/* Find a new usable (we think) address */
uint32_t FAST_FUNC find_free_or_expired_nip(const uint8_t *safe_mac)
{
uint32_t addr;
struct dyn_lease *oldest_lease = NULL;
addr = server_config.start_ip; /* addr is in host order here */
for (; addr <= server_config.end_ip; addr++) {
uint32_t nip;
struct dyn_lease *lease;
/* ie, 192.168.55.0 */
if ((addr & 0xff) == 0)
continue;
/* ie, 192.168.55.255 */
if ((addr & 0xff) == 0xff)
continue;
nip = htonl(addr);
/* is this a static lease addr? */
if (is_nip_reserved(server_config.static_leases, nip))
continue;
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))
return nip;
} else {
if (!oldest_lease || lease->expires < oldest_lease->expires)
oldest_lease = lease;
}
}
if (oldest_lease
&& is_expired_lease(oldest_lease)
&& nobody_responds_to_arp(oldest_lease->lease_nip, safe_mac)
) {
return oldest_lease->lease_nip;
}
return 0;
}
/* Find a new usable (we think) address */
uint32_t FAST_FUNC find_free_or_expired_nip(const uint8_t *safe_mac)
{
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))
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)
) {
return oldest_lease->lease_nip;
}
return 0;
}
void FAST_FUNC read_leases(const char *file)
{
struct dyn_lease lease;
int64_t written_at, time_passed;
int fd;
#if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
unsigned i = 0;
#endif
fd = open_or_warn(file, O_RDONLY);
if (fd < 0)
return;
if (full_read(fd, &written_at, sizeof(written_at)) != sizeof(written_at))
goto ret;
written_at = SWAP_BE64(written_at);
time_passed = time(NULL) - written_at;
/* Strange written_at, or lease file from old version of udhcpd
* which had no "written_at" field? */
if ((uint64_t)time_passed > 12 * 60 * 60)
goto ret;
while (full_read(fd, &lease, sizeof(lease)) == sizeof(lease)) {
uint32_t y = ntohl(lease.lease_nip);
if (y >= server_config.start_ip && y <= server_config.end_ip) {
signed_leasetime_t expires = ntohl(lease.expires) - (signed_leasetime_t)time_passed;
uint32_t static_nip;
if (expires <= 0)
/* We keep expired leases: add_lease() will add
* a lease with 0 seconds remaining.
* Fewer IP address changes this way for mass reboot scenario.
*/
expires = 0;
/* Check if there is a different static lease for this IP or MAC */
static_nip = get_static_nip_by_mac(server_config.static_leases, lease.lease_mac);
if (static_nip) {
/* NB: we do not add lease even if static_nip == lease.lease_nip.
*/
continue;
}
if (is_nip_reserved(server_config.static_leases, lease.lease_nip))
continue;
/* NB: add_lease takes "relative time", IOW,
* lease duration, not lease deadline. */
if (add_lease(lease.lease_mac, lease.lease_nip,
expires,
lease.hostname, sizeof(lease.hostname)
) == 0
) {
bb_error_msg("too many leases while loading %s", file);
break;
}
#if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 1
i++;
#endif
}
}
log1("read %d leases", i);
ret:
close(fd);
}
