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- // Copyright (c) 2012-2014 Jeremy Latt
- // Copyright (c) 2016- Daniel Oaks <daniel@danieloaks.net>
- // released under the MIT license
-
- package irc
-
- import (
- "net"
- "strings"
- )
-
- func IPString(addr net.Addr) string {
- addrStr := addr.String()
- ipaddr, _, err := net.SplitHostPort(addrStr)
- //TODO(dan): Why is this needed, does this happen?
- if err != nil {
- return addrStr
- }
- return ipaddr
- }
-
- // AddrLookupHostname returns the hostname (if possible) or address for the given `net.Addr`.
- func AddrLookupHostname(addr net.Addr) string {
- return LookupHostname(IPString(addr))
- }
-
- // LookupHostname returns the hostname for `addr` if it has one. Otherwise, just returns `addr`.
- func LookupHostname(addr string) string {
- names, err := net.LookupAddr(addr)
- if err != nil || len(names) < 1 || !IsHostname(names[0]) {
- // return original address
- return addr
- }
-
- return names[0]
- }
-
- var allowedHostnameChars = "abcdefghijklmnopqrstuvwxyz1234567890-."
-
- // IsHostname returns whether we consider `name` a valid hostname.
- func IsHostname(name string) bool {
- // IRC hostnames specifically require a period
- if !strings.Contains(name, ".") || len(name) < 1 || len(name) > 253 {
- return false
- }
-
- // ensure each part of hostname is valid
- for _, part := range strings.Split(name, ".") {
- if len(part) < 1 || len(part) > 63 || strings.HasPrefix(part, "-") || strings.HasSuffix(part, "-") {
- return false
- }
- }
-
- // ensure all chars of hostname are valid
- for _, char := range strings.Split(strings.ToLower(name), "") {
- if !strings.Contains(allowedHostnameChars, char) {
- return false
- }
- }
-
- return true
- }
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