195.5.2.2 Tracepoint TCP

195.5.2.2 Tracepoint TCP

Table 23

Structure of the TCP trace record

IP address of remote host

socket state after

socket state after event processing

connection state before

connection state before processing the event; see Table 27

actual chars in buffer

if the location is TA_INPUT or TA_DROP, this items refers to the receive buffer, otherwise to the send buffer

allocated memory

total memory allocated by mbufs and clusters
(1 mbuf=256 byte, 1 clusters=1518 byte)

connection state after

connection state after event processing

retransmit timer

Ticks to retransmit the data starting at

"Seq-Nr: send unacknowledged"

Note: 1 Tick = 0,5 sec.

Ticks to send next data probe

keepalive timer

Ticks to send next keep-alive packet

number retransmissions

rexmit backoff idx

current rexmit interval

current retransmission interval

Seq-Nr: send unackn.

Sequence number send unacknowledged

Seq-Nr: send next

Sequence number send next

max. number of unacknowledged bytes

Seq-Nr: receive next

Sequence number receive next

amount of receive capacity (actually)

advertised rcv window

advertised receive window

Table 24

trace locations and their possible TCP events

attach protocol to socket

detach protocol from socket

bind socket to address

listen for connection

establish connection to peer

accept connection from peer

disconnect from peer

abort (fast DISCONNECT, DETATCH)

TCP-Flags + length of user data in WORDS

TCP-Flags + length of user data in WORDS

the TCP-Flags (see Table 28) of received TCP packet will be saved into the Intel bits 0 - 5 of byte 0 in TCP event,

the length of user data -counted in words- will be saved into the bits 6,7 of byte 0 and bits 0 - 7 of byte 1 (most significant byte)

TCP-Flags + cause for dropping

analogous to TA_INPUT;
the possible values of cause for dropping are listed in Table 25

TA_DROPAFTERACK

TCP-Flags + cause for dropping

analogous to TA_INPUT;
the possible values of cause for dropping are listed in Table 25

TCP-Flags + cause for dropping

analogous to TA_INPUT;
the possible values of cause for dropping are listed in Table 25

Table 25

Reasons for dropping a TCP packet and/or connection

required memory resources not available

creation of new socket failed due to no socket space

unexpected flag received

call of in_pcbconnect failed

unexpected sequence number received

connection already closed

TCP waits for the FIN of communication partner

Table 26

Socket state bits

no file table ref any more

socket connected to a peer

SS_ISCONNECTING

in process of connecting to peer

SS_ISDISCONNECTING

in process of disconnecting

SS_CANTSENDMORE

can’t send more data to peer

can’t receive more data from peer

at mark on input

privileged for broadcast

non-blocking ops

async i/o notify

SS_ISCONFIRMING

deciding to accept connection req

Table 27

TCP FSM state definitions. Per RFC793, September, 1981.

connection closed

listening for connection

active - have sent SYN

TCPS_SYN_RECEIVED

has send and received SYN

TCPS_ESTABLISHED

connection established

TCPS_CLOSE_WAIT

received FIN - waiting for close

TCPS_FIN_WAIT_1

has closed - sent FIN

closed an FIN exchanged - await FIN ACK

had FIN and close - await FIN ACK

TCPS_FIN_WAIT_2

has closed - FIN is acked

quiet wait after close

Table 28

TCP flags and their meaning

Bit nr:¹

"Urgent Pointer"- field is
significant

Acknowledgment field is significant

Reset (Close) the connection

Synchr. sequence numbers; start connection

No more data from sender; connection close

1

numbering in Intel-format (numbers in brackets correspond to network-numbering)

Figure 69

Trace example for trace point TCP

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