http://blog.csdn.net/xuyanbo2008/article/details/7439751
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1．thread的四种创建方法
一个新的thread可以通过如下三种方式被创建，主要是看你需要创建的thread的类型：
1， thread_add_read：添加一个thread到read queue，该thread负责通过socket接受和读取从client端来的数据。
2， thread_add_write：添加一个thread到write queue，该thread负责通过socket向client端填充和写数据。
3， thread_add_timer function calls：添加一个thread到timer queue,该thread负责定时一个event，例如update和redistribute一个route table.
4， thread_add_event：添加一个event thread到event queue。
上面这三个函数的处理过程都差不多：
1， 创建thread。首先在unuse queue查找，如果有unuse thread，就使用它，否则重新分配空间。
2， 根据参数，对thread进行赋值。
3， 将该thread加入到相应的queue中。
2． thread的调用
1，bgp daemon不断地从event queue中取出thread并且执行它。一旦该thread被执行了，将该thread的type设置为unuse。并且将该thread添加到unuse queue中。
2，如果event queue为空时，bgp daemon 通过select函数监控读、写、异常三个描述符集。一旦有某个描述符准备就绪，则将该描述符所对应的thread加入ready queue.
而对于timer queue中的thread，只有当select函数超时后才会进入ready queue.
3．zebrad端的thread
zebrad启动后会，在read queue中会出现两个thread，一个是等待来自local client端bgpd的连接，另一个是等待来自vty client端的连接。
第1个thread
zebra_init ( )-> zebra_serv_un ( )中创建一个thread，加入read queue。该thread的处理函数为zebra_accept，监听内部client的socket。
zebra_client_create (client_sock);创建一个新的zebra client
/* Register myself. */
zebra_event (ZEBRA_SERV, accept_sock, NULL);继续监听server socket
puts("<-zebra_accept");
return 0;
}
vty_accept，加入read queue。作为vty server监听internet的vty socket.。
vty_create(vty_sock, &su);
根据vty_sock和ip地址信息su，创建一个新的vty。
puts("<-vty_accept");
return 0;
}
vty_event (VTY_READ, vty_sock, vty);
根据new client vty的vty_sock创建新的VTY_READ thread，加入read queue，该thread的处理函数为vty_read。
return vty;
}
sockunion_bind(accept_sock, &su, port, NULL);
将accept_socket文件描述符与一个特定的逻辑网络连系起来。服务器端使用su->sin.sin_addr.s_addr = htonl (INADDR_ANY);表示接受任何一个主机网络接口上的连接请求。
if (ret < 0)
{
close (accept_sock); /* Avoid sd leak. */
return;
}
/* Listen socket under queue 3. */
ret = listen (accept_sock, 3);
将accept_sock套接口设置成被动监听状态，用于接受连接，只能在服务器端使用。
if (ret < 0)
{
zlog (NULL, LOG_WARNING, "can't listen socket");
close (accept_sock); /* Avoid sd leak. */
return;
}
/* Add vty server event. */
vty_event(VTY_SERV, accept_sock, NULL);
}
/* Bind socket to specified address. */
int sockunion_bind (int sock, union sockunion *su, unsigned short port,
union sockunion *su_addr)
{
int size = 0;
int ret;
if (su->sa.sa_family == AF_INET)
{
size = sizeof (struct sockaddr_in);
su->sin.sin_port = htons (port);
#ifdef HAVE_SIN_LEN
su->sin.sin_len = size;
#endif /* HAVE_SIN_LEN */
if (su_addr == NULL)
su->sin.sin_addr.s_addr = htonl (INADDR_ANY);
服务器一般将sin_addr.s_addr 字段设置为INADDR_ANY表示套接字应接收任何一个主机网络接口上的连接请求。
客户端将sin_addr.s_addr字段设置为服务器主机的IP地址。
}
#ifdef HAVE_IPV6
else if (su->sa.sa_family == AF_INET6)
{
size = sizeof (struct sockaddr_in6);
su->sin6.sin6_port = htons (port);
#ifdef SIN6_LEN
su->sin6.sin6_len = size;
#endif /* SIN6_LEN */
if (su_addr == NULL)
{
#if defined(LINUX_IPV6) || defined(NRL)
bzero (&su->sin6.sin6_addr, sizeof (struct in6_addr));
#else
su->sin6.sin6_addr = in6addr_any;
#endif /* LINUX_IPV6 */
}
}
#endif /* HAVE_IPV6 */
ret = bind (sock, (struct sockaddr *)su, size);
if (ret < 0)
zlog (NULL, LOG_WARNING, "can't bind socket : %s", strerror (errno));
return ret;
}
/* struct thread_master *master; */
static void vty_event (enum event event, int sock, struct vty *vty)
{
struct thread *vty_serv_thread;
switch (event)
{
case VTY_SERV:
vty_serv_thread = thread_add_read (master, vty_accept, vty, sock);
vector_set_index (Vvty_serv_thread, sock, vty_serv_thread);
break;
case VTY_READ:
vty->t_read = thread_add_read (master, vty_read, vty, sock);
/* Time out treatment. */
if (vty->v_timeout)
{
if (vty->t_timeout)
thread_cancel (vty->t_timeout);
vty->t_timeout =
thread_add_timer (master, vty_timeout, vty, vty->v_timeout);
}
break;
case VTY_WRITE:
if (! vty->t_write)
vty->t_write = thread_add_write (master, vty_flush, vty, sock);
break;
case VTY_TIMEOUT_RESET:
if (vty->t_timeout)
{
thread_cancel (vty->t_timeout);
vty->t_timeout = NULL;
}
if (vty->v_timeout)
{
vty->t_timeout =
thread_add_timer (master, vty_timeout, vty, vty->v_timeout);
}
break;
}
}
第2 个thread
bgp_serv_sock( )-> bgp_serv_sock_family( )中创建一个thread，不是通过event的方式添加的。该thread的处理函数为bgp_accept。作为bgp_server，接受来自 internet上的bgp连接。
bgp_serv_sock_family操作
port = 179 family = AF_INET
/* Make bgpd's server socket. */
void bgp_serv_sock_family (unsigned short port, int family)
{
int ret;
int bgp_sock;
union sockunion su;
bzero (&su, sizeof (union sockunion));
/* Specify address family. */
su.sa.sa_family = family;
bgp_sock = sockunion_stream_socket (&su); 产生一个BGP socket
sockopt_reuseaddr (bgp_sock);
sockopt_reuseport (bgp_sock);
ret = sockunion_bind (bgp_sock, &su, port, NULL);
ret = listen (bgp_sock, 3);
if (ret < 0)
{
zlog (NULL, LOG_INFO, "Can't listen bgp server socket : %s",
strerror (errno));
return;
}
thread_add_read (master, bgp_accept, NULL, bgp_sock); 添加一个thread 到readlist中。
}
VTY server和BGP server 在使用accept操作的方法如下：
他们均是通过创建一个THREAD_READ 类型的thread，加到Master的readlist的队列后面，thread 的处理函数会执行accept操作。
VTY accept：
vty_serv_thread = thread_add_read (master, vty_accept, vty, sock);
BGP server accept:
thread_add_read (master, bgp_accept, NULL, bgp_sock);
bgpd和zebrad间通信
bgp和zebra是通过zebra message进行通信，格式如下：
报文头3字节 （前两字节length，后1字节为command type）
报文体长度不定。
/* Zebra message types. */
#define ZEBRA_INTERFACE_ADD 1
#define ZEBRA_INTERFACE_DELETE 2
#define ZEBRA_INTERFACE_ADDRESS_ADD 3
#define ZEBRA_INTERFACE_ADDRESS_DELETE 4
#define ZEBRA_INTERFACE_UP 5
#define ZEBRA_INTERFACE_DOWN 6
#define ZEBRA_IPV4_ROUTE_ADD 7
#define ZEBRA_IPV4_ROUTE_DELETE 8
#define ZEBRA_IPV6_ROUTE_ADD 9
#define ZEBRA_IPV6_ROUTE_DELETE 10
#define ZEBRA_REDISTRIBUTE_ADD 11
#define ZEBRA_REDISTRIBUTE_DELETE 12
#define ZEBRA_REDISTRIBUTE_DEFAULT_ADD 13
#define ZEBRA_REDISTRIBUTE_DEFAULT_DELETE 14
#define ZEBRA_IPV4_NEXTHOP_LOOKUP 15
#define ZEBRA_IPV6_NEXTHOP_LOOKUP 16
bgpd和zebrad之间的api接口
bgp端接受到message后，会执行相应的bgp action:
bgp action func message type
int (*interface_add) (int, struct zclient *, zebra_size_t); ZEBRA_INTERFACE_ADD
int (*interface_delete) (int, struct zclient *, zebra_size_t); ZEBRA_INTERFACE_DELETE
int (*interface_up) (int, struct zclient *, zebra_size_t); ZEBRA_INTERFACE_UP
int (*interface_down) (int, struct zclient *, zebra_size_t); ZEBRA_INTERFACE_DOWN
int (*interface_address_add) (int, struct zclient *, zebra_size_t); ZEBRA_INTERFACE_ADDRESS_ADD
int (*interface_address_delete) (int, struct zclient *, zebra_size_t); ZEBRA_INTERFACE_ADDRESS_DELETE
int (*ipv4_route_add) (int, struct zclient *, zebra_size_t); ZEBRA_IPV4_ROUTE_ADD
int (*ipv4_route_delete) (int, struct zclient *, zebra_size_t); ZEBRA_IPV4_ROUTE_DELETE
int (*ipv6_route_add) (int, struct zclient *, zebra_size_t); ZEBRA_IPV6_ROUTE_ADD
int (*ipv6_route_delete) (int, struct zclient *, zebra_size_t); ZEBRA_IPV6_ROUTE_DELETE
zebra 端接受到message后，会执行相应的zebra action:
zebra action func message type
void zread_interface_add (struct zserv *client, u_short length) ZEBRA_INTERFACE_ADD
void zread_interface_delete (struct zserv *client, u_short length) ZEBRA_INTERFACE_DELETE
void zread_ipv4_add (struct zserv *client, u_short length) ZEBRA_IPV4_ROUTE_ADD
void zread_ipv4_delete (struct zserv *client, u_short length) ZEBRA_IPV4_ROUTE_DELETE
void zread_ipv6_add (struct zserv *client, u_short length) ZEBRA_IPV6_ROUTE_ADD
void zread_ipv6_delete (struct zserv *client, u_short length) ZEBRA_IPV6_ROUTE_DELETE
void zebra_redistribute_add (int command, struct zserv *client, int length) ZEBRA_REDISTRIBUTE_ADD
void zebra_redistribute_delete (int command, struct zserv *client, int length) ZEBRA_REDISTRIBUTE_DELETE
voidzebra_redistribute_default_add (int command,
struct zserv *client, int length) ZEBRA_REDISTRIBUTE_DEFAULT_ADD
void zebra_redistribute_default_delete (int command,
struct zserv *client, int length) ZEBRA_REDISTRIBUTE_DEFAULT_DELETE
void zread_ipv4_nexthop_lookup (struct zserv *client, u_short length) ZEBRA_IPV4_NEXTHOP_LOOKUP
void zread_ipv6_nexthop_lookup (struct zserv *client, u_short length) ZEBRA_IPV6_NEXTHOP_LOOKUP
bgp action：将local_client_socket中数据，写入bgp数据库。
zebra action：将zebra数据库中的信息写入local_server_subsocket，让local client端进行读取。
bgp peer间通信
bgp_accept操作
/* Accept bgp connection. */
int bgp_accept (struct thread *thread)
{
int bgp_sock;
int accept_sock;
union sockunion su;
struct peer *peer;
struct peer *peer1;
char buf[SU_ADDRSTRLEN];
/* Regiser accept thread. */
accept_sock = THREAD_FD (thread);
printf("->bgp_accept [%d]\n",accept_sock);
thread_add_read (master, bgp_accept, NULL, accept_sock);
/* Accept client connection. */
bgp_sock = sockunion_accept (accept_sock, &su);
if (bgp_sock < 0)
{
zlog_err ("[Error] BGP socket accept failed (%s)", strerror (errno));
printf("[Error] BGP socket accept failed (%s)", strerror (errno));
puts("<-bgp_accept 2");
return -1;
}
if (BGP_DEBUG (events, EVENTS))
zlog_info ("[Event] BGP connection from host %s", inet_sutop (&su, buf));
printf("[Event] BGP connection from host %s", inet_sutop (&su, buf));
/* Check remote IP address */
peer1 = peer_lookup_by_su (&su);
if (! peer1 || peer1->status == Idle)
{
if (BGP_DEBUG (events, EVENTS))
{
if (! peer1)
zlog_info ("[Event] BGP connection IP address %s is not configured",
inet_sutop (&su, buf));
else
zlog_info ("[Event] BGP connection IP address %s is Idle state",
inet_sutop (&su, buf));
}
close (bgp_sock);
puts("<-bgp_accept 2");
return -1;
}
/* Make dummy peer until read Open packet. */
if (BGP_DEBUG (events, EVENTS))
zlog_info ("[Event] Make dummy peer structure until read Open packet");
printf("[Event] Make dummy peer structure until read Open packet\n");
{
char buf[SU_ADDRSTRLEN + 1];
peer = peer_create_accept ();
SET_FLAG (peer->sflags, PEER_STATUS_ACCEPT_PEER);
peer->su = su;
peer->fd = bgp_sock;
peer->status = Active;
/* Make peer's address string. */
sockunion2str (&su, buf, SU_ADDRSTRLEN);
peer->host = strdup (buf);
}
BGP_EVENT_ADD (peer, TCP_connection_open); 创建一个event thread执行bgp_event函数
puts("<-bgp_accept 0");
return 0;
}
bgp_event操作
/* Execute event process. */
int bgp_event (struct thread *thread)
{
int ret;
int event;
int next;
struct peer *peer;
peer = THREAD_ARG (thread); // get peer
event = THREAD_VAL (thread); // get FSM event eg.TCP_connection_open
puts("->bgp_event");
/* Logging this event. */
next = FSM [peer->status -1][event - 1].next_state; next为下一个状态
if (BGP_DEBUG (fsm, FSM))
plog_info (peer->log, "%s [FSM] %s (%s->%s)", peer->host,
bgp_event_str[event],
LOOKUP (bgp_status_msg, peer->status),
LOOKUP (bgp_status_msg, next));
printf("%s [FSM] %s (%s->%s)", peer->host,
bgp_event_str[event],
LOOKUP (bgp_status_msg, peer->status),
LOOKUP (bgp_status_msg, next));
/* Call function. */
ret = (*(FSM [peer->status - 1][event - 1].func))(peer); 执行本状态处理函数
/* When function do not want proceed next job return -1. */
if (ret < 0)
{
puts("<-bgp_event 1");
return ret;
}
/* If status is changed. */
if (next != peer->status) 判断状态是否需要转变
fsm_change_status (peer, next);
/* Make sure timer is set. */
bgp_timer_set (peer);
puts("<-bgp_event 0");
return 0;
}