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-rw-r--r--networking/udhcp/leases.c149
1 files changed, 149 insertions, 0 deletions
diff --git a/networking/udhcp/leases.c b/networking/udhcp/leases.c
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+++ b/networking/udhcp/leases.c
@@ -0,0 +1,149 @@
+/* vi: set sw=4 ts=4: */
+/*
+ * leases.c -- tools to manage DHCP leases
+ * Russ Dill <Russ.Dill@asu.edu> July 2001
+ */
+
+#include "common.h"
+#include "dhcpd.h"
+
+
+/* Find the oldest expired lease, NULL if there are no expired leases */
+static struct dhcpOfferedAddr *oldest_expired_lease(void)
+{
+ struct dhcpOfferedAddr *oldest = NULL;
+// TODO: use monotonic_sec()
+ unsigned long oldest_lease = time(0);
+ unsigned i;
+
+ for (i = 0; i < server_config.max_leases; i++)
+ if (oldest_lease > leases[i].expires) {
+ oldest_lease = leases[i].expires;
+ oldest = &(leases[i]);
+ }
+ return oldest;
+}
+
+
+/* clear every lease out that chaddr OR yiaddr matches and is nonzero */
+static void clear_lease(const uint8_t *chaddr, uint32_t yiaddr)
+{
+ unsigned i, j;
+
+ for (j = 0; j < 16 && !chaddr[j]; j++)
+ continue;
+
+ for (i = 0; i < server_config.max_leases; i++)
+ if ((j != 16 && memcmp(leases[i].chaddr, chaddr, 16) == 0)
+ || (yiaddr && leases[i].yiaddr == yiaddr)
+ ) {
+ memset(&(leases[i]), 0, sizeof(leases[i]));
+ }
+}
+
+
+/* add a lease into the table, clearing out any old ones */
+struct dhcpOfferedAddr* FAST_FUNC add_lease(const uint8_t *chaddr, uint32_t yiaddr, unsigned long lease)
+{
+ struct dhcpOfferedAddr *oldest;
+
+ /* clean out any old ones */
+ clear_lease(chaddr, yiaddr);
+
+ oldest = oldest_expired_lease();
+
+ if (oldest) {
+ memcpy(oldest->chaddr, chaddr, 16);
+ oldest->yiaddr = yiaddr;
+ oldest->expires = time(0) + lease;
+ }
+
+ return oldest;
+}
+
+
+/* true if a lease has expired */
+int FAST_FUNC lease_expired(struct dhcpOfferedAddr *lease)
+{
+ return (lease->expires < (unsigned long) time(0));
+}
+
+
+/* Find the first lease that matches chaddr, NULL if no match */
+struct dhcpOfferedAddr* FAST_FUNC find_lease_by_chaddr(const uint8_t *chaddr)
+{
+ unsigned i;
+
+ for (i = 0; i < server_config.max_leases; i++)
+ if (!memcmp(leases[i].chaddr, chaddr, 16))
+ return &(leases[i]);
+
+ return NULL;
+}
+
+
+/* Find the first lease that matches yiaddr, NULL is no match */
+struct dhcpOfferedAddr* FAST_FUNC find_lease_by_yiaddr(uint32_t yiaddr)
+{
+ unsigned i;
+
+ for (i = 0; i < server_config.max_leases; i++)
+ if (leases[i].yiaddr == yiaddr)
+ return &(leases[i]);
+
+ return NULL;
+}
+
+
+/* check is an IP is taken, if it is, add it to the lease table */
+static int nobody_responds_to_arp(uint32_t addr)
+{
+ /* 16 zero bytes */
+ static const uint8_t blank_chaddr[16] = { 0 };
+ /* = { 0 } helps gcc to put it in rodata, not bss */
+
+ struct in_addr temp;
+ int r;
+
+ r = arpping(addr, server_config.server, server_config.arp, server_config.interface);
+ if (r)
+ return r;
+
+ temp.s_addr = addr;
+ bb_info_msg("%s belongs to someone, reserving it for %u seconds",
+ inet_ntoa(temp), (unsigned)server_config.conflict_time);
+ add_lease(blank_chaddr, addr, server_config.conflict_time);
+ return 0;
+}
+
+
+/* find an assignable address, if check_expired is true, we check all the expired leases as well.
+ * Maybe this should try expired leases by age... */
+uint32_t FAST_FUNC find_address(int check_expired)
+{
+ uint32_t addr, ret;
+ struct dhcpOfferedAddr *lease = NULL;
+
+ addr = server_config.start_ip; /* addr is in host order here */
+ for (; addr <= server_config.end_ip; addr++) {
+ /* ie, 192.168.55.0 */
+ if (!(addr & 0xFF))
+ continue;
+ /* ie, 192.168.55.255 */
+ if ((addr & 0xFF) == 0xFF)
+ continue;
+ /* Only do if it isn't assigned as a static lease */
+ ret = htonl(addr);
+ if (!reservedIp(server_config.static_leases, ret)) {
+ /* lease is not taken */
+ lease = find_lease_by_yiaddr(ret);
+ /* no lease or it expired and we are checking for expired leases */
+ if ((!lease || (check_expired && lease_expired(lease)))
+ && nobody_responds_to_arp(ret) /* it isn't used on the network */
+ ) {
+ return ret;
+ }
+ }
+ }
+ return 0;
+}