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ovs.go
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ovs.go
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// Package ovs provides a wrapper around ovs-vsctl and ovs-ofctl
package ovs
import (
"fmt"
"strconv"
"strings"
"github.com/golang/glog"
"k8s.io/kubernetes/pkg/util/exec"
utilversion "k8s.io/kubernetes/pkg/util/version"
)
const (
OVS_OFCTL = "ovs-ofctl"
OVS_VSCTL = "ovs-vsctl"
)
type Interface struct {
execer exec.Interface
bridge string
}
// New returns a new ovs.Interface
func New(execer exec.Interface, bridge string, minVersion string) (*Interface, error) {
if _, err := execer.LookPath(OVS_OFCTL); err != nil {
return nil, fmt.Errorf("OVS is not installed")
}
if _, err := execer.LookPath(OVS_VSCTL); err != nil {
return nil, fmt.Errorf("OVS is not installed")
}
ovsif := &Interface{execer: execer, bridge: bridge}
if minVersion != "" {
minVer := utilversion.MustParseGeneric(minVersion)
out, err := ovsif.exec(OVS_VSCTL, "--version")
if err != nil {
return nil, fmt.Errorf("could not check OVS version is %s or higher", minVersion)
}
// First output line should end with version
lines := strings.Split(out, "\n")
spc := strings.LastIndex(lines[0], " ")
instVer, err := utilversion.ParseGeneric(lines[0][spc+1:])
if err != nil {
return nil, fmt.Errorf("could not find OVS version in %q", lines[0])
}
if !instVer.AtLeast(minVer) {
return nil, fmt.Errorf("found OVS %v, need %s or later", instVer, minVersion)
}
}
return ovsif, nil
}
func (ovsif *Interface) exec(cmd string, args ...string) (string, error) {
if cmd == OVS_OFCTL {
args = append([]string{"-O", "OpenFlow13"}, args...)
}
glog.V(5).Infof("Executing: %s %s", cmd, strings.Join(args, " "))
output, err := ovsif.execer.Command(cmd, args...).CombinedOutput()
if err != nil {
glog.V(5).Infof("Error executing %s: %s", cmd, string(output))
return "", err
}
outStr := string(output)
if outStr != "" {
// If output is a single line, strip the trailing newline
nl := strings.Index(outStr, "\n")
if nl == len(outStr)-1 {
outStr = outStr[:nl]
}
}
return outStr, nil
}
// AddBridge creates the bridge associated with the interface, optionally setting
// properties on it (as with "ovs-vsctl set Bridge ..."). If the bridge already
// existed, it will be destroyed and recreated.
func (ovsif *Interface) AddBridge(properties ...string) error {
args := []string{"--if-exists", "del-br", ovsif.bridge, "--", "add-br", ovsif.bridge}
if len(properties) > 0 {
args = append(args, "--", "set", "Bridge", ovsif.bridge)
args = append(args, properties...)
}
_, err := ovsif.exec(OVS_VSCTL, args...)
return err
}
// DeleteBridge deletes the bridge associated with the interface. (It is an
// error if the bridge does not exist.)
func (ovsif *Interface) DeleteBridge() error {
_, err := ovsif.exec(OVS_VSCTL, "del-br", ovsif.bridge)
return err
}
// GetOFPort returns the OpenFlow port number of a given network interface
// attached to a bridge.
func (ovsif *Interface) GetOFPort(port string) (int, error) {
ofportStr, err := ovsif.exec(OVS_VSCTL, "get", "Interface", port, "ofport")
if err != nil {
return -1, err
}
ofport, err := strconv.Atoi(ofportStr)
if err != nil {
return -1, fmt.Errorf("Could not parse allocated ofport %q: %v", ofportStr, err)
}
return ofport, nil
}
// AddPort adds an interface to the bridge, requesting the indicated port
// number, and optionally setting properties on it (as with "ovs-vsctl set
// Interface ..."). Returns the allocated port number (or an error).
func (ovsif *Interface) AddPort(port string, ofportRequest int, properties ...string) (int, error) {
args := []string{"--may-exist", "add-port", ovsif.bridge, port}
if ofportRequest > 0 || len(properties) > 0 {
args = append(args, "--", "set", "Interface", port)
if ofportRequest > 0 {
args = append(args, fmt.Sprintf("ofport_request=%d", ofportRequest))
}
if len(properties) > 0 {
args = append(args, properties...)
}
}
_, err := ovsif.exec(OVS_VSCTL, args...)
if err != nil {
return -1, err
}
ofport, err := ovsif.GetOFPort(port)
if ofportRequest > 0 && ofportRequest != ofport {
return -1, fmt.Errorf("Allocated ofport (%d) did not match request (%d)", ofport, ofportRequest)
}
return ofport, nil
}
// DeletePort removes an interface from the bridge. (It is not an
// error if the interface is not currently a bridge port.)
func (ovsif *Interface) DeletePort(port string) error {
_, err := ovsif.exec(OVS_VSCTL, "--if-exists", "del-port", ovsif.bridge, port)
return err
}
type Transaction struct {
ovsif *Interface
err error
}
func (tx *Transaction) exec(cmd string, args ...string) (string, error) {
out := ""
if tx.err == nil {
out, tx.err = tx.ovsif.exec(cmd, args...)
}
return out, tx.err
}
// NewTransaction begins a new OVS transaction. If an error occurs at
// any step in the transaction, it will be recorded until
// EndTransaction(), and any further calls on the transaction will be
// ignored.
func (ovsif *Interface) NewTransaction() *Transaction {
return &Transaction{ovsif: ovsif}
}
// AddFlow adds a flow to the bridge. The arguments are passed to fmt.Sprintf().
func (tx *Transaction) AddFlow(flow string, args ...interface{}) {
if len(args) > 0 {
flow = fmt.Sprintf(flow, args...)
}
tx.exec(OVS_OFCTL, "add-flow", tx.ovsif.bridge, flow)
}
// DeleteFlows deletes all matching flows from the bridge. The arguments are
// passed to fmt.Sprintf().
func (tx *Transaction) DeleteFlows(flow string, args ...interface{}) {
if len(args) > 0 {
flow = fmt.Sprintf(flow, args...)
}
tx.exec(OVS_OFCTL, "del-flows", tx.ovsif.bridge, flow)
}
// EndTransaction ends an OVS transaction and returns any error that occurred
// during the transaction. You should not use the transaction again after
// calling this function.
func (tx *Transaction) EndTransaction() error {
err := tx.err
tx.err = nil
return err
}
// DumpFlows dumps the flow table for the bridge and returns it as an array of
// strings, one per flow.
func (ovsif *Interface) DumpFlows() ([]string, error) {
out, err := ovsif.exec(OVS_OFCTL, "dump-flows", ovsif.bridge)
if err != nil {
return nil, err
}
lines := strings.Split(out, "\n")
flows := make([]string, 0, len(lines))
for _, line := range lines {
if strings.Contains(line, "cookie=") {
flows = append(flows, line)
}
}
return flows, nil
}