netdev - Re: [PATCH v2 net-next] ipv6: Implement limits on Hop-by-Hop and Destination options

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Message-ID: <CALx6S34O8+aKSmbp5FR6X8uKhdZHijkUQFja_rSdyUDKKm4T1Q@mail.gmail.com>
Date:   Mon, 30 Oct 2017 19:39:33 -0700
From:   Tom Herbert <tom@...bertland.com>
To:     David Miller <davem@...emloft.net>
Cc:     Tom Herbert <tom@...ntonium.net>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Rohit Seth <rohit@...ntonium.net>
Subject: Re: [PATCH v2 net-next] ipv6: Implement limits on Hop-by-Hop and
 Destination options

On Mon, Oct 30, 2017 at 7:10 PM, David Miller <davem@...emloft.net> wrote:
> From: Tom Herbert <tom@...ntonium.net>
> Date: Mon, 30 Oct 2017 14:16:00 -0700
>
>> I wrote a quick test program that floods a whole bunch of these
>> packets to a host and sure enough there is substantial time spent
>> in ip6_parse_tlv.
>  ...
>>   25.38%  [kernel]                    [k] __fib6_clean_all
>>   21.63%  [kernel]                    [k] ip6_parse_tlv
>
> Yet the routing code still dominates the cost.

I wouldn't read too much into that. This was unconnected UDP on VMs
and the only purpose here was to demonstrate that ip6_parse_tlv does
get a lot of work with a lot of TLVs. Martin's results listed in the
tested section are probably a more accurate gauge of the impact and
potential to mitigate DOS.

Tom