Refactor Linux Interfaces

This document contains information related to refactor of the linux interfaces (ifplugin) in vpp-agent.

⚠️ NOTE: This document is work in progress!

Motivation

TAP vs VPP

The vpp-agent currently recognizes only a special linux TAP interfaces that are created by VPP.

The current API of linux interface contains defines interface type TAP_TO_VPP for these special VPP-TAP interfaces. This often confuses users and also creates coupling between linux and VPP plugins.

There is no linux interface type for generic TAP and it's not possible to currently manage such interface.

Network Namespaces

The linux interfaces from non-default namespaces can be currently dumped only if the network namespaces is known by the agent. This can come from the desired configuration (NB).

Use Cases

1. Retrieve all supported linux interfaces that already exist in the system.
   • should avoid deleting such interface
2. Allow creating any supported linux interface using the agent.
   • should support at least: loopback, VETH and TAP
3. Allow managing linux TAP interface that is created by the VPP.
   • should wait until it gets created
4. ???

API

Current Linux Interface API

From api/models/linux/interface.proto:

syntax = "proto3";

package linux.interfaces;
// ...
import "models/linux/namespace/namespace.proto";

message Interface {
    enum Type {
        UNDEFINED = 0;
        VETH = 1;
        TAP_TO_VPP = 2;                 /* TAP created by VPP to have the Linux-side further configured */
        LOOPBACK = 3;
    };

    string name = 1;                    /* Logical interface name unique across all configured interfaces (mandatory) */
    Type type = 2;                      /* Interface type (mandatory) */

    linux.namespace.NetNamespace namespace = 3;
    string host_if_name = 4;            /* Name of the interface in the host OS. If not set, the host name
                                           is the same as the interface logical name. */
    bool enabled = 5;
    repeated string ip_addresses = 6;   /* IP addresses in the format <ipAddress>/<ipPrefix> */
    string phys_address = 7;            /* MAC address */
    uint32 mtu = 8;                     /* Maximum transmission unit value */

    oneof link {
        VethLink veth = 20;             /* VETH-specific configuration */
        TapLink tap = 21;               /* TAP_TO_VPP-specific configuration */
    };
};

message VethLink {
    string peer_if_name = 1;        /* Name of the VETH peer, i.e. other end of the linux veth (mandatory for VETH) */

    enum ChecksumOffloading {
        CHKSM_OFFLOAD_DEFAULT = 0;
        CHKSM_OFFLOAD_ENABLED = 1;
        CHKSM_OFFLOAD_DISABLED = 2;
    }
    ChecksumOffloading rx_checksum_offloading = 2; /* checksum offloading - Rx side (enabled by default) */
    ChecksumOffloading tx_checksum_offloading = 3; /* checksum offloading - Tx side (enabled by default) */
};

message TapLink {
    string vpp_tap_if_name = 1;     /* Logical name of the VPP TAP interface (mandatory for TAP_TO_VPP) */
};

source: https://github.com/ligato/vpp-agent/blob/master/api/models/linux/interfaces/interface.proto#L12-L51

Proposal Overview

TAP

The proposal is to define a generic interface type for linux TAP interfaces and look into other ways to keep information for the special linux TAP interfaces that get created by VPP.

1. Deprecate linux interface type TAP_TO_VPP (?)
2. Define a generic linux interface type TAP
3. ?

// TBD