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/* vi: set sw=4 ts=4: */
/*
* Russ Dill <Russ.Dill@asu.edu> July 2001
*
* Licensed under GPLv2, see file LICENSE in this source tree.
*/
#include "common.h"
#include "dhcpd.h"
/* Find the oldest expired lease, NULL if there are no expired leases */
static struct dyn_lease *oldest_expired_lease(void)
{
struct dyn_lease *oldest_lease = NULL;
leasetime_t oldest_time = time(NULL);
unsigned i;
/* Unexpired leases have g_leases[i].expires >= current time
* and therefore can't ever match */
for (i = 0; i < server_config.max_leases; i++) {
if (g_leases[i].expires == 0 /* empty entry */
|| g_leases[i].expires < oldest_time
) {
oldest_time = g_leases[i].expires;
oldest_lease = &g_leases[i];
}
}
return oldest_lease;
}
/* Clear out all leases with matching nonzero chaddr OR yiaddr.
* If chaddr == NULL, this is a conflict lease.
*/
static void clear_leases(const uint8_t *chaddr, uint32_t yiaddr)
{
unsigned i;
for (i = 0; i < server_config.max_leases; i++) {
if ((chaddr && memcmp(g_leases[i].lease_mac, chaddr, 6) == 0)
|| (yiaddr && g_leases[i].lease_nip == yiaddr)
) {
memset(&g_leases[i], 0, sizeof(g_leases[i]));
}
}
}
/* Add a lease into the table, clearing out any old ones.
* If chaddr == NULL, this is a conflict lease.
*/
struct dyn_lease* FAST_FUNC add_lease(
const uint8_t *chaddr, uint32_t yiaddr,
leasetime_t leasetime,
const char *hostname, int hostname_len)
{
struct dyn_lease *oldest;
/* clean out any old ones */
clear_leases(chaddr, yiaddr);
oldest = oldest_expired_lease();
if (oldest) {
memset(oldest, 0, sizeof(*oldest));
if (hostname) {
char *p;
hostname_len++; /* include NUL */
if (hostname_len > sizeof(oldest->hostname))
hostname_len = sizeof(oldest->hostname);
p = safe_strncpy(oldest->hostname, hostname, hostname_len);
/*
* Sanitization (s/bad_char/./g).
* The intent is not to allow only "DNS-valid" hostnames,
* but merely make dumpleases output safe for shells to use.
* We accept "0-9A-Za-z._-", all other chars turn to dots.
*/
while (*p) {
if (!isalnum(*p) && *p != '-' && *p != '_')
*p = '.';
p++;
}
}
if (chaddr)
memcpy(oldest->lease_mac, chaddr, 6);
oldest->lease_nip = yiaddr;
oldest->expires = time(NULL) + leasetime;
}
return oldest;
}
/* True if a lease has expired */
int FAST_FUNC is_expired_lease(struct dyn_lease *lease)
{
return (lease->expires < (leasetime_t) time(NULL));
}
/* Find the first lease that matches MAC, NULL if no match */
struct dyn_lease* FAST_FUNC find_lease_by_mac(const uint8_t *mac)
{
unsigned i;
for (i = 0; i < server_config.max_leases; i++)
if (memcmp(g_leases[i].lease_mac, mac, 6) == 0)
return &g_leases[i];
return NULL;
}
/* Find the first lease that matches IP, NULL is no match */
struct dyn_lease* FAST_FUNC find_lease_by_nip(uint32_t nip)
{
unsigned i;
for (i = 0; i < server_config.max_leases; i++)
if (g_leases[i].lease_nip == nip)
return &g_leases[i];
return NULL;
}
/* Check if the IP is taken; if it is, add it to the lease table */
static int nobody_responds_to_arp(uint32_t nip, const uint8_t *safe_mac, unsigned arpping_ms)
{
struct in_addr temp;
int r;
r = arpping(nip, safe_mac,
server_config.server_nip,
server_config.server_mac,
server_config.interface,
arpping_ms);
if (r)
return r;
temp.s_addr = nip;
bb_error_msg("%s belongs to someone, reserving it for %u seconds",
inet_ntoa(temp), (unsigned)server_config.conflict_time);
add_lease(NULL, nip, server_config.conflict_time, NULL, 0);
return 0;
}
/* Find a new usable (we think) address */
uint32_t FAST_FUNC find_free_or_expired_nip(const uint8_t *safe_mac, unsigned arpping_ms)
{
uint32_t addr;
struct dyn_lease *oldest_lease = NULL;
#if ENABLE_FEATURE_UDHCPD_BASE_IP_ON_MAC
uint32_t stop;
unsigned i, hash;
/* hash hwaddr: use the SDBM hashing algorithm. Seems to give good
* dispersal even with similarly-valued "strings".
*/
hash = 0;
for (i = 0; i < 6; i++)
hash += safe_mac[i] + (hash << 6) + (hash << 16) - hash;
/* pick a seed based on hwaddr then iterate until we find a free address. */
addr = server_config.start_ip
+ (hash % (1 + server_config.end_ip - server_config.start_ip));
stop = addr;
#else
addr = server_config.start_ip;
#define stop (server_config.end_ip + 1)
#endif
do {
uint32_t nip;
struct dyn_lease *lease;
/* ie, 192.168.55.0 */
if ((addr & 0xff) == 0)
goto next_addr;
/* ie, 192.168.55.255 */
if ((addr & 0xff) == 0xff)
goto next_addr;
nip = htonl(addr);
/* skip our own address */
if (nip == server_config.server_nip)
goto next_addr;
/* is this a static lease addr? */
if (is_nip_reserved(server_config.static_leases, nip))
goto next_addr;
lease = find_lease_by_nip(nip);
if (!lease) {
//TODO: DHCP servers do not always sit on the same subnet as clients: should *ping*, not arp-ping!
if (nobody_responds_to_arp(nip, safe_mac, arpping_ms))
return nip;
} else {
if (!oldest_lease || lease->expires < oldest_lease->expires)
oldest_lease = lease;
}
next_addr:
addr++;
#if ENABLE_FEATURE_UDHCPD_BASE_IP_ON_MAC
if (addr > server_config.end_ip)
addr = server_config.start_ip;
#endif
} while (addr != stop);
if (oldest_lease
&& is_expired_lease(oldest_lease)
&& nobody_responds_to_arp(oldest_lease->lease_nip, safe_mac, arpping_ms)
) {
return oldest_lease->lease_nip;
}
return 0;
}
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