Bind-9_6_0-P1源代码分析之一@整体架构.doc

Bind-9.6.0-P1源代码分析之一:整体架构(初稿)一、 说明参考/lxr/http/source/bin/named/main.c这是bind解析程序的入口事件bind程序也事件驱动型，以任务作为主要的执行。当一个解析请求到来时，就会通过事件的产生来触发任务dispatch处理。这样的处理有相应if (event-ev_action != NULL) 861 UNLOCK(&task-lock);862 (event-ev_action)(task,event);863 LOCK(&task-lock);这里 action就是执行函数本文主要关注整体的运行结构，主要参考文件是main.c二、 启动入口870 int871 main(int argc, char *argv) 命令行参数传入以上为设置错误消息895 isc_assertion_setcallback(assertion_failed);896 isc_error_setfatal(library_fatal_error);897 isc_error_setunexpected(library_unexpected_error);898初始化系统日志，权限等899 ns_os_init(program_name);900初始化工作901 dns_result_register();902 dst_result_register();903 isccc_result_register();904 命令行参数分析，如-g将日志输出到front-end905 parse_command_line(argc, argv);注意以下的内存机制，isc_mem可见/lxr/http/source/lib/isc/mem.c#L113定义注意以/lxr/http/source/lib/isc/mem.c#L725用到了锁机制830 LOCK(&lock);831 ISC_LIST_INITANDAPPEND(contexts, ctx, link);832 UNLOCK(&lock);833 内存生成采用标准的系统调用 malloc和free，但考虑到多线程下的竞争情况，对内存块访问需要锁机制。Ns_g_mctx是信号量，要求ns_g_mctx!=NULL&*ns_g_mctx=NULL919 result = isc_mem_create(0, 0, &ns_g_mctx);920 if (result != ISC_R_SUCCESS)921 ns_main_earlyfatal(isc_mem_create() failed: %s,922 isc_result_totext(result);对设置923 isc_mem_setname(ns_g_mctx, main, NULL);924 /setup是重要的一部分，见分析三925 setup();接下来就是解析主体程序了，是通过循环来做的，直到错误或者接收到退出信号。递/*928 * Start things running and then wait for a shutdown request929 * or reload.930 */931 do 932 result = isc_app_run();是重要部分，见分析四933 934 if (result = ISC_R_RELOAD) /通过我们会做这种操作，当配置了一个新的zone文件时935 ns_server_reloadwanted(ns_g_server);936 else if (result != ISC_R_SUCCESS) 937 UNEXPECTED_ERROR(_FILE_, _LINE_,938 isc_app_run(): %s,939 isc_result_totext(result);940 /*941 * Force exit.942 */943 result = ISC_R_SUCCESS;944 945 while (result != ISC_R_SUCCESS);946 947 #ifdef HAVE_LIBSCF948 if (ns_smf_want_disable = 1) 949 result = ns_smf_get_instance(&instance, 1, ns_g_mctx);950 if (result = ISC_R_SUCCESS & instance != NULL) 951 if (smf_disable_instance(instance, 0) != 0)952 UNEXPECTED_ERROR(_FILE_, _LINE_,953 smf_disable_instance() 954 failed for %s : %s,955 instance,956 scf_strerror(scf_error();957 958 if (instance != NULL)959 isc_mem_free(ns_g_mctx, instance);960 961 #endif /* HAVE_LIBSCF */962 963 cleanup();964 965 if (want_stats) 966 isc_mem_stats(ns_g_mctx, stdout);967 isc_mutex_stats(stdout);968 969 970 if (ns_g_memstatistics & memstats != NULL) 971 FILE *fp = NULL;972 result = isc_stdio_open(memstats, w, &fp);973 if (result = ISC_R_SUCCESS) 974 isc_mem_stats(ns_g_mctx, fp);975 isc_mutex_stats(fp);976 isc_stdio_close(fp);977 978 979 isc_mem_destroy(&ns_g_mctx);980 isc_mem_checkdestroyed(stderr);981 982 ns_main_setmemstats(NULL);983 984 isc_app_finish();985 986 ns_os_closedevnull();987 988 ns_os_shutdown();989 990 return (0);991 三、 初始设置setup595 ns_os_tzset(); 初始化时区596 597 ns_os_opendevnull(); 打开空设备以便消息转向599 #ifdef HAVE_LIBSCF 是否solaris的smf管理机制600 /* Check if named is under smf control, before chroot. */601 result = ns_smf_get_instance(&instance, 0, ns_g_mctx);602 /* We dont care about instance, just check if we got one. */603 if (result = ISC_R_SUCCESS)604 ns_smf_got_instance = 1;605 else606 ns_smf_got_instance = 0;607 if (instance != NULL)608 isc_mem_free(ns_g_mctx, instance);609 #endif /* HAVE_LIBSCF */如果是chroot运行方式化，初始化可用资源。Chroot是以普通用户运行超级资源，是unix系统的一种机制611 #ifdef PATH_RANDOMDEV612 /*613 * Initialize systems random device as fallback entropy source614 * if running chrooted.615 */616 if (ns_g_chrootdir != NULL) 617 result = isc_entropy_create(ns_g_mctx, &ns_g_fallbackentropy);618 if (result != ISC_R_SUCCESS)619 ns_main_earlyfatal(isc_entropy_create() failed: %s,620 isc_result_totext(result);621 622 result = isc_entropy_createfilesource(ns_g_fallbackentropy,623 PATH_RANDOMDEV);624 if (result != ISC_R_SUCCESS) 625 ns_main_earlywarning(could not open pre-chroot 626 entropy source %s: %s,627 PATH_RANDOMDEV,628 isc_result_totext(result);629 isc_entropy_detach(&ns_g_fallbackentropy);630 631 632 #endif看cpu数目634 #ifdef ISC_PLATFORM_USETHREADS635 /*636 * Check for the number of cpus before ns_os_chroot().637 */638 ns_g_cpus_detected = isc_os_ncpus();639 #endif以下说明了最小权限运行机制，读config文件需要有root机制，通过unix的sid置位实现，即setsid()/*644 * For operating systems which have a capability mechanism, now645 * is the time to switch to minimal privs and change our user id.646 * On traditional UNIX systems, this call will be a no-op, and we647 * will change the user ID after reading the config file the first648 * time. (We need to read the config file to know which possibly649 * privileged ports to bind() to.)650 */651 ns_os_minprivs();652 日志初始化653 result = ns_log_init(ISC_TF(ns_g_username != NULL);654 if (result != ISC_R_SUCCESS)655 ns_main_earlyfatal(ns_log_init() failed: %s,656 isc_result_totext(result);pid = fork();产生新的子进程，如果是直接named而不是named g的话，因此，需要派生子进程，并关闭父的一些输入输出句柄,参见fork例程if (!ns_g_foreground)666 ns_os_daemonize();/*669 * We call isc_app_start() here as some versions of FreeBSDs fork()670 * destroys all the signal handling it sets up.671 */Isc_app_start主要是处理fork的信号机制的恢复672 result = isc_app_start();673 if (result != ISC_R_SUCCESS)674 ns_main_earlyfatal(isc_app_start() failed: %s,675 isc_result_totext(result);676 写日志文件，开始启动677 isc_log_write(ns_g_lctx, NS_LOGCATEGORY_GENERAL, NS_LOGMODULE_MAIN,678 ISC_LOG_NOTICE, starting BIND %s%s, ns_g_version,679 saved_command_line);680 681 isc_log_write(ns_g_lctx, NS_LOGCATEGORY_GENERAL, NS_LOGMODULE_MAIN,682 ISC_LOG_NOTICE, built with %s, ns_g_configargs);683 接下来是资源限制部分，可用#ulimit a来理解 /*729 * Record the servers startup time.730 */731 result = isc_time_now(&ns_g_boottime);732 if (result != ISC_R_SUCCESS)733 ns_main_earlyfatal(isc_time_now() failed: %s,734 isc_result_totext(result);735 生成管理器，如任务、超时、entropy、hash,socket等管理器736 result = create_managers();737 if (result != ISC_R_SUCCESS)738 ns_main_earlyfatal(create_managers() failed: %s,739 isc_result_totext(result);740 741 ns_builtin_init();742 743 /*744 * Add calls to register sdb drivers here.745 */746 /* xxdb_init(); */747 748 #ifdef DLZ749 /*750 * Registyer any DLZ drivers.751 */752 result = dlz_drivers_init();753 if (result != ISC_R_SUCCESS)754 ns_main_earlyfatal(dlz_drivers_init() failed: %s,755 isc_result_totext(result);756 #endif757 生成服务，重要部分，见分析六758 ns_server_create(ns_g_mctx, &ns_g_server);759 760 四、 运行主体程序文件/lxr/http/source/lib/isc/unix/app.c#L431430 isc_result_t431 isc_app_run(void) 432 int result;433 isc_event_t *event, *next_event;434 isc_task_t *task;435 #ifdef ISC_PLATFORM_USETHREADS436 sigset_t sset;437 char strbufISC_STRERRORSIZE;438 #ifdef HAVE_SIGWAIT439 int sig;440 #endif441 #endif /* ISC_PLATFORM_USETHREADS */442 443 #ifdef HAVE_LINUXTHREADS 如果启用了多线程编译，目前我们编译的是单线程，可用ps em|grep named查看线程数444 REQUIRE(main_thread = pthread_self();445 #endif446 加锁，事件队列是关键区，race condition447 LOCK(&lock);448 449 if (!running) 450 running = ISC_TRUE;451 事件结构有sender,type,action,arguments，而采用队列ev_link实现，事件FIFO依序处理。452 /*453 * Post any on-run events (in FIFO order).454 */主循环455 for (event = ISC_LIST_HEAD(on_run);456 event != NULL;457 event = next_event) 458 next_event = ISC_LIST_NEXT(event, ev_link);459 ISC_LIST_UNLINK(on_run, event, ev_link);460 task = event-ev_sender;461 event-ev_sender = NULL;事件任务机制，见分析五462 isc_task_sendanddetach(&task, &event);463 464 465 466 467 UNLOCK(&lock);468 以下主要为信号捕获处理机制，特别注意shutdown退出时的处理。信号catch处理机制能够使应用更安全退出。469 #ifndef HAVE_SIGWAIT470 /*471 * Catch SIGHUP.472 *473 * We do this here to ensure that the signal handler is installed474 * (i.e. that it wasnt a one-shot handler).475 */476 result = handle_signal(SIGHUP, reload_action);477 if (result != ISC_R_SUCCESS)478 return (ISC_R_SUCCESS);479 #endif480 481 #ifdef ISC_PLATFORM_USETHREADS482 /*483 * There is no danger if isc_app_shutdown() is called before we wait484 * for signals. Signals are blocked, so any such signal will simply485 * be made pending and we will get it when we call sigwait().486 */487 488 while (!want_shutdown) 489 #ifdef HAVE_SIGWAIT490 /*491 * Wait for SIGHUP, SIGINT, or SIGTERM.492 */493 if (sigemptyset(&sset) != 0 |494 sigaddset(&sset, SIGHUP) != 0 |495 sigaddset(&sset, SIGINT) != 0 |496 sigaddset(&sset, SIGTERM) != 0) 497 isc_strerror(errno, strbuf, sizeof(strbuf);498 UNEXPECTED_ERROR(_FILE_, _LINE_,499 isc_app_run() sigsetops: %s, strbuf);500 return (ISC_R_UNEXPECTED);501 502 503 #ifndef HAVE_UNIXWARE_SIGWAIT504 result = sigwait(&sset, &sig);505 if (result = 0) 506 if (sig = SIGINT |507 sig = SIGTERM)508 want_shutdown = ISC_TRUE;509 else if (sig = SIGHUP)510 want_reload = ISC_TRUE;511 512 513 #else /* Using UnixWare sigwait semantics. */514 sig = sigwait(&sset);515 if (sig = 0) 516 if (sig = SIGINT |517 sig = SIGTERM)518 want_shutdown = ISC_TRUE;519 else if (sig = SIGHUP)520 want_reload = ISC_TRUE;521 522 523 #endif /* HAVE_UNIXWARE_SIGWAIT */524 #else /* Dont have sigwait(). */525 /*526 * Listen for all signals.527 */528 if (sigemptyset(&sset) != 0) 529 isc_strerror(errno, strbuf, sizeof(strbuf);530 UNEXPECTED_ERROR(_FILE_, _LINE_,531 isc_app_run() sigsetops: %s, strbuf);532 return (ISC_R_UNEXPECTED);533 534 result = sigsuspend(&sset);535 #endif /* HAVE_SIGWAIT */536 537 if (want_reload) 538 want_reload = ISC_FALSE;539 return (ISC_R_RELOAD);540 541 542 if (want_shutdown & blocked)543 exit(1);544 545 546 #else /* ISC_PLATFORM_USETHREADS */547 548 (void)isc_taskmgr_dispatch();549 550 result = evloop();551 if (result != ISC_R_SUCCESS)552 return (result);553 554 #endif /* ISC_PLATFORM_USETHREADS */555 556 return (ISC_R_SUCCESS);557 正常关闭时，需要将相关线程也中止558 559 isc_result_t560 isc_app_shutdown(void) 561 isc_boolean_t want_kill = ISC_TRUE;562 char strbufISC_STRERRORSIZE;563 564 LOCK(&lock);565 566 REQUIRE(running);567 568 if (shutdown_requested)569 want_kill = ISC_FALSE;570 else571 shutdown_requested = ISC_TRUE;572 573 UNLOCK(&lock);574 575 if (want_kill) 576 #ifdef HAVE_LINUXTHREADS577 int result;578 579 result = pthread_kill(main_thread, SIGTERM);580 if (result != 0) 581 isc_strerror(result, strbuf, sizeof(strbuf);582 UNEXPECTED_ERROR(_FILE_, _LINE_,583 isc_app_shutdown() pthread_kill: %s,584 strbuf);585 return (ISC_R_UNEXPECTED);586 587 #else588 if (kill(getpid(), SIGTERM) ev_sender;event-ev_sender = NULL;isc_task_sendanddetach(&task, &event);void430 isc_task_sendanddetach(isc_task_t *taskp, isc_event_t *eventp) 431 isc_boolean_t idle1, idle2;432 isc_task_t *task;433 434 /*435 * Send *event to *taskp and then detach *taskp from its436 * task.437 */438 439 REQUIRE(taskp != NULL);440 task = *taskp;441 REQUIRE(VALID_TASK(task);442 443 XTRACE(isc_task_sendanddetach);444 445 LOCK(&task-lock);446 idle1 = task_send(task, eventp);447 idle2 = task_detach(task);448 UNLOCK(&task-lock);449 450 /*451 * If idle1, then idle2 shouldnt be true as well since were holding452 * the task lock, and thus the task cannot switch from ready back to453 * idle.454 */455 INSIST(!(idle1 & idle2);456 457 if (idle1 | idle2)458 task_ready(task);459 460 *taskp = NULL;461 462 463 #define PURGE_OK(event) (event)-ev_attributes & ISC_EVENTATTR_NOPURGE) = 0)464 六 服务任务生成(主要与rndc的channel通信)3826 void3827 ns_server_create(isc_mem_t *mctx, ns_server_t *serverp) 3828 isc_result_t result;3829 3830 ns_server_t *server = isc_mem_get(mctx, sizeof(*server);3831 if (server = NULL)3832 fatal(allocating server object, ISC_R_NOMEMORY);3833 3834 server-mctx = mctx;3835 server-task = NULL;3836 3837 /* Initialize configuration data with default values. */3838 3839 result = isc_quota_init(&server-xfroutquota, 10);3840 RUNTIME_CHECK(result = ISC_R_SUCCESS);3841 result = isc_quota_init(&server-tcpquota, 10);3842 RUNTIME_CHECK(result = ISC_R_SUCCESS);3843 result = isc_quota_init(&server-recursionquota, 100);3844 RUNTIME_CHECK(result = ISC_R_SUCCESS);3845 3846 result = dns_aclenv_init(mctx, &server-ac