Re: NMap Slowness (and Partial Fix) on Ubuntu-Based Distros

[Daniel Miller <bonsaiviking () gmail com>]

Davide,

Thanks for the detailed bug report. This is a known issue that stems from a
Linux kernel bug that was fixed in kernel 3.19. You can read all the gory
details in our own bug tracker here: http://issues.nmap.org/34

Dan

On Wed, Sep 9, 2015 at 11:13 AM, Davide Girardi <davidegirardi () gmail com>
wrote:

> Hi guys,
> This is my first message and is going to be long!
>
>
> --- Quick Summary ---
> Nmap is really slow on Ubuntu-based distros (tested on Ubuntu,
> BackBox, Mint) working at top 163 packets per seconds on a LAN, while
> it's blazing fast on Debian 7.8 and Kali v1 working at top 20803
> packets per second in the same environment. This has been tested with
> nmap 6.47. Physical and virtual machines.
>
> For example, scanning a host with nmap -sS -n <target IP> takes about
> 1.5 - 1.8 seconds on Ubuntu and just 0.10 - 0.15 seconds on Debian.
> Compiling nmap from source gives the same results: Debian is fast
> while Ubuntu is slow.
>
> This behavior seems to be related to how libpcap has been compiled
> (there is the same version on both systems by the way).
>
>
> --- Workaround for Version 6.47 ---
> Compiling nmap with the included libpcap (./configure
> --with-libpcap=included) fixes the slowness on Ubuntu based systems.
> Thanks to d33tah on the #nmap Freenode IRC channel for helping me with
> the hunt :)
>
>
> --- About Version 6.49beta4 ---
> The workaround does not seem to work with the latest beta: it compiles
> fine in BackBox, but has the same performance of the nmap shipped with
> the distro (1.80 seconds to scan a LAN host vs. 0.10 seconds).
> Moreover if I compile the latest beta on Kali v1 my test scan runs in
> about 70 seconds no matter what version of libpcap I use during the
> configuration.
>
>
> I don't want to make this too long to read, so I am available to
> provide any other information or test results.
>
> Thank to everyone for creating and mantaining such a great tool!
> --
>   Davide Girardi
>   <davidegirardi () gmail com>
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