diff options
Diffstat (limited to 'contrib/syslinux-4.02/gpxe/src/net/tcp.c')
| -rw-r--r-- | contrib/syslinux-4.02/gpxe/src/net/tcp.c | 1156 |
1 files changed, 1156 insertions, 0 deletions
diff --git a/contrib/syslinux-4.02/gpxe/src/net/tcp.c b/contrib/syslinux-4.02/gpxe/src/net/tcp.c new file mode 100644 index 0000000..a061962 --- /dev/null +++ b/contrib/syslinux-4.02/gpxe/src/net/tcp.c @@ -0,0 +1,1156 @@ +#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, +}; + |