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Parallelize forward DNS name resolution #1451

dmiller-nmap opened this issue Jan 31, 2019 · 0 comments

Parallelize forward DNS name resolution #1451

dmiller-nmap opened this issue Jan 31, 2019 · 0 comments


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This is a known source of slowness that should have been made a tracking issue long ago.

Nmap has a fast parallel DNS resolver, but it currently only works for PTR requests. For forward lookups (such as a list of domain names provided via -iL), it uses the system's own blocking resolver. We could really speed up scanning if we did these in batches instead, but it will require some re-engineering of how Nmap processes target inputs:

  • Currently, name resolution is done in the various subclasses of NetBlock in This is to handle cases like (scan the /24 CIDR block that contains the address for "").
  • We'll likely need to implement a different intermediate class that takes target specifications and returns a stream/list/queue of net blocks.
  • We need to extend the parallel DNS resolver in to handle different request types. This functionality could be useful in other areas of Nmap, too, but don't worry about that yet.
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