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xNBA/src/net/tcp.c
Michael Brown c57e26381c [tcp] Use a dedicated timer for the TIME_WAIT state 
iPXE currently repurposes the retransmission timer to hold the TCP
connection in the TIME_WAIT state (i.e. waiting for up to 2*MSL in
case we are required to re-ACK our peer's FIN due to a lost ACK).
However, the fact that this timer is running will prevent such an ACK
from ever being sent, since the logic in tcp_xmit() assumes that a
running timer indicates that we ourselves are waiting for an ACK and
so blocks the transmission.  (We always wait for an ACK before sending
our next packet, to keep our transmit data path as simple as
possible.)

Fix by using an entirely separate timer for the TIME_WAIT state, so
that packets can still be sent.

Reported-by: Piotr Jaroszyński <p.jaroszynski@gmail.com>
Signed-off-by: Michael Brown <mcb30@ipxe.org>
2010-07-15 19:59:34 +01:00

1181 lines
30 KiB
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#include <string.h>
#include <stdlib.h>
#include <stdio.h>
#include <assert.h>
#include <errno.h>
#include <byteswap.h>
#include <ipxe/timer.h>
#include <ipxe/iobuf.h>
#include <ipxe/malloc.h>
#include <ipxe/retry.h>
#include <ipxe/refcnt.h>
#include <ipxe/xfer.h>
#include <ipxe/open.h>
#include <ipxe/uri.h>
#include <ipxe/tcpip.h>
#include <ipxe/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 interface xfer;
/** Data transfer interface closed flag */
int xfer_closed;
/** Remote socket address */
struct sockaddr_tcpip peer;
/** Local port */
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;
/** Shutdown (TIME_WAIT) timer */
struct retry_timer wait;
};
/**
* List of registered TCP connections
*/
static LIST_HEAD ( tcp_conns );
/* Forward declarations */
static struct interface_descriptor tcp_xfer_desc;
static void tcp_expired ( struct retry_timer *timer, int over );
static void tcp_wait_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
* @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;
uint16_t try_port;
unsigned int i;
/* If no port is specified, find an available port */
if ( ! port ) {
try_port = random();
for ( i = 0 ; i < 65536 ; i++ ) {
try_port++;
if ( try_port < 1024 )
continue;
if ( tcp_bind ( tcp, 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, port );
return -EADDRINUSE;
}
}
tcp->local_port = port;
DBGC ( tcp, "TCP %p bound to port %d\n", tcp, 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 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 );
ref_init ( &tcp->refcnt, NULL );
intf_init ( &tcp->xfer, &tcp_xfer_desc, &tcp->refcnt );
timer_init ( &tcp->timer, tcp_expired );
timer_init ( &tcp->wait, tcp_wait_expired );
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 );
memcpy ( &tcp->peer, st_peer, sizeof ( tcp->peer ) );
/* Bind to local port */
bind_port = ( st_local ? ntohs ( 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
*/
intf_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 */
intf_shutdown ( &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 = htonl ( currticks() );
tsopt->tsopt.tsecr = htonl ( tcp->ts_recent );
}
if ( ! ( flags & TCP_SYN ) )
flags |= TCP_PSH;
tcphdr = iob_push ( iobuf, sizeof ( *tcphdr ) );
memset ( tcphdr, 0, sizeof ( *tcphdr ) );
tcphdr->src = htons ( 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 Retransmission 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 );
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_CLOSE_WAIT ) ||
( tcp->tcp_state == TCP_CLOSING_OR_LAST_ACK ) );
if ( over ) {
/* If we have finally timed out and given up,
* 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 );
}
}
/**
* Shutdown timer expired
*
* @v timer Shutdown timer
* @v over Failure indicator
*/
static void tcp_wait_expired ( struct retry_timer *timer, int over __unused ) {
struct tcp_connection *tcp =
container_of ( timer, struct tcp_connection, wait );
assert ( tcp->tcp_state == TCP_TIME_WAIT );
DBGC ( tcp, "TCP %p wait complete in %s for %08x..%08x %08x\n", tcp,
tcp_state ( tcp->tcp_state ), tcp->snd_seq,
( tcp->snd_seq + tcp->snd_sent ), tcp->rcv_ack );
tcp->tcp_state = TCP_CLOSED;
tcp_dump_state ( tcp );
tcp_close ( 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
* @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;
/* Acknowledge SYN */
tcp_rx_seq ( tcp, 1 );
/* Mark SYN as received and start sending ACKs with each packet */
tcp->tcp_state |= ( TCP_STATE_SENT ( TCP_ACK ) |
TCP_STATE_RCVD ( TCP_SYN ) );
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;
/* Acknowledge new data */
tcp_rx_seq ( tcp, len );
/* 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;
}
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;
/* Acknowledge FIN */
tcp_rx_seq ( tcp, 1 );
/* Mark FIN as received */
tcp->tcp_state |= TCP_STATE_RCVD ( TCP_FIN );
/* 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;
uint32_t ts_recent;
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 ( ntohs ( 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 );
ts_recent = ( options.tsopt ?
ntohl ( options.tsopt->tsval ) : tcp->ts_recent );
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, iob_disown ( iobuf ) );
seq += len;
/* Handle FIN, if present */
if ( flags & TCP_FIN ) {
tcp_rx_fin ( tcp, seq );
seq++;
}
/* Update timestamp, if applicable */
if ( seq == tcp->rcv_ack )
tcp->ts_recent = ts_recent;
/* 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 ) ) {
stop_timer ( &tcp->wait );
start_timer_fixed ( &tcp->wait, ( 2 * TCP_MSL ) );
}
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 tcp TCP connection
* @v rc Reason for close
*/
static void tcp_xfer_close ( struct tcp_connection *tcp, int rc ) {
/* Close data transfer interface */
tcp_close ( tcp, rc );
/* Transmit FIN, if possible */
tcp_xmit ( tcp, 0 );
}
/**
* Check flow control window
*
* @v tcp TCP connection
* @ret len Length of window
*/
static size_t tcp_xfer_window ( struct tcp_connection *tcp ) {
/* 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 tcp TCP connection
* @v iobuf Datagram I/O buffer
* @v meta Data transfer metadata
* @ret rc Return status code
*/
static int tcp_xfer_deliver ( struct tcp_connection *tcp,
struct io_buffer *iobuf,
struct xfer_metadata *meta __unused ) {
/* 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 interface_operation tcp_xfer_operations[] = {
INTF_OP ( xfer_deliver, struct tcp_connection *, tcp_xfer_deliver ),
INTF_OP ( xfer_window, struct tcp_connection *, tcp_xfer_window ),
INTF_OP ( intf_close, struct tcp_connection *, tcp_xfer_close ),
};
/** TCP data transfer interface descriptor */
static struct interface_descriptor tcp_xfer_desc =
INTF_DESC ( struct tcp_connection, xfer, tcp_xfer_operations );
/***************************************************************************
*
* 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 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,
};
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