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

[David Miller <davem@davemloft.net>]

From: Tom Herbert <tom@quantonium.net>
Date: Mon, 30 Oct 2017 14:16:00 -0700

> RFC 8200 (IPv6) defines Hop-by-Hop options and Destination options
> extension headers. Both of these carry a list of TLVs which is
> only limited by the maximum length of the extension header (2048
> bytes). By the spec a host must process all the TLVs in these
> options, however these could be used as a fairly obvious
> denial of service attack. I think this could in fact be
> a significant DOS vector on the Internet, one mitigating
> factor might be that many FWs drop all packets with EH (and
> obviously this is only IPv6) so an Internet wide attack might not
> be so effective (yet!).
 ...
> This patch adds configurable limits to Destination and Hop-by-Hop
> options. There are three limits that may be set:
>   - Limit the number of options in a Hop-by-Hop or Destination options
>     extension header.
>   - Limit the byte length of a Hop-by-Hop or Destination options
>     extension header.
>   - Disallow unrecognized options in a Hop-by-Hop or Destination
>     options extension header.
> 
> The limits are set in corresponding sysctls:
> 
>   ipv6.sysctl.max_dst_opts_cnt
>   ipv6.sysctl.max_hbh_opts_cnt
>   ipv6.sysctl.max_dst_opts_len
>   ipv6.sysctl.max_hbh_opts_len
 ...
> Signed-off-by: Tom Herbert <tom@quantonium.net>

Applied to net-next, let's see how this goes.

Thanks.