Is there a preferred way to get the VXLAN port number?

I was wondering if someone would happen to know if there is already a preferred way to get the VXLAN port number for things such as configuring a device to recognize a VXLAN frame on receive for parsing purposes?

I just wanted to check to make sure I hadn't missed something before submitting a patch that would export a simple function for supplying the vxlan_port value.

Thanks,

Alex

There isn't a good way to do this at the moment. One thing that would be nice though is if we can make this as generic as possible to different tunneling formats that might need to be configured in this way rather than specific to VXLAN.

Another area think about is how best to supply the information to GRO/RPS to do the software version of these offloads.

The problem is what I am looking for is very specific to VXLAN. I need the port number so I can tell the hardware where to expect the VXLAN frames to be bound to so that the hardware will recognize them and parse them correctly.

In the case of GRO/RPS the situation is somewhat reversed. You have a packet with a given port number and you need to offload it. In that case you can probably do a socket search to determine which offload to use and have those offloads associated with the socket via something like the encap_rcv pointer that exists in the udp socket.

The main think I want to do is keep this simple since I would prefer to not build up any infrastructure that will just get in the way. My thought for now is to just export a function to allow drivers to fetch the port number of VXLAN. The only downside is that it forces the VXLAN module to load if a driver comes up with offload support, similar to how we have been loading the 8021q module for many of the drivers that support VLAN offloads. Hopefully if the fixed port number approach wins out we can simplify things by replacing the function call with a static define.

Thanks,

Alex

[email protected] wrote on 03/27/2013 02:32:59 PM:

I guess you mean you need to find it within the kernel.

I think whether or not it remains a single port for the machine,
it would be just silly to make it a fixed port, period. Virtually any service allows an administrator to specify an alternate port to run a service on.
I think one of the primary reasons is that you may want to run
more than one instance on the same host (e.g., a sandbox installation alongside a production installation) -- a capability not there now, even though you can specify an alternate port now.
But if for whatever reason an adminstrator cares that it uses
a particular port number, even in a single instance, there is no technical reason to disallow it. It'd be bad to assume all VXLAN must be on the particular port, and equally bad to assume all traffic for that port is VXLAN (esp. on a host that is not using VXLAN at all, but very well may want to use a lot of ports, including 8472).

I think it ought to be fully general -- different devices may
use different ports and one device may use multiple listeners on different ports (to split flows for security, load balancing, or whatever).
I'd make it a per-device function interface that gives you a port
list
for that device (e.g., an array and length or count). Right now, all devices
would return the single module parameter value, but in the future those ought
to be capable of being entirely distinct lists of ports.

                                                                +-DLS

Agreed, the likelihood of a single port winning in the foreseeable future seems low and not really consistent with the usage of other L4 ports. Even settling on a single tunneling protocol is unlikely to happen, so I don't think this problem is specific to VXLAN. From a layering perspective, it also seems better to have the protocol implementation tell the driver what to use rather than inferring it the other way around.

As far as GRO/RPS, we really want to do this as early in the processing path as possible and not wait until the socket lookup since the more work we do first, the less the benefit. I think the position in the stack for both the hardware and software versions are very analogous.

There are two views of the world. One view is that the UDP port number should be a fixed assigned number by IANA, and since VXLAN looks exactly like Cisco LISP, that is what most people use. Others like DOVE seem to want to use lots of values.

[email protected] wrote on 03/27/2013 01:52:54 PM:

the

To answer your question, though, the current vxlan can only listen
on one port per host, supplied with by a module parameter. You can find what port it's listening on by:

cat /sys/modules/vxlan/parameters/udp_port

[which you can also read with a program, of course].

If multi-port server support is added, that should probably include the port as part of the current "ip -d link show dev XXX" output, where other per-device parameters are found.

                                                        +-DLS