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Npcap should perhaps not report a zero RSSI value #1528

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guyharris opened this Issue Mar 26, 2019 · 2 comments

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guyharris commented Mar 26, 2019

It appears that, for some devices, the signal strength is reported as 0 dBm; this probably means that the device doesn't report the signal strength, not that the signal strength was 1 milliwatt.

See, for example, this ask.wireshark.org question.

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dmiller-nmap commented Mar 28, 2019

Raw WiFi capture support is problematic right now for a few reasons, but I'm hopeful we'll be able to improve things.

First, Npcap makes use of the Native 802.11 Wireless API which is deprecated in Windows 10. Newer drivers will be using the WLAN Device Driver Interface (WDI), and I haven't figured out how a NDIS filter driver like ours would be able to get similar information for packets under that API.

Also, support is dependent on the device driver delivering accurate information. This can break down a number of ways:

  1. The hardware may not make some information available to the driver.
  2. The driver may not make the information available to higher layers.
  3. The driver may use a different API (WDI, Native 802.11, etc.) than we expect to make the information available.
  4. The driver may provide incorrect information (zero, uninitialized, stale, etc) to higher layers.

The change I just pushed ought to prevent us from interpreting uninitialized or zeroed memory as out-of-band media-specific information, but there's no guarantees that the underlying drivers are behaving correctly.

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guyharris commented Apr 5, 2019

Raw WiFi capture support is problematic right now for a few reasons

It appears to be even more problematic with WDI. To quote "Features not carried over in WDI":

The following features are available in the previous Native WLAN driver model, but are not available in WDI.

...

  • Netmon
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