stream: RST no longer acks all data #12300
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Since forever (1578ef1) a valid RST would update the internal `last_ack` representation to include all unack'd data. This was originally done to make sure the unACK'd data was inspected/processed at flow timeout. It was observed however, that if GAPs existed in this unACK'd data, a GAP could be reported in the stats and a GAP event would be raised. This doesn't make sense, as missing segments in the unACK'd part of the stream are completely normal. Segments simply do not all arrive in order. It turns out that the original behavior of updating `last_ack` to include all unACK'd data is no longer needed. For raw stream inspection, the detection engine will already include the unACK'd data on flow end. For app-layer updates the unACK'd data is often harmful, as the data often has GAPs. Parser like the http parser would report these GAPs and could also get confused about the post-GAP data being a new transaction including a file. This lead to many reported errors and fantom txs and files. Since the GAP detection uses `last_ack` to determine GAPs, not moving `last_ack` addresses the GAP false positives. Ticket: OISF#7422.
Codecov ReportAttention: Patch coverage is
Additional details and impacted files@@ Coverage Diff @@
## master #12300 +/- ##
==========================================
- Coverage 83.22% 79.55% -3.68%
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Files 912 912
Lines 257311 257427 +116
==========================================
- Hits 214154 204788 -9366
- Misses 43157 52639 +9482
Flags with carried forward coverage won't be shown. Click here to find out more. |
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Information: ERROR: QA failed on SURI_TLPW1_files_sha256.
Pipeline 23981 |
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replaced by #12341 |
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Since forever (1578ef1) a valid RST would update the internal
last_ackrepresentation to include all unack'd data. This was originally done to make sure the unACK'd data was inspected/processed at flow timeout.It was observed however, that if GAPs existed in this unACK'd data, a GAP could be reported in the stats and a GAP event would be raised. This doesn't make sense, as missing segments in the unACK'd part of the stream are completely normal. Segments simply do not all arrive in order.
It turns out that the original behavior of updating
last_ackto include all unACK'd data is no longer needed.For raw stream inspection, the detection engine will already include the unACK'd data on flow end.
For app-layer updates the unACK'd data is often harmful, as the data often has GAPs. Parser like the http parser would report these GAPs and could also get confused about the post-GAP data being a new transaction including a file. This lead to many reported errors and fantom txs and files.
Since the GAP detection uses
last_ackto determine GAPs, not movinglast_ackaddresses the GAP false positives.Ticket: #7422.
Rebases #12186.
SV_BRANCH=OISF/suricata-verify#2154
https://redmine.openinfosecfoundation.org/issues/7422