mem-pool: Reject the creation of unintentionally empty pools

If a base address is configured, we don't expect the pool to be empty,
so reject the creation (e.g. with the broadcast address as base).

References #2205

src/libcharon/attributes/mem_pool.c

@@ -702,6 +702,13 @@ mem_pool_t *mem_pool_create(char *name, host_t *base, int bits)
 		{	/* only serve the second address of the subnet */
 			this->size--;
 		}
+		if (!this->size)
+		{
+			DBG1(DBG_CFG, "virtual IP pool %H/%d is empty",
+				 base, addr_bits - bits);
+			destroy(this);
+			return NULL;
+		}
 	}
 	return &this->public;
 }

src/libcharon/plugins/load_tester/load_tester_config.c

@@ -286,11 +286,20 @@ static void load_addrs(private_load_tester_config_t *this)
 				from = host_create_from_subnet(token, &bits);
 				if (from)
 				{
-					DBG1(DBG_CFG, "loaded load-tester address pool %H/%d on %s",
-						 from, bits, iface);
 					pool = mem_pool_create(iface, from, bits);
+					if (pool)
+					{
+						DBG1(DBG_CFG, "loaded load-tester address pool %H/%d "
+							 "on %s", from, bits, iface);
+						this->pools->insert_last(this->pools, pool);
+					}
+					else
+					{
+
+						DBG1(DBG_CFG, "invalid load-tester address pool %H/%d "
+							 "on %s, skipped", from, bits, iface);
+					}
 					from->destroy(from);
-					this->pools->insert_last(this->pools, pool);
 				}
 				else
 				{

src/libcharon/tests/suites/test_mem_pool.c

@@ -153,13 +153,10 @@ START_TEST(test_cidr_offset)
 	pool->destroy(pool);
 	base->destroy(base);
 
-	/* due to size == 0 we get the requested IP back */
+	/* this results in an empty pool, which is rejected */
 	base = host_create_from_string("192.168.0.255", 0);
 	pool = mem_pool_create("test", base, 24);
-	ck_assert_int_eq(0, pool->get_size(pool));
-	assert_acquire(pool, "192.168.0.1", "192.168.0.1", MEM_POOL_NEW);
-	pool->destroy(pool);
-
+	ck_assert(!pool);
 	base->destroy(base);
 }
 END_TEST