LWIP的底层结构

{

LOCK_TCPIP_CORE();

apimsg->function(&(apimsg->msg)); UNLOCK_TCPIP_CORE(); return ERR_OK; }

* Call the lower part of a netconn_* function * This function is then running in the thread context * of tcpip_thread and has exclusive access to lwIP core code. err_t tcpip_apimsg(struct api_msg *apimsg)【此为非locking的】 {

struct tcpip_msg msg;

if (mbox != SYS_MBOX_NULL) { msg.type = TCPIP_MSG_API; msg.msg.apimsg = apimsg; sys_mbox_post(mbox, &msg);

sys_arch_sem_wait(apimsg->msg.conn->op_completed, 0); return ERR_OK; }

return ERR_VAL; }

其实，功能都是一样的，都是要对apimsg->function函数的调用。只是途径不一样而已。看看它们的功能说明就知道了。这么来说apimsg->function的调用很重要了。从netconn_new_with_proto_and_callback函数的实现，可以知道这个function就是do_newconn

Void do_newconn(struct api_msg_msg *msg) {

if(msg->conn->pcb.tcp == NULL) { pcb_new(msg); }

/* Else? This \ /* Is this an error condition? Should it be deleted? */ /* We currently just are happy and return. */

TCPIP_APIMSG_ACK(msg); }

还是看TCP的，在pcb_new函数中有如下代码： case NETCONN_TCP:

msg->conn->pcb.tcp = tcp_new(); if(msg->conn->pcb.tcp == NULL) { msg->conn->err = ERR_MEM;

break; }

setup_tcp(msg->conn); break;

我们知道在这里建立了这个tcp的连接。至于这个超级牛的函数，以后再做介绍。

嗯，还是回过头来接着看accept函数吧。

Sock获得了，接着就是newconn = netconn_accept(sock->conn);通过mbox取得新的

连接。粗略的估计了一下，这个新的连接应该和listen有关系。那就再次打断一下，看看那个listen操作。

lwip_listen --? netconn_listen_with_backlog--? do_listen--? tcp_arg(msg->conn->pcb.tcp, msg->conn);

tcp_accept(msg->conn->pcb.tcp, accept_function);//注册了一个接受函数

* Accept callback function for TCP netconns.

* Allocates a new netconn and posts that to conn->acceptmbox.

static err_t accept_function(void *arg, struct tcp_pcb *newpcb, err_t err) {

struct netconn *newconn; struct netconn *conn;

conn = (struct netconn *)arg;

/* We have to set the callback here even though

* the new socket is unknown. conn->socket is marked as -1. */ newconn = netconn_alloc(conn->type, conn->callback); if (newconn == NULL) { return ERR_MEM; }

newconn->pcb.tcp = newpcb; setup_tcp(newconn); newconn->err = err;

/* Register event with callback */ API_EVENT(conn, NETCONN_EVT_RCVPLUS, 0);

if (sys_mbox_trypost(conn->acceptmbox, newconn) != ERR_OK) {

/* When returning != ERR_OK, the connection is aborted in tcp_process(), so do nothing here! */ newconn->pcb.tcp = NULL; netconn_free(newconn); return ERR_MEM; }

return ERR_OK; }