[ovs-dev] [#8024 7/7] Support matching and modifying IP TTL.

[Ben Pfaff]

On Mon, Nov 07, 2011 at 10:33:10AM -0800, Justin Pettit wrote:
> Add support matching the IPv4 TTL and IPv6 hop limit fields.  This
> commit also adds support for modifying the IPv4 TTL.  Modifying the IPv6
> hop limit isn't currently supported, since we don't support modifying
> IPv6 headers.
> 
> We will likely want to change the user-space interface, since basic
> matching and setting the TTL are not generally useful.  We will probably
> want the ability to match on extraordinary events (such as TTL of 0 or
> 1) and a decrement action.
> 
> Feature #8024
> 
> Signed-off-by: Justin Pettit <jpettit at nicira.com>

I didn't really look at the kernel code.

Again, do we really need a new action just to set this field, since it
can be done with NXAST_REG_LOAD?

Er, well I guess it can't be done with NXAST_REG_LOAD.  Why not?

In format_odp_key_attr() I'd expect to use PRIu8 for a uint8_t.
(I see that nw_proto uses PRId8 too but that looks to me like a bug.)

I don't think we need a new MAY_* constant in ofputil_normalize_rule()
since TTL always appears along with tos and frag.

Thanks,

Ben.