gateway-diagnostics

name

gateway-diagnostics

description

Show and ping the gateway of a network interface, on a Kubernetes node or inside a pod's network namespace. Auto-detects the gateway from the routing table (ip -j route), reports interface type (RoCE / Ethernet / IB), and tests reachability with ping. Use for default-route / gateway questions, network reachability checks, RoCE/RDMA data-path validation, and "can this node/pod reach its gateway" investigations.

Gateway Diagnostics

Inspect and test the gateway of a network interface. Two operations, one script each; both run identically on a node or inside a pod — the only difference is how you launch them (see Targets below).

Router

Need	Action
See the gateway / default route for an interface (with TYPE)	scripts/show-gateway.sh
Test whether the gateway is reachable	scripts/ping-gateway.sh
Target is a node (or a bound SSH host)	run directly — see Node target
Target is a pod	resolve the netns first — see Pod target
Switchdev PF caveat, or what RoCE/Ethernet/IB means	read references/switchdev-and-interface-types.md

Targets

Node target

Prefer host_script when the node is a bound SSH host (check host_list) — it runs over SSH with no debug pod. Fall back to node_script otherwise. Both take the same skill / script / args.

host_script: host="<host>", skill="gateway-diagnostics", script="show-gateway.sh", args="<args>"
node_script: node="<node>", skill="gateway-diagnostics", script="show-gateway.sh", args="<args>"

Pod target

Runs in the pod's network namespace using host tools. Two steps:

1. Resolve the pod's network namespace:

   resolve_pod_netns: pod="<pod>", namespace="<ns>"
   

2. Run the script with the returned node and netns:

   node_script: node="<node>", netns="<netns>", skill="gateway-diagnostics", script="ping-gateway.sh", args="<args>"
   

The script does not enter the namespace itself — node_script does that via the netns= param. The same script file serves both node and pod targets.

Parameters

show-gateway.sh

Parameter	Required	Description
--interface IFACE	no	Network interface name. If omitted, shows all.
--json	no	Output in JSON format (adds a type field per gateway).

ping-gateway.sh

Parameter	Required	Description
--interface IFACE	yes	Network interface to find the gateway for
--source-ip	no	flag — auto-detect IP from the interface, use as ping source (-I <ip>)
--source-dev	no	flag — use the interface name as ping source (-I <iface>)
--count N	no	Number of ping packets (default: 3)

--source-ip and --source-dev are mutually exclusive flags (no value needed).

Examples

Show all gateways on a node:

node_script: node="nodepool-061", skill="gateway-diagnostics", script="show-gateway.sh"

Show one interface's gateway on a bound host:

host_script: host="nodepool-061", skill="gateway-diagnostics", script="show-gateway.sh", args="--interface eth0"

Ping a node's gateway, sourcing from the interface IP:

node_script: node="nodepool-061", skill="gateway-diagnostics", script="ping-gateway.sh", args="--interface bond0 --source-ip"

Show / ping a pod's gateway (resolve netns first):

resolve_pod_netns: pod="rdma-pod", namespace="rdma-test"
→ node="worker-1", netns="abc123"

node_script: node="worker-1", netns="abc123", skill="gateway-diagnostics", script="show-gateway.sh", args="--interface net1 --json"
node_script: node="worker-1", netns="abc123", skill="gateway-diagnostics", script="ping-gateway.sh", args="--interface net1 --source-dev"

Interface types & switchdev

The output includes a TYPE column (RoCE / Ethernet / IB). If a target interface is a PF in switchdev mode, gateway routes are not meaningful and ping will always fail — this is expected, not a network problem. For the detection logic and what to do instead (use a RoCE pod + the pod target), read references/switchdev-and-interface-types.md.