AdGuardHome/internal/aghnet/hostgen.go

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package aghnet
import (
"net"
"strconv"
)
// The maximum lengths of generated hostnames for different IP versions.
const (
ipv4HostnameMaxLen = len("192-168-100-100")
ipv6HostnameMaxLen = len("ff80-f076-0000-0000-0000-0000-0000-0010")
)
// generateIPv4Hostname generates the hostname by IP address version 4.
func generateIPv4Hostname(ipv4 net.IP) (hostname string) {
hnData := make([]byte, 0, ipv4HostnameMaxLen)
for i, part := range ipv4 {
if i > 0 {
hnData = append(hnData, '-')
}
hnData = strconv.AppendUint(hnData, uint64(part), 10)
}
return string(hnData)
}
// generateIPv6Hostname generates the hostname by IP address version 6.
func generateIPv6Hostname(ipv6 net.IP) (hostname string) {
hnData := make([]byte, 0, ipv6HostnameMaxLen)
for i, partsNum := 0, net.IPv6len/2; i < partsNum; i++ {
if i > 0 {
hnData = append(hnData, '-')
}
for _, val := range ipv6[i*2 : i*2+2] {
if val < 10 {
hnData = append(hnData, '0')
}
hnData = strconv.AppendUint(hnData, uint64(val), 16)
}
}
return string(hnData)
}
// GenerateHostname generates the hostname from ip. In case of using IPv4 the
// result should be like:
//
// 192-168-10-1
//
// In case of using IPv6, the result is like:
//
// ff80-f076-0000-0000-0000-0000-0000-0010
//
// ip must be either an IPv4 or an IPv6.
func GenerateHostname(ip net.IP) (hostname string) {
if ipv4 := ip.To4(); ipv4 != nil {
return generateIPv4Hostname(ipv4)
}
return generateIPv6Hostname(ip)
}