Re: [PATCH] Make hmac algorithm selection for cookie generation dynamic

From: Neil Horman <nhorman@tuxdriver.com>
Date: Fri, 19 Oct 2012 11:52:06 -0400

Currently sctp allows for the optional use of md5 of sha1 hmac algorithms to
generate cookie values when establishing new connections via two build time
config options.  Theres no real reason to make this a static selection.  We can
add a sysctl that allows for the dynamic selection of these algorithms at run
time, with the default value determined by the corresponding crypto library
config options.  It saves us two needless configuration settings and enables the
freedom for administrators to select which algorithm a particular system uses.
This comes in handy when, for example running a system in FIPS mode, where use
of md5 is disallowed, but SHA1 is permitted.

Note: This new sysctl has no corresponding socket option to select the cookie
hmac algorithm.  I chose not to implement that intentionally, as RFC 6458
contains no option for this value, and I opted not to pollute the socket option
namespace.

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>

Neil, please use appropriate subject prefixes in your patch
submissions.  In this case "sctp: " would have been appropriate.

Vlad, this patch looks fine to me, but I'd like you to review
it too before I apply it.

Thanks.