make ovs socket file path as configurable property

docs/cni-plugin.md

@@ -45,6 +45,35 @@ Another example with a trunk port and jumbo frames:
 * `mtu` (integer, optional): MTU.
 * `trunk` (optional): List of VLAN ID's and/or ranges of accepted VLAN
   ID's.
+* `configuration_path` (optional): configuration file containing ovsdb
+  socket file path, etc.
+
+### Flatfile Configuation
+
+There is one option for flat file configuration:
+
+* `configuration_path`: A file path to a OVS CNI configuration file.
+
+OVS CNI will look for the configuration in these locations, in this order:
+
+* The location specified by the `configuration_path` option.
+* `/etc/kubernetes/cni/net.d/ovs.d/ovs.conf`
+* `/etc/cni/net.d/ovs.d/ovs.conf`
+
+You may specify the `configuration_path` to point to another location should it be desired.
+
+Any options added to the `ovs.conf` are overridden by configuration options that are in the
+CNI configuration (e.g. in a custom resource `NetworkAttachmentDefinition` used by Multus CNI
+or in the first file ASCII-betically in the CNI configuration directory -- which is
+`/etc/cni/net.d/` by default).
+
+The sample content of ovs.conf (in JSON format) is as follows:
+
+```json
+{
+  "socket_file": "/usr/local/var/run/openvswitch/db.sock"
+}
+```
 
 ## Manual Testing
 

pkg/ovsdb/ovsdb.go

@@ -53,12 +53,16 @@ func NewOvsDriver(ovsSocket string) (*OvsDriver, error) {
 }
 
 // Create a new OVS driver for a bridge with Unix socket
-func NewOvsBridgeDriver(bridgeName string) (*OvsBridgeDriver, error) {
+func NewOvsBridgeDriver(bridgeName, socketFile string) (*OvsBridgeDriver, error) {
 	ovsDriver := new(OvsBridgeDriver)
 
-	ovsDB, err := libovsdb.ConnectWithUnixSocket("/var/run/openvswitch/db.sock")
+	if socketFile == "" {
+		socketFile = "/var/run/openvswitch/db.sock"
+	}
+
+	ovsDB, err := libovsdb.ConnectWithUnixSocket(socketFile)
 	if err != nil {
-		return nil, fmt.Errorf("failed to connect to ovsdb error: %v", err)
+		return nil, fmt.Errorf("failed to connect to ovsdb socket %s: error: %v", socketFile, err)
 	}
 
 	// Setup state

pkg/plugin/plugin.go

@@ -24,8 +24,10 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"io/ioutil"
 	"log"
 	"net"
+	"os"
 	"runtime"
 	"sort"
 	"time"
@@ -36,6 +38,7 @@ import (
 	"github.com/containernetworking/plugins/pkg/ip"
 	"github.com/containernetworking/plugins/pkg/ipam"
 	"github.com/containernetworking/plugins/pkg/ns"
+	"github.com/imdario/mergo"
 	"github.com/j-keck/arping"
 	"github.com/vishvananda/netlink"
 
@@ -51,11 +54,13 @@ const (
 
 type netConf struct {
 	types.NetConf
-	BrName   string   `json:"bridge,omitempty"`
-	VlanTag  *uint    `json:"vlan"`
-	MTU      int      `json:"mtu"`
-	Trunk    []*trunk `json:"trunk,omitempty"`
-	DeviceID string   `json:"deviceID"` // PCI address of a VF in valid sysfs format
+	BrName            string   `json:"bridge,omitempty"`
+	VlanTag           *uint    `json:"vlan"`
+	MTU               int      `json:"mtu"`
+	Trunk             []*trunk `json:"trunk,omitempty"`
+	DeviceID          string   `json:"deviceID"` // PCI address of a VF in valid sysfs format
+	ConfigurationPath string   `json:"configuration_path"`
+	SocketFile        string   `json:"socket_file"`
 }
 
 type trunk struct {
@@ -109,9 +114,50 @@ func loadNetConf(bytes []byte) (*netConf, error) {
 		return nil, fmt.Errorf("failed to load netconf: %v", err)
 	}
 
+	// default config file dir paths
+	confdirs := []string{"/etc/kubernetes/cni/net.d/ovs.d/ovs.conf", "/etc/cni/net.d/ovs.d/ovs.conf"}
+	// if netconf contains config path already, use that as first
+	if netconf.ConfigurationPath != "" {
+		confdirs = append([]string{netconf.ConfigurationPath}, confdirs...)
+	}
+	// loop through the path and parse the JSON config
+	flatnetConf := &netConf{}
+	for _, confpath := range confdirs {
+		if pathExists(confpath) {
+			jsonFile, err := os.Open(confpath)
+			if err != nil {
+				return nil, fmt.Errorf("open ovs config file %s error: %v", confpath, err)
+			}
+			defer jsonFile.Close()
+			jsonBytes, err := ioutil.ReadAll(jsonFile)
+			if err != nil {
+				return nil, fmt.Errorf("load ovs config file %s: error: %v", confpath, err)
+			}
+			if err := json.Unmarshal(jsonBytes, flatnetConf); err != nil {
+				return nil, fmt.Errorf("parse ovs config file %s: error: %v", confpath, err)
+			}
+			break
+		}
+	}
+	// merge both netconf and flatnetConf configurations
+	if err := mergo.Merge(netconf, flatnetConf); err != nil {
+		return nil, fmt.Errorf("merge with ovs config file: error: %v", err)
+	}
+
 	return netconf, nil
 }
 
+func pathExists(path string) bool {
+	_, err := os.Stat(path)
+	if err == nil {
+		return true
+	}
+	if os.IsNotExist(err) {
+		return false
+	}
+	return true
+}
+
 func generateRandomMac() net.HardwareAddr {
 	prefix := []byte{0x02, 0x00, 0x00} // local unicast prefix
 	suffix := make([]byte, 3)
@@ -306,7 +352,7 @@ func CmdAdd(args *skel.CmdArgs) error {
 		return err
 	}
 
-	ovsDriver, err := ovsdb.NewOvsBridgeDriver(bridgeName)
+	ovsDriver, err := ovsdb.NewOvsBridgeDriver(bridgeName, netconf.SocketFile)
 	if err != nil {
 		return err
 	}
@@ -480,7 +526,7 @@ func CmdDel(args *skel.CmdArgs) error {
 		return err
 	}
 
-	ovsDriver, err := ovsdb.NewOvsBridgeDriver(bridgeName)
+	ovsDriver, err := ovsdb.NewOvsBridgeDriver(bridgeName, netconf.SocketFile)
 	if err != nil {
 		return err
 	}