Merge pull request #21175 from tohojo/dhcp-server-expire

sd-dhcp-server: clear out expired leases when finding new address

1 files changed, 41 insertions, 2 deletions

diff --git a/src/libsystemd-network/sd-dhcp-server.c b/src/libsystemd-network/sd-dhcp-server.c
index 45ac70b461..604c34fe15 100644
--- a/src/libsystemd-network/sd-dhcp-server.c
+++ b/src/libsystemd-network/sd-dhcp-server.c
@@ -854,6 +854,38 @@ static int prepare_new_lease(
         return 0;
 }
 
+static int dhcp_server_cleanup_expired_leases(sd_dhcp_server *server) {
+        DHCPLease *lease;
+        usec_t time_now;
+        int r;
+
+        assert(server);
+
+        r = sd_event_now(server->event, clock_boottime_or_monotonic(), &time_now);
+        if (r < 0)
+                return r;
+
+        HASHMAP_FOREACH(lease, server->bound_leases_by_client_id) {
+                if (lease->expiration < time_now) {
+                        log_dhcp_server(server, "CLEAN (0x%x)", be32toh(lease->address));
+                        dhcp_lease_free(lease);
+                }
+        }
+
+        return 0;
+}
+
+static bool address_available(sd_dhcp_server *server, be32_t address) {
+        assert(server);
+
+        if (hashmap_contains(server->bound_leases_by_address, UINT32_TO_PTR(address)) ||
+            hashmap_contains(server->static_leases_by_address, UINT32_TO_PTR(address)) ||
+            address == server->address)
+                return false;
+
+        return true;
+}
+
 #define HASH_KEY SD_ID128_MAKE(0d,1d,fe,bd,f1,24,bd,b3,47,f1,dd,6e,73,21,93,30)
 
 int dhcp_server_handle_message(sd_dhcp_server *server, DHCPMessage *message, size_t length) {
@@ -883,6 +915,10 @@ int dhcp_server_handle_message(sd_dhcp_server *server, DHCPMessage *message, siz
                 /* this only fails on critical errors */
                 return r;
 
+        r = dhcp_server_cleanup_expired_leases(server);
+        if (r < 0)
+                return r;
+
         existing_lease = hashmap_get(server->bound_leases_by_client_id, &req->client_id);
         static_lease = hashmap_get(server->static_leases_by_client_id, &req->client_id);
 
@@ -918,8 +954,7 @@ int dhcp_server_handle_message(sd_dhcp_server *server, DHCPMessage *message, siz
                                 be32_t tmp_address;
 
                                 tmp_address = server->subnet | htobe32(server->pool_offset + (hash + i) % server->pool_size);
-                                if (!hashmap_contains(server->bound_leases_by_address, &tmp_address) &&
-                                    !hashmap_contains(server->static_leases_by_address, &tmp_address)) {
+                                if (address_available(server, tmp_address)) {
                                         address = tmp_address;
                                         break;
                                 }
@@ -996,6 +1031,10 @@ int dhcp_server_handle_message(sd_dhcp_server *server, DHCPMessage *message, siz
                         address = req->message->ciaddr;
                 }
 
+                /* disallow our own address */
+                if (address == server->address)
+                        return 0;
+
                 pool_offset = get_pool_offset(server, address);
                 existing_lease_by_address = hashmap_get(server->bound_leases_by_address, UINT32_TO_PTR(address));