nmap / nmap/npcap

PCAP_OPENFLAG_NOCAPTURE_LOCAL behaviour

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Dominant language
C
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Description

Let's say we have 2 pcap_t handles A1 and A2 for the same adapter A.

In WinPCAP:
Packets tx on A1 are also rx on both A1 and A2. If we open A1 with flag PCAP_OPENFLAG_NOCAPTURE_LOCAL, the packets tx on A1 will not be rx on A1, but will still be rx on A2.

I see similar behavour with npcap v0.9990.

However, a user of my app who has npcap v1.10 reports a behaviour where it looks like the packets tx on A1 (opened with PCAP_OPENFLAG_NOCAPTURE_LOCAL flag) are not rx on A2.

I don't see anything in the npcap changelog that suggests a change in this behaviour since v0.9990.

Please clarify on the npcap behaviour and if there is any change across versions.

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Research direction

No source files or tests are named. Start by locating the handling of PCAP_OPENFLAG_NOCAPTURE_LOCAL, then compare behavior with two handles on the same adapter across npcap v0.9990 and v1.10. Done means the version-specific behavior is reproduced and clearly documented.

Written by the indexing model from the issue text.

Assessment

Tech stack
c
Domain
networking
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
25/100

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