/**
* Closes the connection held by the PCB.
*
*/
err_t
tcp_close(struct tcp_pcb *pcb)
{
err_t err;
#if TCP_DEBUG
LWIP_DEBUGF(TCP_DEBUG, ("tcp_close: closing in "));
tcp_debug_print_state(pcb->state);
#endif /* TCP_DEBUG */
switch (pcb->state) {
case CLOSED:
/* Closing a pcb in the CLOSED state might seem erroneous,
* however, it is in this state once allocated and as yet unused
* and the user needs some way to free it should the need arise.
* Calling tcp_close() with a pcb that has already been closed, (i.e. twice)
* or for a pcb that has been used and then entered the CLOSED state
* is erroneous, but this should never happen as the pcb has in those cases
* been freed, and so any remaining handles are bogus. */
err = ERR_OK;
memp_free(MEMP_TCP_PCB, pcb);
pcb = NULL;
break;
case LISTEN:
err = ERR_OK;
tcp_pcb_remove((struct tcp_pcb **)&tcp_listen_pcbs.pcbs, pcb);
memp_free(MEMP_TCP_PCB_LISTEN, pcb);
pcb = NULL;
break;
case SYN_SENT:
err = ERR_OK;
tcp_pcb_remove(&tcp_active_pcbs, pcb);
memp_free(MEMP_TCP_PCB, pcb);
pcb = NULL;
snmp_inc_tcpattemptfails();
break;
case SYN_RCVD:
err = tcp_send_ctrl(pcb, TCP_FIN);
if (err == ERR_OK) {
snmp_inc_tcpattemptfails();
pcb->state = FIN_WAIT_1;
}
break;
case ESTABLISHED:
err = tcp_send_ctrl(pcb, TCP_FIN);
if (err == ERR_OK) {
snmp_inc_tcpestabresets();
pcb->state = FIN_WAIT_1;
}
break;
case CLOSE_WAIT:
err = tcp_send_ctrl(pcb, TCP_FIN);
if (err == ERR_OK) {
snmp_inc_tcpestabresets();
pcb->state = LAST_ACK;
}
break;
default:
/* Has already been closed, do nothing. */
err = ERR_OK;
pcb = NULL;
break;
}
if (pcb != NULL && err == ERR_OK) {
err = tcp_output(pcb);
}
return err;
}
/**
* Closes the TX side of a connection held by the PCB.
* For tcp_close(), a RST is sent if the application didn't receive all data
* (tcp_recved() not called for all data passed to recv callback).
*
* Listening pcbs are freed and may not be referenced any more.
* Connection pcbs are freed if not yet connected and may not be referenced
* any more. If a connection is established (at least SYN received or in
* a closing state), the connection is closed, and put in a closing state.
* The pcb is then automatically freed in tcp_slowtmr(). It is therefore
* unsafe to reference it.
*
* @param pcb the tcp_pcb to close
* @return ERR_OK if connection has been closed
* another err_t if closing failed and pcb is not freed
*/
static err_t
tcp_close_shutdown(struct tcp_pcb *pcb, u8_t rst_on_unacked_data)
{
err_t err;
if (rst_on_unacked_data && (pcb->state != LISTEN)) {
if ((pcb->refused_data != NULL) || (pcb->rcv_wnd != TCP_WND)) {
/* Not all data received by application, send RST to tell the remote
side about this. */
LWIP_ASSERT("pcb->flags & TF_RXCLOSED", pcb->flags & TF_RXCLOSED);
/* don't call tcp_abort here: we must not deallocate the pcb since
that might not be expected when calling tcp_close */
tcp_rst(pcb->snd_nxt, pcb->rcv_nxt, &pcb->local_ip, &pcb->remote_ip,
pcb->local_port, pcb->remote_port);
tcp_pcb_purge(pcb);
/* TODO: to which state do we move now? */
/* move to TIME_WAIT since we close actively */
TCP_RMV(&tcp_active_pcbs, pcb);
pcb->state = TIME_WAIT;
TCP_REG(&tcp_tw_pcbs, pcb);
return ERR_OK;
}
}
switch (pcb->state) {
case CLOSED:
/* Closing a pcb in the CLOSED state might seem erroneous,
* however, it is in this state once allocated and as yet unused
* and the user needs some way to free it should the need arise.
* Calling tcp_close() with a pcb that has already been closed, (i.e. twice)
* or for a pcb that has been used and then entered the CLOSED state
* is erroneous, but this should never happen as the pcb has in those cases
* been freed, and so any remaining handles are bogus. */
err = ERR_OK;
if (pcb->local_port != 0) {
TCP_RMV(&tcp_bound_pcbs, pcb);
}
memp_free(MEMP_TCP_PCB, pcb);
pcb = NULL;
break;
case LISTEN:
err = ERR_OK;
tcp_pcb_remove(&tcp_listen_pcbs.pcbs, pcb);
memp_free(MEMP_TCP_PCB_LISTEN, pcb);
pcb = NULL;
break;
case SYN_SENT:
err = ERR_OK;
tcp_pcb_remove(&tcp_active_pcbs, pcb);
memp_free(MEMP_TCP_PCB, pcb);
pcb = NULL;
snmp_inc_tcpattemptfails();
break;
case SYN_RCVD:
err = tcp_send_fin(pcb);
if (err == ERR_OK) {
snmp_inc_tcpattemptfails();
pcb->state = FIN_WAIT_1;
}
break;
case ESTABLISHED:
err = tcp_send_fin(pcb);
if (err == ERR_OK) {
snmp_inc_tcpestabresets();
pcb->state = FIN_WAIT_1;
}
break;
case CLOSE_WAIT:
err = tcp_send_fin(pcb);
if (err == ERR_OK) {
snmp_inc_tcpestabresets();
pcb->state = LAST_ACK;
}
break;
default:
/* Has already been closed, do nothing. */
err = ERR_OK;
pcb = NULL;
break;
}
if (pcb != NULL && err == ERR_OK) {
/* To ensure all data has been sent when tcp_close returns, we have
to make sure tcp_output doesn't fail.
Since we don't really have to ensure all data has been sent when tcp_close
returns (unsent data is sent from tcp timer functions, also), we don't care
for the return value of tcp_output for now. */
/* @todo: When implementing SO_LINGER, this must be changed somehow:
If SOF_LINGER is set, the data should be sent and acked before close returns.
This can only be valid for sequential APIs, not for the raw API. */
tcp_output(pcb);
}
return err;
}
/**
* Closes the connection held by the PCB.
*
* Listening pcbs are freed and may not be referenced any more.
* Connection pcbs are freed if not yet connected and may not be referenced
* any more. If a connection is established (at least SYN received or in
* a closing state), the connection is closed, and put in a closing state.
* The pcb is then automatically freed in tcp_slowtmr(). It is therefore
* unsafe to reference it.
*
* @param pcb the tcp_pcb to close
* @return ERR_OK if connection has been closed
* another err_t if closing failed and pcb is not freed
*/
err_t
tcp_close(struct tcp_pcb *pcb)
{
err_t err;
#if TCP_DEBUG
LWIP_DEBUGF(TCP_DEBUG, ("tcp_close: closing in "));
tcp_debug_print_state(pcb->state);
#endif /* TCP_DEBUG */
switch (pcb->state) {
case CLOSED:
/* Closing a pcb in the CLOSED state might seem erroneous,
* however, it is in this state once allocated and as yet unused
* and the user needs some way to free it should the need arise.
* Calling tcp_close() with a pcb that has already been closed, (i.e. twice)
* or for a pcb that has been used and then entered the CLOSED state
* is erroneous, but this should never happen as the pcb has in those cases
* been freed, and so any remaining handles are bogus. */
err = ERR_OK;
TCP_RMV(&tcp_bound_pcbs, pcb);
memp_free(MEMP_TCP_PCB, pcb);
pcb = NULL;
break;
case LISTEN:
err = ERR_OK;
tcp_pcb_remove((struct tcp_pcb **)&tcp_listen_pcbs.pcbs, pcb);
memp_free(MEMP_TCP_PCB_LISTEN, pcb);
pcb = NULL;
break;
case SYN_SENT:
err = ERR_OK;
tcp_pcb_remove(&tcp_active_pcbs, pcb);
memp_free(MEMP_TCP_PCB, pcb);
pcb = NULL;
snmp_inc_tcpattemptfails();
break;
case SYN_RCVD:
err = tcp_send_ctrl(pcb, TCP_FIN);
if (err == ERR_OK) {
snmp_inc_tcpattemptfails();
pcb->state = FIN_WAIT_1;
}
break;
case ESTABLISHED:
err = tcp_send_ctrl(pcb, TCP_FIN);
if (err == ERR_OK) {
snmp_inc_tcpestabresets();
pcb->state = FIN_WAIT_1;
}
break;
case CLOSE_WAIT:
err = tcp_send_ctrl(pcb, TCP_FIN);
if (err == ERR_OK) {
snmp_inc_tcpestabresets();
pcb->state = LAST_ACK;
}
break;
default:
/* Has already been closed, do nothing. */
err = ERR_OK;
pcb = NULL;
break;
}
if (pcb != NULL && err == ERR_OK) {
/* To ensure all data has been sent when tcp_close returns, we have
to make sure tcp_output doesn't fail.
Since we don't really have to ensure all data has been sent when tcp_close
returns (unsent data is sent from tcp timer functions, also), we don't care
for the return value of tcp_output for now. */
/* @todo: When implementing SO_LINGER, this must be changed somehow:
If SOF_LINGER is set, the data should be sent when tcp_close returns. */
tcp_output(pcb);
}
return err;
}
/**
* Closes the connection held by the PCB.
*
* Listening pcbs are freed and may not be referenced any more.
* Connection pcbs are freed if not yet connected and may not be referenced
* any more. If a connection is established (at least SYN received or in
* a closing state), the connection is closed, and put in a closing state.
* The pcb is then automatically freed in tcp_slowtmr(). It is therefore
* unsafe to reference it.
*
* @param pcb the tcp_pcb to close
* @return ERR_OK if connection has been closed
* another err_t if closing failed and pcb is not freed
*/
err_t
tcp_close(struct tcp_pcb *pcb)
{
err_t err;
#if TCP_DEBUG
LWIP_DEBUGF(TCP_DEBUG, ("tcp_close: closing in "));
tcp_debug_print_state(pcb->state);
#endif /* TCP_DEBUG */
switch (pcb->state) {
/* 若TCP在CLOSE状态，即tcp_new()之后从未使用过 */
case CLOSED:
/* Closing a pcb in the CLOSED state might seem erroneous,
* however, it is in this state once allocated and as yet unused
* and the user needs some way to free it should the need arise.
* Calling tcp_close() with a pcb that has already been closed, (i.e. twice)
* or for a pcb that has been used and then entered the CLOSED state
* is erroneous, but this should never happen as the pcb has in those cases
* been freed, and so any remaining handles are bogus. */
err = ERR_OK;
/* 从tcp_bound_pcbs链表上删除(如果已经调用tcp_bind()的话) */
TCP_RMV(&tcp_bound_pcbs, pcb);
/* 释放TCP控制所占内存 */
memp_free(MEMP_TCP_PCB, pcb);
pcb = NULL;
break;
case LISTEN:
err = ERR_OK;
/* 从LISTEN链表上删除，并发送可能存在的delayed ACKs */
tcp_pcb_remove((struct tcp_pcb **)&tcp_listen_pcbs.pcbs, pcb);
/* 释放LISTEN类型的TCP控制块 */
memp_free(MEMP_TCP_PCB_LISTEN, pcb);
pcb = NULL;
break;
case SYN_SENT:
err = ERR_OK;
tcp_pcb_remove(&tcp_active_pcbs, pcb);
memp_free(MEMP_TCP_PCB, pcb);
pcb = NULL;
snmp_inc_tcpattemptfails();
break;
case SYN_RCVD:
/* 构造FIN报文，主动关闭 */
err = tcp_send_ctrl(pcb, TCP_FIN);
if (err == ERR_OK) {
snmp_inc_tcpattemptfails();
/* 进入FIN_WAIT_1状态 */
pcb->state = FIN_WAIT_1;
}
break;
case ESTABLISHED:
/* 构造FIN报文，主动关闭 */
err = tcp_send_ctrl(pcb, TCP_FIN);
if (err == ERR_OK) {
snmp_inc_tcpestabresets();
/* 进入FIN_WAIT_1状态 */
pcb->state = FIN_WAIT_1;
}
break;
/* 被动关闭，收到对方的FIN后，构造FIN关闭另一个方向传输 */
case CLOSE_WAIT:
err = tcp_send_ctrl(pcb, TCP_FIN);
if (err == ERR_OK) {
snmp_inc_tcpestabresets();
/* 进入LAST_ACK状态 */
pcb->state = LAST_ACK;
}
break;
/* 其他状态，用TCP定时器函数实现 */
default:
/* Has already been closed, do nothing. */
err = ERR_OK;
pcb = NULL;
break;
}
/* 发送TCP控制块中剩余的报文段，包括FIN报文 */
if (pcb != NULL && err == ERR_OK) {
/* To ensure all data has been sent when tcp_close returns, we have
to make sure tcp_output doesn't fail.
Since we don't really have to ensure all data has been sent when tcp_close
returns (unsent data is sent from tcp timer functions, also), we don't care
for the return value of tcp_output for now. */
/* @todo: When implementing SO_LINGER, this must be changed somehow:
If SOF_LINGER is set, the data should be sent when tcp_close returns. */
tcp_output(pcb);
}
return err;
}