[3320] | 1 | /* vi: set sw=4 ts=4: */
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| 2 | /*
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| 3 | * Russ Dill <Russ.Dill@asu.edu> July 2001
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| 4 | *
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| 5 | * Licensed under GPLv2, see file LICENSE in this source tree.
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| 6 | */
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| 7 | #include "common.h"
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| 8 | #include "dhcpd.h"
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| 9 |
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| 10 | /* Find the oldest expired lease, NULL if there are no expired leases */
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| 11 | static struct dyn_lease *oldest_expired_lease(void)
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| 12 | {
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| 13 | struct dyn_lease *oldest_lease = NULL;
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| 14 | leasetime_t oldest_time = time(NULL);
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| 15 | unsigned i;
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| 16 |
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| 17 | /* Unexpired leases have g_leases[i].expires >= current time
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| 18 | * and therefore can't ever match */
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| 19 | for (i = 0; i < server_config.max_leases; i++) {
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| 20 | if (g_leases[i].expires < oldest_time) {
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| 21 | oldest_time = g_leases[i].expires;
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| 22 | oldest_lease = &g_leases[i];
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| 23 | }
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| 24 | }
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| 25 | return oldest_lease;
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| 26 | }
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| 27 |
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| 28 | /* Clear out all leases with matching nonzero chaddr OR yiaddr.
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| 29 | * If chaddr == NULL, this is a conflict lease.
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| 30 | */
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| 31 | static void clear_leases(const uint8_t *chaddr, uint32_t yiaddr)
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| 32 | {
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| 33 | unsigned i;
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| 34 |
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| 35 | for (i = 0; i < server_config.max_leases; i++) {
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| 36 | if ((chaddr && memcmp(g_leases[i].lease_mac, chaddr, 6) == 0)
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| 37 | || (yiaddr && g_leases[i].lease_nip == yiaddr)
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| 38 | ) {
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| 39 | memset(&g_leases[i], 0, sizeof(g_leases[i]));
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| 40 | }
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| 41 | }
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| 42 | }
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| 43 |
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| 44 | /* Add a lease into the table, clearing out any old ones.
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| 45 | * If chaddr == NULL, this is a conflict lease.
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| 46 | */
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| 47 | struct dyn_lease* FAST_FUNC add_lease(
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| 48 | const uint8_t *chaddr, uint32_t yiaddr,
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| 49 | leasetime_t leasetime,
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| 50 | const char *hostname, int hostname_len)
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| 51 | {
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| 52 | struct dyn_lease *oldest;
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| 53 |
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| 54 | /* clean out any old ones */
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| 55 | clear_leases(chaddr, yiaddr);
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| 56 |
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| 57 | oldest = oldest_expired_lease();
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| 58 |
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| 59 | if (oldest) {
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| 60 | memset(oldest, 0, sizeof(*oldest));
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| 61 | if (hostname) {
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| 62 | char *p;
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| 63 |
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| 64 | hostname_len++; /* include NUL */
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| 65 | if (hostname_len > sizeof(oldest->hostname))
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| 66 | hostname_len = sizeof(oldest->hostname);
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| 67 | p = safe_strncpy(oldest->hostname, hostname, hostname_len);
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| 68 | /* sanitization (s/non-ASCII/^/g) */
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| 69 | while (*p) {
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| 70 | if (*p < ' ' || *p > 126)
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| 71 | *p = '^';
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| 72 | p++;
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| 73 | }
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| 74 | }
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| 75 | if (chaddr)
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| 76 | memcpy(oldest->lease_mac, chaddr, 6);
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| 77 | oldest->lease_nip = yiaddr;
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| 78 | oldest->expires = time(NULL) + leasetime;
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| 79 | }
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| 80 |
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| 81 | return oldest;
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| 82 | }
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| 83 |
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| 84 | /* True if a lease has expired */
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| 85 | int FAST_FUNC is_expired_lease(struct dyn_lease *lease)
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| 86 | {
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| 87 | return (lease->expires < (leasetime_t) time(NULL));
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| 88 | }
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| 89 |
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| 90 | /* Find the first lease that matches MAC, NULL if no match */
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| 91 | struct dyn_lease* FAST_FUNC find_lease_by_mac(const uint8_t *mac)
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| 92 | {
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| 93 | unsigned i;
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| 94 |
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| 95 | for (i = 0; i < server_config.max_leases; i++)
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| 96 | if (memcmp(g_leases[i].lease_mac, mac, 6) == 0)
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| 97 | return &g_leases[i];
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| 98 |
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| 99 | return NULL;
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| 100 | }
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| 101 |
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| 102 | /* Find the first lease that matches IP, NULL is no match */
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| 103 | struct dyn_lease* FAST_FUNC find_lease_by_nip(uint32_t nip)
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| 104 | {
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| 105 | unsigned i;
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| 106 |
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| 107 | for (i = 0; i < server_config.max_leases; i++)
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| 108 | if (g_leases[i].lease_nip == nip)
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| 109 | return &g_leases[i];
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| 110 |
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| 111 | return NULL;
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| 112 | }
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| 113 |
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| 114 | /* Check if the IP is taken; if it is, add it to the lease table */
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| 115 | static int nobody_responds_to_arp(uint32_t nip, const uint8_t *safe_mac)
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| 116 | {
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| 117 | struct in_addr temp;
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| 118 | int r;
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| 119 |
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| 120 | r = arpping(nip, safe_mac,
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| 121 | server_config.server_nip,
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| 122 | server_config.server_mac,
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| 123 | server_config.interface);
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| 124 | if (r)
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| 125 | return r;
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| 126 |
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| 127 | temp.s_addr = nip;
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| 128 | bb_info_msg("%s belongs to someone, reserving it for %u seconds",
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| 129 | inet_ntoa(temp), (unsigned)server_config.conflict_time);
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| 130 | add_lease(NULL, nip, server_config.conflict_time, NULL, 0);
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| 131 | return 0;
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| 132 | }
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| 133 |
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| 134 | /* Find a new usable (we think) address */
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| 135 | uint32_t FAST_FUNC find_free_or_expired_nip(const uint8_t *safe_mac)
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| 136 | {
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| 137 | uint32_t addr;
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| 138 | struct dyn_lease *oldest_lease = NULL;
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| 139 |
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| 140 | addr = server_config.start_ip; /* addr is in host order here */
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| 141 | for (; addr <= server_config.end_ip; addr++) {
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| 142 | uint32_t nip;
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| 143 | struct dyn_lease *lease;
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| 144 |
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| 145 | /* ie, 192.168.55.0 */
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| 146 | if ((addr & 0xff) == 0)
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| 147 | continue;
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| 148 | /* ie, 192.168.55.255 */
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| 149 | if ((addr & 0xff) == 0xff)
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| 150 | continue;
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| 151 | nip = htonl(addr);
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| 152 | /* is this a static lease addr? */
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| 153 | if (is_nip_reserved(server_config.static_leases, nip))
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| 154 | continue;
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| 155 |
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| 156 | lease = find_lease_by_nip(nip);
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| 157 | if (!lease) {
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| 158 | //TODO: DHCP servers do not always sit on the same subnet as clients: should *ping*, not arp-ping!
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| 159 | if (nobody_responds_to_arp(nip, safe_mac))
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| 160 | return nip;
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| 161 | } else {
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| 162 | if (!oldest_lease || lease->expires < oldest_lease->expires)
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| 163 | oldest_lease = lease;
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| 164 | }
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| 165 | }
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| 166 |
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| 167 | if (oldest_lease
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| 168 | && is_expired_lease(oldest_lease)
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| 169 | && nobody_responds_to_arp(oldest_lease->lease_nip, safe_mac)
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| 170 | ) {
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| 171 | return oldest_lease->lease_nip;
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| 172 | }
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| 173 |
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| 174 | return 0;
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| 175 | }
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