integration: simplify CNI-fp and add README.md

* Use delegated plugin call to simplify cni-bridge-cni
* Add README.md for cni-bridge-cni

Signed-off-by: Wei Fu <fuweid89@gmail.com>
(cherry picked from commit e6a2c07)
Signed-off-by: Qiutong Song <songqt01@gmail.com>

go.mod

@@ -19,6 +19,7 @@ require (
 	github.com/containerd/ttrpc v1.1.0
 	github.com/containerd/typeurl v1.0.2
 	github.com/containerd/zfs v1.0.0
+	github.com/containernetworking/cni v1.1.1
 	github.com/containernetworking/plugins v1.1.1
 	github.com/coreos/go-systemd/v22 v22.3.2
 	github.com/davecgh/go-spew v1.1.1
@@ -83,7 +84,6 @@ require (
 	github.com/cenkalti/backoff/v4 v4.1.2 // indirect
 	github.com/cespare/xxhash/v2 v2.1.2 // indirect
 	github.com/cilium/ebpf v0.7.0 // indirect
-	github.com/containernetworking/cni v1.1.1 // indirect
 	github.com/containers/ocicrypt v1.1.3 // indirect
 	github.com/cpuguy83/go-md2man/v2 v2.0.0 // indirect
 	github.com/go-logr/logr v1.2.2 // indirect

integration/failpoint/cmd/cni-bridge-fp/README.md

@@ -0,0 +1,159 @@
+## cni-bridge-f(ail)p(oint)
+
+### Overview
+
+The `cni-bridge-fp` is a CNI plugin which delegates interface-creating function
+to [CNI bridge plugin][1] and allows user to inject failpoint before delegation.
+
+Since the CNI plugin is invoked by binary call from CRI and it is short-lived,
+the failpoint need to be configured by a JSON file, which can be persisted.
+There is an example about failpoint description.
+
+```json
+{
+	"cmdAdd":   "1*error(you-shall-not-pass!)->1*panic(again)",
+	"cmdDel":   "1*error(try-again)",
+	"cmdCheck": "10*off"
+}
+```
+
+* `cmdAdd` (string, optional): The failpoint for `ADD` command.
+* `cmdDel` (string, optional): The failpoint for `DEL` command.
+* `cmdCheck` (string, optional): The failpoint for `CHECK` command.
+
+Since the `cmdXXX` can be multiple failpoints, each CNI binary call will update
+the current state to make sure the order of execution is expected.
+
+And the failpoint injection is enabled by pod's annotation. Currently, the key
+of customized CNI capabilities in containerd can only be `io.kubernetes.cri.pod-annotations`
+and containerd will pass pod's annotations to CNI under the that object. The
+user can use the `failpoint.cni.containerd.io/confpath` annotation to enable
+failpoint for the pod.
+
+```yaml
+apiVersion: v1
+kind: Pod
+metadata:
+  name: nginx
+  annotations:
+    failpoint.cni.containerd.io/confpath: "/tmp/pod-failpoints.json"
+spec:
+  containers:
+  - name: nginx
+    image: nginx:1.14.2
+    ports:
+    - containerPort: 80
+```
+
+### Example
+
+Let's use the following json as failpoint description.
+
+```bash
+$ cat <<EOF | tee /tmp/cni-failpoint.json
+{
+	"cmdAdd":   "1*error(try-again)",
+	"cmdDel":   "2*error(oops)",
+	"cmdCheck": "1*off->1*panic(sorry)"
+}
+EOF
+```
+
+And use `ip netns` to create persisted net namespace named by `failpoint`.
+
+```bash
+$ sudo ip netns add failpoint
+```
+
+And then setup the following bash script for demo.
+
+```bash
+$ cat <<EOFDEMO | tee /tmp/cni-failpoint-demo-helper.sh
+#!/usr/bin/env bash
+
+export CNI_CONTAINERID=failpoint-testing
+export CNI_NETNS=/run/netns/failpoint
+export CNI_IFNAME=fpeni0
+export CNI_PATH=/opt/cni/bin/
+
+cat <<EOF | /opt/cni/bin/cni-bridge-fp
+{
+  "cniVersion": "0.3.0",
+  "name": "containerd-net-fp",
+  "type": "cni-bridge-fp",
+  "bridge": "fp-cni0",
+  "isGateway": true,
+  "ipMasq": true,
+  "promiscMode": true,
+  "ipam": {
+    "type": "host-local",
+    "ranges": [
+      [{
+        "subnet": "10.88.0.0/16"
+      }],
+      [{
+        "subnet": "2001:4860:4860::/64"
+      }]
+    ],
+    "routes": [
+      { "dst": "0.0.0.0/0" },
+      { "dst": "::/0" }
+    ]
+  },
+  "runtimeConfig": {
+    "io.kubernetes.cri.pod-annotations": {
+      "failpoint.cni.containerd.io/confpath": "/tmp/cni-failpoint.json"
+    }
+  }
+}
+EOF
+
+EOFDEMO
+```
+
+Let's try to setup CNI and we should get a error `try-again`.
+
+```bash
+$ sudo CNI_COMMAND=ADD bash /tmp/cni-failpoint-demo-helper.sh
+{
+    "code": 999,
+    "msg": "try-again"
+}
+
+# there is no failpoint for ADD command.
+$ cat /tmp/cni-failpoint.json | jq .
+{
+  "cmdAdd": "0*error(try-again)",
+  "cmdDel": "2*error(oops)",
+  "cmdCheck": "1*off->1*panic(sorry)"
+}
+```
+
+We should setup CNI successfully after retry. When we teardown the interface,
+there should be two failpoints.
+
+```bash
+$ sudo CNI_COMMAND=ADD bash /tmp/cni-failpoint-demo-helper.sh
+...
+
+$ sudo CNI_COMMAND=DEL bash /tmp/cni-failpoint-demo-helper.sh
+{
+    "code": 999,
+    "msg": "oops"
+}
+
+$ sudo CNI_COMMAND=DEL bash /tmp/cni-failpoint-demo-helper.sh
+{
+    "code": 999,
+    "msg": "oops"
+}
+
+$ cat /tmp/cni-failpoint.json | jq .
+{
+  "cmdAdd": "0*error(try-again)",
+  "cmdDel": "0*error(oops)",
+  "cmdCheck": "1*off->1*panic(sorry)"
+}
+```
+
+[1]: <https://www.cni.dev/plugins/current/main/bridge/>