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package dns
import (
"sync"
)
// ServeMux is an DNS request multiplexer. It matches the zone name of
// each incoming request against a list of registered patterns add calls
// the handler for the pattern that most closely matches the zone name.
//
// ServeMux is DNSSEC aware, meaning that queries for the DS record are
// redirected to the parent zone (if that is also registered), otherwise
// the child gets the query.
//
// ServeMux is also safe for concurrent access from multiple goroutines.
//
// The zero ServeMux is empty and ready for use.
type ServeMux struct {
z map[string]Handler
m sync.RWMutex
}
// NewServeMux allocates and returns a new ServeMux.
func NewServeMux() *ServeMux {
return new(ServeMux)
}
// DefaultServeMux is the default ServeMux used by Serve.
var DefaultServeMux = NewServeMux()
func (mux *ServeMux) match(q string, t uint16) Handler {
mux.m.RLock()
defer mux.m.RUnlock()
if mux.z == nil {
return nil
}
q = CanonicalName(q)
var handler Handler
for off, end := 0, false; !end; off, end = NextLabel(q, off) {
if h, ok := mux.z[q[off:]]; ok {
if t != TypeDS {
return h
}
// Continue for DS to see if we have a parent too, if so delegate to the parent
handler = h
}
}
// Wildcard match, if we have found nothing try the root zone as a last resort.
if h, ok := mux.z["."]; ok {
return h
}
return handler
}
// Handle adds a handler to the ServeMux for pattern.
func (mux *ServeMux) Handle(pattern string, handler Handler) {
if pattern == "" {
panic("dns: invalid pattern " + pattern)
}
mux.m.Lock()
if mux.z == nil {
mux.z = make(map[string]Handler)
}
mux.z[CanonicalName(pattern)] = handler
mux.m.Unlock()
}
// HandleFunc adds a handler function to the ServeMux for pattern.
func (mux *ServeMux) HandleFunc(pattern string, handler func(ResponseWriter, *Msg)) {
mux.Handle(pattern, HandlerFunc(handler))
}
// HandleRemove deregisters the handler specific for pattern from the ServeMux.
func (mux *ServeMux) HandleRemove(pattern string) {
if pattern == "" {
panic("dns: invalid pattern " + pattern)
}
mux.m.Lock()
delete(mux.z, CanonicalName(pattern))
mux.m.Unlock()
}
// ServeDNS dispatches the request to the handler whose pattern most
// closely matches the request message.
//
// ServeDNS is DNSSEC aware, meaning that queries for the DS record
// are redirected to the parent zone (if that is also registered),
// otherwise the child gets the query.
//
// If no handler is found, or there is no question, a standard REFUSED
// message is returned
func (mux *ServeMux) ServeDNS(w ResponseWriter, req *Msg) {
var h Handler
if len(req.Question) >= 1 { // allow more than one question
h = mux.match(req.Question[0].Name, req.Question[0].Qtype)
}
if h != nil {
h.ServeDNS(w, req)
} else {
handleRefused(w, req)
}
}
// Handle registers the handler with the given pattern
// in the DefaultServeMux. The documentation for
// ServeMux explains how patterns are matched.
func Handle(pattern string, handler Handler) { DefaultServeMux.Handle(pattern, handler) }
// HandleRemove deregisters the handle with the given pattern
// in the DefaultServeMux.
func HandleRemove(pattern string) { DefaultServeMux.HandleRemove(pattern) }
// HandleFunc registers the handler function with the given pattern
// in the DefaultServeMux.
func HandleFunc(pattern string, handler func(ResponseWriter, *Msg)) {
DefaultServeMux.HandleFunc(pattern, handler)
}
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