nmap / nmap/npcap

Npcap 1.50 receives ICMP Protocol Unreachable messages when sending ICMP Echo Request with Nping

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Dominant language
C
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Description

This was reported on nmap-dev mailing list: https://seclists.org/nmap-dev/2021/q2/12

My response:

The extra packets I believe are "protocol unreachable" errors that we had previously been stripping out within Npcap. We had removed the code that stripped them from the packet stream in the interest of transparency and simplicity, so the solution is likely to restore that code, but I will investigate other ways as well.

Contributor guide

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the linked nmap-dev report and trace Npcap's packet-stream handling for ICMP Echo Requests sent by Nping. Compare the current behavior with the earlier handling of protocol-unreachable packets described in the issue. Done means the reported extra ICMP protocol-unreachable messages are no longer exposed during this operation, with the chosen handling covered by relevant verification.

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
Mostly clear
Newbie friendliness
35/100

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