f3066b9463
This fix adds unit tests for `ExtractAddressFromReverse`. It also updates the implementation of `ExtractAddressFromReverse` so that only a valid IPv4 or IPv6 address (in string format) is returned. If the addresses is not valid and can not be handled by golang's `net.ParseIP` then an empty string (`""`) will be returned. Signed-off-by: Yong Tang <yong.tang.github@outlook.com>
68 lines
1.7 KiB
Go
68 lines
1.7 KiB
Go
package dnsutil
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import (
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"net"
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"strings"
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)
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// ExtractAddressFromReverse turns a standard PTR reverse record name
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// into an IP address. This works for ipv4 or ipv6.
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//
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// 54.119.58.176.in-addr.arpa. becomes 176.58.119.54. If the conversion
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// failes the empty string is returned.
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func ExtractAddressFromReverse(reverseName string) string {
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search := ""
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f := reverse
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switch {
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case strings.HasSuffix(reverseName, v4arpaSuffix):
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search = strings.TrimSuffix(reverseName, v4arpaSuffix)
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case strings.HasSuffix(reverseName, v6arpaSuffix):
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search = strings.TrimSuffix(reverseName, v6arpaSuffix)
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f = reverse6
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default:
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return ""
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}
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// Reverse the segments and then combine them.
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return f(strings.Split(search, "."))
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}
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func reverse(slice []string) string {
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for i := 0; i < len(slice)/2; i++ {
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j := len(slice) - i - 1
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slice[i], slice[j] = slice[j], slice[i]
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}
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ip := net.ParseIP(strings.Join(slice, ".")).To4()
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if ip == nil {
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return ""
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}
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return ip.String()
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}
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// reverse6 reverse the segments and combine them according to RFC3596:
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// b.a.9.8.7.6.5.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.b.d.0.1.0.0.2
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// is reversed to 2001:db8::567:89ab
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func reverse6(slice []string) string {
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for i := 0; i < len(slice)/2; i++ {
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j := len(slice) - i - 1
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slice[i], slice[j] = slice[j], slice[i]
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}
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slice6 := []string{}
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for i := 0; i < len(slice)/4; i++ {
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slice6 = append(slice6, strings.Join(slice[i*4:i*4+4], ""))
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}
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ip := net.ParseIP(strings.Join(slice6, ":")).To16()
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if ip == nil {
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return ""
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}
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return ip.String()
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}
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const (
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// v4arpaSuffix is the reverse tree suffix for v4 IP addresses.
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v4arpaSuffix = ".in-addr.arpa."
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// v6arpaSuffix is the reverse tree suffix for v6 IP addresses.
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v6arpaSuffix = ".ip6.arpa."
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)
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