2011-04-13 05:44:56 +10:00
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package dns
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// A concurrent client implementation.
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// Client sends query to a channel which
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// will then handle the query. Returned replys
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// are return on another channel. Ready for handling --- same
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// setup for server - a HANDLER function that gets run
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// when the query returns.
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// This completely mirrors server.go impl.
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import (
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"os"
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// "net"
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2011-04-13 05:44:56 +10:00
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)
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type QueryHandler interface {
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QueryDNS(w RequestWriter, q *Msg)
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}
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// A RequestWriter interface is used by an DNS query handler to
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// construct an DNS request.
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type RequestWriter interface {
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WriteMessages([]*Msg)
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Write(*Msg)
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}
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2011-04-15 06:11:41 +10:00
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// hijacked connections...?
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type reply struct {
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Client *Client
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req *Msg
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}
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2011-04-13 05:44:56 +10:00
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// QueryMux is an DNS request multiplexer. It matches the
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// zone name of each incoming request against a list of
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// registered patterns add calls the handler for the pattern
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// that most closely matches the zone name.
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type QueryMux struct {
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m map[string]QueryHandler
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}
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// NewQueryMux allocates and returns a new QueryMux.
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func NewQueryMux() *QueryMux { return &QueryMux{make(map[string]QueryHandler)} }
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// DefaultQueryMux is the default QueryMux used by Query.
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var DefaultQueryMux = NewQueryMux()
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func newQueryChanSlice() chan []*Msg { return make(chan []*Msg) }
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func newQueryChan() chan *Msg { return make(chan *Msg) }
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// Default channel to use for the resolver
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var DefaultReplyChan = newQueryChanSlice()
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var DefaultQueryChan = newQueryChan()
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// The HandlerQueryFunc type is an adapter to allow the use of
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// ordinary functions as DNS query handlers. If f is a function
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// with the appropriate signature, HandlerQueryFunc(f) is a
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// QueryHandler object that calls f.
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type HandlerQueryFunc func(RequestWriter, *Msg)
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// QueryDNS calls f(w, reg)
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func (f HandlerQueryFunc) QueryDNS(w RequestWriter, r *Msg) {
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go f(w, r)
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}
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func HandleQueryFunc(pattern string, handler func(RequestWriter, *Msg)) {
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DefaultQueryMux.HandleQueryFunc(pattern, handler)
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}
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// Helper handlers
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// Todo
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// reusing zoneMatch from server.go
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func (mux *QueryMux) match(zone string) QueryHandler {
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var h QueryHandler
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var n = 0
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for k, v := range mux.m {
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if !zoneMatch(k, zone) {
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continue
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}
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if h == nil || len(k) > n {
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n = len(k)
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h = v
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}
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}
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return h
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}
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func (mux *QueryMux) Handle(pattern string, handler QueryHandler) {
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if pattern == "" {
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panic("dns: invalid pattern " + pattern)
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}
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if pattern[len(pattern)-1] != '.' { // no ending .
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mux.m[pattern+"."] = handler
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} else {
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mux.m[pattern] = handler
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}
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}
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func (mux *QueryMux) HandleQueryFunc(pattern string, handler func(RequestWriter, *Msg)) {
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mux.Handle(pattern, HandlerQueryFunc(handler))
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}
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func (mux *QueryMux) QueryDNS(w RequestWriter, request *Msg) {
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h := mux.match(request.Question[0].Name)
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if h == nil {
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// h = RefusedHandler()
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// something else
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}
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h.QueryDNS(w, request)
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}
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type Client struct {
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Network string // if "tcp" a TCP query will be initiated, otherwise an UDP one
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Attempts int // number of attempts
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Retry bool // retry with TCP
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ChannelQuery chan *Msg // read DNS request from this channel
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ChannelReply chan []*Msg // read DNS request from this channel
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Handler QueryHandler // handler to invoke, dns.DefaultQueryMux if nil
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ReadTimeout int64 // the net.Conn.SetReadTimeout value for new connections
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WriteTimeout int64 // the net.Conn.SetWriteTimeout value for new connections
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}
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// Query accepts incoming DNS request,
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// Write to in
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// creating a new service thread for each. The service threads
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// read requests and then call handler to reply to them.
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// Handler is typically nil, in which case the DefaultServeMux is used.
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func Query(c chan *Msg, handler QueryHandler) os.Error {
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client := &Client{ChannelQuery: c, Handler: handler}
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return client.Query()
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}
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func (c *Client) Query() os.Error {
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handler := c.Handler
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if handler == nil {
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handler = DefaultQueryMux
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}
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forever:
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for {
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select {
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case in := <-c.ChannelQuery:
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w := new(reply)
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w.Client = c
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w.req = in
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handler.QueryDNS(w, w.req)
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}
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}
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return nil
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}
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func (c *Client) ListenAndQuery() os.Error {
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if c.ChannelQuery == nil {
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c.ChannelQuery = DefaultQueryChan
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}
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if c.ChannelReply == nil {
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c.ChannelReply = DefaultReplyChan
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}
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return c.Query()
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}
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func (c *Client) Do(m *Msg, addr string) {
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// addr !!!
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if c.ChannelQuery == nil {
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DefaultQueryChan <- m
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}
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}
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func ListenAndQuery(c chan *Msg, handler QueryHandler) {
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client := &Client{ChannelQuery: c, Handler: handler}
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go client.ListenAndQuery()
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}
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func (w *reply) Write(m *Msg) {
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// Write to the channel
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w.Client.ChannelReply <- []*Msg{w.req, m}
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}
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func (w *reply) WriteMessages(m []*Msg) {
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// Write to the channel
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m1 := append([]*Msg{w.req}, m...) // Really the way?
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w.Client.ChannelReply <- m1
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}
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