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Add script to detect filtered TCP traces, addresses BIT-1119.

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If reading a trace file w/ only TCP control packets, a warning is
emitted to suggest the 'detect_filtered_traces' option if the user
doesn't desire Bro to report missing TCP segments for such a trace file.
This commit is contained in:
Jon Siwek 2014-01-31 17:04:58 -06:00
parent c671491149
commit 0cb2a90da4
7 changed files with 58 additions and 2 deletions
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49
scripts/base/misc/find-filtered-trace.bro Normal file
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##! Discovers trace files that contain TCP traffic consisting only of
##! control packets (e.g. it's been filtered to contain only SYN/FIN/RST
##! packets and no content). On finding such a trace, a warning is
##! emitted that suggests toggling the :bro:see:`detect_filtered_trace`
##! option may be desired if the user does not want Bro to report
##! missing TCP segments.
module FilteredTraceDetection;
export {
## Flag to enable filtered trace file detection and warning message.
global enable: bool = T &redef;
}
global saw_tcp_conn_with_data: bool = F;
global saw_a_tcp_conn: bool = F;
event connection_state_remove(c: connection)
{
if ( ! reading_traces() )
return;
if ( ! enable )
return;
if ( saw_tcp_conn_with_data )
return;
if ( ! is_tcp_port(c$id$orig_p) )
return;
saw_a_tcp_conn = T;
if ( /[Dd]/ in c$history )
saw_tcp_conn_with_data = T;
}
event bro_done()
{
if ( ! enable )
return;
if ( ! saw_a_tcp_conn )
return;
if ( ! saw_tcp_conn_with_data )
Reporter::warning("The analyzed trace file was determined to contain only TCP control packets, which may indicate it's been pre-filtered. By default, Bro reports the missing segments for this type of trace, but the 'detect_filtered_trace' option may be toggled if that's not desired.");
}