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ergo/irc/utils/net.go

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// Copyright (c) 2012-2014 Jeremy Latt
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// Copyright (c) 2016 Daniel Oaks <daniel@danieloaks.net>
// released under the MIT license
package utils
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import (
"net"
"strings"
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)
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// IPString returns a simple IP string from the given net.Addr.
func IPString(addr net.Addr) string {
addrStr := addr.String()
ipaddr, _, err := net.SplitHostPort(addrStr)
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//TODO(dan): Why is this needed, does this happen?
if err != nil {
return addrStr
}
return ipaddr
}
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// AddrLookupHostname returns the hostname (if possible) or address for the given `net.Addr`.
func AddrLookupHostname(addr net.Addr) string {
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if AddrIsUnix(addr) {
return "localhost"
}
return LookupHostname(IPString(addr))
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}
// AddrIsLocal returns whether the address is from a trusted local connection (loopback or unix).
func AddrIsLocal(addr net.Addr) bool {
if tcpaddr, ok := addr.(*net.TCPAddr); ok {
return tcpaddr.IP.IsLoopback()
}
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_, ok := addr.(*net.UnixAddr)
return ok
}
// AddrToIP returns the IP address for a net.Addr, or nil if it's a unix domain socket.
func AddrToIP(addr net.Addr) net.IP {
if tcpaddr, ok := addr.(*net.TCPAddr); ok {
return tcpaddr.IP
}
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return nil
}
// AddrIsUnix returns whether the address is a unix domain socket.
func AddrIsUnix(addr net.Addr) bool {
_, ok := addr.(*net.UnixAddr)
return ok
}
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// 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) > 0 {
candidate := strings.TrimSuffix(names[0], ".")
if IsHostname(candidate) {
return candidate
}
}
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// return original address if no hostname found
if len(addr) > 0 && addr[0] == ':' {
// fix for IPv6 hostnames (so they don't start with a colon), same as all other IRCds
addr = "0" + addr
}
return addr
}
var allowedHostnameChars = "abcdefghijklmnopqrstuvwxyz1234567890-."
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// 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
}