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ipxe/src/net/tcp.c

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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/init.h>
#include <ipxe/retry.h>
#include <ipxe/refcnt.h>
#include <ipxe/pending.h>
#include <ipxe/xfer.h>
#include <ipxe/open.h>
#include <ipxe/uri.h>
#include <ipxe/netdevice.h>
#include <ipxe/profile.h>
#include <ipxe/process.h>
#include <ipxe/tcpip.h>
#include <ipxe/tcp.h>
/** @file
*
* TCP protocol
*
*/
FILE_LICENCE ( GPL2_OR_LATER_OR_UBDL );
/** A TCP connection */
struct tcp_connection {
/** Reference counter */
struct refcnt refcnt;
/** List of TCP connections */
struct list_head list;
/** Flags */
unsigned int flags;
/** Data transfer interface */
struct interface xfer;
/** Remote socket address */
struct sockaddr_tcpip peer;
/** Local port */
unsigned int local_port;
/** Maximum segment size */
size_t mss;
/** 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;
/** Received timestamp value
*
* Updated when a packet is received; copied to ts_recent when
* the window is advanced.
*/
uint32_t ts_val;
/** Most recent received timestamp that advanced the window
*
* Equivalent to TS.Recent in RFC 1323 terminology.
*/
uint32_t ts_recent;
/** Send window scale
*
* Equivalent to Snd.Wind.Scale in RFC 1323 terminology
*/
uint8_t snd_win_scale;
/** Receive window scale
*
* Equivalent to Rcv.Wind.Scale in RFC 1323 terminology
*/
uint8_t rcv_win_scale;
/** Selective acknowledgement list (in host-endian order) */
struct tcp_sack_block sack[TCP_SACK_MAX];
/** Transmit queue */
struct list_head tx_queue;
/** Receive queue */
struct list_head rx_queue;
/** Transmission process */
struct process process;
/** Retransmission timer */
struct retry_timer timer;
/** Keepalive timer */
struct retry_timer keepalive;
/** Shutdown (TIME_WAIT) timer */
struct retry_timer wait;
/** Pending operations for SYN and FIN */
struct pending_operation pending_flags;
/** Pending operations for transmit queue */
struct pending_operation pending_data;
};
/** TCP flags */
enum tcp_flags {
/** TCP data transfer interface has been closed */
TCP_XFER_CLOSED = 0x0001,
/** TCP timestamps are enabled */
TCP_TS_ENABLED = 0x0002,
/** TCP acknowledgement is pending */
TCP_ACK_PENDING = 0x0004,
/** TCP selective acknowledgement is enabled */
TCP_SACK_ENABLED = 0x0008,
};
/** TCP internal header
*
* This is the header that replaces the TCP header for packets
* enqueued on the receive queue.
*/
struct tcp_rx_queued_header {
/** SEQ value, in host-endian order
*
* This represents the SEQ value at the time the packet is
* enqueued, and so excludes the SYN, if present.
*/
uint32_t seq;
/** Next SEQ value, in host-endian order */
uint32_t nxt;
/** Flags
*
* Only FIN is valid within this flags byte; all other flags
* have already been processed by the time the packet is
* enqueued.
*/
uint8_t flags;
/** Reserved */
uint8_t reserved[3];
};
/**
* List of registered TCP connections
*/
static LIST_HEAD ( tcp_conns );
/** Transmit profiler */
static struct profiler tcp_tx_profiler __profiler = { .name = "tcp.tx" };
/** Receive profiler */
static struct profiler tcp_rx_profiler __profiler = { .name = "tcp.rx" };
/** Data transfer profiler */
static struct profiler tcp_xfer_profiler __profiler = { .name = "tcp.xfer" };
/* Forward declarations */
static struct process_descriptor tcp_process_desc;
static struct interface_descriptor tcp_xfer_desc;
static void tcp_expired ( struct retry_timer *timer, int over );
static void tcp_keepalive_expired ( struct retry_timer *timer, int over );
static void tcp_wait_expired ( struct retry_timer *timer, int over );
static struct tcp_connection * tcp_demux ( unsigned int local_port );
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
*
***************************************************************************
*/
/**
* Check if local TCP port is available
*
* @v port Local port number
* @ret port Local port number, or negative error
*/
static int tcp_port_available ( int port ) {
return ( tcp_demux ( port ) ? -EADDRINUSE : port );
}
/**
* 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;
size_t mtu;
int 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 );
process_init_stopped ( &tcp->process, &tcp_process_desc, &tcp->refcnt );
timer_init ( &tcp->timer, tcp_expired, &tcp->refcnt );
timer_init ( &tcp->keepalive, tcp_keepalive_expired, &tcp->refcnt );
timer_init ( &tcp->wait, tcp_wait_expired, &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->tx_queue );
INIT_LIST_HEAD ( &tcp->rx_queue );
memcpy ( &tcp->peer, st_peer, sizeof ( tcp->peer ) );
/* Calculate MSS */
mtu = tcpip_mtu ( &tcp->peer );
if ( ! mtu ) {
DBGC ( tcp, "TCP %p has no route to %s\n",
tcp, sock_ntoa ( peer ) );
rc = -ENETUNREACH;
goto err;
}
tcp->mss = ( mtu - sizeof ( struct tcp_header ) );
/* Bind to local port */
port = tcpip_bind ( st_local, tcp_port_available );
if ( port < 0 ) {
rc = port;
DBGC ( tcp, "TCP %p could not bind: %s\n",
tcp, strerror ( rc ) );
goto err;
}
tcp->local_port = port;
DBGC ( tcp, "TCP %p bound to port %d\n", tcp, tcp->local_port );
/* Start timer to initiate SYN */
start_timer_nodelay ( &tcp->timer );
/* Add a pending operation for the SYN */
pending_get ( &tcp->pending_flags );
/* 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->flags |= TCP_XFER_CLOSED;
/* 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 unprocessed I/O buffers */
list_for_each_entry_safe ( iobuf, tmp, &tcp->rx_queue, list ) {
list_del ( &iobuf->list );
free_iob ( iobuf );
}
/* Free any unsent I/O buffers */
list_for_each_entry_safe ( iobuf, tmp, &tcp->tx_queue, list ) {
list_del ( &iobuf->list );
free_iob ( iobuf );
pending_put ( &tcp->pending_data );
}
assert ( ! is_pending ( &tcp->pending_data ) );
/* Remove pending operations for SYN and FIN, if applicable */
pending_put ( &tcp->pending_flags );
pending_put ( &tcp->pending_flags );
/* Remove from list and drop reference */
process_del ( &tcp->process );
stop_timer ( &tcp->timer );
stop_timer ( &tcp->keepalive );
stop_timer ( &tcp->wait );
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 );
/* Stop keepalive timer */
stop_timer ( &tcp->keepalive );
/* If we have no data remaining to send, start sending FIN */
if ( list_empty ( &tcp->tx_queue ) &&
! ( tcp->tcp_state & TCP_STATE_SENT ( TCP_FIN ) ) ) {
tcp->tcp_state |= TCP_STATE_SENT ( TCP_FIN );
tcp_dump_state ( tcp );
process_add ( &tcp->process );
/* Add a pending operation for the FIN */
pending_get ( &tcp->pending_flags );
}
}
/***************************************************************************
*
* 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;
}
/**
* Check data-transfer 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->tx_queue ) )
return 0;
/* Return TCP window length */
return tcp_xmit_win ( tcp );
}
/**
* Find selective acknowledgement block
*
* @v tcp TCP connection
* @v seq SEQ value in SACK block (in host-endian order)
* @v sack SACK block to fill in (in host-endian order)
* @ret len Length of SACK block
*/
static uint32_t tcp_sack_block ( struct tcp_connection *tcp, uint32_t seq,
struct tcp_sack_block *sack ) {
struct io_buffer *iobuf;
struct tcp_rx_queued_header *tcpqhdr;
uint32_t left = tcp->rcv_ack;
uint32_t right = left;
/* Find highest block which does not start after SEQ */
list_for_each_entry ( iobuf, &tcp->rx_queue, list ) {
tcpqhdr = iobuf->data;
if ( tcp_cmp ( tcpqhdr->seq, right ) > 0 ) {
if ( tcp_cmp ( tcpqhdr->seq, seq ) > 0 )
break;
left = tcpqhdr->seq;
}
if ( tcp_cmp ( tcpqhdr->nxt, right ) > 0 )
right = tcpqhdr->nxt;
}
/* Fail if this block does not contain SEQ */
if ( tcp_cmp ( right, seq ) < 0 )
return 0;
/* Populate SACK block */
sack->left = left;
sack->right = right;
return ( right - left );
}
/**
* Update TCP selective acknowledgement list
*
* @v tcp TCP connection
* @v seq SEQ value in first SACK block (in host-endian order)
* @ret count Number of SACK blocks
*/
static unsigned int tcp_sack ( struct tcp_connection *tcp, uint32_t seq ) {
struct tcp_sack_block sack[TCP_SACK_MAX];
unsigned int old = 0;
unsigned int new = 0;
unsigned int i;
uint32_t len;
/* Populate first new SACK block */
len = tcp_sack_block ( tcp, seq, &sack[0] );
if ( len )
new++;
/* Populate remaining new SACK blocks based on old SACK blocks */
for ( old = 0 ; old < TCP_SACK_MAX ; old++ ) {
/* Stop if we run out of space in the new list */
if ( new == TCP_SACK_MAX )
break;
/* Skip empty old SACK blocks */
if ( tcp->sack[old].left == tcp->sack[old].right )
continue;
/* Populate new SACK block */
len = tcp_sack_block ( tcp, tcp->sack[old].left, &sack[new] );
if ( len == 0 )
continue;
/* Eliminate duplicates */
for ( i = 0 ; i < new ; i++ ) {
if ( sack[i].left == sack[new].left ) {
new--;
break;
}
}
new++;
}
/* Update SACK list */
memset ( tcp->sack, 0, sizeof ( tcp->sack ) );
memcpy ( tcp->sack, sack, ( new * sizeof ( tcp->sack[0] ) ) );
return new;
}
/**
* 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_tx_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->tx_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 );
pending_put ( &tcp->pending_data );
}
}
len += frag_len;
max_len -= frag_len;
}
return len;
}
/**
* Transmit any outstanding data (with selective acknowledgement)
*
* @v tcp TCP connection
* @v sack_seq SEQ for first selective acknowledgement (if any)
*
* 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 void tcp_xmit_sack ( struct tcp_connection *tcp, uint32_t sack_seq ) {
struct io_buffer *iobuf;
struct tcp_header *tcphdr;
struct tcp_mss_option *mssopt;
struct tcp_window_scale_padded_option *wsopt;
struct tcp_timestamp_padded_option *tsopt;
struct tcp_sack_permitted_padded_option *spopt;
struct tcp_sack_padded_option *sackopt;
struct tcp_sack_block *sack;
void *payload;
unsigned int flags;
unsigned int sack_count;
unsigned int i;
size_t len = 0;
size_t sack_len;
uint32_t seq_len;
uint32_t max_rcv_win;
uint32_t max_representable_win;
int rc;
/* Start profiling */
profile_start ( &tcp_tx_profiler );
/* If retransmission timer is already running, do nothing */
if ( timer_running ( &tcp->timer ) )
return;
/* 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_tx_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 ) && ! ( tcp->flags & TCP_ACK_PENDING ) )
return;
/* 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 + TCP_MAX_HEADER_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;
}
iob_reserve ( iobuf, TCP_MAX_HEADER_LEN );
/* Fill data payload from transmit queue */
tcp_process_tx_queue ( tcp, len, iobuf, 0 );
/* Expand receive window if possible */
max_rcv_win = xfer_window ( &tcp->xfer );
if ( max_rcv_win > TCP_MAX_WINDOW_SIZE )
max_rcv_win = TCP_MAX_WINDOW_SIZE;
max_representable_win = ( 0xffff << tcp->rcv_win_scale );
if ( max_rcv_win > max_representable_win )
max_rcv_win = max_representable_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 );
wsopt = iob_push ( iobuf, sizeof ( *wsopt ) );
wsopt->nop = TCP_OPTION_NOP;
wsopt->wsopt.kind = TCP_OPTION_WS;
wsopt->wsopt.length = sizeof ( wsopt->wsopt );
wsopt->wsopt.scale = TCP_RX_WINDOW_SCALE;
spopt = iob_push ( iobuf, sizeof ( *spopt ) );
memset ( spopt->nop, TCP_OPTION_NOP, sizeof ( spopt->nop ) );
spopt->spopt.kind = TCP_OPTION_SACK_PERMITTED;
spopt->spopt.length = sizeof ( spopt->spopt );
}
if ( ( flags & TCP_SYN ) || ( tcp->flags & TCP_TS_ENABLED ) ) {
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 ( ( tcp->flags & TCP_SACK_ENABLED ) &&
( ! list_empty ( &tcp->rx_queue ) ) &&
( ( sack_count = tcp_sack ( tcp, sack_seq ) ) != 0 ) ) {
sack_len = ( sack_count * sizeof ( *sack ) );
sackopt = iob_push ( iobuf, ( sizeof ( *sackopt ) + sack_len ));
memset ( sackopt->nop, TCP_OPTION_NOP, sizeof ( sackopt->nop ));
sackopt->sackopt.kind = TCP_OPTION_SACK;
sackopt->sackopt.length =
( sizeof ( sackopt->sackopt ) + sack_len );
sack = ( ( ( void * ) sackopt ) + sizeof ( *sackopt ) );
for ( i = 0 ; i < sack_count ; i++, sack++ ) {
sack->left = htonl ( tcp->sack[i].left );
sack->right = htonl ( tcp->sack[i].right );
}
}
if ( len != 0 )
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 >> tcp->rcv_win_scale );
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;
}
/* Clear ACK-pending flag */
tcp->flags &= ~TCP_ACK_PENDING;
profile_stop ( &tcp_tx_profiler );
}
/**
* Transmit any outstanding data
*
* @v tcp TCP connection
*/
static void tcp_xmit ( struct tcp_connection *tcp ) {
/* Transmit without an explicit first SACK */
tcp_xmit_sack ( tcp, tcp->rcv_ack );
}
/** TCP process descriptor */
static struct process_descriptor tcp_process_desc =
PROC_DESC_ONCE ( struct tcp_connection, process, tcp_xmit );
/**
* 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 );
}
}
/**
* Keepalive timer expired
*
* @v timer Keepalive timer
* @v over Failure indicator
*/
static void tcp_keepalive_expired ( struct retry_timer *timer,
int over __unused ) {
struct tcp_connection *tcp =
container_of ( timer, struct tcp_connection, keepalive );
DBGC ( tcp, "TCP %p sending keepalive\n", tcp );
/* Reset keepalive timer */
start_timer_fixed ( &tcp->keepalive, TCP_KEEPALIVE_DELAY );
/* Send keepalive. We do this only to preserve or restore
* state in intermediate devices (e.g. firewall NAT tables);
* we don't actually care about eliciting a response to verify
* that the peer is still alive. We therefore send just a
* pure ACK, to keep our transmit path simple.
*/
tcp->flags |= TCP_ACK_PENDING;
tcp_xmit ( tcp );
}
/**
* 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 ( TCP_MAX_HEADER_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, TCP_MAX_HEADER_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 ( 0 );
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 (may be NULL)
* @v tcphdr TCP header
* @v hlen TCP header length
* @v options Options structure to fill in
* @ret rc Return status code
*/
static int tcp_rx_opts ( struct tcp_connection *tcp,
const struct tcp_header *tcphdr, size_t hlen,
struct tcp_options *options ) {
const void *data = ( ( ( void * ) tcphdr ) + sizeof ( *tcphdr ) );
const void *end = ( ( ( void * ) tcphdr ) + hlen );
const struct tcp_option *option;
unsigned int kind;
size_t remaining;
size_t min;
/* Sanity check */
assert ( hlen >= sizeof ( *tcphdr ) );
/* Parse options */
memset ( options, 0, sizeof ( *options ) );
while ( ( remaining = ( end - data ) ) ) {
/* Extract option code */
option = data;
kind = option->kind;
/* Handle single-byte options */
if ( kind == TCP_OPTION_END )
break;
if ( kind == TCP_OPTION_NOP ) {
data++;
continue;
}
/* Handle multi-byte options */
min = sizeof ( *option );
switch ( kind ) {
case TCP_OPTION_MSS:
/* Ignore received MSS */
break;
case TCP_OPTION_WS:
options->wsopt = data;
min = sizeof ( *options->wsopt );
break;
case TCP_OPTION_SACK_PERMITTED:
options->spopt = data;
min = sizeof ( *options->spopt );
break;
case TCP_OPTION_SACK:
/* Ignore received SACKs */
break;
case TCP_OPTION_TS:
options->tsopt = data;
min = sizeof ( *options->tsopt );
break;
default:
DBGC ( tcp, "TCP %p received unknown option %d\n",
tcp, kind );
break;
}
if ( remaining < min ) {
DBGC ( tcp, "TCP %p received truncated option %d\n",
tcp, kind );
return -EINVAL;
}
if ( option->length < min ) {
DBGC ( tcp, "TCP %p received underlength option %d\n",
tcp, kind );
return -EINVAL;
}
if ( option->length > remaining ) {
DBGC ( tcp, "TCP %p received overlength option %d\n",
tcp, kind );
return -EINVAL;
}
data += option->length;
}
return 0;
}
/**
* 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 ) {
unsigned int sack;
/* Sanity check */
assert ( seq_len > 0 );
/* Update acknowledgement number */
tcp->rcv_ack += seq_len;
/* Update window */
if ( tcp->rcv_win > seq_len ) {
tcp->rcv_win -= seq_len;
} else {
tcp->rcv_win = 0;
}
/* Update timestamp */
tcp->ts_recent = tcp->ts_val;
/* Update SACK list */
for ( sack = 0 ; sack < TCP_SACK_MAX ; sack++ ) {
if ( tcp->sack[sack].left == tcp->sack[sack].right )
continue;
if ( tcp_cmp ( tcp->sack[sack].left, tcp->rcv_ack ) < 0 )
tcp->sack[sack].left = tcp->rcv_ack;
if ( tcp_cmp ( tcp->sack[sack].right, tcp->rcv_ack ) < 0 )
tcp->sack[sack].right = tcp->rcv_ack;
}
/* Mark ACK as pending */
tcp->flags |= TCP_ACK_PENDING;
}
/**
* 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->flags |= TCP_TS_ENABLED;
if ( options->spopt )
tcp->flags |= TCP_SACK_ENABLED;
if ( options->wsopt ) {
tcp->snd_win_scale = options->wsopt->scale;
tcp->rcv_win_scale = TCP_RX_WINDOW_SCALE;
}
DBGC ( tcp, "TCP %p using %stimestamps, %sSACK, TX window "
"x%d, RX window x%d\n", tcp,
( ( tcp->flags & TCP_TS_ENABLED ) ? "" : "no " ),
( ( tcp->flags & TCP_SACK_ENABLED ) ? "" : "no " ),
( 1 << tcp->snd_win_scale ),
( 1 << tcp->rcv_win_scale ) );
}
/* Ignore duplicate SYN */
if ( seq != tcp->rcv_ack )
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;
}
}
/* Update window size */
tcp->snd_win = win;
/* Hold off (or start) the keepalive timer, if applicable */
if ( ! ( tcp->tcp_state & TCP_STATE_SENT ( TCP_FIN ) ) )
start_timer_fixed ( &tcp->keepalive, TCP_KEEPALIVE_DELAY );
/* 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--;
pending_put ( &tcp->pending_flags );
}
/* Update SEQ and sent counters */
tcp->snd_seq = ack;
tcp->snd_sent = 0;
/* Remove any acknowledged data from transmit queue */
tcp_process_tx_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->tx_queue ) &&
( tcp->flags & TCP_XFER_CLOSED ) &&
! ( tcp->tcp_state & TCP_STATE_SENT ( TCP_FIN ) ) ) {
tcp->tcp_state |= TCP_STATE_SENT ( TCP_FIN );
pending_get ( &tcp->pending_flags );
}
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 */
profile_start ( &tcp_xfer_profiler );
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;
}
profile_stop ( &tcp_xfer_profiler );
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 ( seq != tcp->rcv_ack )
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 ( ! tcp_in_window ( 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;
}
/**
* Enqueue received TCP packet
*
* @v tcp TCP connection
* @v seq SEQ value (in host-endian order)
* @v flags TCP flags
* @v iobuf I/O buffer
*/
static void tcp_rx_enqueue ( struct tcp_connection *tcp, uint32_t seq,
uint8_t flags, struct io_buffer *iobuf ) {
struct tcp_rx_queued_header *tcpqhdr;
struct io_buffer *queued;
size_t len;
uint32_t seq_len;
uint32_t nxt;
/* Calculate remaining flags and sequence length. Note that
* SYN, if present, has already been processed by this point.
*/
flags &= TCP_FIN;
len = iob_len ( iobuf );
seq_len = ( len + ( flags ? 1 : 0 ) );
nxt = ( seq + seq_len );
/* Discard immediately (to save memory) if:
*
* a) we have not yet received a SYN (and so have no defined
* receive window), or
* b) the packet lies entirely outside the receive window, or
* c) there is no further content to process.
*/
if ( ( ! ( tcp->tcp_state & TCP_STATE_RCVD ( TCP_SYN ) ) ) ||
( tcp_cmp ( seq, tcp->rcv_ack + tcp->rcv_win ) >= 0 ) ||
( tcp_cmp ( nxt, tcp->rcv_ack ) < 0 ) ||
( seq_len == 0 ) ) {
free_iob ( iobuf );
return;
}
/* Add internal header */
tcpqhdr = iob_push ( iobuf, sizeof ( *tcpqhdr ) );
tcpqhdr->seq = seq;
tcpqhdr->nxt = nxt;
tcpqhdr->flags = flags;
/* Add to RX queue */
list_for_each_entry ( queued, &tcp->rx_queue, list ) {
tcpqhdr = queued->data;
if ( tcp_cmp ( seq, tcpqhdr->seq ) < 0 )
break;
}
list_add_tail ( &iobuf->list, &queued->list );
}
/**
* Process receive queue
*
* @v tcp TCP connection
*/
static void tcp_process_rx_queue ( struct tcp_connection *tcp ) {
struct io_buffer *iobuf;
struct tcp_rx_queued_header *tcpqhdr;
uint32_t seq;
unsigned int flags;
size_t len;
/* Process all applicable received buffers. Note that we
* cannot use list_for_each_entry() to iterate over the RX
* queue, since tcp_discard() may remove packets from the RX
* queue while we are processing.
*/
while ( ( iobuf = list_first_entry ( &tcp->rx_queue, struct io_buffer,
list ) ) ) {
/* Stop processing when we hit the first gap */
tcpqhdr = iobuf->data;
if ( tcp_cmp ( tcpqhdr->seq, tcp->rcv_ack ) > 0 )
break;
/* Strip internal header and remove from RX queue */
list_del ( &iobuf->list );
seq = tcpqhdr->seq;
flags = tcpqhdr->flags;
iob_pull ( iobuf, sizeof ( *tcpqhdr ) );
len = iob_len ( iobuf );
/* 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++;
}
}
}
/**
* Process received packet
*
* @v iobuf I/O buffer
* @v netdev Network device
* @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 net_device *netdev __unused,
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 seq;
uint32_t ack;
uint16_t raw_win;
uint32_t win;
unsigned int flags;
size_t len;
uint32_t seq_len;
size_t old_xfer_window;
int rc;
/* Start profiling */
profile_start ( &tcp_rx_profiler );
/* 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 ) );
seq = ntohl ( tcphdr->seq );
ack = ntohl ( tcphdr->ack );
raw_win = ntohs ( tcphdr->win );
flags = tcphdr->flags;
if ( ( rc = tcp_rx_opts ( tcp, tcphdr, hlen, &options ) ) != 0 )
goto discard;
if ( tcp && options.tsopt )
tcp->ts_val = ntohl ( options.tsopt->tsval );
iob_pull ( iobuf, hlen );
len = iob_len ( iobuf );
seq_len = ( len + ( ( flags & TCP_SYN ) ? 1 : 0 ) +
( ( flags & TCP_FIN ) ? 1 : 0 ) );
/* Dump header */
DBGC2 ( tcp, "TCP %p RX %d<-%d %08x %08x..%08x %4zd",
tcp, ntohs ( tcphdr->dest ), ntohs ( tcphdr->src ),
ntohl ( tcphdr->ack ), ntohl ( tcphdr->seq ),
( ntohl ( tcphdr->seq ) + seq_len ), len );
tcp_dump_flags ( tcp, tcphdr->flags );
DBGC2 ( tcp, "\n" );
/* If no connection was found, silently drop packet */
if ( ! tcp ) {
rc = -ENOTCONN;
goto discard;
}
/* Record old data-transfer window */
old_xfer_window = tcp_xfer_window ( tcp );
/* Handle ACK, if present */
if ( flags & TCP_ACK ) {
win = ( raw_win << tcp->snd_win_scale );
if ( ( rc = tcp_rx_ack ( tcp, ack, win ) ) != 0 ) {
tcp_xmit_reset ( tcp, st_src, tcphdr );
goto discard;
}
}
/* Force an ACK if this packet is out of order */
if ( ( tcp->tcp_state & TCP_STATE_RCVD ( TCP_SYN ) ) &&
( seq != tcp->rcv_ack ) ) {
tcp->flags |= TCP_ACK_PENDING;
}
/* 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;
}
/* Enqueue received data */
tcp_rx_enqueue ( tcp, seq, flags, iob_disown ( iobuf ) );
/* Process receive queue */
tcp_process_rx_queue ( tcp );
/* Dump out any state change as a result of the received packet */
tcp_dump_state ( tcp );
/* Schedule transmission of ACK (and any pending data). If we
* have received any out-of-order packets (i.e. if the receive
* queue remains non-empty after processing) then send the ACK
* immediately in order to trigger Fast Retransmission.
*/
if ( list_empty ( &tcp->rx_queue ) ) {
process_add ( &tcp->process );
} else {
tcp_xmit_sack ( tcp, seq );
}
/* 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 ) );
}
/* Notify application if window has changed */
if ( tcp_xfer_window ( tcp ) != old_xfer_window )
xfer_window_changed ( &tcp->xfer );
profile_stop ( &tcp_rx_profiler );
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,
};
/**
* Discard some cached TCP data
*
* @ret discarded Number of cached items discarded
*/
static unsigned int tcp_discard ( void ) {
struct tcp_connection *tcp;
struct io_buffer *iobuf;
unsigned int discarded = 0;
/* Try to drop one queued RX packet from each connection */
list_for_each_entry ( tcp, &tcp_conns, list ) {
list_for_each_entry_reverse ( iobuf, &tcp->rx_queue, list ) {
/* Remove packet from queue */
list_del ( &iobuf->list );
free_iob ( iobuf );
/* Report discard */
discarded++;
break;
}
}
return discarded;
}
/** TCP cache discarder */
struct cache_discarder tcp_discarder __cache_discarder ( CACHE_NORMAL ) = {
.discard = tcp_discard,
};
/**
* Find first TCP connection that has not yet been closed
*
* @ret tcp First unclosed connection, or NULL
*/
static struct tcp_connection * tcp_first_unclosed ( void ) {
struct tcp_connection *tcp;
/* Find first connection which has not yet been closed */
list_for_each_entry ( tcp, &tcp_conns, list ) {
if ( ! ( tcp->flags & TCP_XFER_CLOSED ) )
return tcp;
}
return NULL;
}
/**
* Find first TCP connection that has not yet finished all operations
*
* @ret tcp First unfinished connection, or NULL
*/
static struct tcp_connection * tcp_first_unfinished ( void ) {
struct tcp_connection *tcp;
/* Find first connection which has not yet closed gracefully,
* or which still has a pending transmission (e.g. to ACK the
* received FIN).
*/
list_for_each_entry ( tcp, &tcp_conns, list ) {
if ( ( ! TCP_CLOSED_GRACEFULLY ( tcp->tcp_state ) ) ||
process_running ( &tcp->process ) ) {
return tcp;
}
}
return NULL;
}
/**
* Shut down all TCP connections
*
*/
static void tcp_shutdown ( int booting __unused ) {
struct tcp_connection *tcp;
unsigned long start;
unsigned long elapsed;
/* Initiate a graceful close of all connections, allowing for
* the fact that the connection list may change as we do so.
*/
while ( ( tcp = tcp_first_unclosed() ) ) {
DBGC ( tcp, "TCP %p closing for shutdown\n", tcp );
tcp_close ( tcp, -ECANCELED );
}
/* Wait for all connections to finish closing gracefully */
start = currticks();
while ( ( tcp = tcp_first_unfinished() ) &&
( ( elapsed = ( currticks() - start ) ) < TCP_FINISH_TIMEOUT )){
step();
}
/* Forcibly close any remaining connections */
while ( ( tcp = list_first_entry ( &tcp_conns, struct tcp_connection,
list ) ) != NULL ) {
tcp->tcp_state = TCP_CLOSED;
tcp_dump_state ( tcp );
tcp_close ( tcp, -ECANCELED );
}
}
/** TCP shutdown function */
struct startup_fn tcp_startup_fn __startup_fn ( STARTUP_LATE ) = {
.shutdown = tcp_shutdown,
};
/***************************************************************************
*
* 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 );
}
/**
* 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->tx_queue );
/* Each enqueued packet is a pending operation */
pending_get ( &tcp->pending_data );
/* Transmit data, if possible */
tcp_xmit ( tcp );
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 IPv4 socket opener */
struct socket_opener tcp_ipv4_socket_opener __socket_opener = {
.semantics = TCP_SOCK_STREAM,
.family = AF_INET,
.open = tcp_open,
};
/** TCP IPv6 socket opener */
struct socket_opener tcp_ipv6_socket_opener __socket_opener = {
.semantics = TCP_SOCK_STREAM,
.family = AF_INET6,
.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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