查看iproute2源码文件中的tc文件夹：
先看makefile
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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
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tc qdisc add dev eth0 root handle 1: htb default 12[cmd1] |
下面看tc.c中的main函数
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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：
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argv:{ ` add` ` dev ` `eth0` ` root ` `handle` 1:` `htb` ` default` *`12`} |
Code::do_cmd
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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
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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：
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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
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#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;
}