[821] | 1 | /* serverpacket.c
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| 2 | *
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| 3 | * Construct and send DHCP server packets
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| 4 | *
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| 5 | * Russ Dill <Russ.Dill@asu.edu> July 2001
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| 6 | *
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| 7 | * This program is free software; you can redistribute it and/or modify
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| 8 | * it under the terms of the GNU General Public License as published by
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| 9 | * the Free Software Foundation; either version 2 of the License, or
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| 10 | * (at your option) any later version.
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| 11 | *
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| 12 | * This program is distributed in the hope that it will be useful,
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| 13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 15 | * GNU General Public License for more details.
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| 16 | *
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| 17 | * You should have received a copy of the GNU General Public License
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| 18 | * along with this program; if not, write to the Free Software
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| 19 | * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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| 20 | */
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| 21 |
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| 22 | #include <sys/socket.h>
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| 23 | #include <netinet/in.h>
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| 24 | #include <arpa/inet.h>
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| 25 | #include <string.h>
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| 26 | #include <time.h>
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| 27 |
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| 28 | #include "common.h"
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| 29 | #include "serverpacket.h"
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| 30 | #include "dhcpd.h"
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| 31 | #include "options.h"
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| 32 | #include "static_leases.h"
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| 33 |
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| 34 | /* send a packet to giaddr using the kernel ip stack */
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| 35 | static int send_packet_to_relay(struct dhcpMessage *payload)
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| 36 | {
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| 37 | DEBUG(LOG_INFO, "Forwarding packet to relay");
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| 38 |
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| 39 | return udhcp_kernel_packet(payload, server_config.server, SERVER_PORT,
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| 40 | payload->giaddr, SERVER_PORT);
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| 41 | }
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| 42 |
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| 43 |
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| 44 | /* send a packet to a specific arp address and ip address by creating our own ip packet */
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| 45 | static int send_packet_to_client(struct dhcpMessage *payload, int force_broadcast)
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| 46 | {
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| 47 | uint8_t *chaddr;
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| 48 | uint32_t ciaddr;
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| 49 |
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| 50 | if (force_broadcast) {
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| 51 | DEBUG(LOG_INFO, "broadcasting packet to client (NAK)");
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| 52 | ciaddr = INADDR_BROADCAST;
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| 53 | chaddr = MAC_BCAST_ADDR;
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| 54 | } else if (payload->ciaddr) {
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| 55 | DEBUG(LOG_INFO, "unicasting packet to client ciaddr");
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| 56 | ciaddr = payload->ciaddr;
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| 57 | chaddr = payload->chaddr;
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| 58 | } else if (ntohs(payload->flags) & BROADCAST_FLAG) {
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| 59 | DEBUG(LOG_INFO, "broadcasting packet to client (requested)");
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| 60 | ciaddr = INADDR_BROADCAST;
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| 61 | chaddr = MAC_BCAST_ADDR;
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| 62 | } else {
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| 63 | DEBUG(LOG_INFO, "unicasting packet to client yiaddr");
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| 64 | ciaddr = payload->yiaddr;
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| 65 | chaddr = payload->chaddr;
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| 66 | }
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| 67 | return udhcp_raw_packet(payload, server_config.server, SERVER_PORT,
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| 68 | ciaddr, CLIENT_PORT, chaddr, server_config.ifindex);
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| 69 | }
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| 70 |
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| 71 |
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| 72 | /* send a dhcp packet, if force broadcast is set, the packet will be broadcast to the client */
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| 73 | static int send_packet(struct dhcpMessage *payload, int force_broadcast)
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| 74 | {
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| 75 | int ret;
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| 76 |
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| 77 | if (payload->giaddr)
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| 78 | ret = send_packet_to_relay(payload);
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| 79 | else ret = send_packet_to_client(payload, force_broadcast);
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| 80 | return ret;
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| 81 | }
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| 82 |
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| 83 |
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| 84 | static void init_packet(struct dhcpMessage *packet, struct dhcpMessage *oldpacket, char type)
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| 85 | {
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| 86 | udhcp_init_header(packet, type);
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| 87 | packet->xid = oldpacket->xid;
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| 88 | memcpy(packet->chaddr, oldpacket->chaddr, 16);
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| 89 | packet->flags = oldpacket->flags;
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| 90 | packet->giaddr = oldpacket->giaddr;
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| 91 | packet->ciaddr = oldpacket->ciaddr;
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| 92 | add_simple_option(packet->options, DHCP_SERVER_ID, server_config.server);
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| 93 | }
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| 94 |
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| 95 |
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| 96 | /* add in the bootp options */
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| 97 | static void add_bootp_options(struct dhcpMessage *packet)
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| 98 | {
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| 99 | packet->siaddr = server_config.siaddr;
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| 100 | if (server_config.sname)
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| 101 | strncpy((char*)packet->sname, server_config.sname, sizeof(packet->sname) - 1);
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| 102 | if (server_config.boot_file)
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| 103 | strncpy((char*)packet->file, server_config.boot_file, sizeof(packet->file) - 1);
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| 104 | }
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| 105 |
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| 106 |
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| 107 | /* send a DHCP OFFER to a DHCP DISCOVER */
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| 108 | int sendOffer(struct dhcpMessage *oldpacket)
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| 109 | {
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| 110 | struct dhcpMessage packet;
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| 111 | struct dhcpOfferedAddr *lease = NULL;
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| 112 | uint32_t req_align, lease_time_align = server_config.lease;
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| 113 | uint8_t *req, *lease_time;
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| 114 | struct option_set *curr;
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| 115 | struct in_addr addr;
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| 116 |
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| 117 | uint32_t static_lease_ip;
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| 118 |
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| 119 | init_packet(&packet, oldpacket, DHCPOFFER);
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| 120 |
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| 121 | static_lease_ip = getIpByMac(server_config.static_leases, oldpacket->chaddr);
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| 122 |
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| 123 | /* ADDME: if static, short circuit */
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| 124 | if(!static_lease_ip)
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| 125 | {
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| 126 | /* the client is in our lease/offered table */
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| 127 | if ((lease = find_lease_by_chaddr(oldpacket->chaddr))) {
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| 128 | if (!lease_expired(lease))
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| 129 | lease_time_align = lease->expires - time(0);
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| 130 | packet.yiaddr = lease->yiaddr;
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| 131 |
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| 132 | /* Or the client has a requested ip */
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| 133 | } else if ((req = get_option(oldpacket, DHCP_REQUESTED_IP)) &&
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| 134 |
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| 135 | /* Don't look here (ugly hackish thing to do) */
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| 136 | memcpy(&req_align, req, 4) &&
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| 137 |
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| 138 | /* and the ip is in the lease range */
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| 139 | ntohl(req_align) >= ntohl(server_config.start) &&
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| 140 | ntohl(req_align) <= ntohl(server_config.end) &&
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| 141 |
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| 142 | !static_lease_ip && /* Check that its not a static lease */
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| 143 | /* and is not already taken/offered */
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| 144 | ((!(lease = find_lease_by_yiaddr(req_align)) ||
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| 145 |
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| 146 | /* or its taken, but expired */ /* ADDME: or maybe in here */
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| 147 | lease_expired(lease)))) {
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| 148 | packet.yiaddr = req_align; /* FIXME: oh my, is there a host using this IP? */
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| 149 |
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| 150 | /* otherwise, find a free IP */
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| 151 | } else {
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| 152 | /* Is it a static lease? (No, because find_address skips static lease) */
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| 153 | packet.yiaddr = find_address(0);
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| 154 |
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| 155 | /* try for an expired lease */
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| 156 | if (!packet.yiaddr) packet.yiaddr = find_address(1);
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| 157 | }
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| 158 |
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| 159 | if(!packet.yiaddr) {
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| 160 | LOG(LOG_WARNING, "no IP addresses to give -- OFFER abandoned");
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| 161 | return -1;
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| 162 | }
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| 163 |
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| 164 | if (!add_lease(packet.chaddr, packet.yiaddr, server_config.offer_time)) {
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| 165 | LOG(LOG_WARNING, "lease pool is full -- OFFER abandoned");
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| 166 | return -1;
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| 167 | }
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| 168 |
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| 169 | if ((lease_time = get_option(oldpacket, DHCP_LEASE_TIME))) {
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| 170 | memcpy(&lease_time_align, lease_time, 4);
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| 171 | lease_time_align = ntohl(lease_time_align);
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| 172 | if (lease_time_align > server_config.lease)
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| 173 | lease_time_align = server_config.lease;
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| 174 | }
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| 175 |
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| 176 | /* Make sure we aren't just using the lease time from the previous offer */
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| 177 | if (lease_time_align < server_config.min_lease)
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| 178 | lease_time_align = server_config.lease;
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| 179 | }
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| 180 | /* ADDME: end of short circuit */
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| 181 | else
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| 182 | {
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| 183 | /* It is a static lease... use it */
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| 184 | packet.yiaddr = static_lease_ip;
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| 185 | }
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| 186 |
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| 187 | add_simple_option(packet.options, DHCP_LEASE_TIME, htonl(lease_time_align));
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| 188 |
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| 189 | curr = server_config.options;
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| 190 | while (curr) {
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| 191 | if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
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| 192 | add_option_string(packet.options, curr->data);
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| 193 | curr = curr->next;
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| 194 | }
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| 195 |
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| 196 | add_bootp_options(&packet);
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| 197 |
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| 198 | addr.s_addr = packet.yiaddr;
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| 199 | LOG(LOG_INFO, "sending OFFER of %s", inet_ntoa(addr));
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| 200 | return send_packet(&packet, 0);
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| 201 | }
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| 202 |
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| 203 |
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| 204 | int sendNAK(struct dhcpMessage *oldpacket)
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| 205 | {
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| 206 | struct dhcpMessage packet;
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| 207 |
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| 208 | init_packet(&packet, oldpacket, DHCPNAK);
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| 209 |
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| 210 | DEBUG(LOG_INFO, "sending NAK");
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| 211 | return send_packet(&packet, 1);
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| 212 | }
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| 213 |
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| 214 |
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| 215 | int sendACK(struct dhcpMessage *oldpacket, uint32_t yiaddr)
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| 216 | {
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| 217 | struct dhcpMessage packet;
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| 218 | struct option_set *curr;
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| 219 | uint8_t *lease_time;
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| 220 | uint32_t lease_time_align = server_config.lease;
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| 221 | struct in_addr addr;
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| 222 |
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| 223 | init_packet(&packet, oldpacket, DHCPACK);
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| 224 | packet.yiaddr = yiaddr;
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| 225 |
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| 226 | if ((lease_time = get_option(oldpacket, DHCP_LEASE_TIME))) {
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| 227 | memcpy(&lease_time_align, lease_time, 4);
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| 228 | lease_time_align = ntohl(lease_time_align);
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| 229 | if (lease_time_align > server_config.lease)
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| 230 | lease_time_align = server_config.lease;
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| 231 | else if (lease_time_align < server_config.min_lease)
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| 232 | lease_time_align = server_config.lease;
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| 233 | }
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| 234 |
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| 235 | add_simple_option(packet.options, DHCP_LEASE_TIME, htonl(lease_time_align));
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| 236 |
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| 237 | curr = server_config.options;
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| 238 | while (curr) {
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| 239 | if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
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| 240 | add_option_string(packet.options, curr->data);
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| 241 | curr = curr->next;
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| 242 | }
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| 243 |
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| 244 | add_bootp_options(&packet);
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| 245 |
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| 246 | addr.s_addr = packet.yiaddr;
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| 247 | LOG(LOG_INFO, "sending ACK to %s", inet_ntoa(addr));
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| 248 |
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| 249 | if (send_packet(&packet, 0) < 0)
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| 250 | return -1;
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| 251 |
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| 252 | add_lease(packet.chaddr, packet.yiaddr, lease_time_align);
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| 253 |
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| 254 | return 0;
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| 255 | }
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| 256 |
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| 257 |
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| 258 | int send_inform(struct dhcpMessage *oldpacket)
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| 259 | {
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| 260 | struct dhcpMessage packet;
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| 261 | struct option_set *curr;
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| 262 |
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| 263 | init_packet(&packet, oldpacket, DHCPACK);
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| 264 |
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| 265 | curr = server_config.options;
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| 266 | while (curr) {
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| 267 | if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
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| 268 | add_option_string(packet.options, curr->data);
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| 269 | curr = curr->next;
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| 270 | }
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| 271 |
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| 272 | add_bootp_options(&packet);
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| 273 |
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| 274 | return send_packet(&packet, 0);
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| 275 | }
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