TC执行过程解析

查看iproute2源码文件中的tc文件夹：
先看makefile

TCOBJ= tc.o tc_qdisc.o tc_class.o tc_filter.o tc_util.o /        m_police.o m_estimator.o m_action.o m_ematch.o /        emp_ematch.yacc.o emp_ematch.lex.o   include ../Config   TCMODULES := TCMODULES += q_fifo.o TCMODULES += q_sfq.o TCMODULES += q_red.o TCMODULES += q_prio.o TCMODULES += q_tbf.o TCMODULES += q_cbq.o TCMODULES += f_rsvp.o TCMODULES += f_u32.o TCMODULES += f_route.o TCMODULES += f_fw.o TCMODULES += f_basic.o TCMODULES += q_dsmark.o TCMODULES += q_gred.o TCMODULES += f_tcindex.o TCMODULES += q_ingress.o TCMODULES += q_hfsc.o TCMODULES += q_htb.o TCMODULES += m_gact.o TCMODULES += m_mirred.o TCMODULES += m_ipt.o TCMODULES += m_pedit.o TCMODULES += p_ip.o TCMODULES += p_icmp.o TCMODULES += p_tcp.o TCMODULES += p_udp.o TCMODULES += em_nbyte.o TCMODULES += em_cmp.o TCMODULES += em_u32.o TCMODULES += em_meta.o   TCOBJ += $(TCMODULES)   TCLIB := tc_core.o TCLIB += tc_red.o TCLIB += tc_cbq.o TCLIB += tc_estimator.o   CFLAGS += -DCONFIG_GACT -DCONFIG_GACT_PROB   TCSO := TCSO += q_netem.so ifeq ($(TC_CONFIG_ATM),y)   TCSO += q_atm.so endif   LDLIBS += -L. -ltc -lm -ldl   LDFLAGS += -Wl,-export-dynamic   YACC := bison LEX := flex   %.so: %.c        $(CC) $(CFLAGS) -shared -fpic $< -o $@     all: libtc.a tc $(TCSO)   tc: $(TCOBJ) $(LIBNETLINK) $(LIBUTIL) $(TCLIB)   libtc.a: $(TCLIB)        $(AR) rcs $@ $(TCLIB)   install: all        mkdir -p $(DESTDIR)/usr/lib/tc        install -m 0755 -s tc $(DESTDIR)$(SBINDIR)        for i in $(TCSO); /        do install -m 755 -s $$i $(DESTDIR)/usr/lib/tc; /        done   clean:        rm -f $(TCOBJ) $(TCLIB) libtc.a tc *.so emp_ematch.yacc.h; /        rm -f emp_ematch.yacc.output   q_atm.so: q_atm.c        $(CC) $(CFLAGS) -shared -fpic -o q_atm.so q_atm.c -latm   %.yacc.c: %.y        $(YACC) $(YACCFLAGS) -o $@ $<   %.lex.c: %.l        $(LEX) $(LEXFLAGS) -o$@ $<

 
淡蓝色标记的为我们关注.
为了跟踪程序是如何执行的，以执行下面命令为例：
Code

tc qdisc add dev eth0 root handle 1: htb default 12[cmd1]

 
下面看tc.c中的main函数

int main(int argc, char **argv) { /** *cmd1:argc=11(maybe 12) *argv:{ `tc` ` qdisc` ` add` ` dev ` `eth0` ` root ` `handle`  1:` `htb`` default` *`12`} */        int ret;        int do_batching = 0;        char *batchfile = NULL;          while (argc > 1) {               if (argv[1][0] != '-')                      break;               if (matches(argv[1], "-stats") == 0 ||                       matches(argv[1], "-statistics") == 0) {                      ++show_stats;               } else if (matches(argv[1], "-details") == 0) {                      ++show_details;               } else if (matches(argv[1], "-raw") == 0) {                      ++show_raw;               } else if (matches(argv[1], "-Version") == 0) {                      printf("tc utility, iproute2-ss%s/n", SNAPSHOT);                      return 0;               } else if (matches(argv[1], "-iec") == 0) {                      ++use_iec;               } else if (matches(argv[1], "-help") == 0) {                      usage();                      return 0;               } else if (matches(argv[1], "-force") == 0) {                      ++force;               } else   if (matches(argv[1], "-batch") == 0) {                      do_batching = 1;                      if (argc > 2)                             batchfile = argv[2];                      argc--;  argv++;               } else {                      fprintf(stderr, "Option /"%s/" is unknown, try /"tc -help/"./n", argv[1]);                      return -1;               }               argc--;  argv++;        }          if (do_batching)               return batch(batchfile);          if (argc <= 1) {               usage();               return 0;        }          tc_core_init();//从系统中读出一些设置参数        if (rtnl_open(&rth, 0) < 0) { /** *用户层和系统内核通信采用的是rtnetlink机制， *所以需要rtnetlink的支持 */               fprintf(stderr, "Cannot open rtnetlink/n");               exit(1);        } /** *tc的命令形式：tc …… *所以传递给do_cmd的参数中，去掉了tc这个关键字 *这就是为什么argc-1和argv+1 *argv:{ ` qdisc` ` add` ` dev ` `eth0` ` root ` `handle`  1:` default` *`12`} */        ret = do_cmd(argc-1, argv+1);        rtnl_close(&rth);        return ret; }

do_cmd会根据不同的类型，调用不同的函数来处理，例如，如果是qdisc，那么函数do_qdisc会被调用，当然传递给do_qdisc函数的参数，关键字qdisc也是会被去处的。那么[cmd1]在do_qdisc为：

argv:{ ` add` ` dev ` `eth0` ` root ` `handle`  1:` `htb` ` default` *`12`}

Code::do_cmd

static int do_cmd(int argc, char **argv) { /** *cssalp&csalp： *do argc-1 and argv+1 is to escape the key word, i.e. *do_qdisc must escape 'qdisc' */        if (matches(*argv, "qdisc") == 0)               return do_qdisc(argc-1, argv+1);//这是要跟踪的函数          if (matches(*argv, "class") == 0)               return do_class(argc-1, argv+1);          if (matches(*argv, "filter") == 0)               return do_filter(argc-1, argv+1);          if (matches(*argv, "actions") == 0)               return do_action(argc-1, argv+1);          if (matches(*argv, "help") == 0) {               usage();               return 0;        }               fprintf(stderr, "Object /"%s/" is unknown, try /"tc help/"./n",               *argv);        return -1; }

 
下面看看do_qdisc的

int do_qdisc(int argc, char **argv) {          if (argc < 1)                    return tc_qdisc_list(0, NULL);//列出系统默认的qdisc和filter等信息          if (matches(*argv, "add") == 0)                    return tc_qdisc_modify(RTM_NEWQDISC, NLM_F_EXCL|NLM_F_CREATE, argc-1, argv+1);          if (matches(*argv, "change") == 0)                    return tc_qdisc_modify(RTM_NEWQDISC, 0, argc-1, argv+1);          if (matches(*argv, "replace") == 0)                    return tc_qdisc_modify(RTM_NEWQDISC, NLM_F_CREATE|NLM_F_REPLACE, argc-1, argv+1);          if (matches(*argv, "link") == 0)                    return tc_qdisc_modify(RTM_NEWQDISC, NLM_F_REPLACE, argc-1, argv+1);          if (matches(*argv, "delete") == 0)                    return tc_qdisc_modify(RTM_DELQDISC, 0,  argc-1, argv+1); #if 0          if (matches(*argv, "get") == 0)                    return tc_qdisc_get(RTM_GETQDISC, 0,  argc-1, argv+1); #endif          if (matches(*argv, "list") == 0 || matches(*argv, "show") == 0              || matches(*argv, "lst") == 0)                    return tc_qdisc_list(argc-1, argv+1);          if (matches(*argv, "help") == 0)                    usage();          fprintf(stderr, "Command /"%s/" is unknown, try /"tc qdisc help/"./n", *argv);          return -1; }

 
tc_qdisc_modify函数
 
传递给tc_qdisc_modify函数的argv为：

argv:{ ` dev ` `eth0` ` root ` `handle`  1:` `htb`` default` *`12`}

tc_qdisc_modify(RTM_NEWQDISC, NLM_F_EXCL|NLM_F_CREATE, argc-1, argv+1);
对tc_qdisc_modify函数参数的说明：
1、定义rtnetlink（netlink）消息类型：RTM_NEWQDISC，即新建一个qdisc
2、设置标志flag，flag的有如下几种：
Ø  NLM_F_REPLACE(ox100)覆盖以存在的
Ø  NLM_F_EXCL(ox200)如果存在就不创建
Ø  NLM_F_CREATE(ox400)不存在就创建
Ø  NLM_F_APPEND(ox800)添加到末尾
Code::flag

#define NLM_F_REPLACE       0x100   /* Override existing             */ #define NLM_F_EXCL 0x200  /* Do not touch, if it exists */ #define NLM_F_CREATE  0x400  /* Create, if it does not exist     */ #define NLM_F_APPEND  0x800  /* Add to end of list             */ /*在linux系统里面有相同的定义*/

3、设置命令参数的个数和命令参数
Code：：tc_qdisc_modify

int tc_qdisc_modify(int cmd, unsigned flags, int argc, char **argv) { /** * argv:{ ` dev ` `eth0` ` root ` `handle`  1:` `htb`` default` *`12`} */        struct qdisc_util *q = NULL;        struct tc_estimator est;        char  d[16];        char  k[16];        struct { /** * nlmsghdr为和系统内核通信的消息结构的头 *tcmsg为tc消息结构 */               struct nlmsghdr     n;               struct tcmsg            t;               char                        buf[TCA_BUF_MAX];        } req;          memset(&req, 0, sizeof(req));        memset(&est, 0, sizeof(est));        memset(&d, 0, sizeof(d));        memset(&k, 0, sizeof(k));          req.n.nlmsg_len = NLMSG_LENGTH(sizeof(struct tcmsg));        req.n.nlmsg_flags = NLM_F_REQUEST|flags;        req.n.nlmsg_type = cmd;//对应[cmd1],type=rtm_newqdisc        req.t.tcm_family = AF_UNSPEC;//family          while (argc > 0) {               if (strcmp(*argv, "dev") == 0) {                      NEXT_ARG();//point to nextà ethi(i is number)                      if (d[0])                             duparg("dev", *argv);                      strncpy(d, *argv, sizeof(d)-1);//eth0               } else if (strcmp(*argv, "handle") == 0) {                      __u32 handle;                      if (req.t.tcm_handle)                             duparg("handle", *argv);                      NEXT_ARG();                      if (get_qdisc_handle(&handle, *argv))//handle=1                             invarg(*argv, "invalid qdisc ID");                      req.t.tcm_handle = handle;               } else if (strcmp(*argv, "root") == 0) {                      if (req.t.tcm_parent) { /** *如果存在parent， 那么就不能为root */                             fprintf(stderr, "Error: /"root/" is duplicate parent ID/n");                             return -1;                      }                      req.t.tcm_parent = TC_H_ROOT; #ifdef TC_H_INGRESS               } else if (strcmp(*argv, "ingress") == 0) {                      if (req.t.tcm_parent) {                             fprintf(stderr, "Error: /"ingress/" is a duplicate parent ID/n");                             return -1;                      }                      req.t.tcm_parent = TC_H_INGRESS;                      strncpy(k, "ingress", sizeof(k)-1);                      q = get_qdisc_kind(k);                      req.t.tcm_handle = 0xffff0000;                        argc--; argv++;                      break; #endif               } else if (strcmp(*argv, "parent") == 0) {                      __u32 handle;                      NEXT_ARG();                      if (req.t.tcm_parent)                             duparg("parent", *argv);                      if (get_tc_classid(&handle, *argv))                             invarg(*argv, "invalid parent ID");                      req.t.tcm_parent = handle;               } else if (matches(*argv, "estimator") == 0) {                      if (parse_estimator(&argc, &argv, &est))                             return -1;               } else if (matches(*argv, "help") == 0) {                      usage();               } else {                      strncpy(k, *argv, sizeof(k)-1);//k=`htb` /** *get_qdisc_kind *1、首先查看，与要添加的qdisc相关的qdisc_util是否已经存在了 * 如果存在，那么返回 *2、如果qdisc_util 还存在，那么查找系统的动态链接库，看是否存在 *通过函数dlopen打开动态链接库，然后通过函数q = dlsym(dlh, buf) *得到相应的qdisc_util *3、如果系统的动态链接也不存在,[cmd1]就是这种能够情况 *那么，就创建一个新的(q = malloc(sizeof(*q));)，如果成功 *然后设置一下参数{ *            q->id = strcpy(malloc(strlen(str)+1), str); *            q->parse_qopt = parse_noqopt; *            q->print_qopt = print_noqopt; } *4、最后将找到的qdisc_util,挂载到qdisc_list的上（链表）,并返回q *5、如果不成功，那么返回null(无能为力了) */                      q = get_qdisc_kind(k);                      argc--; argv++;                      break;               }               argc--; argv++;        } /** *addattr函数设置nlmsghdr中的一些参数，为和内核通信传递参数做准备 */        if (k[0])               addattr_l(&req.n, sizeof(req), TCA_KIND, k, strlen(k)+1);        if (est.ewma_log)               addattr_l(&req.n, sizeof(req), TCA_RATE, &est, sizeof(est));          if (q) {               if (!q->parse_qopt) {                      fprintf(stderr, "qdisc '%s' does not support option parsing/n", k);                      return -1;               } /** *在这个例子中，parse_qopt=parse_noqopt, do nothing and return 0 */               if (q->parse_qopt(q, argc, argv, &req.n))                      return 1;        } else {               if (argc) {                      if (matches(*argv, "help") == 0)                             usage();                        fprintf(stderr, "Garbage instead of arguments /"%s .../". Try /"tc qdisc help/"./n", *argv);                      return -1;               }        } /** *根据设备名，找到设备，并设置消息，传递设备信息到内核 */        if (d[0])  {               int idx;                ll_init_map(&rth);                 if ((idx = ll_name_to_index(d)) == 0) {                      fprintf(stderr, "Cannot find device /"%s/"/n", d);                      return 1;               }               req.t.tcm_ifindex = idx;        } /** *rtnl_talk函数，实现和内核通信 *在rtnl_talk函数中，会调用sendmsg函数，将信息传递到内核， *在内核中，最终会调用tc_modify_qidsc函数来创建qdisc *在pktsched_init函数中(linux 内核) *rtnl_register(PF_UNSPEC, RTM_NEWQDISC, tc_modify_qdisc, NULL); *而消息设定信息： *  req.n.nlmsg_type = cmd;//对应[cmd1],type=RTM_NEWQDISC *     req.t.tcm_family = AF_UNSPEC; *当然rtnl_talk会监听内核返回的消息，并做相应的处理 */       if (rtnl_talk(&rth, &req.n, 0, 0, NULL, NULL, NULL) < 0)               return 2;          return 0; }