On Tue, Jan 7, 2020 at 8:25 PM Ben Pfaff <[email protected]> wrote: > > On Tue, Jan 07, 2020 at 09:15:26AM +0100, Dumitru Ceara wrote: > > On Mon, Jan 6, 2020 at 11:11 PM Ben Pfaff <[email protected]> wrote: > > > > > > On Fri, Jan 03, 2020 at 05:27:31PM +0100, Dumitru Ceara wrote: > > > > When ofproto/trace detects a recirc action it resumes execution at the > > > > specified next table. However, if the ct action performs SNAT/DNAT, > > > > e.g., ct(commit,nat(src=1.1.1.1:4000),table=42), the src/dst IPs and > > > > ports in the oftrace_recirc_node->flow field are not updated. This leads > > > > to misleading outputs from ofproto/trace as real packets would actually > > > > first get NATed and might match different flows when recirculated. > > > > > > > > Assume the first IP/port from the NAT src/dst action will be used by > > > > conntrack for the translation and update the oftrace_recirc_node->flow > > > > accordingly. This is not entirely correct as conntrack might choose a > > > > different IP/port but the result is more realistic than before. > > > > > > > > This fix covers new connections. However, for reply traffic that > > > > executes > > > > actions of the form ct(nat, table=42) we still don't update the flow as > > > > we don't have any information about conntrack state when tracing. > > > > > > > > Signed-off-by: Dumitru Ceara <[email protected]> > > > > > > This is a great idea. > > > > > > I have an idea for further improvement. Currently this patch is quiet: > > > it doesn't say what's going on. It would be better if it said that it > > > was replacing the source and/or destination addresses, and by what and > > > why. I think that would be easiest done in ofproto_trace() itself near > > > the existing code that does it already for ct_state. I think we could > > > just save the ofn pointer in the recirc node and move the replacement > > > code to ofproto_trace(). > > > > > > > Thanks for the review! Sounds better indeed. I'll respin the patch > > with your enhancement.
Hi Ben, I sent v2 including your suggestions: https://patchwork.ozlabs.org/patch/1220907/ > > > > As follow up work I was thinking it would be nice to be able to cover > > the other types of nat recirculation too, e.g., ct(nat, table=42), and > > allow the user to specify the outcome of the nat operation in a > > similar way as we do for conntrack with --ct-next. However, I'm not > > sure what the best way is to do that.. I'm open to suggestions. > > > > Could we enhance ofproto/trace such that the user can specify a > > conntrack database in a predefined format? For example, the output of > > "conntrack -L -o xml". Or would that become confusing? > > I have two ideas. > > First, OVS is already able to read and dump the actual connection > tracking database in use (see e.g. the dpctl/dump-conntrack command in > ovs-vswitchd(8)). ofproto/trace could consult this. It would want to > dump out the entry that was found (or not found) while doing it. This is nice, thanks for pointing it out. So I guess when troubleshooting packet forwarding we could insert conntrack entries to guide ofproto/trace. > > Second, I guess we could have an option whose argument is a set of > actions to execute, which could update the source and destination, etc. > That's very general purpose! > I also like this second option because it decouples tracing from the underlying datapath conntrack implementation. I'll give it more thought and follow up when I have something working. Regards, Dumitru _______________________________________________ dev mailing list [email protected] https://mail.openvswitch.org/mailman/listinfo/ovs-dev
