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tcp.c File Reference
`#include "lwip/opt.h"`
`#include "lwip/def.h"`
`#include "lwip/mem.h"`
`#include "lwip/memp.h"`
`#include "lwip/tcp.h"`
`#include "lwip/priv/tcp_priv.h"`
`#include "lwip/debug.h"`
`#include "lwip/stats.h"`
`#include "lwip/ip6.h"`
`#include "lwip/ip6_addr.h"`
`#include "lwip/nd6.h"`
`#include <string.h>`
`#include "path/to/my/lwip_hooks.h"`

## Functions

void | tcp_init (void)
void | tcp_free (struct tcp_pcb *pcb)
void | tcp_tmr (void)
err_t | tcp_close (struct tcp_pcb *pcb)
err_t | tcp_shutdown (struct tcp_pcb *pcb, int shut_rx, int shut_tx)
void | tcp_abandon (struct tcp_pcb *pcb, int reset)
void | tcp_abort (struct tcp_pcb *pcb)
err_t | tcp_bind (struct tcp_pcb *pcb, const ip_addr_t *ipaddr, u16_t port)
void | tcp_bind_netif (struct tcp_pcb *pcb, const struct netif *netif)
struct tcp_pcb * | tcp_listen_with_backlog (struct tcp_pcb *pcb, u8_t backlog)
struct tcp_pcb * | tcp_listen_with_backlog_and_err (struct tcp_pcb *pcb, u8_t backlog, err_t *err)
u32_t | tcp_update_rcv_ann_wnd (struct tcp_pcb *pcb)
void | tcp_recved (struct tcp_pcb *pcb, u16_t len)
err_t | tcp_connect (struct tcp_pcb *pcb, const ip_addr_t *ipaddr, u16_t port, tcp_connected_fn connected)
void | tcp_slowtmr (void)
void | tcp_fasttmr (void)
void | tcp_txnow (void)
err_t | tcp_process_refused_data (struct tcp_pcb *pcb)
void | tcp_segs_free (struct tcp_seg *seg)
void | tcp_seg_free (struct tcp_seg *seg)
void | tcp_setprio (struct tcp_pcb *pcb, u8_t prio)
struct tcp_seg * | tcp_seg_copy (struct tcp_seg *seg)
err_t | tcp_recv_null (void *arg, struct tcp_pcb *pcb, struct pbuf *p, err_t err)
struct tcp_pcb * | tcp_alloc (u8_t prio)
struct tcp_pcb * | tcp_new (void)
struct tcp_pcb * | tcp_new_ip_type (u8_t type)
void | tcp_arg (struct tcp_pcb *pcb, void *arg)
void | tcp_recv (struct tcp_pcb *pcb, tcp_recv_fn recv)
void | tcp_sent (struct tcp_pcb *pcb, tcp_sent_fn sent)
void | tcp_err (struct tcp_pcb *pcb, tcp_err_fn err)
void | tcp_accept (struct tcp_pcb *pcb, tcp_accept_fn accept)
void | tcp_poll (struct tcp_pcb *pcb, tcp_poll_fn poll, u8_t interval)
void | tcp_pcb_purge (struct tcp_pcb *pcb)
void | tcp_pcb_remove (struct tcp_pcb **pcblist, struct tcp_pcb *pcb)
u32_t | tcp_next_iss (struct tcp_pcb *pcb)
u16_t | tcp_eff_send_mss_netif (u16_t sendmss, struct netif *outif, const ip_addr_t *dest)
void | tcp_netif_ip_addr_changed (const ip_addr_t *old_addr, const ip_addr_t *new_addr)
u8_t | tcp_ext_arg_alloc_id (void)
void | tcp_ext_arg_set_callbacks (struct tcp_pcb *pcb, u8_t id, const struct tcp_ext_arg_callbacks *const callbacks)
void | tcp_ext_arg_set (struct tcp_pcb *pcb, u8_t id, void *arg)
void * | tcp_ext_arg_get (const struct tcp_pcb *pcb, u8_t id)
err_t | tcp_ext_arg_invoke_callbacks_passive_open (struct tcp_pcb_listen *lpcb, struct tcp_pcb *cpcb)

## Variables

struct tcp_pcb * | tcp_bound_pcbs
union tcp_listen_pcbs_t | tcp_listen_pcbs
struct tcp_pcb * | tcp_active_pcbs
struct tcp_pcb * | tcp_tw_pcbs
struct tcp_pcb **const | tcp_pcb_lists []
| void

## Detailed Description

Transmission Control Protocol for IP See also TCP

## Function Documentation

## tcp_abandon()

void tcp_abandon | ( | struct tcp_pcb * | pcb,
|  | int | reset )

Abandons a connection and optionally sends a RST to the remote host. Deletes the local protocol control block. This is done when a connection is killed because of shortage of memory.

Parameters

  pcb | the tcp_pcb to abort
  reset | boolean to indicate whether a reset should be sent

## tcp_alloc()

struct tcp_pcb * tcp_alloc | ( | u8_t | prio | ) |

Allocate a new tcp_pcb structure.

Parameters

  prio | priority for the new pcb

Returns
  a new tcp_pcb that initially is in state CLOSED

## tcp_eff_send_mss_netif()

u16_t tcp_eff_send_mss_netif | ( | u16_t | sendmss,
|  | struct netif * | outif,
|  | const ip_addr_t * | dest )

Calculates the effective send mss that can be used for a specific IP address by calculating the minimum of TCP_MSS and the mtu (if set) of the target netif (if not NULL).

## tcp_ext_arg_invoke_callbacks_passive_open()

err_t tcp_ext_arg_invoke_callbacks_passive_open | ( | struct tcp_pcb_listen * | lpcb,
|  | struct tcp_pcb * | cpcb )

This function calls the "passive_open" callback for all ext_args if a connection is in the process of being accepted. This is called just after the SYN is received and before a SYN/ACK is sent, to allow to modify the very first segment sent even on passive open. Naturally, the "accepted" callback of the pcb has not been called yet!

## tcp_fasttmr()

void tcp_fasttmr | ( | void |  | ) |

Is called every TCP_FAST_INTERVAL (250 ms) and process data previously "refused" by upper layer (application) and sends delayed ACKs or pending FINs.

Automatically called from tcp_tmr().

## tcp_free()

void tcp_free | ( | struct tcp_pcb * | pcb | ) |

Free a tcp pcb

## tcp_init()

void tcp_init | ( | void |  | ) |

Initialize this module.

## tcp_netif_ip_addr_changed()

void tcp_netif_ip_addr_changed | ( | const ip_addr_t * | old_addr,
|  | const ip_addr_t * | new_addr )

This function is called from netif.c when address is changed or netif is removed

Parameters

  old_addr | IP address of the netif before change
  new_addr | IP address of the netif after change or NULL if netif has been removed

## tcp_next_iss()

u32_t tcp_next_iss | ( | struct tcp_pcb * | pcb | ) |

Calculates a new initial sequence number for new connections.

Returns
  u32_t pseudo random sequence number

## tcp_pcb_purge()

void tcp_pcb_purge | ( | struct tcp_pcb * | pcb | ) |

Purges a TCP PCB. Removes any buffered data and frees the buffer memory (pcb->ooseq, pcb->unsent and pcb->unacked are freed).

Parameters

  pcb | tcp_pcb to purge. The pcb itself is not deallocated!

## tcp_pcb_remove()

void tcp_pcb_remove | ( | struct tcp_pcb ** | pcblist,
|  | struct tcp_pcb * | pcb )

Purges the PCB and removes it from a PCB list. Any delayed ACKs are sent first.

Parameters

  pcblist | PCB list to purge.
  pcb | tcp_pcb to purge. The pcb itself is NOT deallocated!

## tcp_process_refused_data()

err_t tcp_process_refused_data | ( | struct tcp_pcb * | pcb | ) |

Pass pcb->refused_data to the recv callback

## tcp_recv_null()

err_t tcp_recv_null | ( | void * | arg,
|  | struct tcp_pcb * | pcb,
|  | struct pbuf * | p,
|  | err_t | err )

Default receive callback that is called if the user didn't register a recv callback for the pcb.

## tcp_seg_copy()

struct tcp_seg * tcp_seg_copy | ( | struct tcp_seg * | seg | ) |

Returns a copy of the given TCP segment. The pbuf and data are not copied, only the pointers

Parameters

  seg | the old tcp_seg

Returns
  a copy of seg

## tcp_seg_free()

void tcp_seg_free | ( | struct tcp_seg * | seg | ) |

Frees a TCP segment (tcp_seg structure).

Parameters

  seg | single tcp_seg to free

## tcp_segs_free()

void tcp_segs_free | ( | struct tcp_seg * | seg | ) |

Deallocates a list of TCP segments (tcp_seg structures).

Parameters

  seg | tcp_seg list of TCP segments to free

## tcp_slowtmr()

void tcp_slowtmr | ( | void |  | ) |

Called every 500 ms and implements the retransmission timer and the timer that removes PCBs that have been in TIME-WAIT for enough time. It also increments various timers such as the inactivity timer in each PCB.

Automatically called from tcp_tmr().

## tcp_tmr()

void tcp_tmr | ( | void |  | ) |

Called periodically to dispatch TCP timers.

## tcp_txnow()

void tcp_txnow | ( | void |  | ) |

Call tcp_output for all active pcbs that have TF_NAGLEMEMERR set

## tcp_update_rcv_ann_wnd()

u32_t tcp_update_rcv_ann_wnd | ( | struct tcp_pcb * | pcb | ) |

Update the state that tracks the available window space to advertise.

Returns how much extra window would be advertised if we sent an update now.

## Variable Documentation

## tcp_active_pcbs

struct tcp_pcb* tcp_active_pcbs

List of all TCP PCBs that are in a state in which they accept or send data.

## tcp_bound_pcbs

struct tcp_pcb* tcp_bound_pcbs

List of all TCP PCBs bound but not yet (connected || listening)

## tcp_listen_pcbs

union tcp_listen_pcbs_t tcp_listen_pcbs

List of all TCP PCBs in LISTEN state

## tcp_pcb_lists

struct tcp_pcb** const tcp_pcb_lists[]

Initial value:
= {&tcp_listen_pcbs.pcbs, &tcp_bound_pcbs,
&tcp_active_pcbs, &tcp_tw_pcbs
}
tcp_bound_pcbs
struct tcp_pcb * tcp_bound_pcbs
Definition tcp.c:171
tcp_active_pcbs
struct tcp_pcb * tcp_active_pcbs
Definition tcp.c:176
tcp_listen_pcbs
union tcp_listen_pcbs_t tcp_listen_pcbs
Definition tcp.c:173
tcp_tw_pcbs
struct tcp_pcb * tcp_tw_pcbs
Definition tcp.c:178

An array with all (non-temporary) PCB lists, mainly used for smaller code size

## tcp_tw_pcbs

struct tcp_pcb* tcp_tw_pcbs

List of all TCP PCBs in TIME-WAIT state