bridge: release IP in case of error

If there is an error after an IP has been allocated it is necesary
to release it.

Signed-off-by: Mauricio Vasquez B <mauricio.vasquez@polito.it>

plugins/main/bridge/bridge.go

@@ -19,6 +19,7 @@ import (
 	"errors"
 	"fmt"
 	"net"
+	"os"
 	"runtime"
 	"syscall"
 
@@ -323,6 +324,8 @@ func enableIPForward(family int) error {
 }
 
 func cmdAdd(args *skel.CmdArgs) error {
+	var success bool = false
+
 	n, cniVersion, err := loadNetConf(args.StdinData)
 	if err != nil {
 		return err
@@ -358,6 +361,15 @@ func cmdAdd(args *skel.CmdArgs) error {
 		return err
 	}
 
+	// release IP in case of failure
+	defer func() {
+		if !success {
+			os.Setenv("CNI_COMMAND", "DEL")
+			ipam.ExecDel(n.IPAM.Type, args.StdinData)
+			os.Setenv("CNI_COMMAND", "ADD")
+		}
+	}()
+
 	// Convert whatever the IPAM result was into the current Result type
 	result, err := current.NewResultFromResult(r)
 	if err != nil {
@@ -454,6 +466,8 @@ func cmdAdd(args *skel.CmdArgs) error {
 
 	result.DNS = n.DNS
 
+	success = true
+
 	return types.PrintResult(result, cniVersion)
 }