Summary
Add a gws field to the route object in the CNI result to support ECMP (Equal-Cost Multi-Path) routing by allowing multiple next-hop gateways to be specified for a single destination.
Problem
The current route object only supports a single gw field:
{
"dst": "0.0.0.0/0",
"gw": "192.168.1.1"
}This makes it impossible to express a multipath route at the CNI spec level. To install an ECMP route on Linux, multiple next-hops must be specified in a single route entry (via ip route add ... nexthop via A nexthop via B). There is no way to encode this intent in the currentspec.
Use case
Our use case is as follows:
- In an OpenStack environment, we create multiple routers connected to the same L2 network.
- This network is attached to worker VMs.
- Inside the VM, we attach an additional interface to Pods using ipvlan (as a secondary interface).
- For this interface, we want to configure ECMP routes where multiple OpenStack routers act as gateways.
This requires the ability to define multiple equal-cost default routes in the configuration.
Proposal
Add an optional gws field (array of IP address strings) to the route
object:
{
"dst": "0.0.0.0/0",
"gws": ["192.168.1.1", "192.168.1.2"]
}
Semantics:
- When gws is set, the route is installed as a multipath (ECMP) route using all listed next-hops
- When only gw is set, behaviour is unchanged from today
- (When both fields being set, it we should discuss how it should be handled)
Backward Compatibility
This is a purely additive, optional field. Existing configurations without gws are unaffected.
Runtimes and plugins that do not understand gws will silently ignore it via standard JSON unmarshaling behaviour.
Summary
Add a
gwsfield to the route object in the CNI result to support ECMP (Equal-Cost Multi-Path) routing by allowing multiple next-hop gateways to be specified for a single destination.Problem
The current route object only supports a single
gwfield:{ "dst": "0.0.0.0/0", "gw": "192.168.1.1" }This makes it impossible to express a multipath route at the CNI spec level. To install an ECMP route on Linux, multiple next-hops must be specified in a single route entry (via ip route add ... nexthop via A nexthop via B). There is no way to encode this intent in the currentspec.
Use case
Our use case is as follows:
This requires the ability to define multiple equal-cost default routes in the configuration.
Proposal
Add an optional gws field (array of IP address strings) to the route
object:
Semantics:
Backward Compatibility
This is a purely additive, optional field. Existing configurations without gws are unaffected.
Runtimes and plugins that do not understand gws will silently ignore it via standard JSON unmarshaling behaviour.