diff options
Diffstat (limited to 'gpxe/src/net/tcp.c')
| -rw-r--r-- | gpxe/src/net/tcp.c | 67 |
1 files changed, 50 insertions, 17 deletions
diff --git a/gpxe/src/net/tcp.c b/gpxe/src/net/tcp.c index da8e87b4..df87fc14 100644 --- a/gpxe/src/net/tcp.c +++ b/gpxe/src/net/tcp.c @@ -65,6 +65,11 @@ struct tcp_connection { * 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. @@ -394,7 +399,7 @@ static int tcp_xmit ( struct tcp_connection *tcp, int force_send ) { size_t len = 0; size_t seq_len; size_t app_win; - size_t rcv_win; + size_t max_rcv_win; /* If retransmission timer is already running, do nothing */ if ( timer_running ( &tcp->timer ) ) @@ -439,14 +444,16 @@ static int tcp_xmit ( struct tcp_connection *tcp, int force_send ) { /* Fill data payload from transmit queue */ tcp_process_queue ( tcp, len, iobuf, 0 ); - /* Estimate window size */ - rcv_win = ( ( freemem * 3 ) / 4 ); - if ( rcv_win > TCP_MAX_WINDOW_SIZE ) - rcv_win = TCP_MAX_WINDOW_SIZE; + /* 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 ( rcv_win > app_win ) - rcv_win = app_win; - rcv_win &= ~0x03; /* Keep everything dword-aligned */ + 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; @@ -472,7 +479,7 @@ static int tcp_xmit ( struct tcp_connection *tcp, int force_send ) { tcphdr->ack = htonl ( tcp->rcv_ack ); tcphdr->hlen = ( ( payload - iobuf->data ) << 2 ); tcphdr->flags = flags; - tcphdr->win = htons ( rcv_win ); + tcphdr->win = htons ( tcp->rcv_win ); tcphdr->csum = tcpip_chksum ( iobuf->data, iob_len ( iobuf ) ); /* Dump header */ @@ -633,6 +640,21 @@ static void tcp_rx_opts ( struct tcp_connection *tcp, const void *data, } /** + * 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, size_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 @@ -659,7 +681,7 @@ static int tcp_rx_syn ( struct tcp_connection *tcp, uint32_t seq, TCP_STATE_RCVD ( TCP_SYN ) ); /* Acknowledge SYN */ - tcp->rcv_ack++; + tcp_rx_seq ( tcp, 1 ); return 0; } @@ -747,7 +769,8 @@ static int tcp_rx_data ( struct tcp_connection *tcp, uint32_t seq, return rc; /* Acknowledge new data */ - tcp->rcv_ack += len; + tcp_rx_seq ( tcp, len ); + return 0; } @@ -766,7 +789,7 @@ static int tcp_rx_fin ( struct tcp_connection *tcp, uint32_t seq ) { /* Mark FIN as received and acknowledge it */ tcp->tcp_state |= TCP_STATE_RCVD ( TCP_FIN ); - tcp->rcv_ack++; + tcp_rx_seq ( tcp, 1 ); /* Close connection */ tcp_close ( tcp, 0 ); @@ -789,7 +812,7 @@ static int tcp_rx_rst ( struct tcp_connection *tcp, uint32_t seq ) { * ACKed. */ if ( tcp->tcp_state & TCP_STATE_RCVD ( TCP_SYN ) ) { - if ( ( tcp->rcv_ack - seq ) > 0 ) + if ( ( seq - tcp->rcv_ack ) >= tcp->rcv_win ) return 0; } else { if ( ! ( tcp->tcp_state & TCP_STATE_ACKED ( TCP_SYN ) ) ) @@ -850,7 +873,8 @@ static int tcp_rx ( struct io_buffer *iobuf, rc = -EINVAL; goto discard; } - csum = tcpip_continue_chksum ( pshdr_csum, iobuf->data, iob_len ( iobuf )); + 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 ); @@ -922,10 +946,19 @@ static int tcp_rx ( struct io_buffer *iobuf, /* Dump out any state change as a result of the received packet */ tcp_dump_state ( tcp ); - /* Send out any pending data. If peer is expecting an ACK for - * this packet then force sending a reply. + /* 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 ) ); + 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. |