networking/udhcp/leases.c

   1 /* vi: set sw=4 ts=4: */
   2 /*
   3  * leases.c -- tools to manage DHCP leases
   4  * Russ Dill <Russ.Dill@asu.edu> July 2001
   5  *
   6  * Licensed under GPLv2, see file LICENSE in this tarball for details.
   7  */
   8
   9 #include "common.h"
  10 #include "dhcpd.h"
  11
  12
  13 /* Find the oldest expired lease, NULL if there are no expired leases */
  14 static struct dyn_lease *oldest_expired_lease(void)
  15 {
  16         struct dyn_lease *oldest_lease = NULL;
  17         leasetime_t oldest_time = time(NULL);
  18         unsigned i;
  19
  20         /* Unexpired leases have g_leases[i].expires >= current time
  21          * and therefore can't ever match */
  22         for (i = 0; i < server_config.max_leases; i++) {
  23                 if (g_leases[i].expires < oldest_time) {
  24                         oldest_time = g_leases[i].expires;
  25                         oldest_lease = &g_leases[i];
  26                 }
  27         }
  28         return oldest_lease;
  29 }
  30
  31
  32 /* Clear out all leases with matching nonzero chaddr OR yiaddr.
  33  * If chaddr == NULL, this is a conflict lease.
  34  */
  35 static void clear_leases(const uint8_t *chaddr, uint32_t yiaddr)
  36 {
  37         unsigned i;
  38
  39         for (i = 0; i < server_config.max_leases; i++) {
  40                 if ((chaddr && memcmp(g_leases[i].lease_mac, chaddr, 6) == 0)
  41                  || (yiaddr && g_leases[i].lease_nip == yiaddr)
  42                 ) {
  43                         memset(&g_leases[i], 0, sizeof(g_leases[i]));
  44                 }
  45         }
  46 }
  47
  48
  49 /* Add a lease into the table, clearing out any old ones
  50  * If chaddr == NULL, this is a conflict lease.
  51  */
  52 struct dyn_lease* FAST_FUNC add_lease(
  53                 const uint8_t *chaddr, uint32_t yiaddr,
  54                 leasetime_t leasetime,
  55                 const char *hostname, int hostname_len)
  56 {
  57         struct dyn_lease *oldest;
  58
  59         /* clean out any old ones */
  60         clear_leases(chaddr, yiaddr);
  61
  62         oldest = oldest_expired_lease();
  63
  64         if (oldest) {
  65                 memset(oldest, 0, sizeof(*oldest));
  66                 if (hostname) {
  67                         char *p;
  68                         if (hostname_len > sizeof(oldest->hostname))
  69                                 hostname_len = sizeof(oldest->hostname);
  70                         p = safe_strncpy(oldest->hostname, hostname, hostname_len);
  71                         /* sanitization (s/non-ASCII/^/g) */
  72                         while (*p) {
  73                                 if (*p < ' ' || *p > 126)
  74                                         *p = '^';
  75                                 p++;
  76                         }
  77                 }
  78                 if (chaddr)
  79                         memcpy(oldest->lease_mac, chaddr, 6);
  80                 oldest->lease_nip = yiaddr;
  81                 oldest->expires = time(NULL) + leasetime;
  82         }
  83
  84         return oldest;
  85 }
  86
  87
  88 /* True if a lease has expired */
  89 int FAST_FUNC is_expired_lease(struct dyn_lease *lease)
  90 {
  91         return (lease->expires < (leasetime_t) time(NULL));
  92 }
  93
  94
  95 /* Find the first lease that matches MAC, NULL if no match */
  96 struct dyn_lease* FAST_FUNC find_lease_by_mac(const uint8_t *mac)
  97 {
  98         unsigned i;
  99
 100         for (i = 0; i < server_config.max_leases; i++)
 101                 if (memcmp(g_leases[i].lease_mac, mac, 6) == 0)
 102                         return &g_leases[i];
 103
 104         return NULL;
 105 }
 106
 107
 108 /* Find the first lease that matches IP, NULL is no match */
 109 struct dyn_lease* FAST_FUNC find_lease_by_nip(uint32_t nip)
 110 {
 111         unsigned i;
 112
 113         for (i = 0; i < server_config.max_leases; i++)
 114                 if (g_leases[i].lease_nip == nip)
 115                         return &g_leases[i];
 116
 117         return NULL;
 118 }
 119
 120
 121 /* Check if the IP is taken; if it is, add it to the lease table */
 122 static int nobody_responds_to_arp(uint32_t nip, const uint8_t *safe_mac)
 123 {
 124         struct in_addr temp;
 125         int r;
 126
 127         r = arpping(nip, safe_mac,
 128                         server_config.server_nip,
 129                         server_config.server_mac,
 130                         server_config.interface);
 131         if (r)
 132                 return r;
 133
 134         temp.s_addr = nip;
 135         bb_info_msg("%s belongs to someone, reserving it for %u seconds",
 136                 inet_ntoa(temp), (unsigned)server_config.conflict_time);
 137         add_lease(NULL, nip, server_config.conflict_time, NULL, 0);
 138         return 0;
 139 }
 140
 141
 142 /* Find a new usable (we think) address */
 143 uint32_t FAST_FUNC find_free_or_expired_nip(const uint8_t *safe_mac)
 144 {
 145         uint32_t addr;
 146         struct dyn_lease *oldest_lease = NULL;
 147
 148         addr = server_config.start_ip; /* addr is in host order here */
 149         for (; addr <= server_config.end_ip; addr++) {
 150                 uint32_t nip;
 151                 struct dyn_lease *lease;
 152
 153                 /* ie, 192.168.55.0 */
 154                 if ((addr & 0xff) == 0)
 155                         continue;
 156                 /* ie, 192.168.55.255 */
 157                 if ((addr & 0xff) == 0xff)
 158                         continue;
 159                 nip = htonl(addr);
 160                 /* is this a static lease addr? */
 161                 if (is_nip_reserved(server_config.static_leases, nip))
 162                         continue;
 163
 164                 lease = find_lease_by_nip(nip);
 165                 if (!lease) {
 166                         if (nobody_responds_to_arp(nip, safe_mac))
 167                                 return nip;
 168                 } else {
 169                         if (!oldest_lease || lease->expires < oldest_lease->expires)
 170                                 oldest_lease = lease;
 171                 }
 172         }
 173
 174         if (oldest_lease
 175          && is_expired_lease(oldest_lease)
 176          && nobody_responds_to_arp(oldest_lease->lease_nip, safe_mac)
 177         ) {
 178                 return oldest_lease->lease_nip;
 179         }
 180
 181         return 0;
 182 }