quagga源码分析--大内总管zebra

zebra，中文翻译是斑马，于是我打开了宋冬野的《斑马，斑马》作为BGM来完成这个篇章，嘿嘿，小资一把！

zebra姑且戏称它是quagga项目的大内总管。

因为它负责管理其他所有协议进程的路由信息的更新与交互，并负责与内核交换信息，如下的架构：

1 +----+  +----+  +-----+  +-----+
2 |bgpd|  |ripd|  |ospfd|  |zebra|
3 +----+  +----+  +-----+  +-----+
4                             |
5 +---------------------------|--+
6 |                           v  |
7 |  UNIX Kernel  routing table  |
8 |                              |
9 +------------------------------+

 

好了，简介完了，开始看代码吧：

 

1、zebra作为其他协议进程的服务端：

1 /* Make zebra server socket, wiping any existing one (see bug #403). */
2 void
3 zebra_zserv_socket_init(char *path) {
4 #ifdef HAVE_TCP_ZEBRA
5     zebra_serv();
6 #else
7     zebra_serv_un(path ? path : ZEBRA_SERV_PATH);
8 #endif /* HAVE_TCP_ZEBRA */
9 }

zebra绑定了（loopback，2600）的地址和端口，并开始监听socket，同时加入到thread事件ZEBRA_SERV当中，来接收客户端发送过来的路由信息：

 1 accept_sock = socket(AF_INET, SOCK_STREAM, 0);
 2 
 3 addr.sin_family = AF_INET;
 4 
 5 addr.sin_port = htons(ZEBRA_PORT);
 6 #ifdef HAVE_STRUCT_SOCKADDR_IN_SIN_LEN
 7     addr.sin_len = sizeof(struct sockaddr_in);
 8 #endif /* HAVE_STRUCT_SOCKADDR_IN_SIN_LEN */
 9 addr.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
10 
11 ret  = bind(accept_sock, (struct sockaddr *)&addr, sizeof(struct sockaddr_in));
12   
13 ret = listen(accept_sock, 1);

zebra_event(ZEBRA_SERV, accept_sock, NULL);

2、客户端（比如isis协议）：

2.1 创建客户端，并在初始化加入到thread事件调度当中去。

1 void
2 isis_zebra_init(struct thread_master *master) {
3     zclient = zclient_new(master);
4     zclient_init(zclient, ZEBRA_ROUTE_ISIS);
5     
6     ......
7 
8     return;
9 }

 1 void
 2 zclient_init (struct zclient *zclient, int redist_default)
 3 {
 4   int i;
 5   /* Enable zebra client connection by default. */
 6   zclient->enable = 1;
 7   /* Set -1 to the default socket value. */
 8   zclient->sock = -1;
 9   .....
10   zclient_event (ZCLIENT_SCHEDULE, zclient);
11 }　　

 1 static void
 2 zclient_event(enum event event, struct zclient *zclient) {
 3     switch (event) {
 4     case ZCLIENT_SCHEDULE:
 5         if (!zclient->t_connect) zclient->t_connect =
 6                 thread_add_event(zclient->master, zclient_connect, zclient, 0);
 7         break;
 8         ......
 9     }
10 }

2.2 在zclient_connect里调用zclient_socket完成客户端sock的初始化：

1 int zclient_socket_connect(struct zclient *zclient) {
2 #ifdef HAVE_TCP_ZEBRA
3     zclient->sock = zclient_socket();
4 #else
5     zclient->sock = zclient_socket_un(zclient_serv_path_get());
6 #endif
7     return zclient->sock;
8 }

 1 static int
 2 zclient_socket(void) { 
 3     int sock;
 4     int ret;
 5     struct sockaddr_in serv;
 6 
 7     /* We should think about IPv6 connection. */
 8     sock = socket(AF_INET, SOCK_STREAM, 0);
 9     if (sock < 0) return -1;
10 
11     /* Make server socket. */
12     memset(&serv, 0, sizeof(struct sockaddr_in));
13     serv.sin_family = AF_INET;
14     serv.sin_port = htons(ZEBRA_PORT);
15 #ifdef HAVE_STRUCT_SOCKADDR_IN_SIN_LEN
16     serv.sin_len = sizeof(struct sockaddr_in);
17 #endif /* HAVE_STRUCT_SOCKADDR_IN_SIN_LEN */
18     serv.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
19 
20     /* Connect to zebra. */
21     ret = connect(sock, (struct sockaddr *)&serv, sizeof(serv));
22     if (ret < 0) {
23         close(sock);
24         return -1;
25     }
26     return sock;
27 }

嗯，服务端和客户端就这样完成了tcp通信连接，其他的客户端（如bgpd，ospfd等等）都是调用zclient_socket完成连接，代码复用了哦！

3、下面来看看作为大内总管，zebra如何处理日常事务：

首先是在thread的调度中，增加了read事件（可以看到整个系统，都是由thread模块在在暗中维持的运转）

1 thread_add_read(zebrad.master, zebra_client_read, client, sock);

 1 /* Handler of zebra service request. */
 2 static int
 3 zebra_client_read(struct thread *thread) {
 4     ......
 5     command = stream_getw(client->ibuf);
 6     
 7     .....
 8     
 9     switch (command) {
10     .....
11     
12     case ZEBRA_IPV4_ROUTE_ADD:
13         zread_ipv4_add(client, length, vrf_id);
14         break;
15     case ZEBRA_IPV4_ROUTE_DELETE:
16         zread_ipv4_delete(client, length, vrf_id);
17         break;
18     ......
19     default:
20         zlog_info("Zebra received unknown command %d", command);
21         break;
22     }
23 
24     ......
25     
26     zebra_event(ZEBRA_READ, sock, client);
27     return 0;
28 }

如上述代码，从消息内容中读取到对应事件号，比如ZEBRA_IPV4_ROUTE_ADD，ZEBRA_IPV4_ROUTE_DELETE，即是增加ipv4路由和删除ipv4路由。

4、再来看看大内总管（zebra）如何与皇上（内核）交互的：

在main里对这个过程做了初始化，函数是rib_init。

1 /* Routing information base initialize. */
2 void
3 rib_init(void)
4 {
5     rib_queue_init(&zebrad);
6 }
7 
8     /* fill in the work queue spec */
9     zebra->ribq->spec.workfunc = &meta_queue_process;

上面代码创建一个工作队列，作为thread调度模块的一个低等级的后台调度（THREAD_BACKGROUND）执行的任务。在meta_queue_process函数里处理各个子队列：

 1 /* Dispatch the meta queue by picking, processing and unlocking the next RN from
 2  * a non-empty sub-queue with lowest priority. wq is equal to zebra->ribq and data
 3  * is pointed to the meta queue structure.
 4  */
 5 static wq_item_status
 6 meta_queue_process(struct work_queue *dummy, void *data)
 7 {
 8     struct meta_queue *mq = data;
 9     unsigned i;
10 
11     for (i = 0; i < MQ_SIZE; i++) if (process_subq(mq->subq[i], i))
12         {
13             mq->size--;
14             break;
15         }
16     return mq->size ? WQ_REQUEUE : WQ_SUCCESS;
17 }

process_subq函数里调用rib_process函数，即开始了对路由信息的处理，整个内核的路由的新旧比较与更新：

 1 int
 2 kernel_route_rib (struct prefix *p, struct rib *old, struct rib *new)
 3 {
 4   int route = 0;
 5 
 6   if (zserv_privs.change(ZPRIVS_RAISE))
 7     zlog (NULL, LOG_ERR, "Can't raise privileges");
 8 
 9   if (old)
10     route |= kernel_rtm (RTM_DELETE, p, old);
11 
12   if (new)
13     route |= kernel_rtm (RTM_ADD, p, new);
14 
15   if (zserv_privs.change(ZPRIVS_LOWER))
16     zlog (NULL, LOG_ERR, "Can't lower privileges");
17 
18   return route;
19 }

可以看到，最后使用netlink通信来更新内核的路由信息。

 

 

 

  

 

转载于:https://www.cnblogs.com/danxi/p/6275320.html