base/bif/plugins/Bro_TCP.events.bif.bro

GLOBAL

Namespace:GLOBAL Source File:/scripts/base/bif/plugins/Bro_TCP.events.bif.bro

Summary

Events

connection_EOF: event	Generated at the end of reassembled TCP connections.
connection_SYN_packet: event	Generated for a SYN packet.
connection_attempt: event	Generated for an unsuccessful connection attempt.
connection_established: event	Generated when seeing a SYN-ACK packet from the responder in a TCP handshake.
connection_finished: event	Generated for a TCP connection that finished normally.
connection_first_ACK: event	Generated for the first ACK packet seen for a TCP connection from its originator.
connection_half_finished: event	Generated when one endpoint of a TCP connection attempted to gracefully close the connection, but the other endpoint is in the TCP_INACTIVE state.
connection_partial_close: event	Generated when a previously inactive endpoint attempts to close a TCP connection via a normal FIN handshake or an abort RST sequence.
connection_pending: event	Generated for each still-open TCP connection when Bro terminates.
connection_rejected: event	Generated for a rejected TCP connection.
connection_reset: event	Generated when an endpoint aborted a TCP connection.
contents_file_write_failure: event	Generated when failing to write contents of a TCP stream to a file.
new_connection_contents: event	Generated when reassembly starts for a TCP connection.
partial_connection: event	Generated for a new active TCP connection if Bro did not see the initial handshake.
tcp_contents: event	Generated for each chunk of reassembled TCP payload.
tcp_multiple_checksum_errors: event	Generated if a TCP flow crosses a checksum-error threshold, per ‘C’/’c’ history reporting.
tcp_multiple_retransmissions: event	Generated if a TCP flow crosses a retransmission threshold, per ‘T’/’t’ history reporting.
tcp_multiple_zero_windows: event	Generated if a TCP flow crosses a zero-window threshold, per ‘W’/’w’ history reporting.
tcp_option: event	Generated for each option found in a TCP header.
tcp_packet: event	Generated for every TCP packet.
tcp_rexmit: event	TODO.

Detailed Interface

Events

connection_EOF

Type:event (c: connection, is_orig: bool)

Generated at the end of reassembled TCP connections. The TCP reassembler raised the event once for each endpoint of a connection when it finished reassembling the corresponding side of the communication.

C:The connection. Is_orig:True if the event is raised for the originator side.

See also: connection_SYN_packet, connection_attempt, connection_established, connection_external, connection_finished, connection_first_ACK, connection_half_finished, connection_partial_close, connection_pending, connection_rejected, connection_reset, connection_reused, connection_state_remove, connection_status_update, connection_timeout, scheduled_analyzer_applied, new_connection, new_connection_contents, partial_connection

connection_SYN_packet

Type:event (c: connection, pkt: SYN_packet)

Generated for a SYN packet. Bro raises this event for every SYN packet seen by its TCP analyzer.

C:The connection. Pkt:Information extracted from the SYN packet.

See also: connection_EOF, connection_attempt, connection_established, connection_external, connection_finished, connection_first_ACK, connection_half_finished, connection_partial_close, connection_pending, connection_rejected, connection_reset, connection_reused, connection_state_remove, connection_status_update, connection_timeout, scheduled_analyzer_applied, new_connection, new_connection_contents, partial_connection

Note

This event has quite low-level semantics and can potentially be expensive to generate. It should only be used if one really needs the specific information passed into the handler via the pkt argument. If not, handling one of the other connection_* events is typically the better approach.

connection_attempt

Type:event (c: connection)

Generated for an unsuccessful connection attempt. This event is raised when an originator unsuccessfully attempted to establish a connection. “Unsuccessful” is defined as at least tcp_attempt_delay seconds having elapsed since the originator first sent a connection establishment packet to the destination without seeing a reply.

C:The connection.

See also: connection_EOF, connection_SYN_packet, connection_established, connection_external, connection_finished, connection_first_ACK, connection_half_finished, connection_partial_close, connection_pending, connection_rejected, connection_reset, connection_reused, connection_state_remove, connection_status_update, connection_timeout, scheduled_analyzer_applied, new_connection, new_connection_contents, partial_connection

connection_established

Type:event (c: connection)

Generated when seeing a SYN-ACK packet from the responder in a TCP handshake. An associated SYN packet was not seen from the originator side if its state is not set to TCP_ESTABLISHED. The final ACK of the handshake in response to SYN-ACK may or may not occur later, one way to tell is to check the history field of connection to see if the originator sent an ACK, indicated by ‘A’ in the history string.

C:The connection.

See also: connection_EOF, connection_SYN_packet, connection_attempt, connection_external, connection_finished, connection_first_ACK, connection_half_finished, connection_partial_close, connection_pending, connection_rejected, connection_reset, connection_reused, connection_state_remove, connection_status_update, connection_timeout, scheduled_analyzer_applied, new_connection, new_connection_contents, partial_connection

connection_finished

Type:event (c: connection)

Generated for a TCP connection that finished normally. The event is raised when a regular FIN handshake from both endpoints was observed.

C:The connection.

See also: connection_EOF, connection_SYN_packet, connection_attempt, connection_established, connection_external, connection_first_ACK, connection_half_finished, connection_partial_close, connection_pending, connection_rejected, connection_reset, connection_reused, connection_state_remove, connection_status_update, connection_timeout, scheduled_analyzer_applied, new_connection, new_connection_contents, partial_connection

connection_first_ACK

Type:event (c: connection)

Generated for the first ACK packet seen for a TCP connection from its originator.

C:The connection.

See also: connection_EOF, connection_SYN_packet, connection_attempt, connection_established, connection_external, connection_finished, connection_half_finished, connection_partial_close, connection_pending, connection_rejected, connection_reset, connection_reused, connection_state_remove, connection_status_update, connection_timeout, scheduled_analyzer_applied, new_connection, new_connection_contents, partial_connection

Note

This event has quite low-level semantics and should be used only rarely.

connection_half_finished

Type:event (c: connection)

Generated when one endpoint of a TCP connection attempted to gracefully close the connection, but the other endpoint is in the TCP_INACTIVE state. This can happen due to split routing, in which Bro only sees one side of a connection.

C:The connection.

See also: connection_EOF, connection_SYN_packet, connection_attempt, connection_established, connection_external, connection_finished, connection_first_ACK, connection_partial_close, connection_pending, connection_rejected, connection_reset, connection_reused, connection_state_remove, connection_status_update, connection_timeout, scheduled_analyzer_applied, new_connection, new_connection_contents, partial_connection

connection_partial_close

Type:event (c: connection)

Generated when a previously inactive endpoint attempts to close a TCP connection via a normal FIN handshake or an abort RST sequence. When the endpoint sent one of these packets, Bro waits tcp_partial_close_delay prior to generating the event, to give the other endpoint a chance to close the connection normally.

C:The connection.

See also: connection_EOF, connection_SYN_packet, connection_attempt, connection_established, connection_external, connection_finished, connection_first_ACK, connection_half_finished, connection_pending, connection_rejected, connection_reset, connection_reused, connection_state_remove, connection_status_update, connection_timeout, scheduled_analyzer_applied, new_connection, new_connection_contents, partial_connection

connection_pending

Type:event (c: connection)

Generated for each still-open TCP connection when Bro terminates.

C:The connection.

See also: connection_EOF, connection_SYN_packet, connection_attempt, connection_established, connection_external, connection_finished, connection_first_ACK, connection_half_finished, connection_partial_close, connection_rejected, connection_reset, connection_reused, connection_state_remove, connection_status_update, connection_timeout, scheduled_analyzer_applied, new_connection, new_connection_contents, partial_connection, bro_done

connection_rejected

Type:event (c: connection)

Generated for a rejected TCP connection. This event is raised when an originator attempted to setup a TCP connection but the responder replied with a RST packet denying it.

C:The connection.

See also: connection_EOF, connection_SYN_packet, connection_attempt, connection_established, connection_external, connection_finished, connection_first_ACK, connection_half_finished, connection_partial_close, connection_pending, connection_reset, connection_reused, connection_state_remove, connection_status_update, connection_timeout, scheduled_analyzer_applied, new_connection, new_connection_contents, partial_connection

Note

If the responder does not respond at all, connection_attempt is raised instead. If the responder initially accepts the connection but aborts it later, Bro first generates connection_established and then connection_reset.

connection_reset

Type:event (c: connection)

Generated when an endpoint aborted a TCP connection. The event is raised when one endpoint of an established TCP connection aborted by sending a RST packet.

C:The connection.

See also: connection_EOF, connection_SYN_packet, connection_attempt, connection_established, connection_external, connection_finished, connection_first_ACK, connection_half_finished, connection_partial_close, connection_pending, connection_rejected, connection_reused, connection_state_remove, connection_status_update, connection_timeout, scheduled_analyzer_applied, new_connection, new_connection_contents, partial_connection

contents_file_write_failure

Type:event (c: connection, is_orig: bool, msg: string)

Generated when failing to write contents of a TCP stream to a file.

C:The connection whose contents are being recorded. Is_orig:Which side of the connection encountered a failure to write. Msg:A reason or description for the failure.

See also: set_contents_file, get_contents_file

new_connection_contents

Type:event (c: connection)

Generated when reassembly starts for a TCP connection. This event is raised at the moment when Bro’s TCP analyzer enables stream reassembly for a connection.

C:The connection.

See also: connection_EOF, connection_SYN_packet, connection_attempt, connection_established, connection_external, connection_finished, connection_first_ACK, connection_half_finished, connection_partial_close, connection_pending, connection_rejected, connection_reset, connection_reused, connection_state_remove, connection_status_update, connection_timeout, scheduled_analyzer_applied, new_connection, partial_connection

partial_connection

Type:event (c: connection)

Generated for a new active TCP connection if Bro did not see the initial handshake. This event is raised when Bro has observed traffic from each endpoint, but the activity did not begin with the usual connection establishment.

C:The connection.

See also: connection_EOF, connection_SYN_packet, connection_attempt, connection_established, connection_external, connection_finished, connection_first_ACK, connection_half_finished, connection_partial_close, connection_pending, connection_rejected, connection_reset, connection_reused, connection_state_remove, connection_status_update, connection_timeout, scheduled_analyzer_applied, new_connection, new_connection_contents

tcp_contents

Type:event (c: connection, is_orig: bool, seq: count, contents: string)

Generated for each chunk of reassembled TCP payload. When content delivery is enabled for a TCP connection (via tcp_content_delivery_ports_orig, tcp_content_delivery_ports_resp, tcp_content_deliver_all_orig, tcp_content_deliver_all_resp), this event is raised for each chunk of in-order payload reconstructed from the packet stream. Note that this event is potentially expensive if many connections carry significant amounts of data as then all that data needs to be passed on to the scripting layer.

C:The connection the payload is part of. Is_orig:True if the packet was sent by the connection’s originator. Seq:The sequence number corresponding to the first byte of the payload chunk. Contents:The raw payload, which will be non-empty.

See also: tcp_packet, tcp_option, tcp_rexmit, tcp_content_delivery_ports_orig, tcp_content_delivery_ports_resp, tcp_content_deliver_all_resp, tcp_content_deliver_all_orig

Note

The payload received by this event is the same that is also passed into application-layer protocol analyzers internally. Subsequent invocations of this event for the same connection receive non-overlapping in-order chunks of its TCP payload stream. It is however undefined what size each chunk has; while Bro passes the data on as soon as possible, specifics depend on network-level effects such as latency, acknowledgements, reordering, etc.

tcp_multiple_checksum_errors

Type:event (c: connection, is_orig: bool, threshold: count)

Generated if a TCP flow crosses a checksum-error threshold, per ‘C’/’c’ history reporting.

C:The connection record for the TCP connection. Is_orig:True if the event is raised for the originator side. Threshold:the threshold that was crossed

See also: udp_multiple_checksum_errors, tcp_multiple_zero_windows, tcp_multiple_retransmissions

tcp_multiple_retransmissions

Type:event (c: connection, is_orig: bool, threshold: count)

Generated if a TCP flow crosses a retransmission threshold, per ‘T’/’t’ history reporting.

C:The connection record for the TCP connection. Is_orig:True if the event is raised for the originator side. Threshold:the threshold that was crossed

See also: tcp_multiple_checksum_errors, tcp_multiple_zero_windows

tcp_multiple_zero_windows

Type:event (c: connection, is_orig: bool, threshold: count)

Generated if a TCP flow crosses a zero-window threshold, per ‘W’/’w’ history reporting.

C:The connection record for the TCP connection. Is_orig:True if the event is raised for the originator side. Threshold:the threshold that was crossed

See also: tcp_multiple_checksum_errors, tcp_multiple_retransmissions

tcp_option

Type:event (c: connection, is_orig: bool, opt: count, optlen: count)

Generated for each option found in a TCP header. Like many of the tcp_* events, this is a very low-level event and potentially expensive as it may be raised very often.

C:The connection the packet is part of. Is_orig:True if the packet was sent by the connection’s originator. Opt:The numerical option number, as found in the TCP header. Optlen:The length of the options value.

See also: tcp_packet, tcp_contents, tcp_rexmit

Note

There is currently no way to get the actual option value, if any.

tcp_packet

Type:event (c: connection, is_orig: bool, flags: string, seq: count, ack: count, len: count, payload: string)

Generated for every TCP packet. This is a very low-level and expensive event that should be avoided when at all possible. It’s usually infeasible to handle when processing even medium volumes of traffic in real-time. It’s slightly better than new_packet because it affects only TCP, but not much. That said, if you work from a trace and want to do some packet-level analysis, it may come in handy.

C:The connection the packet is part of. Is_orig:True if the packet was sent by the connection’s originator. Flags:A string with the packet’s TCP flags. In the string, each character corresponds to one set flag, as follows: S -> SYN; F -> FIN; R -> RST; A -> ACK; P -> PUSH. Seq:The packet’s relative TCP sequence number. Ack:If the ACK flag is set for the packet, the packet’s relative ACK number, else zero. Len:The length of the TCP payload, as specified in the packet header. Payload:The raw TCP payload. Note that this may be shorter than len if the packet was not fully captured.

See also: new_packet, packet_contents, tcp_option, tcp_contents, tcp_rexmit

tcp_rexmit

Type:event (c: connection, is_orig: bool, seq: count, len: count, data_in_flight: count, window: count)

TODO.