148 lines
3.8 KiB
Go
148 lines
3.8 KiB
Go
package dns
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import (
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"strings"
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"sync"
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)
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// ServeMux is an DNS request multiplexer. It matches the zone name of
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// each incoming request against a list of registered patterns add calls
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// the handler for the pattern that most closely matches the zone name.
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//
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// ServeMux is DNSSEC aware, meaning that queries for the DS record are
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// redirected to the parent zone (if that is also registered), otherwise
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// the child gets the query.
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//
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// ServeMux is also safe for concurrent access from multiple goroutines.
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//
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// The zero ServeMux is empty and ready for use.
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type ServeMux struct {
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z map[string]Handler
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m sync.RWMutex
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}
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// NewServeMux allocates and returns a new ServeMux.
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func NewServeMux() *ServeMux {
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return new(ServeMux)
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}
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// DefaultServeMux is the default ServeMux used by Serve.
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var DefaultServeMux = NewServeMux()
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func (mux *ServeMux) match(q string, t uint16) Handler {
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mux.m.RLock()
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defer mux.m.RUnlock()
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if mux.z == nil {
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return nil
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}
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var handler Handler
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// TODO(tmthrgd): Once https://go-review.googlesource.com/c/go/+/137575
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// lands in a go release, replace the following with strings.ToLower.
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var sb strings.Builder
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for i := 0; i < len(q); i++ {
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c := q[i]
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if !(c >= 'A' && c <= 'Z') {
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continue
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}
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sb.Grow(len(q))
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sb.WriteString(q[:i])
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for ; i < len(q); i++ {
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c := q[i]
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if c >= 'A' && c <= 'Z' {
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c += 'a' - 'A'
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}
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sb.WriteByte(c)
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}
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q = sb.String()
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break
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}
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for off, end := 0, false; !end; off, end = NextLabel(q, off) {
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if h, ok := mux.z[q[off:]]; ok {
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if t != TypeDS {
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return h
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}
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// Continue for DS to see if we have a parent too, if so delegate to the parent
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handler = h
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}
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}
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// Wildcard match, if we have found nothing try the root zone as a last resort.
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if h, ok := mux.z["."]; ok {
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return h
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}
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return handler
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}
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// Handle adds a handler to the ServeMux for pattern.
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func (mux *ServeMux) Handle(pattern string, handler Handler) {
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if pattern == "" {
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panic("dns: invalid pattern " + pattern)
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}
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mux.m.Lock()
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if mux.z == nil {
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mux.z = make(map[string]Handler)
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}
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mux.z[Fqdn(pattern)] = handler
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mux.m.Unlock()
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}
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// HandleFunc adds a handler function to the ServeMux for pattern.
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func (mux *ServeMux) HandleFunc(pattern string, handler func(ResponseWriter, *Msg)) {
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mux.Handle(pattern, HandlerFunc(handler))
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}
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// HandleRemove deregisters the handler specific for pattern from the ServeMux.
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func (mux *ServeMux) HandleRemove(pattern string) {
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if pattern == "" {
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panic("dns: invalid pattern " + pattern)
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}
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mux.m.Lock()
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delete(mux.z, Fqdn(pattern))
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mux.m.Unlock()
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}
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// ServeDNS dispatches the request to the handler whose pattern most
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// closely matches the request message.
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//
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// ServeDNS is DNSSEC aware, meaning that queries for the DS record
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// are redirected to the parent zone (if that is also registered),
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// otherwise the child gets the query.
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//
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// If no handler is found, or there is no question, a standard SERVFAIL
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// message is returned
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func (mux *ServeMux) ServeDNS(w ResponseWriter, req *Msg) {
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var h Handler
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if len(req.Question) >= 1 { // allow more than one question
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h = mux.match(req.Question[0].Name, req.Question[0].Qtype)
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}
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if h != nil {
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h.ServeDNS(w, req)
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} else {
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HandleFailed(w, req)
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}
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}
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// Handle registers the handler with the given pattern
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// in the DefaultServeMux. The documentation for
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// ServeMux explains how patterns are matched.
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func Handle(pattern string, handler Handler) { DefaultServeMux.Handle(pattern, handler) }
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// HandleRemove deregisters the handle with the given pattern
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// in the DefaultServeMux.
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func HandleRemove(pattern string) { DefaultServeMux.HandleRemove(pattern) }
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// HandleFunc registers the handler function with the given pattern
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// in the DefaultServeMux.
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func HandleFunc(pattern string, handler func(ResponseWriter, *Msg)) {
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DefaultServeMux.HandleFunc(pattern, handler)
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}
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