/** Safely bring a tcp_pcb into the requested state */
void
tcp_set_state(struct tcp_pcb* pcb, enum tcp_state state, ip_addr_t* local_ip,
ip_addr_t* remote_ip, u16_t local_port, u16_t remote_port)
{
/* @todo: are these all states? */
/* @todo: remove from previous list */
pcb->state = state;
if (state == ESTABLISHED) {
TCP_REG(&tcp_active_pcbs, pcb);
pcb->local_ip.addr = local_ip->addr;
pcb->local_port = local_port;
pcb->remote_ip.addr = remote_ip->addr;
pcb->remote_port = remote_port;
} else if(state == LISTEN) {
TCP_REG(&tcp_listen_pcbs.pcbs, pcb);
pcb->local_ip.addr = local_ip->addr;
pcb->local_port = local_port;
} else if(state == TIME_WAIT) {
TCP_REG(&tcp_tw_pcbs, pcb);
pcb->local_ip.addr = local_ip->addr;
pcb->local_port = local_port;
pcb->remote_ip.addr = remote_ip->addr;
pcb->remote_port = remote_port;
} else {
fail();
}
}
struct tcp_pcb *
tcp_listen(struct tcp_pcb *pcb)
{
struct tcp_pcb_listen *lpcb;
/* already listening? */
if (pcb->state == LISTEN) {
return pcb;
}
lpcb = memp_malloc(MEMP_TCP_PCB_LISTEN);
if (lpcb == NULL) {
return NULL;
}
lpcb->callback_arg = pcb->callback_arg;
lpcb->local_port = pcb->local_port;
lpcb->state = LISTEN;
lpcb->so_options = pcb->so_options;
lpcb->so_options |= SOF_ACCEPTCONN;
lpcb->ttl = pcb->ttl;
lpcb->tos = pcb->tos;
ip_addr_set(&lpcb->local_ip, &pcb->local_ip);
memp_free(MEMP_TCP_PCB, pcb);
#if LWIP_CALLBACK_API
lpcb->accept = tcp_accept_null;
#endif /* LWIP_CALLBACK_API */
TCP_REG(&tcp_listen_pcbs.listen_pcbs, lpcb);
return (struct tcp_pcb *)lpcb;
}
/**
* Binds the connection to a local portnumber 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.
*
* @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
*/
err_t
tcp_bind(struct tcp_pcb *pcb, ip_addr_t *ipaddr, u16_t port)
{
int i;
int max_pcb_list = NUM_TCP_PCB_LISTS;
struct tcp_pcb *cpcb;
LWIP_ERROR("tcp_bind: can only bind in state CLOSED", pcb->state == CLOSED, return ERR_ISCONN);
#if SO_REUSE
/* Unless the REUSEADDR flag is set,
we have to check the pcbs in TIME-WAIT state, also.
We do not dump TIME_WAIT pcb's; they can still be matched by incoming
packets using both local and remote IP addresses and ports to distinguish.
*/
#if SO_REUSE
if ((pcb->so_options & SOF_REUSEADDR) != 0) {
max_pcb_list = NUM_TCP_PCB_LISTS_NO_TIME_WAIT;
}
#endif /* SO_REUSE */
#endif /* SO_REUSE */
if (port == 0) {
port = tcp_new_port();
}
/* Check if the address already is in use (on all lists) */
for (i = 0; i < max_pcb_list; i++) {
for(cpcb = *tcp_pcb_lists[i]; cpcb != NULL; cpcb = cpcb->next) {
if (cpcb->local_port == port) {
#if SO_REUSE
/* Omit checking for the same port if both pcbs have REUSEADDR set.
For SO_REUSEADDR, the duplicate-check for a 5-tuple is done in
tcp_connect. */
if (((pcb->so_options & SOF_REUSEADDR) == 0) ||
((cpcb->so_options & SOF_REUSEADDR) == 0))
#endif /* SO_REUSE */
{
if (ip_addr_isany(&(cpcb->local_ip)) ||
ip_addr_isany(ipaddr) ||
ip_addr_cmp(&(cpcb->local_ip), ipaddr)) {
return ERR_USE;
}
}
}
}
}
pcb->bound_to_netif = 0;
if (!ip_addr_isany(ipaddr)) {
pcb->local_ip = *ipaddr;
}
pcb->local_port = port;
TCP_REG(&tcp_bound_pcbs, pcb);
LWIP_DEBUGF(TCP_DEBUG, ("tcp_bind: bind to port %"U16_F"\n", port));
return ERR_OK;
}
/**
* Connects to another host. The function given as the "connected"
* argument will be called when the connection has been established.
*
* @param pcb the tcp_pcb used to establish the connection
* @param ipaddr the remote ip address to connect to
* @param port the remote tcp port to connect to
* @param connected callback function to call when connected (or on error)
* @return ERR_VAL if invalid arguments are given
* ERR_OK if connect request has been sent
* other err_t values if connect request couldn't be sent
*/
err_t
tcp_connect(struct tcp_pcb *pcb, struct ip_addr *ipaddr, u16_t port,
err_t (* connected)(void *arg, struct tcp_pcb *tpcb, err_t err))
{
err_t ret;
u32_t iss;
LWIP_ERROR("tcp_connect: can only connected from state CLOSED", pcb->state == CLOSED, return ERR_ISCONN);
LWIP_DEBUGF(TCP_DEBUG, ("tcp_connect to port %"U16_F"\n", port));
if (ipaddr != NULL) {
pcb->remote_ip = *ipaddr;
} else {
return ERR_VAL;
}
pcb->remote_port = port;
if (pcb->local_port == 0) {
pcb->local_port = tcp_new_port();
}
iss = tcp_next_iss();
pcb->rcv_nxt = 0;
pcb->snd_nxt = iss;
pcb->lastack = iss - 1;
pcb->snd_lbb = iss - 1;
pcb->rcv_wnd = TCP_WND;
pcb->rcv_ann_wnd = TCP_WND;
pcb->rcv_ann_right_edge = pcb->rcv_nxt;
pcb->snd_wnd = TCP_WND;
/* As initial send MSS, we use TCP_MSS but limit it to 536.
The send MSS is updated when an MSS option is received. */
pcb->mss = (TCP_MSS > 536) ? 536 : TCP_MSS;
#if TCP_CALCULATE_EFF_SEND_MSS
pcb->mss = tcp_eff_send_mss(pcb->mss, ipaddr);
#endif /* TCP_CALCULATE_EFF_SEND_MSS */
pcb->cwnd = 1;
pcb->ssthresh = pcb->mss * 10;
pcb->state = SYN_SENT;
#if LWIP_CALLBACK_API
pcb->connected = connected;
#endif /* LWIP_CALLBACK_API */
TCP_RMV(&tcp_bound_pcbs, pcb);
TCP_REG(&tcp_active_pcbs, pcb);
snmp_inc_tcpactiveopens();
ret = tcp_enqueue(pcb, NULL, 0, TCP_SYN, 0, TF_SEG_OPTS_MSS
#if LWIP_TCP_TIMESTAMPS
| TF_SEG_OPTS_TS
#endif
);
if (ret == ERR_OK) {
tcp_output(pcb);
}
return ret;
}
/**
* Set the state of the connection to be LISTEN, which means that it
* is able to accept incoming connections. The protocol control block
* is reallocated in order to consume less memory. Setting the
* connection to LISTEN is an irreversible process.
*
* @param pcb the original tcp_pcb
* @param backlog the incoming connections queue limit
* @return tcp_pcb used for listening, consumes less memory.
*
* @note The original tcp_pcb is freed. This function therefore has to be
* called like this:
* tpcb = tcp_listen(tpcb);
*/
struct tcp_pcb *
tcp_listen_with_backlog(struct tcp_pcb *pcb, u8_t backlog)
{
struct tcp_pcb_listen *lpcb;
LWIP_UNUSED_ARG(backlog);
LWIP_ERROR("tcp_listen: pcb already connected", pcb->state == CLOSED, return NULL);
/* already listening? */
if (pcb->state == LISTEN) {
return pcb;
}
#if SO_REUSE
if ((pcb->so_options & SOF_REUSEADDR) != 0) {
/* Since SOF_REUSEADDR allows reusing a local address before the pcb's usage
is declared (listen-/connection-pcb), we have to make sure now that
this port is only used once for every local IP. */
for(lpcb = tcp_listen_pcbs.listen_pcbs; lpcb != NULL; lpcb = lpcb->next) {
if (lpcb->local_port == pcb->local_port) {
if (ip_addr_cmp(&lpcb->local_ip, &pcb->local_ip)) {
/* this address/port is already used */
return NULL;
}
}
}
}
#endif /* SO_REUSE */
lpcb = (struct tcp_pcb_listen *)memp_malloc(MEMP_TCP_PCB_LISTEN);
if (lpcb == NULL) {
return NULL;
}
lpcb->callback_arg = pcb->callback_arg;
lpcb->local_port = pcb->local_port;
lpcb->state = LISTEN;
lpcb->prio = pcb->prio;
lpcb->so_options = pcb->so_options;
lpcb->so_options |= SOF_ACCEPTCONN;
lpcb->ttl = pcb->ttl;
lpcb->tos = pcb->tos;
ip_addr_copy(lpcb->local_ip, pcb->local_ip);
if (pcb->local_port != 0) {
TCP_RMV(&tcp_bound_pcbs, pcb);
}
memp_free(MEMP_TCP_PCB, pcb);
#if LWIP_CALLBACK_API
lpcb->accept = tcp_accept_null;
#endif /* LWIP_CALLBACK_API */
#if TCP_LISTEN_BACKLOG
lpcb->accepts_pending = 0;
lpcb->backlog = (backlog ? backlog : 1);
#endif /* TCP_LISTEN_BACKLOG */
TCP_REG(&tcp_listen_pcbs.pcbs, (struct tcp_pcb *)lpcb);
return (struct tcp_pcb *)lpcb;
}
/*-----------------------------------------------------------------------------------*/
struct tcp_pcb *
tcp_listen(struct tcp_pcb *pcb)
{
pcb->state = LISTEN;
pcb = (struct tcp_pcb*)memp_realloc(MEMP_TCP_PCB, MEMP_TCP_PCB_LISTEN, pcb);
if(pcb == NULL) {
return NULL;
}
TCP_REG((struct tcp_pcb **)&tcp_listen_pcbs, pcb);
return pcb;
}
/**
* Connects to another host. The function given as the "connected"
* argument will be called when the connection has been established.
*
*/
err_t
tcp_connect(struct tcp_pcb *pcb, struct ip_addr *ipaddr, u16_t port,
err_t (* connected)(void *arg, struct tcp_pcb *tpcb, err_t err))
{
u32_t optdata;
err_t ret;
u32_t iss;
LWIP_DEBUGF(TCP_DEBUG, ("tcp_connect to port %"U16_F"\n", port));
if (ipaddr != NULL) {
pcb->remote_ip = *ipaddr;
} else {
return ERR_VAL;
}
pcb->remote_port = port;
if (pcb->local_port == 0) {
pcb->local_port = tcp_new_port();
}
iss = tcp_next_iss();
pcb->rcv_nxt = 0;
pcb->snd_nxt = iss;
pcb->lastack = iss - 1;
pcb->snd_lbb = iss - 1;
pcb->rcv_wnd = TCP_WND;
pcb->snd_wnd = TCP_WND;
pcb->mss = TCP_MSS;
pcb->cwnd = 1;
pcb->ssthresh = pcb->mss * 10;
pcb->state = SYN_SENT;
#if LWIP_CALLBACK_API
pcb->connected = connected;
#endif /* LWIP_CALLBACK_API */
TCP_REG(&tcp_active_pcbs, pcb);
snmp_inc_tcpactiveopens();
/* Build an MSS option */
optdata = htonl(((u32_t)2 << 24) |
((u32_t)4 << 16) |
(((u32_t)pcb->mss / 256) << 8) |
(pcb->mss & 255));
ret = tcp_enqueue(pcb, NULL, 0, TCP_SYN, 0, (u8_t *)&optdata, 4);
if (ret == ERR_OK) {
tcp_output(pcb);
}
return ret;
}
/**
* Set the state of the connection to be LISTEN, which means that it
* is able to accept incoming connections. The protocol control block
* is reallocated in order to consume less memory. Setting the
* connection to LISTEN is an irreversible process.
*
* @param pcb the original tcp_pcb
* @param backlog the incoming connections queue limit
* @return tcp_pcb used for listening, consumes less memory.
*
* @note The original tcp_pcb is freed. This function therefore has to be
* called like this:
* tpcb = tcp_listen(tpcb);
*/
struct tcp_pcb *
tcp_listen_with_backlog(struct tcp_pcb *pcb, u8_t backlog)
{
struct tcp_pcb_listen *lpcb;
LWIP_UNUSED_ARG(backlog);
LWIP_ERROR("tcp_listen: pcb already connected", pcb->state == CLOSED, return NULL);
/* already listening? */
if (pcb->state == LISTEN) {
return pcb;
}
/* 分配一个监听状态控制块struct tcp_pcb_listen */
lpcb = memp_malloc(MEMP_TCP_PCB_LISTEN);
if (lpcb == NULL) {
return NULL;
}
/* 复制各个字段 */
lpcb->callback_arg = pcb->callback_arg;
lpcb->local_port = pcb->local_port;
lpcb->state = LISTEN;
lpcb->so_options = pcb->so_options;
lpcb->so_options |= SOF_ACCEPTCONN;
lpcb->ttl = pcb->ttl;
lpcb->tos = pcb->tos;
ip_addr_set(&lpcb->local_ip, &pcb->local_ip);
/* 从tcp_bound_pcbs链表删除控制块 */
TCP_RMV(&tcp_bound_pcbs, pcb);
/* 释放控制块 */
memp_free(MEMP_TCP_PCB, pcb);
#if LWIP_CALLBACK_API
lpcb->accept = tcp_accept_null;
#endif /* LWIP_CALLBACK_API */
#if TCP_LISTEN_BACKLOG
lpcb->accepts_pending = 0;
lpcb->backlog = (backlog ? backlog : 1);
#endif /* TCP_LISTEN_BACKLOG */
/* 把新控制块加入tcp_listen_pcbs链表首部 */
TCP_REG(&tcp_listen_pcbs.listen_pcbs, lpcb);
/* 返回新控制块指针 */
return (struct tcp_pcb *)lpcb;
}
/**
* Binds the connection to a local portnumber 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.
*
* @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
*/
err_t
tcp_bind(struct tcp_pcb *pcb, struct ip_addr *ipaddr, u16_t port)
{
struct tcp_pcb *cpcb;
LWIP_ERROR("tcp_bind: can only bind in state CLOSED", pcb->state == CLOSED, return ERR_ISCONN);
if (port == 0) {
port = tcp_new_port();
}
/* Check if the address already is in use. */
/* Check the listen pcbs. */
for(cpcb = (struct tcp_pcb *)tcp_listen_pcbs.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 connected 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. */
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;
}
pcb->local_port = port;
TCP_REG(&tcp_bound_pcbs, pcb);
LWIP_DEBUGF(TCP_DEBUG, ("tcp_bind: bind to port %"U16_F"\n", port));
return ERR_OK;
}
/**
* Connects to another host. The function given as the "connected"
* argument will be called when the connection has been established.
*
* @param pcb the tcp_pcb used to establish the connection
* @param ipaddr the remote ip address to connect to
* @param port the remote tcp port to connect to
* @param connected callback function to call when connected (or on error)
* @return ERR_VAL if invalid arguments are given
* ERR_OK if connect request has been sent
* other err_t values if connect request couldn't be sent
*/
err_t
tcp_connect(struct tcp_pcb *pcb, ip_addr_t *ipaddr, u16_t port,
tcp_connected_fn connected)
{
err_t ret;
u32_t iss;
u16_t old_local_port;
LWIP_ERROR("tcp_connect: can only connect from state CLOSED", pcb->state == CLOSED, return ERR_ISCONN);
LWIP_DEBUGF(TCP_DEBUG, ("tcp_connect to port %"U16_F"\n", port));
if (ipaddr != NULL) {
pcb->remote_ip = *ipaddr;
} else {
return ERR_VAL;
}
pcb->remote_port = port;
/* check if we have a route to the remote host */
if (ip_addr_isany(&(pcb->local_ip))) {
/* no local IP address set, yet. */
struct netif *netif = ip_route(&(pcb->remote_ip));
if (netif == NULL) {
/* Don't even try to send a SYN packet if we have no route
since that will fail. */
return ERR_RTE;
}
/* Use the netif's IP address as local address. */
ip_addr_copy(pcb->local_ip, netif->ip_addr);
}
old_local_port = pcb->local_port;
if (pcb->local_port == 0) {
pcb->local_port = tcp_new_port();
}
#if SO_REUSE
if ((pcb->so_options & SOF_REUSEADDR) != 0) {
/* Since SOF_REUSEADDR allows reusing a local address, we have to make sure
now that the 5-tuple is unique. */
struct tcp_pcb *cpcb;
int i;
/* Don't check listen- and bound-PCBs, check active- and TIME-WAIT PCBs. */
for (i = 2; i < NUM_TCP_PCB_LISTS; i++) {
for(cpcb = *tcp_pcb_lists[i]; cpcb != NULL; cpcb = cpcb->next) {
if ((cpcb->local_port == pcb->local_port) &&
(cpcb->remote_port == port) &&
ip_addr_cmp(&cpcb->local_ip, &pcb->local_ip) &&
ip_addr_cmp(&cpcb->remote_ip, ipaddr)) {
/* linux returns EISCONN here, but ERR_USE should be OK for us */
return ERR_USE;
}
}
}
}
#endif /* SO_REUSE */
iss = tcp_next_iss();
pcb->rcv_nxt = 0;
pcb->snd_nxt = iss;
pcb->lastack = iss - 1;
pcb->snd_lbb = iss - 1;
pcb->rcv_wnd = TCP_WND;
pcb->rcv_ann_wnd = TCP_WND;
pcb->rcv_ann_right_edge = pcb->rcv_nxt;
pcb->snd_wnd = TCP_WND;
/* As initial send MSS, we use TCP_MSS but limit it to 536.
The send MSS is updated when an MSS option is received. */
pcb->mss = (TCP_MSS > 536) ? 536 : TCP_MSS;
#if TCP_CALCULATE_EFF_SEND_MSS
pcb->mss = tcp_eff_send_mss(pcb->mss, ipaddr);
#endif /* TCP_CALCULATE_EFF_SEND_MSS */
pcb->cwnd = 1;
pcb->ssthresh = pcb->mss * 10;
#if LWIP_CALLBACK_API
pcb->connected = connected;
#else /* LWIP_CALLBACK_API */
LWIP_UNUSED_ARG(connected);
#endif /* LWIP_CALLBACK_API */
/* Send a SYN together with the MSS option. */
ret = tcp_enqueue_flags(pcb, TCP_SYN);
if (ret == ERR_OK) {
/* SYN segment was enqueued, changed the pcbs state now */
pcb->state = SYN_SENT;
if (old_local_port != 0) {
TCP_RMV(&tcp_bound_pcbs, pcb);
}
TCP_REG(&tcp_active_pcbs, pcb);
snmp_inc_tcpactiveopens();
tcp_output(pcb);
}
return ret;
}
/**
* 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;
}
/**
* Implements the TCP state machine. Called by tcp_input. In some
* states tcp_receive() is called to receive data. The tcp_seg
* argument will be freed by the caller (tcp_input()) unless the
* recv_data pointer in the pcb is set.
*
* @param pcb the tcp_pcb for which a segment arrived
*
* @note the segment which arrived is saved in global variables, therefore only the pcb
* involved is passed as a parameter to this function
*/
static err_t
tcp_process(struct tcp_pcb *pcb)
{
struct tcp_seg *rseg;
u8_t acceptable = 0;
err_t err;
u8_t accepted_inseq;
err = ERR_OK;
/* Process incoming RST segments. */
if (flags & TCP_RST) {
/* First, determine if the reset is acceptable. */
if (pcb->state == SYN_SENT) {
if (ackno == pcb->snd_nxt) {
acceptable = 1;
}
} else {
if (TCP_SEQ_BETWEEN(seqno, pcb->rcv_nxt,
pcb->rcv_nxt+pcb->rcv_ann_wnd)) {
acceptable = 1;
}
}
if (acceptable) {
LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_process: Connection RESET\n"));
LWIP_ASSERT("tcp_input: pcb->state != CLOSED", pcb->state != CLOSED);
recv_flags = TF_RESET;
pcb->flags &= ~TF_ACK_DELAY;
return ERR_RST;
} else {
LWIP_DEBUGF(TCP_INPUT_DEBUG, ("tcp_process: unacceptable reset seqno %"U32_F" rcv_nxt %"U32_F"\n",
seqno, pcb->rcv_nxt));
LWIP_DEBUGF(TCP_DEBUG, ("tcp_process: unacceptable reset seqno %"U32_F" rcv_nxt %"U32_F"\n",
seqno, pcb->rcv_nxt));
return ERR_OK;
}
}
/* Update the PCB (in)activity timer. */
pcb->tmr = tcp_ticks;
pcb->keep_cnt_sent = 0;
/* Do different things depending on the TCP state. */
switch (pcb->state) {
case SYN_SENT:
LWIP_DEBUGF(TCP_INPUT_DEBUG, ("SYN-SENT: ackno %"U32_F" pcb->snd_nxt %"U32_F" unacked %"U32_F"\n", ackno,
pcb->snd_nxt, ntohl(pcb->unacked->tcphdr->seqno)));
/* received SYN ACK with expected sequence number? */
if ((flags & TCP_ACK) && (flags & TCP_SYN)
&& ackno == ntohl(pcb->unacked->tcphdr->seqno) + 1) {
pcb->snd_buf++;
pcb->rcv_nxt = seqno + 1;
pcb->lastack = ackno;
pcb->snd_wnd = tcphdr->wnd;
pcb->snd_wl1 = seqno - 1; /* initialise to seqno - 1 to force window update */
pcb->state = ESTABLISHED;
/* Parse any options in the SYNACK before using pcb->mss since that
* can be changed by the received options! */
tcp_parseopt(pcb);
#if TCP_CALCULATE_EFF_SEND_MSS
pcb->mss = tcp_eff_send_mss(pcb->mss, &(pcb->remote_ip));
#endif /* TCP_CALCULATE_EFF_SEND_MSS */
/* Set ssthresh again after changing pcb->mss (already set in tcp_connect
* but for the default value of pcb->mss) */
pcb->ssthresh = pcb->mss * 10;
pcb->cwnd = ((pcb->cwnd == 1) ? (pcb->mss * 2) : pcb->mss);
LWIP_ASSERT("pcb->snd_queuelen > 0", (pcb->snd_queuelen > 0));
--pcb->snd_queuelen;
LWIP_DEBUGF(TCP_QLEN_DEBUG, ("tcp_process: SYN-SENT --queuelen %"U16_F"\n", (u16_t)pcb->snd_queuelen));
rseg = pcb->unacked;
pcb->unacked = rseg->next;
/* If there's nothing left to acknowledge, stop the retransmit
timer, otherwise reset it to start again */
if(pcb->unacked == NULL)
pcb->rtime = -1;
else {
pcb->rtime = 0;
pcb->nrtx = 0;
}
tcp_seg_free(rseg);
/* Call the user specified function to call when sucessfully
* connected. */
TCP_EVENT_CONNECTED(pcb, ERR_OK, err);
tcp_ack_now(pcb);
}
/* received ACK? possibly a half-open connection */
else if (flags & TCP_ACK) {
/* send a RST to bring the other side in a non-synchronized state. */
tcp_rst(ackno, seqno + tcplen, &(iphdr->dest), &(iphdr->src),
tcphdr->dest, tcphdr->src);
}
break;
case SYN_RCVD:
if (flags & TCP_ACK &&
!(flags & TCP_RST)) {
/* expected ACK number? */
if (TCP_SEQ_BETWEEN(ackno, pcb->lastack+1, pcb->snd_nxt)) {
u16_t old_cwnd;
pcb->state = ESTABLISHED;
LWIP_DEBUGF(TCP_DEBUG, ("TCP connection established %"U16_F" -> %"U16_F".\n", inseg.tcphdr->src, inseg.tcphdr->dest));
#if LWIP_CALLBACK_API
LWIP_ASSERT("pcb->accept != NULL", pcb->accept != NULL);
#endif
/* Call the accept function. */
TCP_EVENT_ACCEPT(pcb, ERR_OK, err);
if (err != ERR_OK) {
/* If the accept function returns with an error, we abort
* the connection. */
tcp_abort(pcb);
return ERR_ABRT;
}
old_cwnd = pcb->cwnd;
/* If there was any data contained within this ACK,
* we'd better pass it on to the application as well. */
accepted_inseq = tcp_receive(pcb);
pcb->cwnd = ((old_cwnd == 1) ? (pcb->mss * 2) : pcb->mss);
if ((flags & TCP_FIN) && accepted_inseq) {
tcp_ack_now(pcb);
pcb->state = CLOSE_WAIT;
}
}
/* incorrect ACK number */
else {
/* send RST */
tcp_rst(ackno, seqno + tcplen, &(iphdr->dest), &(iphdr->src),
tcphdr->dest, tcphdr->src);
}
}
break;
case CLOSE_WAIT:
/* FALLTHROUGH */
case ESTABLISHED:
accepted_inseq = tcp_receive(pcb);
if ((flags & TCP_FIN) && accepted_inseq) { /* passive close */
tcp_ack_now(pcb);
pcb->state = CLOSE_WAIT;
}
break;
case FIN_WAIT_1:
tcp_receive(pcb);
if (flags & TCP_FIN) {
if (flags & TCP_ACK && ackno == pcb->snd_nxt) {
LWIP_DEBUGF(TCP_DEBUG,
("TCP connection closed %"U16_F" -> %"U16_F".\n", inseg.tcphdr->src, inseg.tcphdr->dest));
tcp_ack_now(pcb);
tcp_pcb_purge(pcb);
TCP_RMV(&tcp_active_pcbs, pcb);
pcb->state = TIME_WAIT;
TCP_REG(&tcp_tw_pcbs, pcb);
} else {
tcp_ack_now(pcb);
pcb->state = CLOSING;
}
} else if (flags & TCP_ACK && ackno == pcb->snd_nxt) {
pcb->state = FIN_WAIT_2;
}
break;
case FIN_WAIT_2:
tcp_receive(pcb);
if (flags & TCP_FIN) {
LWIP_DEBUGF(TCP_DEBUG, ("TCP connection closed %"U16_F" -> %"U16_F".\n", inseg.tcphdr->src, inseg.tcphdr->dest));
tcp_ack_now(pcb);
tcp_pcb_purge(pcb);
TCP_RMV(&tcp_active_pcbs, pcb);
pcb->state = TIME_WAIT;
TCP_REG(&tcp_tw_pcbs, pcb);
}
break;
case CLOSING:
tcp_receive(pcb);
if (flags & TCP_ACK && ackno == pcb->snd_nxt) {
LWIP_DEBUGF(TCP_DEBUG, ("TCP connection closed %"U16_F" -> %"U16_F".\n", inseg.tcphdr->src, inseg.tcphdr->dest));
tcp_ack_now(pcb);
tcp_pcb_purge(pcb);
TCP_RMV(&tcp_active_pcbs, pcb);
pcb->state = TIME_WAIT;
TCP_REG(&tcp_tw_pcbs, pcb);
}
break;
case LAST_ACK:
tcp_receive(pcb);
if (flags & TCP_ACK && ackno == pcb->snd_nxt) {
LWIP_DEBUGF(TCP_DEBUG, ("TCP connection closed %"U16_F" -> %"U16_F".\n", inseg.tcphdr->src, inseg.tcphdr->dest));
/* bugfix #21699: don't set pcb->state to CLOSED here or we risk leaking segments */
recv_flags = TF_CLOSED;
}
break;
default:
break;
}
return ERR_OK;
}
/**
* Called by tcp_input() when a segment arrives for a listening
* connection (from tcp_input()).
*
* @param pcb the tcp_pcb_listen for which a segment arrived
* @return ERR_OK if the segment was processed
* another err_t on error
*
* @note the return value is not (yet?) used in tcp_input()
* @note the segment which arrived is saved in global variables, therefore only the pcb
* involved is passed as a parameter to this function
*/
static err_t
tcp_listen_input(struct tcp_pcb_listen *pcb)
{
struct tcp_pcb *npcb;
u32_t optdata;
/* In the LISTEN state, we check for incoming SYN segments,
creates a new PCB, and responds with a SYN|ACK. */
if (flags & TCP_ACK) {
/* For incoming segments with the ACK flag set, respond with a
RST. */
LWIP_DEBUGF(TCP_RST_DEBUG, ("tcp_listen_input: ACK in LISTEN, sending reset\n"));
tcp_rst(ackno + 1, seqno + tcplen,
&(iphdr->dest), &(iphdr->src),
tcphdr->dest, tcphdr->src);
} else if (flags & TCP_SYN) {
LWIP_DEBUGF(TCP_DEBUG, ("TCP connection request %"U16_F" -> %"U16_F".\n", tcphdr->src, tcphdr->dest));
#if TCP_LISTEN_BACKLOG
if (pcb->accepts_pending >= pcb->backlog) {
return ERR_ABRT;
}
#endif /* TCP_LISTEN_BACKLOG */
npcb = tcp_alloc(pcb->prio);
/* If a new PCB could not be created (probably due to lack of memory),
we don't do anything, but rely on the sender will retransmit the
SYN at a time when we have more memory available. */
if (npcb == NULL) {
LWIP_DEBUGF(TCP_DEBUG, ("tcp_listen_input: could not allocate PCB\n"));
TCP_STATS_INC(tcp.memerr);
return ERR_MEM;
}
#if TCP_LISTEN_BACKLOG
pcb->accepts_pending++;
#endif /* TCP_LISTEN_BACKLOG */
/* Set up the new PCB. */
ip_addr_set(&(npcb->local_ip), &(iphdr->dest));
npcb->local_port = pcb->local_port;
ip_addr_set(&(npcb->remote_ip), &(iphdr->src));
npcb->remote_port = tcphdr->src;
npcb->state = SYN_RCVD;
npcb->rcv_nxt = seqno + 1;
npcb->snd_wnd = tcphdr->wnd;
npcb->ssthresh = npcb->snd_wnd;
npcb->snd_wl1 = seqno - 1;/* initialise to seqno-1 to force window update */
npcb->callback_arg = pcb->callback_arg;
#if LWIP_CALLBACK_API
npcb->accept = pcb->accept;
#endif /* LWIP_CALLBACK_API */
/* inherit socket options */
npcb->so_options = pcb->so_options & (SOF_DEBUG|SOF_DONTROUTE|SOF_KEEPALIVE|SOF_OOBINLINE|SOF_LINGER);
/* Register the new PCB so that we can begin receiving segments
for it. */
TCP_REG(&tcp_active_pcbs, npcb);
/* Parse any options in the SYN. */
tcp_parseopt(npcb);
#if TCP_CALCULATE_EFF_SEND_MSS
npcb->mss = tcp_eff_send_mss(npcb->mss, &(npcb->remote_ip));
#endif /* TCP_CALCULATE_EFF_SEND_MSS */
snmp_inc_tcppassiveopens();
/* Build an MSS option. */
optdata = TCP_BUILD_MSS_OPTION();
/* Send a SYN|ACK together with the MSS option. */
tcp_enqueue(npcb, NULL, 0, TCP_SYN | TCP_ACK, 0, (u8_t *)&optdata, 4);
return tcp_output(npcb);
}
return ERR_OK;
}
/**
* Connects to another host. The function given as the "connected"
* argument will be called when the connection has been established.
*
* @param pcb the tcp_pcb used to establish the connection
* @param ipaddr the remote ip address to connect to
* @param port the remote tcp port to connect to
* @param connected callback function to call when connected (or on error)
* @return ERR_VAL if invalid arguments are given
* ERR_OK if connect request has been sent
* other err_t values if connect request couldn't be sent
*/
err_t
tcp_connect(struct tcp_pcb *pcb, struct ip_addr *ipaddr, u16_t port,
err_t (* connected)(void *arg, struct tcp_pcb *tpcb, err_t err))
{
err_t ret;
u32_t iss;
LWIP_ERROR("tcp_connect: can only connected from state CLOSED", pcb->state == CLOSED, return ERR_ISCONN);
LWIP_DEBUGF(TCP_DEBUG, ("tcp_connect to port %"U16_F"\n", port));
/* 远端IP地址有效，则记录到TCP控制块中 */
if (ipaddr != NULL) {
pcb->remote_ip = *ipaddr;
} else {
return ERR_VAL;
}
/* 记录远端PORT */
pcb->remote_port = port;
/* 如果本地端口未绑定，则绑定一个短暂端口 */
if (pcb->local_port == 0) {
pcb->local_port = tcp_new_port();
}
/* 获取初始序号 */
iss = tcp_next_iss();
/* 设置接收窗口下一个接收的序号 */
pcb->rcv_nxt = 0;
/* 设置发送窗口各个字段 */
pcb->snd_nxt = iss;
pcb->lastack = iss - 1;
pcb->snd_lbb = iss - 1;
/* 设置接收窗口各个字段 */
pcb->rcv_wnd = TCP_WND;
pcb->rcv_ann_wnd = TCP_WND;
pcb->rcv_ann_right_edge = pcb->rcv_nxt;
pcb->snd_wnd = TCP_WND;
/* As initial send MSS, we use TCP_MSS but limit it to 536.
The send MSS is updated when an MSS option is received. */
/* 设置MSS */
pcb->mss = (TCP_MSS > 536) ? 536 : TCP_MSS;
#if TCP_CALCULATE_EFF_SEND_MSS
pcb->mss = tcp_eff_send_mss(pcb->mss, ipaddr);
#endif /* TCP_CALCULATE_EFF_SEND_MSS */
/* 初始化阻塞窗口 */
pcb->cwnd = 1;
pcb->ssthresh = pcb->mss * 10;
/* TCP控制块状态设为SYN_SENT */
pcb->state = SYN_SENT;
#if LWIP_CALLBACK_API
/* 设置回调函数 */
pcb->connected = connected;
#endif /* LWIP_CALLBACK_API */
/* 把TCP控制块从tcp_bound_pcbs链表移除 */
TCP_RMV(&tcp_bound_pcbs, pcb);
/* 把TCP控制块插入tcp_active_pcbs链表 */
TCP_REG(&tcp_active_pcbs, pcb);
snmp_inc_tcpactiveopens();
/* 构造TCP报文，长度为0，SYN置1，并包含MSS选项字段 */
ret = tcp_enqueue(pcb, NULL, 0, TCP_SYN, 0, TF_SEG_OPTS_MSS
#if LWIP_TCP_TIMESTAMPS
| TF_SEG_OPTS_TS
#endif
);
if (ret == ERR_OK) {
/* 发送构造的TCP报文 */
tcp_output(pcb);
}
return ret;
}
/* 绑定TCP控制块到本地端口 */
err_t
tcp_bind(struct tcp_pcb *pcb, struct ip_addr *ipaddr, u16_t port)
{
struct tcp_pcb *cpcb;
LWIP_ERROR("tcp_bind: can only bind in state CLOSED", pcb->state == CLOSED, return ERR_ISCONN);
/* 未指定端口号，则自动分配 */
if (port == 0) {
port = tcp_new_port();
}
/* Check if the address already is in use. */
/* Check the listen pcbs. */
/* 检查指定的 IP:端口号 有没有被其它TCP控制块占用 */
/* 先检查处于LISTEN状态的TCP控制块 */
for(cpcb = (struct tcp_pcb *)tcp_listen_pcbs.pcbs;
cpcb != NULL; cpcb = cpcb->next) {
/* 端口号相同 */
if (cpcb->local_port == port) {
/* 其它TCP控制块绑定到本地所有IP
* 或要绑定的TCP控制块绑定到本地所有IP
* 或要绑定的IP和其它TCP控制块的本地IP相同
*/
if (ip_addr_isany(&(cpcb->local_ip)) ||
ip_addr_isany(ipaddr) ||
ip_addr_cmp(&(cpcb->local_ip), ipaddr)) {
/* 该本地IP:本地PORT已经被占用，返回错误 */
return ERR_USE;
}
}
}
/* Check the connected pcbs. */
/* 检查处于连接状态TCP控制块 */
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. */
/* 检查已绑定但未连接的TCP控制块 */
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: */
/* 检查处于TIME-WAIT状态的TCP控制块 */
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;
}
}
}
/* 设置TCP控制块中的本地IP */
if (!ip_addr_isany(ipaddr)) {
pcb->local_ip = *ipaddr;
}
/* 设置TCP控制块的本地端口号 */
pcb->local_port = port;
TCP_REG(&tcp_bound_pcbs, pcb);
LWIP_DEBUGF(TCP_DEBUG, ("tcp_bind: bind to port %"U16_F"\n", port));
return ERR_OK;
}
