddr *lease = NULL;
uint32_t req_align;
uint32_t lease_time_aligned = server_config.lease;
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uint8_t *req, *lease_time;
struct option_set *curr;
struct in_addr addr;
uint32_t static_lease_ip;
init_packet(&packet, oldpacket, DHCPOFFER);
static_lease_ip = getIpByMac(server_config.static_leases, oldpacket->chaddr);
/* ADDME: if static, short circuit */
if (!static_lease_ip) {
/* the client is in our lease/offered table */
lease = find_lease_by_chaddr(oldpacket->chaddr);
if (lease) {
if (!lease_expired(lease))
lease_time_aligned = 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) >= server_config.start_ip
&& ntohl(req_align) <= server_config.end_ip
&& !static_lease_ip /* Check that its not a static lease */
/* and is not already taken/offered */
&& (!(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? */
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/* otherwise, find a free IP */
} else {
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/* Is it a static lease? (No, because find_address skips static lease) */
packet.yiaddr = find_address(0);
/* try for an expired lease */
if (!packet.yiaddr)
packet.yiaddr = find_address(1);
}
if (!packet.yiaddr) {
bb_error_msg("no IP addresses to give - OFFER abandoned");
return -1;
}
if (!add_lease(packet.chaddr, packet.yiaddr, server_config.offer_time)) {
bb_error_msg("lease pool is full - OFFER abandoned");
return -1;
}
lease_time = get_option(oldpacket, DHCP_LEASE_TIME);
if (lease_time) {
move_from_unaligned32(lease_time_aligned, lease_time);
lease_time_aligned = ntohl(lease_time_aligned);
if (lease_time_aligned > server_config.lease)
lease_time_aligned = server_config.lease;
}
/* Make sure we aren't just using the lease time from the previous offer */
if (lease_time_aligned < server_config.min_lease)
lease_time_aligned = server_config.lease;
/* ADDME: end of short circuit */
} else {
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/* It is a static lease... use it */
packet.yiaddr = static_lease_ip;
}
add_simple_option(packet.options, DHCP_LEASE_TIME, htonl(lease_time_aligned));
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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;
bb_info_msg("Sending OFFER of %s", inet_ntoa(addr));
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return send_packet(&packet, 0);
}
int FAST_FUNC send_NAK(struct dhcpMessage *oldpacket)
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{
struct dhcpMessage packet;
init_packet(&packet, oldpacket, DHCPNAK);
DEBUG("Sending NAK");
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return send_packet(&packet, 1);
}
int FAST_FUNC send_ACK(struct dhcpMessage *oldpacket, uint32_t yiaddr)
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{
struct dhcpMessage packet;
struct option_set *curr;
uint8_t *lease_time;
uint32_t lease_time_aligned = server_config.lease;
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struct in_addr addr;
init_packet(&packet, oldpacket, DHCPACK);
packet.yiaddr = yiaddr;
lease_time = get_option(oldpacket, DHCP_LEASE_TIME);
if (lease_time) {
move_from_unaligned32(lease_time_aligned, lease_time);
lease_time_aligned = ntohl(lease_time_aligned);
if (lease_time_aligned > server_config.lease)
lease_time_aligned = server_config.lease;
else if (lease_time_aligned < server_config.min_lease)
lease_time_aligned = server_config.lease;
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}
add_simple_option(packet.options, DHCP_LEASE_TIME, htonl(lease_time_aligned));
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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;
bb_info_msg("Sending ACK to %s", inet_ntoa(addr));
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if (send_packet(&packet, 0) < 0)
return -1;
add_lease(packet.chaddr, packet.yiaddr, lease_time_aligned);
if (ENABLE_FEATURE_UDHCPD_WRITE_LEASES_EARLY) {
/* rewrite the file with leases at every new acceptance */
write_leases();
}
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return 0;
}
int FAST_FUNC send_inform(struct dhcpMessage *oldpacket)
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{
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);
}