On Fri, Nov 27, 2015 at 11:23:09PM -1000, Nicholas Bastin wrote: > On Thu, Nov 26, 2015 at 9:44 PM, Chao Hu <[email protected]> wrote: > > > In the ovs-ofctl manual, it’s said in dec_ttl action that “If controller > > ids are not specified, the “packet_in” message will be sent only to the > > controllers having controller id zero which have registered for the invalid > > ttl packets.” In my test, I didn’t specify the controller’s controller-id, > > which should have 0 by default. And it’s said in the code of ofproto.c > > that “OFPC_INVALID_TTL_TO_CONTROLLER is deprecated in OF 1.3”, does it > > mean in OF1.3, “packet_in” on invalid ttl will be sent by default and no > > register is needed? Or such packet-in is not supported in OF1.3? > > > > The spec is unclear. In fact it doesn't even specify what an "invalid TTL" > value would actually be. (The OF 1.1 spec specified "invalid" as 0 or 1 in > a code comment, but future specs seem to have eliminated even that hint of > what values qualifies as "invalid" - I did not then, nor do I now, know why > 1 would be regarded as an invalid TTL value for a packet transiting a > layer-2 switch).
Well, that's a mess. I've filed a bug report EXT-559 with the ONF working group, so perhaps we can at least get "invalid TTL" defined for OF1.6. > > BTW, match on “nw_ttl” seems also not supported in OF1.3. > > > > This was never supported in the spec, but it's possible that OVS supported > that match field at some point (I'm not sure). Yes, OVS has supported matching on the IPv4/v6 TTL/hop limit since Open vSwitch version 1.4. > > How to solve this problem? > > > > You probably can't, at least not in a wholly satisfactory way, without > modifying the source to OVS, or inlining a function (linux tap interface > driver, etc.) in the path on each port. What you really want to do is get > OVS to issue a packet-out of an ICMP Time Exceeded when an incoming packet > reaches a TTL of 0 within the pipeline (modulo the times when you actually > should send a Destination Unreachable reply), but this has all kinds of > nasty edge cases. We're working to make this possible. What kinds of nasty edge cases do you have in mind? I'd like to make everything as correct as possible, obviously. _______________________________________________ discuss mailing list [email protected] http://openvswitch.org/mailman/listinfo/discuss
