static uint32_t find_free_or_expired_nip(GDHCPServer *dhcp_server,
const uint8_t *safe_mac)
{
uint32_t ip_addr;
struct dhcp_lease *lease;
GList *list;
ip_addr = dhcp_server->start_ip;
for (; ip_addr <= dhcp_server->end_ip; ip_addr++) {
/* e.g. 192.168.55.0 */
if ((ip_addr & 0xff) == 0)
continue;
/* e.g. 192.168.55.255 */
if ((ip_addr & 0xff) == 0xff)
continue;
lease = find_lease_by_nip(dhcp_server,
(uint32_t) htonl(ip_addr));
if (lease != NULL)
continue;
if (arp_check(htonl(ip_addr), safe_mac) == TRUE)
return htonl(ip_addr);
}
/* The last lease is the oldest one */
list = g_list_last(dhcp_server->lease_list);
if (list == NULL)
return 0;
lease = list->data;
if (lease == NULL)
return 0;
if (is_expired_lease(lease) == FALSE)
return 0;
if (arp_check(lease->lease_nip, safe_mac) == FALSE)
return 0;
return lease->lease_nip;
}
/* 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;
}
static bool check_requested_nip(GDHCPServer *dhcp_server,
uint32_t requested_nip)
{
struct dhcp_lease *lease;
if (requested_nip == 0)
return false;
if (requested_nip < dhcp_server->start_ip)
return false;
if (requested_nip > dhcp_server->end_ip)
return false;
lease = find_lease_by_nip(dhcp_server, requested_nip);
if (!lease)
return true;
if (!is_expired_lease(lease))
return false;
return true;
}
static gboolean check_requested_nip(GDHCPServer *dhcp_server,
uint32_t requested_nip)
{
struct dhcp_lease *lease;
if (requested_nip == 0)
return FALSE;
if (ntohl(requested_nip) < dhcp_server->start_ip)
return FALSE;
if (ntohl(requested_nip) > dhcp_server->end_ip)
return FALSE;
lease = find_lease_by_nip(dhcp_server, requested_nip);
if (lease == NULL)
return TRUE;
if (is_expired_lease(lease) == FALSE)
return FALSE;
return TRUE;
}
/* NOINLINE: limit stack usage in caller */
static NOINLINE void send_offer(struct dhcp_packet *oldpacket,
uint32_t static_lease_nip,
struct dyn_lease *lease,
uint8_t *requested_ip_opt,
unsigned arpping_ms)
{
struct dhcp_packet packet;
uint32_t lease_time_sec;
struct in_addr addr;
init_packet(&packet, oldpacket, DHCPOFFER);
/* If it is a static lease, use its IP */
packet.yiaddr = static_lease_nip;
/* Else: */
if (!static_lease_nip) {
/* We have no static lease for client's chaddr */
uint32_t req_nip;
const char *p_host_name;
if (lease) {
/* We have a dynamic lease for client's chaddr.
* Reuse its IP (even if lease is expired).
* Note that we ignore requested IP in this case.
*/
packet.yiaddr = lease->lease_nip;
}
/* Or: if client has requested an IP */
else if (requested_ip_opt != NULL
/* (read IP) */
&& (move_from_unaligned32(req_nip, requested_ip_opt), 1)
/* and the IP is in the lease range */
&& ntohl(req_nip) >= server_config.start_ip
&& ntohl(req_nip) <= server_config.end_ip
/* and */
&& ( !(lease = find_lease_by_nip(req_nip)) /* is not already taken */
|| is_expired_lease(lease) /* or is taken, but expired */
)
) {
packet.yiaddr = req_nip;
}
else {
/* Otherwise, find a free IP */
packet.yiaddr = find_free_or_expired_nip(oldpacket->chaddr, arpping_ms);
}
if (!packet.yiaddr) {
bb_error_msg("no free IP addresses. OFFER abandoned");
return;
}
/* Reserve the IP for a short time hoping to get DHCPREQUEST soon */
p_host_name = (const char*) udhcp_get_option(oldpacket, DHCP_HOST_NAME);
lease = add_lease(packet.chaddr, packet.yiaddr,
server_config.offer_time,
p_host_name,
p_host_name ? (unsigned char)p_host_name[OPT_LEN - OPT_DATA] : 0
);
if (!lease) {
bb_error_msg("no free IP addresses. OFFER abandoned");
return;
}
}
lease_time_sec = select_lease_time(oldpacket);
udhcp_add_simple_option(&packet, DHCP_LEASE_TIME, htonl(lease_time_sec));
add_server_options(&packet);
addr.s_addr = packet.yiaddr;
bb_info_msg("Sending OFFER of %s", inet_ntoa(addr));
/* send_packet emits error message itself if it detects failure */
send_packet(&packet, /*force_bcast:*/ 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;
}
