pkg/utils/hwaddr: migrate code from IPAM pkg

pkg/utils/hwaddr/hwaddr.go

@@ -0,0 +1,68 @@
+// Copyright 2016 CNI authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package hwaddr
+
+import (
+	"fmt"
+	"net"
+	"strconv"
+	"strings"
+)
+
+const (
+	// private mac prefix safe to use
+	PrivateMACPrefix = "0a:58"
+)
+
+type SupportIp4OnlyErr struct{ msg string }
+
+func (e SupportIp4OnlyErr) Error() string { return e.msg }
+
+type MacParseErr struct{ msg string }
+
+func (e MacParseErr) Error() string { return e.msg }
+
+type InvalidPrefixLengthErr struct{ msg string }
+
+func (e InvalidPrefixLengthErr) Error() string { return e.msg }
+
+// GenerateHardwareAddr4 generates 48 bit virtual mac addresses based on the IP4 input.
+func GenerateHardwareAddr4(ip net.IP, prefix string) (net.HardwareAddr, error) {
+	switch {
+
+	case ip.To4() == nil:
+		return nil, SupportIp4OnlyErr{msg: "GenerateHardwareAddr4 only supports valid IPv4 address as input"}
+
+	case len(prefix) != len(PrivateMACPrefix):
+		return nil, InvalidPrefixLengthErr{msg: fmt.Sprintf(
+			"Prefix has length %d instead  of %d", len(prefix), len(PrivateMACPrefix)),
+		}
+	}
+
+	mac := prefix
+	sections := strings.Split(ip.String(), ".")
+	for _, s := range sections {
+		i, _ := strconv.Atoi(s)
+		mac += fmt.Sprintf(":%02x", i)
+	}
+
+	hwAddr, err := net.ParseMAC(mac)
+	if err != nil {
+		return nil, MacParseErr{msg: fmt.Sprintf(
+			"Failed to parse mac address %q generated based on IP %q due to: %v", mac, ip, err),
+		}
+	}
+	return hwAddr, nil
+}