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1楼 bomail 2008-01-12
ktcpvs是LVS的一个子项目，主要是针对layer-7的负载均衡，具体介绍参考www.linuxvirtualserver.org。本文是针
对ktcpvs2.6.9版本的，对应linux2.6内核的，下面进入正题，对我理解的ktcpvs源码进行一个描述。
1.整个module的入口文件是tcp_vs.c: module_init(ktcpvs_init); 这是module的初始化接口，由此转到ktcpvs_init。 2.ktcpvs_init函数 static int __init ktcpvs_init(void) { tcp_vs_control_start(); tcp_vs_slowtimer_init(); tcp_vs_srvconn_init(); (void) kernel_thread(master_daemon, NULL, 0); } 做一些初始化工作之后，进入master_daemon线程。 3.master_daemon线程 static int master_daemon(void *unused) { /* main loop */ while (sysctl_ktcpvs_unload == 0) { read_lock(&__tcp_vs_svc_lock); list_for_each(l, &tcp_vs_svc_list) { svc = list_entry(l, struct tcp_vs_service, list); if (!atomic_read(&svc->running) && svc->start) kernel_thread(tcp_vs_daemon, svc, 0); } read_unlock(&__tcp_vs_svc_lock); } return 0; } 这是主工作线程，只有一个，遍历tcp_vs_svc_list（相当于config文件），启动每个service（ktcpvs的一个service 就对应一个虚拟服务，相当于config文件中的其中一个vitual web）就是svc，每个svc开启tcp_vs_daemon线程。 4.tcp_vs_daemon线程 static int tcp_vs_daemon(void *__svc) { /* Then start listening and spawn the daemons */ if (StartListening(svc) < 0) goto out; for (i = 0; i < svc->conf.startservers; i++) make_child(child_table, i, svc); /* dynamically keep enough thread to handle load */ child_pool_maintenance(child_table, svc); } /* stop listening */ StopListening(svc); return 0; } 每个虚拟服务svc都会启动这样一个线程，对于一个svc，主要调用StartListening函数创建socket，启动监听，然后根据config 文件startserver参数通过make_child函数初始启动相应的多个children与svc相关的连接准备，放到child_table 中，child_table主要由struct tcp_vs_child数组children构成，每个数组元素主要有个指向svc的指针。最后是关闭监听，退出，不再跟下去了，主要看 StartListening和make_child。 5.StartListening函数，在Misc.c文件 int StartListening(struct tcp_vs_service *svc) { /* First create a socket */ error = sock_create(PF_INET, SOCK_STREAM, IPPROTO_TCP, &sock); /* Now bind the socket */ sin.sin_family = AF_INET; sin.sin_addr.s_addr = svc->conf.addr; sin.sin_port = svc->conf.port; error = sock->ops->bind(sock, (struct sockaddr *) &sin, sizeof(sin)); /* Now, start listening on the socket */ error = sock->ops->listen(sock, sysctl_ktcpvs_max_backlog); svc->mainsock = sock; return 0; } 就是创建socket，绑定制定地址和端口，开始监听。 6.make_child函数 static inline void make_child(struct tcp_vs_child_table *tbl, int slot, struct tcp_vs_service *svc) { tbl->children[slot].svc = svc; if (kernel_thread(tcp_vs_child, &tbl->children[slot], CLONE_VM | CLONE_FS | CLONE_FILES) < 0) TCP_VS_ERR("spawn child failed\n"); } 把tcp_vs_child_table的children[i]跟svc关联上，然后启动tcp_vs_child线程。 7.tcp_vs_child线程 static int tcp_vs_child(void *__child) { struct tcp_vs_child *chd = (struct tcp_vs_child *) __child; struct tcp_vs_service *svc = chd->svc; chd->pid = current->pid; sock = svc->mainsock; while (svc->stop == 0 && sysctl_ktcpvs_unload == 0) { /* create tcp_vs_conn object */ conn = tcp_vs_conn_create(sock, Buffer, BufLen); /* Do the actual accept */ ret = sock->ops->accept(sock, conn->csock, O_NONBLOCK); /* Do the work */ ret = tcp_vs_conn_handle(conn, svc); } return 0; } 一个虚拟服务会根据配置启动tcp_vs_child的线程池，把sock指向之前在监听的mainsock，初始化一个与client之间的 tcp_vs_conn对象conn，从监听socket accpet一个socket指定由conn->csock处理（就是与client之间的socket），然后就处理进入 tcp_vs_conn_handle函数进行具体数据报处理。 8.tcp_vs_conn_handle函数 int tcp_vs_conn_handle(struct tcp_vs_conn *conn, struct tcp_vs_service *svc) { csock = conn->csock; if (csock->sk->sk_state != TCP_ESTABLISHED) { if (csock->sk->sk_state == TCP_CLOSE_WAIT) return 0; return -1; } switch (svc->scheduler->schedule(conn, svc)) { case 1: /* scheduler has done all the work */ return 0; case 0: /* further process needed */ break; case -1: /* try to redirect the connection to other sockets */ /* fault tolerance function*/ if (!fault_redirect(conn,svc)) break; if (svc->conf.redirect_port) { redirect_to_local(conn, svc->conf.redirect_addr, svc->conf.redirect_port); return 0; } return -1; default: return 0; } dsock = conn->dsock; lastupdated = jiffies; while ((jiffies - lastupdated) < sysctl_ktcpvs_read_timeout * HZ) { /* if the connection is closed, go out of this loop */ if (dsock->sk->sk_state != TCP_ESTABLISHED && dsock->sk->sk_state != TCP_CLOSE_WAIT) break; if (csock->sk->sk_state != TCP_ESTABLISHED && csock->sk->sk_state != TCP_CLOSE_WAIT) break; /* Do we have data from server? */ if (!skb_queue_empty(&(dsock->sk->sk_receive_queue))) { if (tcp_vs_relay_socket(dsock, csock) == 0) break; lastupdated = jiffies; } /* Do we have data from client? */ if (!skb_queue_empty(&(csock->sk->sk_receive_queue))) { if (tcp_vs_relay_socket(csock, dsock) == 0) break; lastupdated = jiffies; } if (skb_queue_empty(&(dsock->sk->sk_receive_queue)) && skb_queue_empty(&(csock->sk->sk_receive_queue))) { if (dsock->sk->sk_state == TCP_CLOSE_WAIT || csock->sk->sk_state == TCP_CLOSE_WAIT) break; /* * Put the current task on the sleep wait queue * of both the sockets, wake up the task if one * socket has some data ready. */ add_wait_queue(csock->sk->sk_sleep, &wait1); add_wait_queue(dsock->sk->sk_sleep, &wait2); __set_current_state(TASK_INTERRUPTIBLE); __set_current_state(TASK_RUNNING); remove_wait_queue(csock->sk->sk_sleep, &wait1); remove_wait_queue(dsock->sk->sk_sleep, &wait2); } } return 0; } 根据config中配置的scheduler来处理client的请求，如果scheduler配置为http，则在tcp_vs_http.c这定义了static struct tcp_vs_scheduler tcp_vs_http_scheduler = { {0}, /* n_list */ "http", /* name */ THIS_MODULE, /* this module */ tcp_vs_http_init_svc, /* initializer */ tcp_vs_http_done_svc, /* done */ tcp_vs_http_update_svc, /* update */ tcp_vs_http_schedule, /* select a server by http request */ };调度函数是tcp_vs_http_schedule，负责选择一个realserver并与之建立连接，把client过来的数据包转发过去，调度完之后，再由tcp_vs_relay_socket把realserver得到响应再响应给client。
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