networking/udhcp/leases.c

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