net: add function to convert IPv6 into dot format

This function only useful for expanding SPF macro "i" or when generating
query for DNS PTR.

2 files changed, 71 insertions, 0 deletions

diff --git a/lib/net/net.go b/lib/net/net.go
index db926f4c..afbd7c19 100644
--- a/lib/net/net.go
+++ b/lib/net/net.go
@@ -7,6 +7,7 @@ package net
 
 import (
 	"errors"
+	"net"
 	"strings"
 )
 
@@ -104,3 +105,54 @@ func IsTypeUDP(t Type) bool {
 func IsTypeTransport(t Type) bool {
 	return IsTypeTCP(t) || IsTypeUDP(t)
 }
+
+//
+// ToDotIPv6 convert the IPv6 address format from "::1" format into
+// "0.0.0.0 ... 0.0.0.1".
+//
+// This function only useful for expanding SPF macro "i" or when generating
+// query for DNS PTR.
+//
+func ToDotIPv6(ip net.IP) (out []byte) {
+	addrs := strings.Split(ip.String(), ":")
+
+	var notempty int
+	for x := 0; x < len(addrs); x++ {
+		if len(addrs[x]) != 0 {
+			notempty++
+		}
+	}
+	gap := 8 - notempty
+
+	for x := 0; x < len(addrs); x++ {
+		addr := addrs[x]
+
+		// Fill the gap "::" with one or more "0.0.0.0".
+		if len(addr) == 0 {
+			for ; gap > 0; gap-- {
+				if len(out) > 0 {
+					out = append(out, '.')
+				}
+				out = append(out, []byte("0.0.0.0")...)
+			}
+			continue
+		}
+
+		// Fill the sub address with zero.
+		for y := len(addr); y < 4; y++ {
+			if len(out) > 0 {
+				out = append(out, '.')
+			}
+			out = append(out, '0')
+		}
+
+		for y := 0; y < len(addr); y++ {
+			if len(out) > 0 {
+				out = append(out, '.')
+			}
+			out = append(out, addr[y])
+		}
+	}
+
+	return
+}
diff --git a/lib/net/net_test.go b/lib/net/net_test.go
index 66dc2233..4fe506a2 100644
--- a/lib/net/net_test.go
+++ b/lib/net/net_test.go
@@ -5,6 +5,7 @@
 package net
 
 import (
+	"net"
 	"testing"
 
 	"github.com/shuLhan/share/lib/test"
@@ -189,3 +190,21 @@ func TestIsTypeTransport(t *testing.T) {
 		test.Assert(t, "IsTypeTransport", c.exp, got, true)
 	}
 }
+
+func TestToDotIPv6(t *testing.T) {
+	cases := []struct {
+		ip  net.IP
+		exp []byte
+	}{{
+		ip:  net.ParseIP("2001:db8::68"),
+		exp: []byte("2.0.0.1.0.d.b.8.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.6.8"),
+	}, {
+		ip:  net.ParseIP("::1"),
+		exp: []byte("0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.1"),
+	}}
+
+	for _, c := range cases {
+		got := ToDotIPv6(c.ip)
+		test.Assert(t, "ToDotIPv6", c.exp, got, true)
+	}
+}