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 dhcpOfferedAddr *oldest_expired_lease(void)
  15 {
  16         struct dhcpOfferedAddr *oldest_lease = NULL;
  17         leasetime_t oldest_time = time(NULL);
  18         unsigned i;
  19
  20         /* Unexpired leases have leases[i].expires >= current time
  21          * and therefore can't ever match */
  22         for (i = 0; i < server_config.max_leases; i++) {
  23                 if (leases[i].expires < oldest_time) {
  24                         oldest_time = leases[i].expires;
  25                         oldest_lease = &(leases[i]);
  26                 }
  27         }
  28         return oldest_lease;
  29 }
  30
  31
  32 /* Clear every lease out that chaddr OR yiaddr matches and is nonzero */
  33 static void clear_lease(const uint8_t *chaddr, uint32_t yiaddr)
  34 {
  35         unsigned i, j;
  36
  37         for (j = 0; j < 16 && !chaddr[j]; j++)
  38                 continue;
  39
  40         for (i = 0; i < server_config.max_leases; i++) {
  41                 if ((j != 16 && memcmp(leases[i].chaddr, chaddr, 16) == 0)
  42                  || (yiaddr && leases[i].yiaddr == yiaddr)
  43                 ) {
  44                         memset(&(leases[i]), 0, sizeof(leases[i]));
  45                 }
  46         }
  47 }
  48
  49
  50 /* Add a lease into the table, clearing out any old ones */
  51 struct dhcpOfferedAddr* FAST_FUNC add_lease(
  52                 const uint8_t *chaddr, uint32_t yiaddr,
  53                 leasetime_t leasetime, uint8_t *hostname)
  54 {
  55         struct dhcpOfferedAddr *oldest;
  56         uint8_t hostname_length;
  57
  58         /* clean out any old ones */
  59         clear_lease(chaddr, yiaddr);
  60
  61         oldest = oldest_expired_lease();
  62
  63         if (oldest) {
  64                 oldest->hostname[0] = '\0';
  65                 if (hostname) {
  66                         /* option size byte, + 1 for NUL */
  67                         hostname_length = hostname[-1] + 1;
  68                         if (hostname_length > sizeof(oldest->hostname))
  69                                 hostname_length = sizeof(oldest->hostname);
  70                         hostname = (uint8_t*) safe_strncpy((char*)oldest->hostname, (char*)hostname, hostname_length);
  71                         /* sanitization (s/non-ASCII/^/g) */
  72                         while (*hostname) {
  73                                 if (*hostname < ' ' || *hostname > 126)
  74                                         *hostname = '^';
  75                                 hostname++;
  76                         }
  77                 }
  78                 memcpy(oldest->chaddr, chaddr, 16);
  79                 oldest->yiaddr = yiaddr;
  80                 oldest->expires = time(NULL) + leasetime;
  81         }
  82
  83         return oldest;
  84 }
  85
  86
  87 /* True if a lease has expired */
  88 int FAST_FUNC lease_expired(struct dhcpOfferedAddr *lease)
  89 {
  90         return (lease->expires < (leasetime_t) time(NULL));
  91 }
  92
  93
  94 /* Find the first lease that matches chaddr, NULL if no match */
  95 struct dhcpOfferedAddr* FAST_FUNC find_lease_by_chaddr(const uint8_t *chaddr)
  96 {
  97         unsigned i;
  98
  99         for (i = 0; i < server_config.max_leases; i++)
 100                 if (!memcmp(leases[i].chaddr, chaddr, 16))
 101                         return &(leases[i]);
 102
 103         return NULL;
 104 }
 105
 106
 107 /* Find the first lease that matches yiaddr, NULL is no match */
 108 struct dhcpOfferedAddr* FAST_FUNC find_lease_by_yiaddr(uint32_t yiaddr)
 109 {
 110         unsigned i;
 111
 112         for (i = 0; i < server_config.max_leases; i++)
 113                 if (leases[i].yiaddr == yiaddr)
 114                         return &(leases[i]);
 115
 116         return NULL;
 117 }
 118
 119
 120 /* check is an IP is taken, if it is, add it to the lease table */
 121 static int nobody_responds_to_arp(uint32_t addr)
 122 {
 123         /* 16 zero bytes */
 124         static const uint8_t blank_chaddr[16] = { 0 };
 125         /* = { 0 } helps gcc to put it in rodata, not bss */
 126
 127         struct in_addr temp;
 128         int r;
 129
 130         r = arpping(addr, server_config.server, server_config.arp, server_config.interface);
 131         if (r)
 132                 return r;
 133
 134         temp.s_addr = addr;
 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(blank_chaddr, addr, server_config.conflict_time, NULL);
 138         return 0;
 139 }
 140
 141
 142 /* Find a new usable (we think) address. */
 143 uint32_t FAST_FUNC find_free_or_expired_address(void)
 144 {
 145         uint32_t addr;
 146         struct dhcpOfferedAddr *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 net_addr;
 151                 struct dhcpOfferedAddr *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                 net_addr = htonl(addr);
 160                 /* addr has a static lease? */
 161                 if (reservedIp(server_config.static_leases, net_addr))
 162                         continue;
 163
 164                 lease = find_lease_by_yiaddr(net_addr);
 165                 if (!lease) {
 166                         if (nobody_responds_to_arp(net_addr))
 167                                 return net_addr;
 168                 } else {
 169                         if (!oldest_lease || lease->expires < oldest_lease->expires)
 170                                 oldest_lease = lease;
 171                 }
 172         }
 173
 174         if (oldest_lease && lease_expired(oldest_lease)
 175          && nobody_responds_to_arp(oldest_lease->yiaddr)
 176         ) {
 177                 return oldest_lease->yiaddr;
 178         }
 179
 180         return 0;
 181 }