[3320] | 1 | /* vi: set sw=4 ts=4: */
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| 2 | /*
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| 3 | * udhcp server
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| 4 | * Copyright (C) 1999 Matthew Ramsay <matthewr@moreton.com.au>
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| 5 | * Chris Trew <ctrew@moreton.com.au>
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| 6 | *
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| 7 | * Rewrite by Russ Dill <Russ.Dill@asu.edu> July 2001
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| 8 | *
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| 9 | * This program is free software; you can redistribute it and/or modify
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| 10 | * it under the terms of the GNU General Public License as published by
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| 11 | * the Free Software Foundation; either version 2 of the License, or
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| 12 | * (at your option) any later version.
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| 13 | *
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| 14 | * This program is distributed in the hope that it will be useful,
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| 15 | * but WITHOUT ANY WARRANTY; without even the implied warranty of
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| 16 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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| 17 | * GNU General Public License for more details.
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| 18 | *
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| 19 | * You should have received a copy of the GNU General Public License
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| 20 | * along with this program; if not, write to the Free Software
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| 21 | * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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| 22 | */
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| 23 | #include <syslog.h>
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| 24 | #include "common.h"
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| 25 | #include "dhcpc.h"
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| 26 | #include "dhcpd.h"
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| 27 |
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| 28 |
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| 29 | /* Send a packet to a specific mac address and ip address by creating our own ip packet */
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| 30 | static void send_packet_to_client(struct dhcp_packet *dhcp_pkt, int force_broadcast)
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| 31 | {
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| 32 | const uint8_t *chaddr;
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| 33 | uint32_t ciaddr;
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| 34 |
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| 35 | // Was:
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| 36 | //if (force_broadcast) { /* broadcast */ }
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| 37 | //else if (dhcp_pkt->ciaddr) { /* unicast to dhcp_pkt->ciaddr */ }
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| 38 | //else if (dhcp_pkt->flags & htons(BROADCAST_FLAG)) { /* broadcast */ }
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| 39 | //else { /* unicast to dhcp_pkt->yiaddr */ }
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| 40 | // But this is wrong: yiaddr is _our_ idea what client's IP is
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| 41 | // (for example, from lease file). Client may not know that,
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| 42 | // and may not have UDP socket listening on that IP!
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| 43 | // We should never unicast to dhcp_pkt->yiaddr!
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| 44 | // dhcp_pkt->ciaddr, OTOH, comes from client's request packet,
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| 45 | // and can be used.
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| 46 |
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| 47 | if (force_broadcast
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| 48 | || (dhcp_pkt->flags & htons(BROADCAST_FLAG))
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| 49 | || dhcp_pkt->ciaddr == 0
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| 50 | ) {
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| 51 | log1("Broadcasting packet to client");
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| 52 | ciaddr = INADDR_BROADCAST;
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| 53 | chaddr = MAC_BCAST_ADDR;
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| 54 | } else {
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| 55 | log1("Unicasting packet to client ciaddr");
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| 56 | ciaddr = dhcp_pkt->ciaddr;
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| 57 | chaddr = dhcp_pkt->chaddr;
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| 58 | }
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| 59 |
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| 60 | udhcp_send_raw_packet(dhcp_pkt,
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| 61 | /*src*/ server_config.server_nip, SERVER_PORT,
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| 62 | /*dst*/ ciaddr, CLIENT_PORT, chaddr,
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| 63 | server_config.ifindex);
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| 64 | }
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| 65 |
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| 66 | /* Send a packet to gateway_nip using the kernel ip stack */
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| 67 | static void send_packet_to_relay(struct dhcp_packet *dhcp_pkt)
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| 68 | {
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| 69 | log1("Forwarding packet to relay");
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| 70 |
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| 71 | udhcp_send_kernel_packet(dhcp_pkt,
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| 72 | server_config.server_nip, SERVER_PORT,
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| 73 | dhcp_pkt->gateway_nip, SERVER_PORT);
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| 74 | }
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| 75 |
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| 76 | static void send_packet(struct dhcp_packet *dhcp_pkt, int force_broadcast)
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| 77 | {
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| 78 | if (dhcp_pkt->gateway_nip)
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| 79 | send_packet_to_relay(dhcp_pkt);
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| 80 | else
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| 81 | send_packet_to_client(dhcp_pkt, force_broadcast);
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| 82 | }
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| 83 |
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| 84 | static void init_packet(struct dhcp_packet *packet, struct dhcp_packet *oldpacket, char type)
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| 85 | {
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| 86 | /* Sets op, htype, hlen, cookie fields
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| 87 | * and adds DHCP_MESSAGE_TYPE option */
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| 88 | udhcp_init_header(packet, type);
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| 89 |
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| 90 | packet->xid = oldpacket->xid;
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| 91 | memcpy(packet->chaddr, oldpacket->chaddr, sizeof(oldpacket->chaddr));
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| 92 | packet->flags = oldpacket->flags;
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| 93 | packet->gateway_nip = oldpacket->gateway_nip;
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| 94 | packet->ciaddr = oldpacket->ciaddr;
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| 95 | udhcp_add_simple_option(packet, DHCP_SERVER_ID, server_config.server_nip);
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| 96 | }
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| 97 |
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| 98 | /* Fill options field, siaddr_nip, and sname and boot_file fields.
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| 99 | * TODO: teach this code to use overload option.
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| 100 | */
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| 101 | static void add_server_options(struct dhcp_packet *packet)
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| 102 | {
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| 103 | struct option_set *curr = server_config.options;
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| 104 |
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| 105 | while (curr) {
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| 106 | if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
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| 107 | udhcp_add_binary_option(packet, curr->data);
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| 108 | curr = curr->next;
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| 109 | }
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| 110 |
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| 111 | packet->siaddr_nip = server_config.siaddr_nip;
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| 112 |
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| 113 | if (server_config.sname)
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| 114 | strncpy((char*)packet->sname, server_config.sname, sizeof(packet->sname) - 1);
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| 115 | if (server_config.boot_file)
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| 116 | strncpy((char*)packet->file, server_config.boot_file, sizeof(packet->file) - 1);
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| 117 | }
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| 118 |
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| 119 | static uint32_t select_lease_time(struct dhcp_packet *packet)
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| 120 | {
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| 121 | uint32_t lease_time_sec = server_config.max_lease_sec;
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| 122 | uint8_t *lease_time_opt = udhcp_get_option(packet, DHCP_LEASE_TIME);
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| 123 | if (lease_time_opt) {
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| 124 | move_from_unaligned32(lease_time_sec, lease_time_opt);
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| 125 | lease_time_sec = ntohl(lease_time_sec);
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| 126 | if (lease_time_sec > server_config.max_lease_sec)
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| 127 | lease_time_sec = server_config.max_lease_sec;
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| 128 | if (lease_time_sec < server_config.min_lease_sec)
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| 129 | lease_time_sec = server_config.min_lease_sec;
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| 130 | }
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| 131 | return lease_time_sec;
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| 132 | }
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| 133 |
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| 134 | /* We got a DHCP DISCOVER. Send an OFFER. */
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| 135 | /* NOINLINE: limit stack usage in caller */
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| 136 | static NOINLINE void send_offer(struct dhcp_packet *oldpacket, uint32_t static_lease_nip, struct dyn_lease *lease)
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| 137 | {
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| 138 | struct dhcp_packet packet;
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| 139 | uint32_t lease_time_sec;
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| 140 | struct in_addr addr;
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| 141 |
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| 142 | init_packet(&packet, oldpacket, DHCPOFFER);
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| 143 |
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| 144 | /* If it is a static lease, use its IP */
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| 145 | packet.yiaddr = static_lease_nip;
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| 146 | /* Else: */
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| 147 | if (!static_lease_nip) {
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| 148 | /* We have no static lease for client's chaddr */
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| 149 | uint32_t req_nip;
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| 150 | uint8_t *req_ip_opt;
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| 151 | const char *p_host_name;
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| 152 |
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| 153 | if (lease) {
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| 154 | /* We have a dynamic lease for client's chaddr.
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| 155 | * Reuse its IP (even if lease is expired).
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| 156 | * Note that we ignore requested IP in this case.
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| 157 | */
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| 158 | packet.yiaddr = lease->lease_nip;
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| 159 | }
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| 160 | /* Or: if client has requested an IP */
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| 161 | else if ((req_ip_opt = udhcp_get_option(oldpacket, DHCP_REQUESTED_IP)) != NULL
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| 162 | /* (read IP) */
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| 163 | && (move_from_unaligned32(req_nip, req_ip_opt), 1)
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| 164 | /* and the IP is in the lease range */
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| 165 | && ntohl(req_nip) >= server_config.start_ip
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| 166 | && ntohl(req_nip) <= server_config.end_ip
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| 167 | /* and */
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| 168 | && ( !(lease = find_lease_by_nip(req_nip)) /* is not already taken */
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| 169 | || is_expired_lease(lease) /* or is taken, but expired */
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| 170 | )
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| 171 | ) {
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| 172 | packet.yiaddr = req_nip;
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| 173 | }
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| 174 | else {
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| 175 | /* Otherwise, find a free IP */
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| 176 | packet.yiaddr = find_free_or_expired_nip(oldpacket->chaddr);
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| 177 | }
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| 178 |
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| 179 | if (!packet.yiaddr) {
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| 180 | bb_error_msg("no free IP addresses. OFFER abandoned");
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| 181 | return;
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| 182 | }
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| 183 | /* Reserve the IP for a short time hoping to get DHCPREQUEST soon */
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| 184 | p_host_name = (const char*) udhcp_get_option(oldpacket, DHCP_HOST_NAME);
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| 185 | lease = add_lease(packet.chaddr, packet.yiaddr,
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| 186 | server_config.offer_time,
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| 187 | p_host_name,
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| 188 | p_host_name ? (unsigned char)p_host_name[OPT_LEN - OPT_DATA] : 0
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| 189 | );
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| 190 | if (!lease) {
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| 191 | bb_error_msg("no free IP addresses. OFFER abandoned");
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| 192 | return;
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| 193 | }
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| 194 | }
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| 195 |
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| 196 | lease_time_sec = select_lease_time(oldpacket);
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| 197 | udhcp_add_simple_option(&packet, DHCP_LEASE_TIME, htonl(lease_time_sec));
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| 198 | add_server_options(&packet);
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| 199 |
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| 200 | addr.s_addr = packet.yiaddr;
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| 201 | bb_info_msg("Sending OFFER of %s", inet_ntoa(addr));
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| 202 | /* send_packet emits error message itself if it detects failure */
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| 203 | send_packet(&packet, /*force_bcast:*/ 0);
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| 204 | }
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| 205 |
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| 206 | /* NOINLINE: limit stack usage in caller */
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| 207 | static NOINLINE void send_NAK(struct dhcp_packet *oldpacket)
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| 208 | {
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| 209 | struct dhcp_packet packet;
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| 210 |
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| 211 | init_packet(&packet, oldpacket, DHCPNAK);
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| 212 |
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| 213 | log1("Sending NAK");
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| 214 | send_packet(&packet, /*force_bcast:*/ 1);
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| 215 | }
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| 216 |
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| 217 | /* NOINLINE: limit stack usage in caller */
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| 218 | static NOINLINE void send_ACK(struct dhcp_packet *oldpacket, uint32_t yiaddr)
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| 219 | {
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| 220 | struct dhcp_packet packet;
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| 221 | uint32_t lease_time_sec;
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| 222 | struct in_addr addr;
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| 223 | const char *p_host_name;
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| 224 |
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| 225 | init_packet(&packet, oldpacket, DHCPACK);
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| 226 | packet.yiaddr = yiaddr;
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| 227 |
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| 228 | lease_time_sec = select_lease_time(oldpacket);
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| 229 | udhcp_add_simple_option(&packet, DHCP_LEASE_TIME, htonl(lease_time_sec));
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| 230 |
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| 231 | add_server_options(&packet);
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| 232 |
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| 233 | addr.s_addr = yiaddr;
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| 234 | bb_info_msg("Sending ACK to %s", inet_ntoa(addr));
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| 235 | send_packet(&packet, /*force_bcast:*/ 0);
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| 236 |
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| 237 | p_host_name = (const char*) udhcp_get_option(oldpacket, DHCP_HOST_NAME);
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| 238 | add_lease(packet.chaddr, packet.yiaddr,
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| 239 | lease_time_sec,
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| 240 | p_host_name,
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| 241 | p_host_name ? (unsigned char)p_host_name[OPT_LEN - OPT_DATA] : 0
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| 242 | );
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| 243 | if (ENABLE_FEATURE_UDHCPD_WRITE_LEASES_EARLY) {
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| 244 | /* rewrite the file with leases at every new acceptance */
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| 245 | write_leases();
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| 246 | }
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| 247 | }
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| 248 |
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| 249 | /* NOINLINE: limit stack usage in caller */
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| 250 | static NOINLINE void send_inform(struct dhcp_packet *oldpacket)
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| 251 | {
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| 252 | struct dhcp_packet packet;
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| 253 |
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| 254 | /* "If a client has obtained a network address through some other means
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| 255 | * (e.g., manual configuration), it may use a DHCPINFORM request message
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| 256 | * to obtain other local configuration parameters. Servers receiving a
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| 257 | * DHCPINFORM message construct a DHCPACK message with any local
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| 258 | * configuration parameters appropriate for the client without:
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| 259 | * allocating a new address, checking for an existing binding, filling
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| 260 | * in 'yiaddr' or including lease time parameters. The servers SHOULD
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| 261 | * unicast the DHCPACK reply to the address given in the 'ciaddr' field
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| 262 | * of the DHCPINFORM message.
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| 263 | * ...
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| 264 | * The server responds to a DHCPINFORM message by sending a DHCPACK
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| 265 | * message directly to the address given in the 'ciaddr' field
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| 266 | * of the DHCPINFORM message. The server MUST NOT send a lease
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| 267 | * expiration time to the client and SHOULD NOT fill in 'yiaddr'."
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| 268 | */
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| 269 | //TODO: do a few sanity checks: is ciaddr set?
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| 270 | //Better yet: is ciaddr == IP source addr?
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| 271 | init_packet(&packet, oldpacket, DHCPACK);
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| 272 | add_server_options(&packet);
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| 273 |
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| 274 | send_packet(&packet, /*force_bcast:*/ 0);
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| 275 | }
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| 276 |
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| 277 |
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| 278 | /* globals */
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| 279 | struct dyn_lease *g_leases;
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| 280 | /* struct server_config_t server_config is in bb_common_bufsiz1 */
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| 281 |
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| 282 |
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| 283 | int udhcpd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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| 284 | int udhcpd_main(int argc UNUSED_PARAM, char **argv)
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| 285 | {
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| 286 | fd_set rfds;
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| 287 | int server_socket = -1, retval, max_sock;
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| 288 | struct dhcp_packet packet;
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| 289 | uint8_t *state;
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| 290 | uint32_t static_lease_nip;
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| 291 | unsigned timeout_end;
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| 292 | unsigned num_ips;
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| 293 | unsigned opt;
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| 294 | struct option_set *option;
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| 295 | struct dyn_lease *lease, fake_lease;
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| 296 | IF_FEATURE_UDHCP_PORT(char *str_P;)
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| 297 |
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| 298 | #if ENABLE_FEATURE_UDHCP_PORT
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| 299 | SERVER_PORT = 67;
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| 300 | CLIENT_PORT = 68;
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| 301 | #endif
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| 302 |
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| 303 | #if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
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| 304 | opt_complementary = "vv";
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| 305 | #endif
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| 306 | opt = getopt32(argv, "fSv"
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| 307 | IF_FEATURE_UDHCP_PORT("P:", &str_P)
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| 308 | #if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
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| 309 | , &dhcp_verbose
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| 310 | #endif
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| 311 | );
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| 312 | if (!(opt & 1)) { /* no -f */
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| 313 | bb_daemonize_or_rexec(0, argv);
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| 314 | logmode = LOGMODE_NONE;
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| 315 | }
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| 316 | /* update argv after the possible vfork+exec in daemonize */
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| 317 | argv += optind;
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| 318 | if (opt & 2) { /* -S */
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| 319 | openlog(applet_name, LOG_PID, LOG_DAEMON);
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| 320 | logmode |= LOGMODE_SYSLOG;
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| 321 | }
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| 322 | #if ENABLE_FEATURE_UDHCP_PORT
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| 323 | if (opt & 8) { /* -P */
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| 324 | SERVER_PORT = xatou16(str_P);
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| 325 | CLIENT_PORT = SERVER_PORT + 1;
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| 326 | }
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| 327 | #endif
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| 328 | /* Would rather not do read_config before daemonization -
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| 329 | * otherwise NOMMU machines will parse config twice */
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| 330 | read_config(argv[0] ? argv[0] : DHCPD_CONF_FILE);
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| 331 |
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| 332 | /* Make sure fd 0,1,2 are open */
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| 333 | bb_sanitize_stdio();
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| 334 | /* Equivalent of doing a fflush after every \n */
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| 335 | setlinebuf(stdout);
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| 336 |
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| 337 | /* Create pidfile */
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| 338 | write_pidfile(server_config.pidfile);
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| 339 | /* if (!..) bb_perror_msg("can't create pidfile %s", pidfile); */
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| 340 |
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| 341 | bb_info_msg("%s (v"BB_VER") started", applet_name);
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| 342 |
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| 343 | option = udhcp_find_option(server_config.options, DHCP_LEASE_TIME);
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| 344 | server_config.max_lease_sec = DEFAULT_LEASE_TIME;
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| 345 | if (option) {
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| 346 | move_from_unaligned32(server_config.max_lease_sec, option->data + OPT_DATA);
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| 347 | server_config.max_lease_sec = ntohl(server_config.max_lease_sec);
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| 348 | }
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| 349 |
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| 350 | /* Sanity check */
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| 351 | num_ips = server_config.end_ip - server_config.start_ip + 1;
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| 352 | if (server_config.max_leases > num_ips) {
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| 353 | bb_error_msg("max_leases=%u is too big, setting to %u",
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| 354 | (unsigned)server_config.max_leases, num_ips);
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| 355 | server_config.max_leases = num_ips;
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| 356 | }
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| 357 |
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| 358 | g_leases = xzalloc(server_config.max_leases * sizeof(g_leases[0]));
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| 359 | read_leases(server_config.lease_file);
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| 360 |
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| 361 | if (udhcp_read_interface(server_config.interface,
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| 362 | &server_config.ifindex,
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| 363 | &server_config.server_nip,
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| 364 | server_config.server_mac)
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| 365 | ) {
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| 366 | retval = 1;
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| 367 | goto ret;
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| 368 | }
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| 369 |
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| 370 | /* Setup the signal pipe */
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| 371 | udhcp_sp_setup();
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| 372 |
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| 373 | timeout_end = monotonic_sec() + server_config.auto_time;
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| 374 | while (1) { /* loop until universe collapses */
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| 375 | int bytes;
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| 376 | struct timeval tv;
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| 377 | uint8_t *server_id_opt;
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| 378 | uint8_t *requested_opt;
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| 379 | uint32_t requested_nip = requested_nip; /* for compiler */
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| 380 |
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| 381 | if (server_socket < 0) {
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| 382 | server_socket = udhcp_listen_socket(/*INADDR_ANY,*/ SERVER_PORT,
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| 383 | server_config.interface);
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| 384 | }
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| 385 |
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| 386 | max_sock = udhcp_sp_fd_set(&rfds, server_socket);
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| 387 | if (server_config.auto_time) {
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| 388 | tv.tv_sec = timeout_end - monotonic_sec();
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| 389 | tv.tv_usec = 0;
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| 390 | }
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| 391 | retval = 0;
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| 392 | if (!server_config.auto_time || tv.tv_sec > 0) {
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| 393 | retval = select(max_sock + 1, &rfds, NULL, NULL,
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| 394 | server_config.auto_time ? &tv : NULL);
|
---|
| 395 | }
|
---|
| 396 | if (retval == 0) {
|
---|
| 397 | write_leases();
|
---|
| 398 | timeout_end = monotonic_sec() + server_config.auto_time;
|
---|
| 399 | continue;
|
---|
| 400 | }
|
---|
| 401 | if (retval < 0 && errno != EINTR) {
|
---|
| 402 | log1("Error on select");
|
---|
| 403 | continue;
|
---|
| 404 | }
|
---|
| 405 |
|
---|
| 406 | switch (udhcp_sp_read(&rfds)) {
|
---|
| 407 | case SIGUSR1:
|
---|
| 408 | bb_info_msg("Received SIGUSR1");
|
---|
| 409 | write_leases();
|
---|
| 410 | /* why not just reset the timeout, eh */
|
---|
| 411 | timeout_end = monotonic_sec() + server_config.auto_time;
|
---|
| 412 | continue;
|
---|
| 413 | case SIGTERM:
|
---|
| 414 | bb_info_msg("Received SIGTERM");
|
---|
| 415 | goto ret0;
|
---|
| 416 | case 0: /* no signal: read a packet */
|
---|
| 417 | break;
|
---|
| 418 | default: /* signal or error (probably EINTR): back to select */
|
---|
| 419 | continue;
|
---|
| 420 | }
|
---|
| 421 |
|
---|
| 422 | bytes = udhcp_recv_kernel_packet(&packet, server_socket);
|
---|
| 423 | if (bytes < 0) {
|
---|
| 424 | /* bytes can also be -2 ("bad packet data") */
|
---|
| 425 | if (bytes == -1 && errno != EINTR) {
|
---|
| 426 | log1("Read error: %s, reopening socket", strerror(errno));
|
---|
| 427 | close(server_socket);
|
---|
| 428 | server_socket = -1;
|
---|
| 429 | }
|
---|
| 430 | continue;
|
---|
| 431 | }
|
---|
| 432 | if (packet.hlen != 6) {
|
---|
| 433 | bb_error_msg("MAC length != 6, ignoring packet");
|
---|
| 434 | continue;
|
---|
| 435 | }
|
---|
| 436 | if (packet.op != BOOTREQUEST) {
|
---|
| 437 | bb_error_msg("not a REQUEST, ignoring packet");
|
---|
| 438 | continue;
|
---|
| 439 | }
|
---|
| 440 | state = udhcp_get_option(&packet, DHCP_MESSAGE_TYPE);
|
---|
| 441 | if (state == NULL || state[0] < DHCP_MINTYPE || state[0] > DHCP_MAXTYPE) {
|
---|
| 442 | bb_error_msg("no or bad message type option, ignoring packet");
|
---|
| 443 | continue;
|
---|
| 444 | }
|
---|
| 445 |
|
---|
| 446 | /* Look for a static/dynamic lease */
|
---|
| 447 | static_lease_nip = get_static_nip_by_mac(server_config.static_leases, &packet.chaddr);
|
---|
| 448 | if (static_lease_nip) {
|
---|
| 449 | bb_info_msg("Found static lease: %x", static_lease_nip);
|
---|
| 450 | memcpy(&fake_lease.lease_mac, &packet.chaddr, 6);
|
---|
| 451 | fake_lease.lease_nip = static_lease_nip;
|
---|
| 452 | fake_lease.expires = 0;
|
---|
| 453 | lease = &fake_lease;
|
---|
| 454 | } else {
|
---|
| 455 | lease = find_lease_by_mac(packet.chaddr);
|
---|
| 456 | }
|
---|
| 457 |
|
---|
| 458 | /* Get REQUESTED_IP and SERVER_ID if present */
|
---|
| 459 | server_id_opt = udhcp_get_option(&packet, DHCP_SERVER_ID);
|
---|
| 460 | if (server_id_opt) {
|
---|
| 461 | uint32_t server_id_net;
|
---|
| 462 | move_from_unaligned32(server_id_net, server_id_opt);
|
---|
| 463 | if (server_id_net != server_config.server_nip) {
|
---|
| 464 | /* client talks to somebody else */
|
---|
| 465 | log1("server ID doesn't match, ignoring");
|
---|
| 466 | continue;
|
---|
| 467 | }
|
---|
| 468 | }
|
---|
| 469 | requested_opt = udhcp_get_option(&packet, DHCP_REQUESTED_IP);
|
---|
| 470 | if (requested_opt) {
|
---|
| 471 | move_from_unaligned32(requested_nip, requested_opt);
|
---|
| 472 | }
|
---|
| 473 |
|
---|
| 474 | switch (state[0]) {
|
---|
| 475 |
|
---|
| 476 | case DHCPDISCOVER:
|
---|
| 477 | log1("Received DISCOVER");
|
---|
| 478 |
|
---|
| 479 | send_offer(&packet, static_lease_nip, lease);
|
---|
| 480 | break;
|
---|
| 481 |
|
---|
| 482 | case DHCPREQUEST:
|
---|
| 483 | log1("Received REQUEST");
|
---|
| 484 | /* RFC 2131:
|
---|
| 485 |
|
---|
| 486 | o DHCPREQUEST generated during SELECTING state:
|
---|
| 487 |
|
---|
| 488 | Client inserts the address of the selected server in 'server
|
---|
| 489 | identifier', 'ciaddr' MUST be zero, 'requested IP address' MUST be
|
---|
| 490 | filled in with the yiaddr value from the chosen DHCPOFFER.
|
---|
| 491 |
|
---|
| 492 | Note that the client may choose to collect several DHCPOFFER
|
---|
| 493 | messages and select the "best" offer. The client indicates its
|
---|
| 494 | selection by identifying the offering server in the DHCPREQUEST
|
---|
| 495 | message. If the client receives no acceptable offers, the client
|
---|
| 496 | may choose to try another DHCPDISCOVER message. Therefore, the
|
---|
| 497 | servers may not receive a specific DHCPREQUEST from which they can
|
---|
| 498 | decide whether or not the client has accepted the offer.
|
---|
| 499 |
|
---|
| 500 | o DHCPREQUEST generated during INIT-REBOOT state:
|
---|
| 501 |
|
---|
| 502 | 'server identifier' MUST NOT be filled in, 'requested IP address'
|
---|
| 503 | option MUST be filled in with client's notion of its previously
|
---|
| 504 | assigned address. 'ciaddr' MUST be zero. The client is seeking to
|
---|
| 505 | verify a previously allocated, cached configuration. Server SHOULD
|
---|
| 506 | send a DHCPNAK message to the client if the 'requested IP address'
|
---|
| 507 | is incorrect, or is on the wrong network.
|
---|
| 508 |
|
---|
| 509 | Determining whether a client in the INIT-REBOOT state is on the
|
---|
| 510 | correct network is done by examining the contents of 'giaddr', the
|
---|
| 511 | 'requested IP address' option, and a database lookup. If the DHCP
|
---|
| 512 | server detects that the client is on the wrong net (i.e., the
|
---|
| 513 | result of applying the local subnet mask or remote subnet mask (if
|
---|
| 514 | 'giaddr' is not zero) to 'requested IP address' option value
|
---|
| 515 | doesn't match reality), then the server SHOULD send a DHCPNAK
|
---|
| 516 | message to the client.
|
---|
| 517 |
|
---|
| 518 | If the network is correct, then the DHCP server should check if
|
---|
| 519 | the client's notion of its IP address is correct. If not, then the
|
---|
| 520 | server SHOULD send a DHCPNAK message to the client. If the DHCP
|
---|
| 521 | server has no record of this client, then it MUST remain silent,
|
---|
| 522 | and MAY output a warning to the network administrator. This
|
---|
| 523 | behavior is necessary for peaceful coexistence of non-
|
---|
| 524 | communicating DHCP servers on the same wire.
|
---|
| 525 |
|
---|
| 526 | If 'giaddr' is 0x0 in the DHCPREQUEST message, the client is on
|
---|
| 527 | the same subnet as the server. The server MUST broadcast the
|
---|
| 528 | DHCPNAK message to the 0xffffffff broadcast address because the
|
---|
| 529 | client may not have a correct network address or subnet mask, and
|
---|
| 530 | the client may not be answering ARP requests.
|
---|
| 531 |
|
---|
| 532 | If 'giaddr' is set in the DHCPREQUEST message, the client is on a
|
---|
| 533 | different subnet. The server MUST set the broadcast bit in the
|
---|
| 534 | DHCPNAK, so that the relay agent will broadcast the DHCPNAK to the
|
---|
| 535 | client, because the client may not have a correct network address
|
---|
| 536 | or subnet mask, and the client may not be answering ARP requests.
|
---|
| 537 |
|
---|
| 538 | o DHCPREQUEST generated during RENEWING state:
|
---|
| 539 |
|
---|
| 540 | 'server identifier' MUST NOT be filled in, 'requested IP address'
|
---|
| 541 | option MUST NOT be filled in, 'ciaddr' MUST be filled in with
|
---|
| 542 | client's IP address. In this situation, the client is completely
|
---|
| 543 | configured, and is trying to extend its lease. This message will
|
---|
| 544 | be unicast, so no relay agents will be involved in its
|
---|
| 545 | transmission. Because 'giaddr' is therefore not filled in, the
|
---|
| 546 | DHCP server will trust the value in 'ciaddr', and use it when
|
---|
| 547 | replying to the client.
|
---|
| 548 |
|
---|
| 549 | A client MAY choose to renew or extend its lease prior to T1. The
|
---|
| 550 | server may choose not to extend the lease (as a policy decision by
|
---|
| 551 | the network administrator), but should return a DHCPACK message
|
---|
| 552 | regardless.
|
---|
| 553 |
|
---|
| 554 | o DHCPREQUEST generated during REBINDING state:
|
---|
| 555 |
|
---|
| 556 | 'server identifier' MUST NOT be filled in, 'requested IP address'
|
---|
| 557 | option MUST NOT be filled in, 'ciaddr' MUST be filled in with
|
---|
| 558 | client's IP address. In this situation, the client is completely
|
---|
| 559 | configured, and is trying to extend its lease. This message MUST
|
---|
| 560 | be broadcast to the 0xffffffff IP broadcast address. The DHCP
|
---|
| 561 | server SHOULD check 'ciaddr' for correctness before replying to
|
---|
| 562 | the DHCPREQUEST.
|
---|
| 563 |
|
---|
| 564 | The DHCPREQUEST from a REBINDING client is intended to accommodate
|
---|
| 565 | sites that have multiple DHCP servers and a mechanism for
|
---|
| 566 | maintaining consistency among leases managed by multiple servers.
|
---|
| 567 | A DHCP server MAY extend a client's lease only if it has local
|
---|
| 568 | administrative authority to do so.
|
---|
| 569 | */
|
---|
| 570 | if (!requested_opt) {
|
---|
| 571 | requested_nip = packet.ciaddr;
|
---|
| 572 | if (requested_nip == 0) {
|
---|
| 573 | log1("no requested IP and no ciaddr, ignoring");
|
---|
| 574 | break;
|
---|
| 575 | }
|
---|
| 576 | }
|
---|
| 577 | if (lease && requested_nip == lease->lease_nip) {
|
---|
| 578 | /* client requested or configured IP matches the lease.
|
---|
| 579 | * ACK it, and bump lease expiration time. */
|
---|
| 580 | send_ACK(&packet, lease->lease_nip);
|
---|
| 581 | break;
|
---|
| 582 | }
|
---|
| 583 | if (server_id_opt) {
|
---|
| 584 | /* client was talking specifically to us.
|
---|
| 585 | * "No, we don't have this IP for you". */
|
---|
| 586 | send_NAK(&packet);
|
---|
| 587 | }
|
---|
| 588 | break;
|
---|
| 589 |
|
---|
| 590 | case DHCPDECLINE:
|
---|
| 591 | /* RFC 2131:
|
---|
| 592 | * "If the server receives a DHCPDECLINE message,
|
---|
| 593 | * the client has discovered through some other means
|
---|
| 594 | * that the suggested network address is already
|
---|
| 595 | * in use. The server MUST mark the network address
|
---|
| 596 | * as not available and SHOULD notify the local
|
---|
| 597 | * sysadmin of a possible configuration problem."
|
---|
| 598 | *
|
---|
| 599 | * SERVER_ID must be present,
|
---|
| 600 | * REQUESTED_IP must be present,
|
---|
| 601 | * chaddr must be filled in,
|
---|
| 602 | * ciaddr must be 0 (we do not check this)
|
---|
| 603 | */
|
---|
| 604 | log1("Received DECLINE");
|
---|
| 605 | if (server_id_opt
|
---|
| 606 | && requested_opt
|
---|
| 607 | && lease /* chaddr matches this lease */
|
---|
| 608 | && requested_nip == lease->lease_nip
|
---|
| 609 | ) {
|
---|
| 610 | memset(lease->lease_mac, 0, sizeof(lease->lease_mac));
|
---|
| 611 | lease->expires = time(NULL) + server_config.decline_time;
|
---|
| 612 | }
|
---|
| 613 | break;
|
---|
| 614 |
|
---|
| 615 | case DHCPRELEASE:
|
---|
| 616 | /* "Upon receipt of a DHCPRELEASE message, the server
|
---|
| 617 | * marks the network address as not allocated."
|
---|
| 618 | *
|
---|
| 619 | * SERVER_ID must be present,
|
---|
| 620 | * REQUESTED_IP must not be present (we do not check this),
|
---|
| 621 | * chaddr must be filled in,
|
---|
| 622 | * ciaddr must be filled in
|
---|
| 623 | */
|
---|
| 624 | log1("Received RELEASE");
|
---|
| 625 | if (server_id_opt
|
---|
| 626 | && lease /* chaddr matches this lease */
|
---|
| 627 | && packet.ciaddr == lease->lease_nip
|
---|
| 628 | ) {
|
---|
| 629 | lease->expires = time(NULL);
|
---|
| 630 | }
|
---|
| 631 | break;
|
---|
| 632 |
|
---|
| 633 | case DHCPINFORM:
|
---|
| 634 | log1("Received INFORM");
|
---|
| 635 | send_inform(&packet);
|
---|
| 636 | break;
|
---|
| 637 | }
|
---|
| 638 | }
|
---|
| 639 | ret0:
|
---|
| 640 | retval = 0;
|
---|
| 641 | ret:
|
---|
| 642 | /*if (server_config.pidfile) - server_config.pidfile is never NULL */
|
---|
| 643 | remove_pidfile(server_config.pidfile);
|
---|
| 644 | return retval;
|
---|
| 645 | }
|
---|