lwIP(V1.3.0) RAW API函数源码分析2----tcp_bind()函数

1万 · 2018-9-15 22:46

原文网址：https://blog.csdn.net/zhzht19861011/article/details/6188400

位于: 位于:lwip-x.x.x/src/core/tcp.c

原型: err_t tcp_bind(struct tcp_pcb *pcb, struct ip_addr *ipaddr, u16_t port)

功能:绑定连接到一个本地端口号和IP地址.

函数源码:

[cpp] view plain copy

/**
* Binds the connection to a local port number and IP address. If the
* IP address is not given (i.e., ipaddr == NULL), the IP address of
* the outgoing network interface is used instead.
*IP地址没有给出(即ipaddr==NULL),则IP地址由输出网络接口代替
* @param pcb the tcp_pcb to bind (no check is done whether this pcb is
* already bound!)
* @param ipaddr the local ip address to bind to (use IP_ADDR_ANY to bind
* to any local address
* @param port the local port to bind to
* @return ERR_USE if the port is already in use
* ERR_OK if bound 成功绑定
*/
err_t
tcp_bind(struct tcp_pcb *pcb, struct ip_addr *ipaddr, u16_t port)
{
struct tcp_pcb *cpcb;
LWIP_ERROR("tcp_connect: can only bind in state CLOSED", pcb->state == CLOSED, return ERR_ISCONN);
if (port == 0) {
port = tcp_new_port(); //返回一个新的(自由的)本地TCP端口号
}
/* Check if the address already is in use. */
/* Check the listen pcbs. */
/* 检查*/
for(cpcb = (struct tcp_pcb *)tcp_listen_pcbs.pcbs;/*注1 */
cpcb != NULL; cpcb = cpcb->next) {
if (cpcb->local_port == port) {
if (ip_addr_isany (&(cpcb->local_ip)) /*已监听pcb列表中IP地址全为0或没有分配IP地址,则函数返回1*/||
ip_addr_isany(ipaddr) /*检验参数IP地址*/||
ip_addr_cmp(&(cpcb->local_ip), ipaddr)) /*检验参数IP和已监听pcb列表中IP地址是否相同*/{
return ERR_USE; //返回端口已被使用信息
}
}
}
/* Check the connected pcbs. 检查当前连接的pcbs*/
for(cpcb = tcp_active_pcbs;
cpcb != NULL; cpcb = cpcb->next) {
if (cpcb->local_port == port) {
if (ip_addr_isany(&(cpcb->local_ip)) ||
ip_addr_isany(ipaddr) ||
ip_addr_cmp(&(cpcb->local_ip), ipaddr)) {
return ERR_USE;
}
}
}
/* Check the bound, not yet connected pcbs.检查已绑定的还没有连接的pcbs */
for(cpcb = tcp_bound_pcbs; cpcb != NULL; cpcb = cpcb->next) {
if (cpcb->local_port == port) {
if (ip_addr_isany(&(cpcb->local_ip)) ||
ip_addr_isany(ipaddr) ||
ip_addr_cmp(&(cpcb->local_ip), ipaddr)) {
return ERR_USE;
}
}
}
/* @todo: until SO_REUSEADDR is implemented (see task #6995 on savannah),
* we have to check the pcbs in TIME-WAIT state, also: */
for(cpcb = tcp_tw_pcbs; cpcb != NULL; cpcb = cpcb->next) {
if (cpcb->local_port == port) {
if (ip_addr_cmp(&(cpcb->local_ip), ipaddr)) {
return ERR_USE;
}
}
}
if (!ip_addr_isany(ipaddr)) {
pcb->local_ip = *ipaddr; //IP地址给当前连接的pcb
}
pcb->local_port = port;
TCP_REG(&tcp_bound_pcbs, pcb); //将当前pcb放入已绑定tcp_pcb列表
LWIP_DEBUGF(TCP_DEBUG, ("tcp_bind: bind to port %"U16_F"/n", port));
return ERR_OK;
}