1 files changed, 34 insertions, 6 deletions

diff --git a/networking/udhcp/leases.c b/networking/udhcp/leases.c
index 7aeb37bae..c5b60b108 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)