This code was taken from VPP's src/plugins/linux-cp/ directory, originally by: Signed-off-by: Neale Ranns [email protected] Signed-off-by: Matthew Smith [email protected] Signed-off-by: Jon Loeliger [email protected] Signed-off-by: Pim van Pelt [email protected] Signed-off-by: Neale Ranns [email protected]

See previous work: https://gerrit.fd.io/r/c/vpp/+/30759 (interface mirroring) https://gerrit.fd.io/r/c/vpp/+/31122 (netlink listener)

It's intended to be re-submitted for review as a cleanup/rewrite of the existing Linux CP interface mirror and netlink syncer.

FAQ

Why doesn't the plugin listen to new linux interfaces?

Consider the following two commands:

ip link add link e0 name foo type vlan id 10 protocol 802.1ad
ip link add link foo name bar type vlan id 20

The two effectively create a dot1ad with an outer tag of 10 and an inner tag of 20 (you could also read this as e0.10.20). The foo interface is the untagged VLAN 10 on e0 with ethernet type 0x8aa8, and the bar interface carries any tagged traffic on foo, thus is ethernet type 0x8100 within the e0's ethernet type 0x8aa8 outer frame.

It's easy to listen to netlink messages like these, but their name will in no way be easy to map to a VPP subinterface concept. In VPP, all subinterfaces are numbered on their phy, such as TenGigabitEthernet0/0/0.1000. It is not clear how to map the linux host interface name foo and bar to this numbering scheme in a way that doesn't create collissions.

A second consideration is that these QinQ interfaces can be 802.1ad or 802.1q tagged on the outer. So what happens if after the above, a new foo2 interface is created with protocol 802.1q ? VPP only allows sub interfaces to carry one (1) number.

Rather than applying heuristics and adding bugs, it is not possible to create VPP interfaces via Linux, only the other way around. Create any L3 capable interface or subinterface in VPP, and it'll be created in Linux as well.

Notes

We'll be able to see if VPP changes the interfaces with a bunch of callback functions:

pim@hippo:~/src/vpp$ grep -r VNET.*_FUNCTION src/vnet/interface.h
#define VNET_HW_INTERFACE_ADD_DEL_FUNCTION(f)                   \
#define VNET_HW_INTERFACE_LINK_UP_DOWN_FUNCTION(f)              \
#define VNET_SW_INTERFACE_MTU_CHANGE_FUNCTION(f)                \
#define VNET_SW_INTERFACE_ADD_DEL_FUNCTION(f)                   \
#define VNET_SW_INTERFACE_ADMIN_UP_DOWN_FUNCTION(f)             \

Super useful for MTU changes, admin up/dn and link up/dn changes (to copy these into the TAP and the host interface).

Notably missing here is some form of SW_INTERFACE_L2_L3_CHANGE_FUNCTION(f) which would be useful to remove an LCP if the iface goes into L2 mode, and (re)create an LCP if the iface goes into L3 mode.

It will also be very useful to create an IP_ADDRESS_ADD_DEL_FUNCTION(f) of sorts so that we know when VPP sets an IPv4/IPv6 address (so that we can copy this into the host interface).

LCP names

The maximum length of an interface name in Linux is 15 characters. I'd love to be able to make interfaces like you might find in DANOS: dp0p6s0f1 but this is already 9 characters, and the slot and PCI bus can be double digits. The Linux idiom is to make a link as a child of another link, like: ip link add link eth0 name eth0.1234 type vlan id 1234 proto dot1q

You can also make QinQ interfaces in the same way: ip link add link eth0.1234 name eth0.1234.1000 type vlan id 1234

This last interface will have 5 characters .1000 for the inner, 5 characters .1234 for the outer, leaving 5 characters for the full interface name.

I can see two ways out of this:

1. Make main interfaces very short For example et0 for DPDK interfaces, be1 for BondEthernet, lo4 for Loopback interfaces, and possibly bvi5 for BridgeVirtualInterface (these are the L3 interfaces in an L2 bridge-group). In such a world, we can create any number of subinterfaces in a Linux idiomatic way, like et192.1234.1000 but BVIs will be limited to 100 interfaces and ethernet's to 1000. This seems okay, but does paint us in the corner possibly in the future.

2. Strictly follow VPP's naming VPP will always have exactly one (integer) numbered subinterface, like TenGigabitEthernet3/0/2.1234567890 and the function of such a subint can take multiple forms (dot1q, dot1ad, double-tagged, etc). In this world, we can create interface names in Linux that map very cleanly to VPP's subinterfaces, and we can also auto-create subinterfaces by reading a netlink link message, provided the chosen name follows an . pattern, and maps to a known LCP.

Here's how I can see the latter approach working:

Creation of VPP sub-interface directly creates the corresponding LCP device name e0.1234. Creating a more complex dot1q/dot1q or dot1ad or dot1ad/dot1q sub-interface will again create a mirror LCP with device name e0.1235, reusing the sub-int number from VPP directly. That's good.

Reading a netlink new link message is a bit trickier, but here's what I propose:

• On a physical interface e0, one can create a dot1q or dot1ad link with a linux name of e0.1234; in such a case, a corresponding sub-int will be made by the plugin in VPP.
• On a linux interface e0.1234, only a dot1q interface can be made, but its name is required to follow the . pattern, and if so, the plugin will make a VPP interface corresponding to that number, but considering we already know if the parent is either a .1q interface or a .1ad interface, the correct type of VPP interface can be selected.
  • If an interface name is not valid, the plugin will destroy the link and log an error.
  • Because we'll want to use one TAP interface per LCP (see rationale above), the plugin will have to destroy the link and recreate it as a new interface with the same name, but not as a child of the originally requested parent interface.

With this, we can:

1. Create a dot1q subinterface on e0: ip link add link e0 name e0.1234 type vlan id 1234
2. Create a dot1q outer, dot1q inner subinterface on e0: ip link add link e0.1234 name e0.1235 type vlan id 1000
3. Create a dot1ad subinterface on e0: ip link add link e0 name e0.1236 type vlan id 2345 proto 802.1ad
4. Create a dot1ad outer, dot1q inner subinterface on e0: ip link add link e0.1236 name e0.1237 type vlan id 2345 proto 802.1q
5. Fail to create an interface which has an invalid name: ip link add link e0.1234 name e0.1234.2345 type vlan id 2345 proto 802.1q (this interface will be destroyed by the plugin and an error logged)

For each of these interface creations, the user is asking them to be created as a child of an existing interface (either e0 or e0.1234), but the plugin will destroy that interface again, and recreate it as a top-level interface int the namespace, with an accompanying tap interface. So in this plugin, every LCP has exactly one TAP, and that TAP interface is never a sub-int.