63 lines
1.5 KiB
Go
63 lines
1.5 KiB
Go
package aghnet
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import (
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"net"
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"strconv"
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)
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// The maximum lengths of generated hostnames for different IP versions.
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const (
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ipv4HostnameMaxLen = len("192-168-100-100")
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ipv6HostnameMaxLen = len("ff80-f076-0000-0000-0000-0000-0000-0010")
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)
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// generateIPv4Hostname generates the hostname for specific IP version.
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func generateIPv4Hostname(ipv4 net.IP) (hostname string) {
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hnData := make([]byte, 0, ipv4HostnameMaxLen)
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for i, part := range ipv4 {
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if i > 0 {
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hnData = append(hnData, '-')
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}
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hnData = strconv.AppendUint(hnData, uint64(part), 10)
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}
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return string(hnData)
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}
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// generateIPv6Hostname generates the hostname for specific IP version.
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func generateIPv6Hostname(ipv6 net.IP) (hostname string) {
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hnData := make([]byte, 0, ipv6HostnameMaxLen)
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for i, partsNum := 0, net.IPv6len/2; i < partsNum; i++ {
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if i > 0 {
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hnData = append(hnData, '-')
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}
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for _, val := range ipv6[i*2 : i*2+2] {
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if val < 10 {
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hnData = append(hnData, '0')
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}
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hnData = strconv.AppendUint(hnData, uint64(val), 16)
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}
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}
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return string(hnData)
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}
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// GenerateHostname generates the hostname from ip. In case of using IPv4 the
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// result should be like:
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//
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// 192-168-10-1
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//
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// In case of using IPv6, the result is like:
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//
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// ff80-f076-0000-0000-0000-0000-0000-0010
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//
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func GenerateHostname(ip net.IP) (hostname string) {
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if ipv4 := ip.To4(); ipv4 != nil {
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return generateIPv4Hostname(ipv4)
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} else if ipv6 := ip.To16(); ipv6 != nil {
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return generateIPv6Hostname(ipv6)
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}
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return ""
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}
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