397 lines
9.0 KiB
Go
397 lines
9.0 KiB
Go
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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import (
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"os"
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"io"
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"net"
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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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Send(*Msg) os.Error
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Receive() (*Msg, os.Error)
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}
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// hijacked connections...?
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type reply struct {
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client *Client
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addr string
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req *Msg
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conn net.Conn
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tsigRequestMAC string
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tsigTimersOnly bool
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}
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type Request struct {
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Request *Msg
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Addr string
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Client *Client
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}
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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 *Request { return make(chan *Request) }
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// Default channels 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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// 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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mux.m[pattern] = handler
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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, r *Msg) {
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h := mux.match(r.Question[0].Name)
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if h == nil {
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panic("dns: no handler found for " + r.Question[0].Name)
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}
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h.QueryDNS(w, r)
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}
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type Client struct {
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Net 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 *Request // read DNS request from this channel
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ChannelReply chan []*Msg // read DNS request from this channel
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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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TsigSecret map[string]string // secret(s) for Tsig map[<zonename>]<base64 secret>
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// LocalAddr string // Local address to use
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}
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// Create a new client, with some default values filled in.
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func NewClient() *Client {
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c := new(Client)
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c.Net = "udp"
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c.Attempts = 1
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c.ChannelReply = DefaultReplyChan
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return c
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}
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type Query struct {
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ChannelQuery chan *Request // read DNS request from this channel
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Handler QueryHandler // handler to invoke, dns.DefaultQueryMux if nil
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}
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func (q *Query) Query() os.Error {
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handler := q.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 := <-q.ChannelQuery:
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w := new(reply)
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w.req = in.Request
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w.addr = in.Addr
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w.client = in.Client
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handler.QueryDNS(w, in.Request)
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}
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}
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return nil
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}
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func (q *Query) ListenAndQuery() os.Error {
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if q.ChannelQuery == nil {
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q.ChannelQuery = DefaultQueryChan
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}
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return q.Query()
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}
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// Start listener for firing off the queries. If
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// c is nil DefaultQueryChan is used. If handler is nil
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// DefaultQueryMux is used.
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func ListenAndQuery(c chan *Request, handler QueryHandler) {
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q := &Query{ChannelQuery: c, Handler: handler}
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go q.ListenAndQuery()
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}
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func (w *reply) Write(m *Msg) {
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w.Client().ChannelReply <- []*Msg{w.req, m}
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}
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// Do performs an asynchronous query. The result is returned on the
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// channel set in the c.
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func (c *Client) Do(m *Msg, a string) {
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if c.ChannelQuery == nil {
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DefaultQueryChan <- &Request{Client: c, Addr: a, Request: m}
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} else {
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c.ChannelQuery <- &Request{Client: c, Addr: a, Request: m}
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}
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}
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// Perform an synchronous query. Send the message m to the address
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// contained in a and wait for an reply.
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func (c *Client) Exchange(m *Msg, a string) *Msg {
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w := new(reply)
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w.client = c
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w.addr = a
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out, ok := m.Pack()
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if !ok {
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//
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}
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_, err := w.writeClient(out)
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if err != nil {
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return nil
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}
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// udp / tcp
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p := make([]byte, DefaultMsgSize)
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n, err := w.readClient(p)
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if err != nil {
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return nil
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}
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p = p[:n]
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r := new(Msg)
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if ok := r.Unpack(p); !ok {
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return nil
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}
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return r
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}
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func (w *reply) WriteMessages(m []*Msg) {
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m1 := append([]*Msg{w.req}, m...)
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w.Client().ChannelReply <- m1
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}
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func (w *reply) Client() *Client {
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return w.client
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}
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func (w *reply) Request() *Msg {
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return w.req
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}
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func (w *reply) Receive() (*Msg, os.Error) {
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var p []byte
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m := new(Msg)
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switch w.Client().Net {
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case "tcp", "tcp4", "tcp6":
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p = make([]byte, MaxMsgSize)
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case "udp", "udp4", "udp6":
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p = make([]byte, DefaultMsgSize)
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}
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n, err := w.readClient(p)
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if err != nil {
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return nil, err
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}
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p = p[:n]
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if ok := m.Unpack(p); !ok {
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return nil, ErrUnpack
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}
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// Tsig
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if m.IsTsig() {
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secret := m.Extra[len(m.Extra)-1].(*RR_TSIG).Hdr.Name
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_, ok := w.Client().TsigSecret[secret]
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if !ok {
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return m, ErrNoSig
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}
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ok, err := TsigVerify(p, w.Client().TsigSecret[secret], w.tsigRequestMAC, w.tsigTimersOnly)
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if !ok {
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return m, err
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}
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}
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return m, nil
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}
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func (w *reply) readClient(p []byte) (n int, err os.Error) {
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if w.conn == nil {
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panic("no connection")
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}
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switch w.Client().Net {
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case "tcp", "tcp4", "tcp6":
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if len(p) < 1 {
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return 0, io.ErrShortBuffer
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}
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n, err = w.conn.(*net.TCPConn).Read(p[0:2])
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if err != nil || n != 2 {
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return n, err
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}
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l, _ := unpackUint16(p[0:2], 0)
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if l == 0 {
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return 0, ErrShortRead
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}
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if int(l) > len(p) {
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return int(l), io.ErrShortBuffer
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}
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n, err = w.conn.(*net.TCPConn).Read(p[:l])
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if err != nil {
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return n, err
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}
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i := n
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for i < int(l) {
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j, err := w.conn.(*net.TCPConn).Read(p[i:int(l)])
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if err != nil {
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return i, err
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}
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i += j
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}
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n = i
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case "udp", "udp4", "udp6":
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n, _, err = w.conn.(*net.UDPConn).ReadFromUDP(p)
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if err != nil {
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return n, err
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}
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}
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return
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}
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// Send a msg to the address specified in w.
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// If the message m contains a TSIG record the transaction
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// signature is calculated.
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func (w *reply) Send(m *Msg) os.Error {
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if m.IsTsig() {
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secret := m.Extra[len(m.Extra)-1].(*RR_TSIG).Hdr.Name
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_, ok := w.Client().TsigSecret[secret]
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if !ok {
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return ErrNoSig
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}
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m, _ = TsigGenerate(m, w.Client().TsigSecret[secret], w.tsigRequestMAC, w.tsigTimersOnly)
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w.tsigRequestMAC = m.Extra[len(m.Extra)-1].(*RR_TSIG).MAC // Safe the requestMAC
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}
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out, ok := m.Pack()
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if !ok {
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return ErrPack
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}
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_, err := w.writeClient(out)
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if err != nil {
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return err
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}
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return nil
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}
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func (w *reply) writeClient(p []byte) (n int, err os.Error) {
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c := w.Client()
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if c.Attempts == 0 {
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panic("c.Attempts 0")
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}
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if c.Net == "" {
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panic("c.Net empty")
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}
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conn, err := net.Dial(c.Net, w.addr)
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if err != nil {
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return 0, err
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}
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w.conn = conn
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switch c.Net {
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case "tcp", "tcp4", "tcp6":
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if len(p) < 2 {
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return 0, io.ErrShortBuffer
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}
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for a := 0; a < c.Attempts; a++ {
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l := make([]byte, 2)
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l[0], l[1] = packUint16(uint16(len(p)))
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n, err = conn.Write(l)
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if err != nil {
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if e, ok := err.(net.Error); ok && e.Timeout() {
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continue
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}
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return n, err
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}
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if n != 2 {
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return n, io.ErrShortWrite
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}
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n, err = conn.Write(p)
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if err != nil {
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if e, ok := err.(net.Error); ok && e.Timeout() {
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continue
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}
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return n, err
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}
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i := n
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if i < len(p) {
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j, err := conn.Write(p[i:len(p)])
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if err != nil {
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if e, ok := err.(net.Error); ok && e.Timeout() {
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// We are half way in our write...
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continue
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}
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return i, err
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}
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i += j
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}
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n = i
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}
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case "udp", "udp4", "udp6":
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for a := 0; a < c.Attempts; a++ {
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n, err = conn.(*net.UDPConn).WriteTo(p, conn.RemoteAddr())
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if err != nil {
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if e, ok := err.(net.Error); ok && e.Timeout() {
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continue
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}
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return 0, err
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}
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}
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}
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return 0, nil
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}
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