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[tcp][RFC] Cleanup tcp_close()
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The complexity of tcp_close() makes the TCP closing control
hard to maintain.
This patch try to solve it by separating tcp_terminate() and
tcp_dataxfer_close() from tcp_close().

Use tcp_terminate() to immediately free all tcp resources, and
close data transfer interface by calling tcp_dataxfer_close().

tcp_close() now simply bing TCP connection to closing state.
Which makes it safe to call in tcp_rx_fin().

tcp_dataxfer_close() is separated due to early close timing of
tcp_xfer_close() which is called by upper-layer to indicate no
more data to send or receive.
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@cooldavid
cooldavid committed Jul 30, 2010
1 parent cad4a4a commit 8aa458e
Showing 1 changed file with 54 additions and 50 deletions.
104 changes: 54 additions & 50 deletions src/net/tcp.c
View file
Expand Up @@ -298,52 +298,63 @@ static int tcp_open ( struct interface *xfer, struct sockaddr *peer,
}

/**
* Close TCP connection
* Close data transfer interface
*
* @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.
* Closes the data transfer interface.
*/
static void tcp_close ( struct tcp_connection *tcp, int rc ) {
struct io_buffer *iobuf;
struct io_buffer *tmp;

/* Close data transfer interface */
static void tcp_dataxfer_close ( struct tcp_connection *tcp, int rc ) {
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 ) ) ) {
/**
* Terminate TCP connection and free all resources
*
* @v tcp TCP connection
* @v rc Reason for close
*
* Closes the data transfer interface, and free all resources of current TCP
* connection.
*/
static void tcp_terminate ( struct tcp_connection *tcp, int rc ) {
struct io_buffer *iobuf;
struct io_buffer *tmp;

/* Transition to CLOSED for the sake of debugging messages */
tcp->tcp_state = TCP_CLOSED;
tcp_dump_state ( tcp );
/* Close data transfer interface */
tcp_dataxfer_close(tcp, rc);

/* Free any unprocessed I/O buffers */
list_for_each_entry_safe ( iobuf, tmp, &tcp->rx_queue, list ) {
list_del ( &iobuf->list );
free_iob ( iobuf );
}
/* 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->tx_queue, list ) {
list_del ( &iobuf->list );
free_iob ( iobuf );
}
/* Free any unprocessed I/O buffers */
list_for_each_entry_safe ( iobuf, tmp, &tcp->rx_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;
/* Free any unsent I/O buffers */
list_for_each_entry_safe ( iobuf, tmp, &tcp->tx_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 );
}

/**
* Bring TCP connection to closing state
*
* @v tcp TCP connection
*/
static void tcp_close ( struct tcp_connection *tcp ) {
/* 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.
Expand Down Expand Up @@ -586,9 +597,7 @@ static void tcp_expired ( struct retry_timer *timer, int 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 );
tcp_terminate ( tcp, -ETIMEDOUT );
} else {
/* Otherwise, retransmit the packet */
tcp_xmit ( tcp );
Expand All @@ -611,9 +620,7 @@ static void tcp_wait_expired ( struct retry_timer *timer, int over __unused ) {
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 );
tcp_terminate ( tcp, 0 );
}

/**
Expand Down Expand Up @@ -910,6 +917,9 @@ static int tcp_rx_fin ( struct tcp_connection *tcp, uint32_t seq ) {
DBGC ( tcp, "TCP %p passive closing.\n", tcp );
}

/* Bring TCP connection to closing state */
tcp_close ( tcp );

return 0;
}

Expand All @@ -936,9 +946,7 @@ static int tcp_rx_rst ( struct tcp_connection *tcp, uint32_t seq ) {
}

/* Abort connection */
tcp->tcp_state = TCP_CLOSED;
tcp_dump_state ( tcp );
tcp_close ( tcp, -ECONNRESET );
tcp_terminate ( tcp, -ECONNRESET );

DBGC ( tcp, "TCP %p connection reset by peer\n", tcp );
return -ECONNRESET;
Expand Down Expand Up @@ -1048,11 +1056,6 @@ static void tcp_process_rx_queue ( struct tcp_connection *tcp ) {
seq, strerror ( rc ) );
}
}

if ( tcp->tcp_state & TCP_STATE_RCVD ( TCP_FIN ) ) {
/* Close connection */
tcp_close ( tcp, 0 );
}
}

/**
Expand Down Expand Up @@ -1187,9 +1190,7 @@ static int tcp_rx ( struct io_buffer *iobuf,
* Set up timer to expire and cause the connection to be freed.
*/
if ( tcp->tcp_state == TCP_PASV_CLOSED ) {
tcp->tcp_state = TCP_CLOSED;
tcp_dump_state ( tcp );
tcp_close ( tcp, 0 );
tcp_terminate ( tcp, 0 );
} else if ( TCP_CLOSED_GRACEFULLY ( tcp->tcp_state ) ) {
stop_timer ( &tcp->wait );
start_timer_fixed ( &tcp->wait, ( 2 * TCP_MSL ) );
Expand Down Expand Up @@ -1254,7 +1255,10 @@ struct cache_discarder tcp_cache_discarder __cache_discarder = {
static void tcp_xfer_close ( struct tcp_connection *tcp, int rc ) {

/* Close data transfer interface */
tcp_close ( tcp, rc );
tcp_dataxfer_close ( tcp, rc );

/* Bring TCP connection to closing state */
tcp_close ( tcp );

/* Transmit FIN, if possible */
tcp_xmit ( tcp );
Expand Down

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