On Mon, 6 Feb 2017, Paul Warren wrote:
Please could you try the latest in git?
https://code.blinkace.com/pdw/iftop/commit/35af3cf65f17961d173b31fd3b00166ec...
It looks like the key used for caching DNS lookups was assumed to be in6_addr, but in fact was a larger struct that wrapped the IP address. This means that the comparison looking for NS lookups was effectively ignoring 64 of the 128 bits in the v6 address, leading to very unpredictable results.
That seems to fix it.