pkg/ip: introduce a new type IP to support formated <ip>[/<prefix>]

Signed-off-by: Bruce Ma <brucema19901024@gmail.com>

pkg/ip/ip.go

@@ -0,0 +1,105 @@
+// Copyright 2021 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 ip
+
+import (
+	"fmt"
+	"net"
+	"strings"
+)
+
+// IP is a CNI maintained type inherited from net.IPNet which can
+// represent a single IP address with or without prefix.
+type IP struct {
+	net.IPNet
+}
+
+// newIP will create an IP with net.IP and net.IPMask
+func newIP(ip net.IP, mask net.IPMask) *IP {
+	return &IP{
+		IPNet: net.IPNet{
+			IP:   ip,
+			Mask: mask,
+		},
+	}
+}
+
+// ParseIP will parse string s as an IP, and return it.
+// The string s must be formed like <ip>[/<prefix>].
+// If s is not a valid textual representation of an IP,
+// will return nil.
+func ParseIP(s string) *IP {
+	if strings.ContainsAny(s, "/") {
+		ip, ipNet, err := net.ParseCIDR(s)
+		if err != nil {
+			return nil
+		}
+		return newIP(ip, ipNet.Mask)
+	} else {
+		ip := net.ParseIP(s)
+		if ip == nil {
+			return nil
+		}
+		return newIP(ip, nil)
+	}
+}
+
+// ToIP will return a net.IP in standard form from this IP.
+// If this IP can not be converted to a valid net.IP, will return nil.
+func (i *IP) ToIP() net.IP {
+	switch {
+	case i.IP.To4() != nil:
+		return i.IP.To4()
+	case i.IP.To16() != nil:
+		return i.IP.To16()
+	default:
+		return nil
+	}
+}
+
+// String returns the string form of this IP.
+func (i *IP) String() string {
+	if len(i.Mask) > 0 {
+		return i.IPNet.String()
+	}
+	return i.IP.String()
+}
+
+// MarshalText implements the encoding.TextMarshaler interface.
+// The encoding is the same as returned by String,
+// But when len(ip) is zero, will return an empty slice.
+func (i *IP) MarshalText() ([]byte, error) {
+	if len(i.IP) == 0 {
+		return []byte{}, nil
+	}
+	return []byte(i.String()), nil
+}
+
+// UnmarshalText implements the encoding.TextUnmarshaler interface.
+// The textual bytes are expected in a form accepted by Parse,
+// But when len(b) is zero, will return an empty IP.
+func (i *IP) UnmarshalText(b []byte) error {
+	if len(b) == 0 {
+		*i = IP{}
+		return nil
+	}
+
+	ip := ParseIP(string(b))
+	if ip == nil {
+		return fmt.Errorf("invalid IP address %s", string(b))
+	}
+	*i = *ip
+	return nil
+}