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tcp.c File Reference

tcp.c File Reference

Transmission Control Protocol for IP. More...

Go to the source code of this file.

Functions

static u16_t tcp_new_port (void)
 A nastly hack featuring 'goto' statements that allocates a new TCP local port.
void tcp_tmr (void)
 Called periodically to dispatch TCP timers.
static err_t tcp_close_shutdown (struct tcp_pcb *pcb, u8_t rst_on_unacked_data)
 Closes the TX side of a connection held by the PCB.
err_t tcp_close (struct tcp_pcb *pcb)
 Closes the connection held by the PCB.
err_t tcp_shutdown (struct tcp_pcb *pcb, int shut_rx, int shut_tx)
 Causes all or part of a full-duplex connection of this PCB to be shut down.
void tcp_abandon (struct tcp_pcb *pcb, int reset)
 Abandons a connection and optionally sends a RST to the remote host.
void tcp_abort (struct tcp_pcb *pcb)
 Aborts the connection by sending a RST (reset) segment to the remote host.
err_t tcp_bind (struct tcp_pcb *pcb, ip_addr_t *ipaddr, u16_t port)
 Binds the connection to a local portnumber and IP address.
static err_t tcp_accept_null (void *arg, struct tcp_pcb *pcb, err_t err)
 Default accept callback if no accept callback is specified by the user.
struct tcp_pcb * tcp_listen_with_backlog (struct tcp_pcb *pcb, u8_t backlog)
 Set the state of the connection to be LISTEN, which means that it is able to accept incoming connections.
u32_t tcp_update_rcv_ann_wnd (struct tcp_pcb *pcb)
 Update the state that tracks the available window space to advertise.
void tcp_recved (struct tcp_pcb *pcb, u16_t len)
 This function should be called by the application when it has processed the data.
err_t tcp_connect (struct tcp_pcb *pcb, ip_addr_t *ipaddr, u16_t port, tcp_connected_fn connected)
 Connects to another host.
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.
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.
void tcp_segs_free (struct tcp_seg *seg)
 Deallocates a list of TCP segments (tcp_seg structures).
void tcp_seg_free (struct tcp_seg *seg)
 Frees a TCP segment (tcp_seg structure).
void tcp_setprio (struct tcp_pcb *pcb, u8_t prio)
 Sets the priority of a connection.
struct tcp_seg * tcp_seg_copy (struct tcp_seg *seg)
 Returns a copy of the given TCP segment.
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.
static void tcp_kill_prio (u8_t prio)
 Kills the oldest active connection that has lower priority than prio.
static void tcp_kill_timewait (void)
 Kills the oldest connection that is in TIME_WAIT state.
struct tcp_pcb * tcp_alloc (u8_t prio)
 Allocate a new tcp_pcb structure.
struct tcp_pcb * tcp_new (void)
 Creates a new TCP protocol control block but doesn't place it on any of the TCP PCB lists.
void tcp_arg (struct tcp_pcb *pcb, void *arg)
 Used to specify the argument that should be passed callback functions.
void tcp_recv (struct tcp_pcb *pcb, tcp_recv_fn recv)
 Used to specify the function that should be called when a TCP connection receives data.
void tcp_sent (struct tcp_pcb *pcb, tcp_sent_fn sent)
 Used to specify the function that should be called when TCP data has been successfully delivered to the remote host.
void tcp_err (struct tcp_pcb *pcb, tcp_err_fn err)
 Used to specify the function that should be called when a fatal error has occured on the connection.
void tcp_accept (struct tcp_pcb *pcb, tcp_accept_fn accept)
 Used for specifying the function that should be called when a LISTENing connection has been connected to another host.
void tcp_poll (struct tcp_pcb *pcb, tcp_poll_fn poll, u8_t interval)
 Used to specify the function that should be called periodically from TCP.
void tcp_pcb_purge (struct tcp_pcb *pcb)
 Purges a TCP PCB.
void tcp_pcb_remove (struct tcp_pcb **pcblist, struct tcp_pcb *pcb)
 Purges the PCB and removes it from a PCB list.
u32_t tcp_next_iss (void)
 Calculates a new initial sequence number for new connections.
u16_t tcp_eff_send_mss (u16_t sendmss, ip_addr_t *addr)
 Calcluates the effective send mss that can be used for a specific IP address by using ip_route to determin the netif used to send to the address and calculating the minimum of TCP_MSS and that netif's mtu (if set).
void tcp_debug_print (struct tcp_hdr *tcphdr)
 Print a tcp header for debugging purposes.
void tcp_debug_print_state (enum tcp_state s)
 Print a tcp state for debugging purposes.
void tcp_debug_print_flags (u8_t flags)
 Print tcp flags for debugging purposes.
void tcp_debug_print_pcbs (void)
 Print all tcp_pcbs in every list for debugging purposes.
s16_t tcp_pcbs_sane (void)
 Check state consistency of the tcp_pcb lists.

Variables

struct tcp_pcb * tcp_bound_pcbs
 List of all TCP PCBs bound but not yet (connected || listening)
union tcp_listen_pcbs_t tcp_listen_pcbs
 List of all TCP PCBs in LISTEN state.
struct tcp_pcb * tcp_active_pcbs
 List of all TCP PCBs that are in a state in which they accept or send data.
struct tcp_pcb * tcp_tw_pcbs
 List of all TCP PCBs in TIME-WAIT state.
struct tcp_pcb **const tcp_pcb_lists []
 An array with all (non-temporary) PCB lists, mainly used for smaller code size.
struct tcp_pcb * tcp_tmp_pcb
 Only used for temporary storage.
static u8_t tcp_timer
 Timer counter to handle calling slow-timer from tcp_tmr()

Detailed Description

Transmission Control Protocol for IP.

This file contains common functions for the TCP implementation, such as functinos for manipulating the data structures and the TCP timer functions. TCP functions related to input and output is found in tcp_in.c and tcp_out.c respectively.

Definition in file tcp.c.


Function Documentation

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:
pcbthe tcp_pcb to abort
resetboolean to indicate whether a reset should be sent

Definition at line 318 of file tcp.c.

void tcp_abort ( struct tcp_pcb *  pcb )

Aborts the connection by sending a RST (reset) segment to the remote host.

The pcb is deallocated. This function never fails.

ATTENTION: When calling this from one of the TCP callbacks, make sure you always return ERR_ABRT (and never return ERR_ABRT otherwise or you will risk accessing deallocated memory or memory leaks!

Parameters:
pcbthe tcp pcb to abort

Definition at line 380 of file tcp.c.

void tcp_accept ( struct tcp_pcb *  pcb,
tcp_accept_fn  accept 
)

Used for specifying the function that should be called when a LISTENing connection has been connected to another host.

Parameters:
pcbtcp_pcb to set the accept callback
acceptcallback function to call for this pcb when LISTENing connection has been connected to another host

Definition at line 1332 of file tcp.c.

static err_t tcp_accept_null ( void *  arg,
struct tcp_pcb *  pcb,
err_t  err 
) [static]

Default accept callback if no accept callback is specified by the user.

Definition at line 458 of file tcp.c.

struct tcp_pcb* tcp_alloc ( u8_t  prio ) [read]

Allocate a new tcp_pcb structure.

Parameters:
priopriority for the new pcb
Returns:
a new tcp_pcb that initially is in state CLOSED

Definition at line 1180 of file tcp.c.

void tcp_arg ( struct tcp_pcb *  pcb,
void *  arg 
)

Used to specify the argument that should be passed callback functions.

Parameters:
pcbtcp_pcb to set the callback argument
argvoid pointer argument to pass to callback functions

Definition at line 1277 of file tcp.c.

err_t tcp_bind ( struct tcp_pcb *  pcb,
ip_addr_t *  ipaddr,
u16_t  port 
)

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.

Parameters:
pcbthe tcp_pcb to bind (no check is done whether this pcb is already bound!)
ipaddrthe local ip address to bind to (use IP_ADDR_ANY to bind to any local address
portthe local port to bind to
Returns:
ERR_USE if the port is already in use ERR_VAL if bind failed because the PCB is not in a valid state ERR_OK if bound

Definition at line 400 of file tcp.c.

err_t tcp_close ( struct tcp_pcb *  pcb )

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 (unless an error is returned).

Parameters:
pcbthe tcp_pcb to close
Returns:
ERR_OK if connection has been closed another err_t if closing failed and pcb is not freed

Definition at line 252 of file tcp.c.

static err_t tcp_close_shutdown ( struct tcp_pcb *  pcb,
u8_t  rst_on_unacked_data 
) [static]

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.

Parameters:
pcbthe tcp_pcb to close
Returns:
ERR_OK if connection has been closed another err_t if closing failed and pcb is not freed

Definition at line 138 of file tcp.c.

err_t tcp_connect ( struct tcp_pcb *  pcb,
ip_addr_t *  ipaddr,
u16_t  port,
tcp_connected_fn  connected 
)

Connects to another host.

The function given as the "connected" argument will be called when the connection has been established.

Parameters:
pcbthe tcp_pcb used to establish the connection
ipaddrthe remote ip address to connect to
portthe remote tcp port to connect to
connectedcallback function to call when connected (or on error)
Returns:
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

Definition at line 649 of file tcp.c.

void tcp_debug_print ( struct tcp_hdr *  tcphdr )

Print a tcp header for debugging purposes.

Parameters:
tcphdrpointer to a struct tcp_hdr

Definition at line 1510 of file tcp.c.

void tcp_debug_print_flags ( u8_t  flags )

Print tcp flags for debugging purposes.

Parameters:
flagstcp flags, all active flags are printed

Definition at line 1557 of file tcp.c.

void tcp_debug_print_pcbs ( void   )

Print all tcp_pcbs in every list for debugging purposes.

Definition at line 1590 of file tcp.c.

void tcp_debug_print_state ( enum tcp_state  s )

Print a tcp state for debugging purposes.

Parameters:
senum tcp_state to print

Definition at line 1546 of file tcp.c.

u16_t tcp_eff_send_mss ( u16_t  sendmss,
ip_addr_t *  addr 
)

Calcluates the effective send mss that can be used for a specific IP address by using ip_route to determin the netif used to send to the address and calculating the minimum of TCP_MSS and that netif's mtu (if set).

Definition at line 1479 of file tcp.c.

void tcp_err ( struct tcp_pcb *  pcb,
tcp_err_fn  err 
)

Used to specify the function that should be called when a fatal error has occured on the connection.

Parameters:
pcbtcp_pcb to set the err callback
errcallback function to call for this pcb when a fatal error has occured on the connection

Definition at line 1318 of file tcp.c.

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.

Automatically called from tcp_tmr().

Definition at line 993 of file tcp.c.

static void tcp_kill_prio ( u8_t  prio ) [static]

Kills the oldest active connection that has lower priority than prio.

Parameters:
priominimum priority

Definition at line 1119 of file tcp.c.

static void tcp_kill_timewait ( void   ) [static]

Kills the oldest connection that is in TIME_WAIT state.

Called from tcp_alloc() if no more connections are available.

Definition at line 1152 of file tcp.c.

struct tcp_pcb* tcp_listen_with_backlog ( struct tcp_pcb *  pcb,
u8_t  backlog 
) [read]

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.

Parameters:
pcbthe original tcp_pcb
backlogthe incoming connections queue limit
Returns:
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);

Definition at line 483 of file tcp.c.

struct tcp_pcb* tcp_new ( void   ) [read]

Creates a new TCP protocol control block but doesn't place it on any of the TCP PCB lists.

The pcb is not put on any list until binding using tcp_bind().

Definition at line 1264 of file tcp.c.

static u16_t tcp_new_port ( void   ) [static]

A nastly hack featuring 'goto' statements that allocates a new TCP local port.

Returns:
a new (free) local TCP port number

Definition at line 609 of file tcp.c.

u32_t tcp_next_iss ( void   )

Calculates a new initial sequence number for new connections.

Returns:
u32_t pseudo random sequence number

Definition at line 1464 of file tcp.c.

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:
pcbtcp_pcb to purge. The pcb itself is not deallocated!

Definition at line 1363 of file tcp.c.

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:
pcblistPCB list to purge.
pcbtcp_pcb to purge. The pcb itself is NOT deallocated!

Definition at line 1431 of file tcp.c.

s16_t tcp_pcbs_sane ( void   )

Check state consistency of the tcp_pcb lists.

Definition at line 1620 of file tcp.c.

void tcp_poll ( struct tcp_pcb *  pcb,
tcp_poll_fn  poll,
u8_t  interval 
)

Used to specify the function that should be called periodically from TCP.

The interval is specified in terms of the TCP coarse timer interval, which is called twice a second.

Definition at line 1346 of file tcp.c.

void tcp_recv ( struct tcp_pcb *  pcb,
tcp_recv_fn  recv 
)

Used to specify the function that should be called when a TCP connection receives data.

Parameters:
pcbtcp_pcb to set the recv callback
recvcallback function to call for this pcb when data is received

Definition at line 1291 of file tcp.c.

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.

Definition at line 1100 of file tcp.c.

void tcp_recved ( struct tcp_pcb *  pcb,
u16_t  len 
)

This function should be called by the application when it has processed the data.

The purpose is to advertise a larger window when the data has been processed.

Parameters:
pcbthe tcp_pcb for which data is read
lenthe amount of bytes that have been read by the application

Definition at line 575 of file tcp.c.

struct tcp_seg* tcp_seg_copy ( struct tcp_seg *  seg ) [read]

Returns a copy of the given TCP segment.

The pbuf and data are not copied, only the pointers

Parameters:
segthe old tcp_seg
Returns:
a copy of seg

Definition at line 1080 of file tcp.c.

void tcp_seg_free ( struct tcp_seg *  seg )

Frees a TCP segment (tcp_seg structure).

Parameters:
segsingle tcp_seg to free

Definition at line 1046 of file tcp.c.

void tcp_segs_free ( struct tcp_seg *  seg )

Deallocates a list of TCP segments (tcp_seg structures).

Parameters:
segtcp_seg list of TCP segments to free

Definition at line 1031 of file tcp.c.

void tcp_sent ( struct tcp_pcb *  pcb,
tcp_sent_fn  sent 
)

Used to specify the function that should be called when TCP data has been successfully delivered to the remote host.

Parameters:
pcbtcp_pcb to set the sent callback
sentcallback function to call for this pcb when data is successfully sent

Definition at line 1304 of file tcp.c.

void tcp_setprio ( struct tcp_pcb *  pcb,
u8_t  prio 
)

Sets the priority of a connection.

Parameters:
pcbthe tcp_pcb to manipulate
prionew priority

Definition at line 1066 of file tcp.c.

err_t tcp_shutdown ( struct tcp_pcb *  pcb,
int  shut_rx,
int  shut_tx 
)

Causes all or part of a full-duplex connection of this PCB to be shut down.

This doesn't deallocate the PCB!

Parameters:
pcbPCB to shutdown
shut_rxshut down receive side if this is != 0
shut_txshut down send side if this is != 0
Returns:
ERR_OK if shutdown succeeded (or the PCB has already been shut down) another err_t on error.

Definition at line 278 of file tcp.c.

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().

Definition at line 750 of file tcp.c.

void tcp_tmr ( void   )

Called periodically to dispatch TCP timers.

Definition at line 109 of file tcp.c.

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.

Definition at line 543 of file tcp.c.


Variable Documentation

struct tcp_pcb* tcp_active_pcbs

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

Definition at line 87 of file tcp.c.

struct tcp_pcb* tcp_bound_pcbs

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

Definition at line 82 of file tcp.c.

union tcp_listen_pcbs_t tcp_listen_pcbs

List of all TCP PCBs in LISTEN state.

Definition at line 84 of file tcp.c.

struct tcp_pcb** const tcp_pcb_lists[]
Initial value:

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

Definition at line 94 of file tcp.c.

u8_t tcp_timer [static]

Timer counter to handle calling slow-timer from tcp_tmr()

Definition at line 101 of file tcp.c.

struct tcp_pcb* tcp_tmp_pcb

Only used for temporary storage.

Definition at line 98 of file tcp.c.

struct tcp_pcb* tcp_tw_pcbs

List of all TCP PCBs in TIME-WAIT state.

Definition at line 89 of file tcp.c.