diff options
Diffstat (limited to 'networking/udhcp/leases.c')
-rw-r--r-- | networking/udhcp/leases.c | 149 |
1 files changed, 149 insertions, 0 deletions
diff --git a/networking/udhcp/leases.c b/networking/udhcp/leases.c new file mode 100644 index 0000000..ff52da9 --- /dev/null +++ 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; +} |