#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <assert.h>
#include <errno.h>
#include <byteswap.h>
#include <gpxe/timer.h>
#include <gpxe/iobuf.h>
#include <gpxe/malloc.h>
#include <gpxe/retry.h>
#include <gpxe/refcnt.h>
#include <gpxe/xfer.h>
#include <gpxe/open.h>
#include <gpxe/uri.h>
#include <gpxe/tcpip.h>
#include <gpxe/tcp.h>
/** @file
*
* TCP protocol
*
*/
FILE_LICENCE ( GPL2_OR_LATER );
/** A TCP connection */
struct tcp_connection {
/** Reference counter */
struct refcnt refcnt;
/** List of TCP connections */
struct list_head list;
/** Data transfer interface */
struct xfer_interface xfer;
/** Data transfer interface closed flag */
int xfer_closed;
/** Remote socket address */
struct sockaddr_tcpip peer;
/** Local port, in network byte order */
unsigned int local_port;
/** Current TCP state */
unsigned int tcp_state;
/** Previous TCP state
*
* Maintained only for debug messages
*/
unsigned int prev_tcp_state;
/** Current sequence number
*
* Equivalent to SND.UNA in RFC 793 terminology.
*/
uint32_t snd_seq;
/** Unacknowledged sequence count
*
* Equivalent to (SND.NXT-SND.UNA) in RFC 793 terminology.
*/
uint32_t snd_sent;
/** Send window
*
* Equivalent to SND.WND in RFC 793 terminology
*/
uint32_t snd_win;
/** Current acknowledgement number
*
* Equivalent to RCV.NXT in RFC 793 terminology.
*/
uint32_t rcv_ack;
/** Receive window
*
* Equivalent to RCV.WND in RFC 793 terminology.
*/
uint32_t rcv_win;
/** Most recent received timestamp
*
* Equivalent to TS.Recent in RFC 1323 terminology.
*/
uint32_t ts_recent;
/** Timestamps enabled */
int timestamps;
/** Transmit queue */
struct list_head queue;
/** Retransmission timer */
struct retry_timer timer;
};
/**
* List of registered TCP connections
*/
static LIST_HEAD ( tcp_conns );
/* Forward declarations */
static struct xfer_interface_operations tcp_xfer_operations;
static void tcp_expired ( struct retry_timer *timer, int over );
static int tcp_rx_ack ( struct tcp_connection *tcp, uint32_t ack,
uint32_t win );
/**
* Name TCP state
*
* @v state TCP state
* @ret name Name of TCP state
*/
static inline __attribute__ (( always_inline )) const char *
tcp_state ( int state ) {
switch ( state ) {
case TCP_CLOSED: return "CLOSED";
case TCP_LISTEN: return "LISTEN";
case TCP_SYN_SENT: return "SYN_SENT";
case TCP_SYN_RCVD: return "SYN_RCVD";
case TCP_ESTABLISHED: return "ESTABLISHED";
case TCP_FIN_WAIT_1: return "FIN_WAIT_1";
case TCP_FIN_WAIT_2: return "FIN_WAIT_2";
case TCP_CLOSING_OR_LAST_ACK: return "CLOSING/LAST_ACK";
case TCP_TIME_WAIT: return "TIME_WAIT";
case TCP_CLOSE_WAIT: return "CLOSE_WAIT";
default: return "INVALID";
}
}
/**
* Dump TCP state transition
*
* @v tcp TCP connection
*/
static inline __attribute__ (( always_inline )) void
tcp_dump_state ( struct tcp_connection *tcp ) {
if ( tcp->tcp_state != tcp->prev_tcp_state ) {
DBGC ( tcp, "TCP %p transitioned from %s to %s\n", tcp,
tcp_state ( tcp->prev_tcp_state ),
tcp_state ( tcp->tcp_state ) );
}
tcp->prev_tcp_state = tcp->tcp_state;
}
/**
* Dump TCP flags
*
* @v flags TCP flags
*/
static inline __attribute__ (( always_inline )) void
tcp_dump_flags ( struct tcp_connection *tcp, unsigned int flags ) {
if ( flags & TCP_RST )
DBGC2 ( tcp, " RST" );
if ( flags & TCP_SYN )
DBGC2 ( tcp, " SYN" );
if ( flags & TCP_PSH )
DBGC2 ( tcp, " PSH" );
if ( flags & TCP_FIN )
DBGC2 ( tcp, " FIN" );
if ( flags & TCP_ACK )
DBGC2 ( tcp, " ACK" );
}
/***************************************************************************
*
* Open and close
*
***************************************************************************
*/
/**
* Bind TCP connection to local port
*
* @v tcp TCP connection
* @v port Local port number, in network-endian order
* @ret rc Return status code
*
* If the port is 0, the connection is assigned an available port
* between 1024 and 65535.
*/
static int tcp_bind ( struct tcp_connection *tcp, unsigned int port ) {
struct tcp_connection *existing;
static uint16_t try_port = 1023;
/* If no port specified, find the first available port */
if ( ! port ) {
while ( try_port ) {
try_port++;
if ( try_port < 1024 )
continue;
if ( tcp_bind ( tcp, htons ( try_port ) ) == 0 )
return 0;
}
DBGC ( tcp, "TCP %p could not bind: no free ports\n", tcp );
return -EADDRINUSE;
}
/* Attempt bind to local port */
list_for_each_entry ( existing, &tcp_conns, list ) {
if ( existing->local_port == port ) {
DBGC ( tcp, "TCP %p could not bind: port %d in use\n",
tcp, ntohs ( port ) );
return -EADDRINUSE;
}
}
tcp->local_port = port;
DBGC ( tcp, "TCP %p bound to port %d\n", tcp, ntohs ( port ) );
return 0;
}
/**
* Open a TCP connection
*
* @v xfer Data transfer interface
* @v peer Peer socket address
* @v local Local socket address, or NULL
* @ret rc Return status code
*/
static int tcp_open ( struct xfer_interface *xfer, struct sockaddr *peer,
struct sockaddr *local ) {
struct sockaddr_tcpip *st_peer = ( struct sockaddr_tcpip * ) peer;
struct sockaddr_tcpip *st_local = ( struct sockaddr_tcpip * ) local;
struct tcp_connection *tcp;
unsigned int bind_port;
int rc;
/* Allocate and initialise structure */
tcp = zalloc ( sizeof ( *tcp ) );
if ( ! tcp )
return -ENOMEM;
DBGC ( tcp, "TCP %p allocated\n", tcp );
xfer_init ( &tcp->xfer, &tcp_xfer_operations, &tcp->refcnt );
tcp->prev_tcp_state = TCP_CLOSED;
tcp->tcp_state = TCP_STATE_SENT ( TCP_SYN );
tcp_dump_state ( tcp );
tcp->snd_seq = random();
INIT_LIST_HEAD ( &tcp->queue );
tcp->timer.expired = tcp_expired;
memcpy ( &tcp->peer, st_peer, sizeof ( tcp->peer ) );
/* Bind to local port */
bind_port = ( st_local ? st_local->st_port : 0 );
if ( ( rc = tcp_bind ( tcp, bind_port ) ) != 0 )
goto err;
/* Start timer to initiate SYN */
start_timer_nodelay ( &tcp->timer );
/* Attach parent interface, transfer reference to connection
* list and return
*/
xfer_plug_plug ( &tcp->xfer, xfer );
list_add ( &tcp->list, &tcp_conns );
return 0;
err:
ref_put ( &tcp->refcnt );
return rc;
}
/**
* Close TCP connection
*
* @v tcp TCP connection
* @v rc Reason for close
*
* Closes the data transfer interface. If the TCP state machine is in
* a suitable state, the connection will be deleted.
*/
static void tcp_close ( struct tcp_connection *tcp, int rc ) {
struct io_buffer *iobuf;
struct io_buffer *tmp;
/* Close data transfer interface */
xfer_nullify ( &tcp->xfer );
xfer_close ( &tcp->xfer, rc );
tcp->xfer_closed = 1;
/* If we are in CLOSED, or have otherwise not yet received a
* SYN (i.e. we are in LISTEN or SYN_SENT), just delete the
* connection.
*/
if ( ! ( tcp->tcp_state & TCP_STATE_RCVD ( TCP_SYN ) ) ) {
/* Transition to CLOSED for the sake of debugging messages */
tcp->tcp_state = TCP_CLOSED;
tcp_dump_state ( tcp );
/* Free any unsent I/O buffers */
list_for_each_entry_safe ( iobuf, tmp, &tcp->queue, list ) {
list_del ( &iobuf->list );
free_iob ( iobuf );
}
/* Remove from list and drop reference */
stop_timer ( &tcp->timer );
list_del ( &tcp->list );
ref_put ( &tcp->refcnt );
DBGC ( tcp, "TCP %p connection deleted\n", tcp );
return;
}
/* If we have not had our SYN acknowledged (i.e. we are in
* SYN_RCVD), pretend that it has been acknowledged so that we
* can send a FIN without breaking things.
*/
if ( ! ( tcp->tcp_state & TCP_STATE_ACKED ( TCP_SYN ) ) )
tcp_rx_ack ( tcp, ( tcp->snd_seq + 1 ), 0 );
/* If we have no data remaining to send, start sending FIN */
if ( list_empty ( &tcp->queue ) ) {
tcp->tcp_state |= TCP_STATE_SENT ( TCP_FIN );
tcp_dump_state ( tcp );
}
}
/***************************************************************************
*
* Transmit data path
*
***************************************************************************
*/
/**
* Calculate transmission window
*
* @v tcp TCP connection
* @ret len Maximum length that can be sent in a single packet
*/
static size_t tcp_xmit_win ( struct tcp_connection *tcp ) {
size_t len;
/* Not ready if we're not in a suitable connection state */
if ( ! TCP_CAN_SEND_DATA ( tcp->tcp_state ) )
return 0;
/* Length is the minimum of the receiver's window and the path MTU */
len = tcp->snd_win;
if ( len > TCP_PATH_MTU )
len = TCP_PATH_MTU;
return len;
}
/**
* Process TCP transmit queue
*
* @v tcp TCP connection
* @v max_len Maximum length to process
* @v dest I/O buffer to fill with data, or NULL
* @v remove Remove data from queue
* @ret len Length of data processed
*
* This processes at most @c max_len bytes from the TCP connection's
* transmit queue. Data will be copied into the @c dest I/O buffer
* (if provided) and, if @c remove is true, removed from the transmit
* queue.
*/
static size_t tcp_process_queue ( struct tcp_connection *tcp, size_t max_len,
struct io_buffer *dest, int remove ) {
struct io_buffer *iobuf;
struct io_buffer *tmp;
size_t frag_len;
size_t len = 0;
list_for_each_entry_safe ( iobuf, tmp, &tcp->queue, list ) {
frag_len = iob_len ( iobuf );
if ( frag_len > max_len )
frag_len = max_len;
if ( dest ) {
memcpy ( iob_put ( dest, frag_len ), iobuf->data,
frag_len );
}
if ( remove ) {
iob_pull ( iobuf, frag_len );
if ( ! iob_len ( iobuf ) ) {
list_del ( &iobuf->list );
free_iob ( iobuf );
}
}
len += frag_len;
max_len -= frag_len;
}
return len;
}
/**
* Transmit any outstanding data
*
* @v tcp TCP connection
* @v force_send Force sending of packet
*
* Transmits any outstanding data on the connection.
*
* Note that even if an error is returned, the retransmission timer
* will have been started if necessary, and so the stack will
* eventually attempt to retransmit the failed packet.
*/
static int tcp_xmit ( struct tcp_connection *tcp, int force_send ) {
struct io_buffer *iobuf;
struct tcp_header *tcphdr;
struct tcp_mss_option *mssopt;
struct tcp_timestamp_padded_option *tsopt;
void *payload;
unsigned int flags;
size_t len = 0;
uint32_t seq_len;
uint32_t app_win;
uint32_t max_rcv_win;
int rc;
/* If retransmission timer is already running, do nothing */
if ( timer_running ( &tcp->timer ) )
return 0;
/* Calculate both the actual (payload) and sequence space
* lengths that we wish to transmit.
*/
if ( TCP_CAN_SEND_DATA ( tcp->tcp_state ) ) {
len = tcp_process_queue ( tcp, tcp_xmit_win ( tcp ),
NULL, 0 );
}
seq_len = len;
flags = TCP_FLAGS_SENDING ( tcp->tcp_state );
if ( flags & ( TCP_SYN | TCP_FIN ) ) {
/* SYN or FIN consume one byte, and we can never send both */
assert ( ! ( ( flags & TCP_SYN ) && ( flags & TCP_FIN ) ) );
seq_len++;
}
tcp->snd_sent = seq_len;
/* If we have nothing to transmit, stop now */
if ( ( seq_len == 0 ) && ! force_send )
return 0;
/* If we are transmitting anything that requires
* acknowledgement (i.e. consumes sequence space), start the
* retransmission timer. Do this before attempting to
* allocate the I/O buffer, in case allocation itself fails.
*/
if ( seq_len )
start_timer ( &tcp->timer );
/* Allocate I/O buffer */
iobuf = alloc_iob ( len + MAX_HDR_LEN );
if ( ! iobuf ) {
DBGC ( tcp, "TCP %p could not allocate iobuf for %08x..%08x "
"%08x\n", tcp, tcp->snd_seq, ( tcp->snd_seq + seq_len ),
tcp->rcv_ack );
return -ENOMEM;
}
iob_reserve ( iobuf, MAX_HDR_LEN );
/* Fill data payload from transmit queue */
tcp_process_queue ( tcp, len, iobuf, 0 );
/* Expand receive window if possible */
max_rcv_win = ( ( freemem * 3 ) / 4 );
if ( max_rcv_win > TCP_MAX_WINDOW_SIZE )
max_rcv_win = TCP_MAX_WINDOW_SIZE;
app_win = xfer_window ( &tcp->xfer );
if ( max_rcv_win > app_win )
max_rcv_win = app_win;
max_rcv_win &= ~0x03; /* Keep everything dword-aligned */
if ( tcp->rcv_win < max_rcv_win )
tcp->rcv_win = max_rcv_win;
/* Fill up the TCP header */
payload = iobuf->data;
if ( flags & TCP_SYN ) {
mssopt = iob_push ( iobuf, sizeof ( *mssopt ) );
mssopt->kind = TCP_OPTION_MSS;
mssopt->length = sizeof ( *mssopt );
mssopt->mss = htons ( TCP_MSS );
}
if ( ( flags & TCP_SYN ) || tcp->timestamps ) {
tsopt = iob_push ( iobuf, sizeof ( *tsopt ) );
memset ( tsopt->nop, TCP_OPTION_NOP, sizeof ( tsopt->nop ) );
tsopt->tsopt.kind = TCP_OPTION_TS;
tsopt->tsopt.length = sizeof ( tsopt->tsopt );
tsopt->tsopt.tsval = ntohl ( currticks() );
tsopt->tsopt.tsecr = ntohl ( tcp->ts_recent );
}
if ( ! ( flags & TCP_SYN ) )
flags |= TCP_PSH;
tcphdr = iob_push ( iobuf, sizeof ( *tcphdr ) );
memset ( tcphdr, 0, sizeof ( *tcphdr ) );
tcphdr->src = tcp->local_port;
tcphdr->dest = tcp->peer.st_port;
tcphdr->seq = htonl ( tcp->snd_seq );
tcphdr->ack = htonl ( tcp->rcv_ack );
tcphdr->hlen = ( ( payload - iobuf->data ) << 2 );
tcphdr->flags = flags;
tcphdr->win = htons ( tcp->rcv_win );
tcphdr->csum = tcpip_chksum ( iobuf->data, iob_len ( iobuf ) );
/* Dump header */
DBGC2 ( tcp, "TCP %p TX %d->%d %08x..%08x %08x %4zd",
tcp, ntohs ( tcphdr->src ), ntohs ( tcphdr->dest ),
ntohl ( tcphdr->seq ), ( ntohl ( tcphdr->seq ) + seq_len ),
ntohl ( tcphdr->ack ), len );
tcp_dump_flags ( tcp, tcphdr->flags );
DBGC2 ( tcp, "\n" );
/* Transmit packet */
if ( ( rc = tcpip_tx ( iobuf, &tcp_protocol, NULL, &tcp->peer, NULL,
&tcphdr->csum ) ) != 0 ) {
DBGC ( tcp, "TCP %p could not transmit %08x..%08x %08x: %s\n",
tcp, tcp->snd_seq, ( tcp->snd_seq + tcp->snd_sent ),
tcp->rcv_ack, strerror ( rc ) );
return rc;
}
return 0;
}
/**
* Retransmission timer expired
*
* @v timer Retry timer
* @v over Failure indicator
*/
static void tcp_expired ( struct retry_timer *timer, int over ) {
struct tcp_connection *tcp =
container_of ( timer, struct tcp_connection, timer );
int graceful_close = TCP_CLOSED_GRACEFULLY ( tcp->tcp_state );
DBGC ( tcp, "TCP %p timer %s in %s for %08x..%08x %08x\n", tcp,
( over ? "expired" : "fired" ), tcp_state ( tcp->tcp_state ),
tcp->snd_seq, ( tcp->snd_seq + tcp->snd_sent ), tcp->rcv_ack );
assert ( ( tcp->tcp_state == TCP_SYN_SENT ) ||
( tcp->tcp_state == TCP_SYN_RCVD ) ||
( tcp->tcp_state == TCP_ESTABLISHED ) ||
( tcp->tcp_state == TCP_FIN_WAIT_1 ) ||
( tcp->tcp_state == TCP_TIME_WAIT ) ||
( tcp->tcp_state == TCP_CLOSE_WAIT ) ||
( tcp->tcp_state == TCP_CLOSING_OR_LAST_ACK ) );
if ( over || graceful_close ) {
/* If we have finally timed out and given up, or if
* this is the result of a graceful close, terminate
* the connection
*/
tcp->tcp_state = TCP_CLOSED;
tcp_dump_state ( tcp );
tcp_close ( tcp, -ETIMEDOUT );
} else {
/* Otherwise, retransmit the packet */
tcp_xmit ( tcp, 0 );
}
}
/**
* Send RST response to incoming packet
*
* @v in_tcphdr TCP header of incoming packet
* @ret rc Return status code
*/
static int tcp_xmit_reset ( struct tcp_connection *tcp,
struct sockaddr_tcpip *st_dest,
struct tcp_header *in_tcphdr ) {
struct io_buffer *iobuf;
struct tcp_header *tcphdr;
int rc;
/* Allocate space for dataless TX buffer */
iobuf = alloc_iob ( MAX_HDR_LEN );
if ( ! iobuf ) {
DBGC ( tcp, "TCP %p could not allocate iobuf for RST "
"%08x..%08x %08x\n", tcp, ntohl ( in_tcphdr->ack ),
ntohl ( in_tcphdr->ack ), ntohl ( in_tcphdr->seq ) );
return -ENOMEM;
}
iob_reserve ( iobuf, MAX_HDR_LEN );
/* Construct RST response */
tcphdr = iob_push ( iobuf, sizeof ( *tcphdr ) );
memset ( tcphdr, 0, sizeof ( *tcphdr ) );
tcphdr->src = in_tcphdr->dest;
tcphdr->dest = in_tcphdr->src;
tcphdr->seq = in_tcphdr->ack;
tcphdr->ack = in_tcphdr->seq;
tcphdr->hlen = ( ( sizeof ( *tcphdr ) / 4 ) << 4 );
tcphdr->flags = ( TCP_RST | TCP_ACK );
tcphdr->win = htons ( TCP_MAX_WINDOW_SIZE );
tcphdr->csum = tcpip_chksum ( iobuf->data, iob_len ( iobuf ) );
/* Dump header */
DBGC2 ( tcp, "TCP %p TX %d->%d %08x..%08x %08x %4d",
tcp, ntohs ( tcphdr->src ), ntohs ( tcphdr->dest ),
ntohl ( tcphdr->seq ), ( ntohl ( tcphdr->seq ) ),
ntohl ( tcphdr->ack ), 0 );
tcp_dump_flags ( tcp, tcphdr->flags );
DBGC2 ( tcp, "\n" );
/* Transmit packet */
if ( ( rc = tcpip_tx ( iobuf, &tcp_protocol, NULL, st_dest,
NULL, &tcphdr->csum ) ) != 0 ) {
DBGC ( tcp, "TCP %p could not transmit RST %08x..%08x %08x: "
"%s\n", tcp, ntohl ( in_tcphdr->ack ),
ntohl ( in_tcphdr->ack ), ntohl ( in_tcphdr->seq ),
strerror ( rc ) );
return rc;
}
return 0;
}
/***************************************************************************
*
* Receive data path
*
***************************************************************************
*/
/**
* Identify TCP connection by local port number
*
* @v local_port Local port (in network-endian order)
* @ret tcp TCP connection, or NULL
*/
static struct tcp_connection * tcp_demux ( unsigned int local_port ) {
struct tcp_connection *tcp;
list_for_each_entry ( tcp, &tcp_conns, list ) {
if ( tcp->local_port == local_port )
return tcp;
}
return NULL;
}
/**
* Parse TCP received options
*
* @v tcp TCP connection
* @v data Raw options data
* @v len Raw options length
* @v options Options structure to fill in
*/
static void tcp_rx_opts ( struct tcp_connection *tcp, const void *data,
size_t len, struct tcp_options *options ) {
const void *end = ( data + len );
const struct tcp_option *option;
unsigned int kind;
memset ( options, 0, sizeof ( *options ) );
while ( data < end ) {
option = data;
kind = option->kind;
if ( kind == TCP_OPTION_END )
return;
if ( kind == TCP_OPTION_NOP ) {
data++;
continue;
}
switch ( kind ) {
case TCP_OPTION_MSS:
options->mssopt = data;
break;
case TCP_OPTION_TS:
options->tsopt = data;
break;
default:
DBGC ( tcp, "TCP %p received unknown option %d\n",
tcp, kind );
break;
}
data += option->length;
}
}
/**
* Consume received sequence space
*
* @v tcp TCP connection
* @v seq_len Sequence space length to consume
*/
static void tcp_rx_seq ( struct tcp_connection *tcp, uint32_t seq_len ) {
tcp->rcv_ack += seq_len;
if ( tcp->rcv_win > seq_len ) {
tcp->rcv_win -= seq_len;
} else {
tcp->rcv_win = 0;
}
}
/**
* Handle TCP received SYN
*
* @v tcp TCP connection
* @v seq SEQ value (in host-endian order)
* @v options TCP options
* @ret rc Return status code
*/
static int tcp_rx_syn ( struct tcp_connection *tcp, uint32_t seq,
struct tcp_options *options ) {
/* Synchronise sequence numbers on first SYN */
if ( ! ( tcp->tcp_state & TCP_STATE_RCVD ( TCP_SYN ) ) ) {
tcp->rcv_ack = seq;
if ( options->tsopt )
tcp->timestamps = 1;
}
/* Ignore duplicate SYN */
if ( ( tcp->rcv_ack - seq ) > 0 )
return 0;
/* Mark SYN as received and start sending ACKs with each packet */
tcp->tcp_state |= ( TCP_STATE_SENT ( TCP_ACK ) |
TCP_STATE_RCVD ( TCP_SYN ) );
/* Acknowledge SYN */
tcp_rx_seq ( tcp, 1 );
return 0;
}
/**
* Handle TCP received ACK
*
* @v tcp TCP connection
* @v ack ACK value (in host-endian order)
* @v win WIN value (in host-endian order)
* @ret rc Return status code
*/
static int tcp_rx_ack ( struct tcp_connection *tcp, uint32_t ack,
uint32_t win ) {
uint32_t ack_len = ( ack - tcp->snd_seq );
size_t len;
unsigned int acked_flags;
/* Check for out-of-range or old duplicate ACKs */
if ( ack_len > tcp->snd_sent ) {
DBGC ( tcp, "TCP %p received ACK for %08x..%08x, "
"sent only %08x..%08x\n", tcp, tcp->snd_seq,
( tcp->snd_seq + ack_len ), tcp->snd_seq,
( tcp->snd_seq + tcp->snd_sent ) );
if ( TCP_HAS_BEEN_ESTABLISHED ( tcp->tcp_state ) ) {
/* Just ignore what might be old duplicate ACKs */
return 0;
} else {
/* Send RST if an out-of-range ACK is received
* on a not-yet-established connection, as per
* RFC 793.
*/
return -EINVAL;
}
}
/* Ignore ACKs that don't actually acknowledge any new data.
* (In particular, do not stop the retransmission timer; this
* avoids creating a sorceror's apprentice syndrome when a
* duplicate ACK is received and we still have data in our
* transmit queue.)
*/
if ( ack_len == 0 )
return 0;
/* Stop the retransmission timer */
stop_timer ( &tcp->timer );
/* Determine acknowledged flags and data length */
len = ack_len;
acked_flags = ( TCP_FLAGS_SENDING ( tcp->tcp_state ) &
( TCP_SYN | TCP_FIN ) );
if ( acked_flags )
len--;
/* Update SEQ and sent counters, and window size */
tcp->snd_seq = ack;
tcp->snd_sent = 0;
tcp->snd_win = win;
/* Remove any acknowledged data from transmit queue */
tcp_process_queue ( tcp, len, NULL, 1 );
/* Mark SYN/FIN as acknowledged if applicable. */
if ( acked_flags )
tcp->tcp_state |= TCP_STATE_ACKED ( acked_flags );
/* Start sending FIN if we've had all possible data ACKed */
if ( list_empty ( &tcp->queue ) && tcp->xfer_closed )
tcp->tcp_state |= TCP_STATE_SENT ( TCP_FIN );
return 0;
}
/**
* Handle TCP received data
*
* @v tcp TCP connection
* @v seq SEQ value (in host-endian order)
* @v iobuf I/O buffer
* @ret rc Return status code
*
* This function takes ownership of the I/O buffer.
*/
static int tcp_rx_data ( struct tcp_connection *tcp, uint32_t seq,
struct io_buffer *iobuf ) {
uint32_t already_rcvd;
uint32_t len;
int rc;
/* Ignore duplicate or out-of-order data */
already_rcvd = ( tcp->rcv_ack - seq );
len = iob_len ( iobuf );
if ( already_rcvd >= len ) {
free_iob ( iobuf );
return 0;
}
iob_pull ( iobuf, already_rcvd );
len -= already_rcvd;
/* Deliver data to application */
if ( ( rc = xfer_deliver_iob ( &tcp->xfer, iobuf ) ) != 0 ) {
DBGC ( tcp, "TCP %p could not deliver %08x..%08x: %s\n",
tcp, seq, ( seq + len ), strerror ( rc ) );
return rc;
}
/* Acknowledge new data */
tcp_rx_seq ( tcp, len );
return 0;
}
/**
* Handle TCP received FIN
*
* @v tcp TCP connection
* @v seq SEQ value (in host-endian order)
* @ret rc Return status code
*/
static int tcp_rx_fin ( struct tcp_connection *tcp, uint32_t seq ) {
/* Ignore duplicate or out-of-order FIN */
if ( ( tcp->rcv_ack - seq ) > 0 )
return 0;
/* Mark FIN as received and acknowledge it */
tcp->tcp_state |= TCP_STATE_RCVD ( TCP_FIN );
tcp_rx_seq ( tcp, 1 );
/* Close connection */
tcp_close ( tcp, 0 );
return 0;
}
/**
* Handle TCP received RST
*
* @v tcp TCP connection
* @v seq SEQ value (in host-endian order)
* @ret rc Return status code
*/
static int tcp_rx_rst ( struct tcp_connection *tcp, uint32_t seq ) {
/* Accept RST only if it falls within the window. If we have
* not yet received a SYN, then we have no window to test
* against, so fall back to checking that our SYN has been
* ACKed.
*/
if ( tcp->tcp_state & TCP_STATE_RCVD ( TCP_SYN ) ) {
if ( ( seq - tcp->rcv_ack ) >= tcp->rcv_win )
return 0;
} else {
if ( ! ( tcp->tcp_state & TCP_STATE_ACKED ( TCP_SYN ) ) )
return 0;
}
/* Abort connection */
tcp->tcp_state = TCP_CLOSED;
tcp_dump_state ( tcp );
tcp_close ( tcp, -ECONNRESET );
DBGC ( tcp, "TCP %p connection reset by peer\n", tcp );
return -ECONNRESET;
}
/**
* Process received packet
*
* @v iobuf I/O buffer
* @v st_src Partially-filled source address
* @v st_dest Partially-filled destination address
* @v pshdr_csum Pseudo-header checksum
* @ret rc Return status code
*/
static int tcp_rx ( struct io_buffer *iobuf,
struct sockaddr_tcpip *st_src,
struct sockaddr_tcpip *st_dest __unused,
uint16_t pshdr_csum ) {
struct tcp_header *tcphdr = iobuf->data;
struct tcp_connection *tcp;
struct tcp_options options;
size_t hlen;
uint16_t csum;
uint32_t start_seq;
uint32_t seq;
uint32_t ack;
uint32_t win;
unsigned int flags;
size_t len;
int rc;
/* Sanity check packet */
if ( iob_len ( iobuf ) < sizeof ( *tcphdr ) ) {
DBG ( "TCP packet too short at %zd bytes (min %zd bytes)\n",
iob_len ( iobuf ), sizeof ( *tcphdr ) );
rc = -EINVAL;
goto discard;
}
hlen = ( ( tcphdr->hlen & TCP_MASK_HLEN ) / 16 ) * 4;
if ( hlen < sizeof ( *tcphdr ) ) {
DBG ( "TCP header too short at %zd bytes (min %zd bytes)\n",
hlen, sizeof ( *tcphdr ) );
rc = -EINVAL;
goto discard;
}
if ( hlen > iob_len ( iobuf ) ) {
DBG ( "TCP header too long at %zd bytes (max %zd bytes)\n",
hlen, iob_len ( iobuf ) );
rc = -EINVAL;
goto discard;
}
csum = tcpip_continue_chksum ( pshdr_csum, iobuf->data,
iob_len ( iobuf ) );
if ( csum != 0 ) {
DBG ( "TCP checksum incorrect (is %04x including checksum "
"field, should be 0000)\n", csum );
rc = -EINVAL;
goto discard;
}
/* Parse parameters from header and strip header */
tcp = tcp_demux ( tcphdr->dest );
start_seq = seq = ntohl ( tcphdr->seq );
ack = ntohl ( tcphdr->ack );
win = ntohs ( tcphdr->win );
flags = tcphdr->flags;
tcp_rx_opts ( tcp, ( ( ( void * ) tcphdr ) + sizeof ( *tcphdr ) ),
( hlen - sizeof ( *tcphdr ) ), &options );
iob_pull ( iobuf, hlen );
len = iob_len ( iobuf );
/* Dump header */
DBGC2 ( tcp, "TCP %p RX %d<-%d %08x %08x..%08zx %4zd",
tcp, ntohs ( tcphdr->dest ), ntohs ( tcphdr->src ),
ntohl ( tcphdr->ack ), ntohl ( tcphdr->seq ),
( ntohl ( tcphdr->seq ) + len +
( ( tcphdr->flags & ( TCP_SYN | TCP_FIN ) ) ? 1 : 0 )), len);
tcp_dump_flags ( tcp, tcphdr->flags );
DBGC2 ( tcp, "\n" );
/* If no connection was found, send RST */
if ( ! tcp ) {
tcp_xmit_reset ( tcp, st_src, tcphdr );
rc = -ENOTCONN;
goto discard;
}
/* Handle ACK, if present */
if ( flags & TCP_ACK ) {
if ( ( rc = tcp_rx_ack ( tcp, ack, win ) ) != 0 ) {
tcp_xmit_reset ( tcp, st_src, tcphdr );
goto discard;
}
}
/* Handle SYN, if present */
if ( flags & TCP_SYN ) {
tcp_rx_syn ( tcp, seq, &options );
seq++;
}
/* Handle RST, if present */
if ( flags & TCP_RST ) {
if ( ( rc = tcp_rx_rst ( tcp, seq ) ) != 0 )
goto discard;
}
/* Handle new data, if any */
tcp_rx_data ( tcp, seq, iobuf );
seq += len;
/* Handle FIN, if present */
if ( flags & TCP_FIN ) {
tcp_rx_fin ( tcp, seq );
seq++;
}
/* Update timestamp, if present and applicable */
if ( ( seq == tcp->rcv_ack ) && options.tsopt )
tcp->ts_recent = ntohl ( options.tsopt->tsval );
/* Dump out any state change as a result of the received packet */
tcp_dump_state ( tcp );
/* Send out any pending data. We force sending a reply if either
*
* a) the peer is expecting an ACK (i.e. consumed sequence space), or
* b) either end of the packet was outside the receive window
*
* Case (b) enables us to support TCP keepalives using
* zero-length packets, which we would otherwise ignore. Note
* that for case (b), we need *only* consider zero-length
* packets, since non-zero-length packets will already be
* caught by case (a).
*/
tcp_xmit ( tcp, ( ( start_seq != seq ) ||
( ( seq - tcp->rcv_ack ) > tcp->rcv_win ) ) );
/* If this packet was the last we expect to receive, set up
* timer to expire and cause the connection to be freed.
*/
if ( TCP_CLOSED_GRACEFULLY ( tcp->tcp_state ) ) {
tcp->timer.timeout = ( 2 * TCP_MSL );
start_timer ( &tcp->timer );
}
return 0;
discard:
/* Free received packet */
free_iob ( iobuf );
return rc;
}
/** TCP protocol */
struct tcpip_protocol tcp_protocol __tcpip_protocol = {
.name = "TCP",
.rx = tcp_rx,
.tcpip_proto = IP_TCP,
};
/***************************************************************************
*
* Data transfer interface
*
***************************************************************************
*/
/**
* Close interface
*
* @v xfer Data transfer interface
* @v rc Reason for close
*/
static void tcp_xfer_close ( struct xfer_interface *xfer, int rc ) {
struct tcp_connection *tcp =
container_of ( xfer, struct tcp_connection, xfer );
/* Close data transfer interface */
tcp_close ( tcp, rc );
/* Transmit FIN, if possible */
tcp_xmit ( tcp, 0 );
}
/**
* Check flow control window
*
* @v xfer Data transfer interface
* @ret len Length of window
*/
static size_t tcp_xfer_window ( struct xfer_interface *xfer ) {
struct tcp_connection *tcp =
container_of ( xfer, struct tcp_connection, xfer );
/* Not ready if data queue is non-empty. This imposes a limit
* of only one unACKed packet in the TX queue at any time; we
* do this to conserve memory usage.
*/
if ( ! list_empty ( &tcp->queue ) )
return 0;
/* Return TCP window length */
return tcp_xmit_win ( tcp );
}
/**
* Deliver datagram as I/O buffer
*
* @v xfer Data transfer interface
* @v iobuf Datagram I/O buffer
* @v meta Data transfer metadata
* @ret rc Return status code
*/
static int tcp_xfer_deliver_iob ( struct xfer_interface *xfer,
struct io_buffer *iobuf,
struct xfer_metadata *meta __unused ) {
struct tcp_connection *tcp =
container_of ( xfer, struct tcp_connection, xfer );
/* Enqueue packet */
list_add_tail ( &iobuf->list, &tcp->queue );
/* Transmit data, if possible */
tcp_xmit ( tcp, 0 );
return 0;
}
/** TCP data transfer interface operations */
static struct xfer_interface_operations tcp_xfer_operations = {
.close = tcp_xfer_close,
.vredirect = ignore_xfer_vredirect,
.window = tcp_xfer_window,
.alloc_iob = default_xfer_alloc_iob,
.deliver_iob = tcp_xfer_deliver_iob,
.deliver_raw = xfer_deliver_as_iob,
};
/***************************************************************************
*
* Openers
*
***************************************************************************
*/
/** TCP socket opener */
struct socket_opener tcp_socket_opener __socket_opener = {
.semantics = TCP_SOCK_STREAM,
.family = AF_INET,
.open = tcp_open,
};
/** Linkage hack */
int tcp_sock_stream = TCP_SOCK_STREAM;
/**
* Open TCP URI
*
* @v xfer Data transfer interface
* @v uri URI
* @ret rc Return status code
*/
static int tcp_open_uri ( struct xfer_interface *xfer, struct uri *uri ) {
struct sockaddr_tcpip peer;
/* Sanity check */
if ( ! uri->host )
return -EINVAL;
memset ( &peer, 0, sizeof ( peer ) );
peer.st_port = htons ( uri_port ( uri, 0 ) );
return xfer_open_named_socket ( xfer, SOCK_STREAM,
( struct sockaddr * ) &peer,
uri->host, NULL );
}
/** TCP URI opener */
struct uri_opener tcp_uri_opener __uri_opener = {
.scheme = "tcp",
.open = tcp_open_uri,
};