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authorVladislav Grishenko <themiron@mail.ru>2011-02-16 12:31:30 (GMT)
committer Denys Vlasenko <vda.linux@googlemail.com>2011-02-16 12:31:30 (GMT)
commit582716733895946b2729acdf18a32532567b973a (patch)
tree433dbc03b2c71768c4477d0f3f4e41c95dc2fa66
parent4fdb67cc65e93967448bb28e4cb810ad5648bfea (diff)
downloadbusybox-582716733895946b2729acdf18a32532567b973a.tar.gz
busybox-582716733895946b2729acdf18a32532567b973a.tar.bz2
udhcpd: optional IP selection based on MAC hash
function old new delta find_free_or_expired_nip 153 225 +72 Signed-off-by: Vladislav Grishenko <themiron@mail.ru> Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
-rw-r--r--networking/udhcp/Config.src18
-rw-r--r--networking/udhcp/leases.c40
2 files changed, 50 insertions, 8 deletions
diff --git a/networking/udhcp/Config.src b/networking/udhcp/Config.src
index dcd493f..750a53a 100644
--- a/networking/udhcp/Config.src
+++ b/networking/udhcp/Config.src
@@ -39,7 +39,21 @@ config FEATURE_UDHCPD_WRITE_LEASES_EARLY
If selected, udhcpd will write a new file with leases every
time a new lease has been accepted, thus eliminating the need
to send SIGUSR1 for the initial writing or updating. Any timed
- rewriting remains undisturbed
+ rewriting remains undisturbed.
+
+config FEATURE_UDHCPD_BASE_IP_ON_MAC
+ bool "Select IP address based on client MAC"
+ default n
+ depends on UDHCPD
+ help
+ If selected, udhcpd will base its selection of IP address to offer
+ on the client's hardware address. Otherwise udhcpd uses the next
+ consecutive free address.
+
+ This reduces the frequency of IP address changes for clients
+ which let their lease expire, and makes consecutive DHCPOFFERS
+ for the same client to (almost always) contain the same
+ IP address.
config DHCPD_LEASES_FILE
string "Absolute path to lease file"
@@ -72,7 +86,7 @@ config FEATURE_UDHCPC_ARPING
config FEATURE_UDHCP_PORT
bool "Enable '-P port' option for udhcpd and udhcpc"
- default y
+ default n
depends on UDHCPD || UDHCPC
help
At the cost of ~300 bytes, enables -P port option.
diff --git a/networking/udhcp/leases.c b/networking/udhcp/leases.c
index 7aeb37b..c5b60b1 100644
--- a/networking/udhcp/leases.c
+++ b/networking/udhcp/leases.c
@@ -137,21 +137,42 @@ 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++) {
+#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)
- continue;
+ goto next_addr;
/* ie, 192.168.55.255 */
if ((addr & 0xff) == 0xff)
- continue;
+ 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))
- continue;
+ goto next_addr;
lease = find_lease_by_nip(nip);
if (!lease) {
@@ -162,7 +183,14 @@ uint32_t FAST_FUNC find_free_or_expired_nip(const uint8_t *safe_mac)
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)