#include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /** @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; /** Flags */ unsigned int flags; /** Data transfer interface */ struct xfer_interface xfer; /** 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; /** Transmit queue */ struct list_head tx_queue; /** Receive queue */ struct list_head rx_queue; /** Retransmission timer */ struct retry_timer timer; /** Shutdown (TIME_WAIT) timer */ struct retry_timer wait; }; /** 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 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; /** 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 ); /* Forward declarations */ static struct xfer_interface_operations tcp_xfer_operations; 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; int i; /* If no port specified, find an available port */ if ( ! port ) { try_port = ( random() % 64512 ) + 1023; for ( i = 0 ; i < 65536 ; ++i ) { 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 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 ); ref_init ( &tcp->refcnt, NULL ); xfer_init ( &tcp->xfer, &tcp_xfer_operations, &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->tx_queue ); INIT_LIST_HEAD ( &tcp->rx_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 */ 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->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 ); } /* 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->tx_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_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 ); } } len += frag_len; max_len -= frag_len; } return len; } /** * Transmit any outstanding data * * @v tcp TCP connection * * 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 ) { 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_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 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_tx_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->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 ( ! ( 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; } /* Clear ACK-pending flag */ tcp->flags &= ~TCP_ACK_PENDING; 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 ); } } /** * 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; } 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; } /* 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; } } /* 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_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 ); 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 ( 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; /* 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 ) ); /* 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 ( seq + seq_len, tcp->rcv_ack ) < 0 ) || ( seq_len == 0 ) ) { free_iob ( iobuf ); return; } /* Add internal header */ tcpqhdr = iob_push ( iobuf, sizeof ( *tcpqhdr ) ); tcpqhdr->seq = seq; 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 ( ! list_empty ( &tcp->rx_queue ) ) { list_for_each_entry ( iobuf, &tcp->rx_queue, list ) break; /* 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 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 seq; uint32_t ack; uint32_t win; unsigned int flags; size_t len; uint32_t seq_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 ) ); 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 ); 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, send RST */ if ( ! tcp ) { tcp_xmit_reset ( tcp, st_src, tcphdr ); rc = -ENOTCONN; goto discard; } /* Update timestamp, if applicable */ if ( options.tsopt && tcp_in_window ( tcp->rcv_ack, seq, seq_len ) ) tcp->ts_recent = ntohl ( options.tsopt->tsval ); /* 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; } } /* 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 ); /* Send out any pending data */ tcp_xmit ( tcp ); /* 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, }; /** * 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 ) { list_del ( &iobuf->list ); free_iob ( iobuf ); discarded++; break; } } return discarded; } /** TCP cache discarder */ struct cache_discarder tcp_cache_discarder __cache_discarder = { .discard = tcp_discard, }; /*************************************************************************** * * 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 ); } /** * 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->tx_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->tx_queue ); /* Transmit data, if possible */ tcp_xmit ( tcp ); 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, };