Proposed patch for Port Randomization modifications according to RFC6056

[John Baldwin]

On Wednesday, January 26, 2011 6:28:07 am Ivo Vachkov wrote:
> Hello,
> 
> I would like to propose a patch (against FreeBSD RELENG_8) to extend
> the port randomization support in FreeBSD, according to RFC6056
> (https://www.rfc-editor.org/rfc/rfc6056.txt)
> 
> Currently the patch implements:
> - Algorithm 1 (default in FreeBSD 8)
> - Algorithm 2
> - Algorithm 5
> from the aforementioned RFC6056.
> 
> Any of those algorithms can be chosen with the sysctl variable
> net.inet.ip.portrange.rfc6056_algorithm.
> 
> I deliberately skipped Algorithm 3 and Algorithm 4, because I believe
> usage of cryptographic hash functions will introduce unnecessary
> latency in vital network operations. However, in case of expressed
> interest, I will be glad to add those too.
> 
> I would like to ask what is the proper way to validate the sysctl
> input in order to accept only a specific values? In my case only '1',
> '2' and '5'.

Use a SYSCTL_PROC and write your own handler that does a sanity check on the
value set by userland and returns EINVAL if the value is not correct.

-- 
John Baldwin