detect: investigation on single-pkt flows inspection (5180) - v3#14747
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jufajardini wants to merge 3 commits intoOISF:mainfrom
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detect: investigation on single-pkt flows inspection (5180) - v3#14747jufajardini wants to merge 3 commits intoOISF:mainfrom
jufajardini wants to merge 3 commits intoOISF:mainfrom
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During initialization, the engine reports how many rules were loaded, as well as which types. Pkt-only or stream-pkt rules would cause a "hole" in such stats, as they're not counted.
Commit 497394e removed inspection of app-proto txs for packets without an established TCP connection. But this meant that the first packet seen in a session pick mid-stream could go without inspection (previous bug 5510 seemed to point towards this behavior, too). If a flow has more packets, the stream will be inspected as part of the upcoming packets and this would go unnoticed. In a single-packet flow, however, the inspection for the packed would be skipped. Although this might not affect alerts -- as they could be processed as part of the flow timeout logic, the actual traffic could be evaded in IPS, in case of a drop rule. From the above, the most visible scenario is when there is only one packet on the flow, as then the engine doesn't have "more time" to pick-up real-packets to inspect for that given flow. But certain tests show that this can also happen for more than one packet scenarios: there will be one less drop event, or traffic from a packet that should have been already dropped will be logged. This led to the possibility of a real packet not being blocked, in IPS, or matched against rules, as the corresponding portion of the stream was only inspected later, as part of the stream/flow-timeout logic. To ensure that we correctly flag the first packet seen for a given mid-stream session, we must check for the session state *after* we have dealt with TCP flags and state. Related to Bug OISF#5510 As part of Bug OISF#5180
jufajardini
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Feb 4, 2026
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| if (ssn->state >= TCP_ESTABLISHED) { | ||
| p->flags |= PKT_STREAM_EST; | ||
| } |
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Should this change go in a separate commit?
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Yeah I think that is cleaner.
Codecov Report❌ Patch coverage is Additional details and impacted files@@ Coverage Diff @@
## main #14747 +/- ##
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- Coverage 82.17% 82.16% -0.01%
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Files 1008 1008
Lines 263938 263952 +14
==========================================
+ Hits 216878 216883 +5
- Misses 47060 47069 +9
Flags with carried forward coverage won't be shown. Click here to find out more. 🚀 New features to boost your workflow:
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Information: QA ran without warnings. Pipeline = 29408 |
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Passed my QA. Ran this PR with SV PR OISF/suricata-verify#2901. Local pipeline 6175, run 1203. |
victorjulien
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Feb 4, 2026
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I think this looks good. Can you do a non-draft PR with the commit split you suggested?
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Followed by: #14752 |
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Link to ticket: https://redmine.openinfosecfoundation.org/issues/
https://redmine.openinfosecfoundation.org/issues/5180
Previous PR: #14704
Describe changes:
To consider:
I assumed that, with this approach, we shouldn't need to flag the packet stream as established in the TCP fast open scenario (done here
suricata/src/stream-tcp.c
Line 1467 in c1d6958
pcap_cnt 3, instead ofpcap_cnt 1Could this be related to this being non-IPS mode?For now, then, I have not removed that bit. But this might need further investigation -- for this patch, or for a follow-up work?
Provide values to any of the below to override the defaults.
SV_BRANCH=OISF/suricata-verify#2901