314 lines
8.2 KiB
Go
314 lines
8.2 KiB
Go
// Copyright 2011 Miek Gieben. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package dns
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// A client implementation.
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import (
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"io"
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"net"
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"time"
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)
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const dnsTimeout time.Duration = 2 * 1e9
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const tcpIdleTimeout time.Duration = 8 * time.Second
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// A Conn represents a connection to a DNS server.
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type Conn struct {
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net.Conn // a net.Conn holding the connection
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UDPSize uint16 // Minimum receive buffer for UDP messages
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TsigSecret map[string]string // Secret(s) for Tsig map[<zonename>]<base64 secret>, zonename must be fully qualified
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rtt time.Duration
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t time.Time
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tsigRequestMAC string
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}
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// A Client defines parameters for a DNS client. A nil Client is usable for sending queries.
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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 (default is "" for UDP)
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DialTimeout time.Duration // net.DialTimeout (ns), defaults to 2 * 1e9
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ReadTimeout time.Duration // net.Conn.SetReadTimeout value for connections (ns), defaults to 2 * 1e9
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WriteTimeout time.Duration // net.Conn.SetWriteTimeout value for connections (ns), defaults to 2 * 1e9
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TsigSecret map[string]string // secret(s) for Tsig map[<zonename>]<base64 secret>, zonename must be fully qualified
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SingleInflight bool // if true suppress multiple outstanding queries for the same Qname, Qtype and Qclass
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group singleflight
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}
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// Exchange performs a synchronous UDP query. It sends the message m to the address
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// contained in a and waits for an reply.
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func Exchange(m *Msg, a string) (r *Msg, err error) {
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var co *Conn
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co, err = DialTimeout("udp", a, dnsTimeout)
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if err != nil {
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return nil, err
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}
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defer co.Close()
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co.SetReadDeadline(time.Now().Add(dnsTimeout))
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co.SetWriteDeadline(time.Now().Add(dnsTimeout))
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if err = co.WriteMsg(m); err != nil {
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return nil, err
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}
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r, err = co.ReadMsg()
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return r, err
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}
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// ExchangeConn performs a synchronous query. It sends the message m via the connection
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// c and waits for a reply. The connection c is not closed by ExchangeConn.
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// This function is going away, but can easily be mimicked:
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//
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// co := &dns.Conn{Conn: c} // c is your net.Conn
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// co.WriteMsg(m)
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// in, _ := co.ReadMsg()
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// co.Close()
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//
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func ExchangeConn(c net.Conn, m *Msg) (r *Msg, err error) {
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println("dns: this function is deprecated")
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co := new(Conn)
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co.Conn = c
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if err = co.WriteMsg(m); err != nil {
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return nil, err
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}
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r, err = co.ReadMsg()
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return r, err
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}
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// Exchange performs an synchronous query. It sends the message m to the address
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// contained in a and waits for an reply. Basic use pattern with a *dns.Client:
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//
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// c := new(dns.Client)
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// in, rtt, err := c.Exchange(message, "127.0.0.1:53")
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//
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func (c *Client) Exchange(m *Msg, a string) (r *Msg, rtt time.Duration, err error) {
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if !c.SingleInflight {
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return c.exchange(m, a)
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}
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// This adds a bunch of garbage, TODO(miek).
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t := "nop"
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if t1, ok := TypeToString[m.Question[0].Qtype]; ok {
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t = t1
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}
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cl := "nop"
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if cl1, ok := ClassToString[m.Question[0].Qclass]; ok {
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cl = cl1
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}
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r, rtt, err, shared := c.group.Do(m.Question[0].Name+t+cl, func() (*Msg, time.Duration, error) {
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return c.exchange(m, a)
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})
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if err != nil {
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return r, rtt, err
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}
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if shared {
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r1 := r.copy()
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r = r1
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}
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return r, rtt, nil
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}
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func (c *Client) exchange(m *Msg, a string) (r *Msg, rtt time.Duration, err error) {
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timeout := dnsTimeout
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var co *Conn
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if c.DialTimeout != 0 {
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timeout = c.DialTimeout
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}
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if c.Net == "" {
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co, err = DialTimeout("udp", a, timeout)
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} else {
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co, err = DialTimeout(c.Net, a, timeout)
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}
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if err != nil {
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return nil, 0, err
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}
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timeout = dnsTimeout
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if c.ReadTimeout != 0 {
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timeout = c.ReadTimeout
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}
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co.SetReadDeadline(time.Now().Add(timeout))
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timeout = dnsTimeout
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if c.WriteTimeout != 0 {
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timeout = c.WriteTimeout
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}
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co.SetWriteDeadline(time.Now().Add(timeout))
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defer co.Close()
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opt := m.IsEdns0()
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if opt != nil && opt.UDPSize() >= MinMsgSize {
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co.UDPSize = opt.UDPSize()
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}
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co.TsigSecret = c.TsigSecret
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if err = co.WriteMsg(m); err != nil {
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return nil, 0, err
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}
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r, err = co.ReadMsg()
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return r, co.rtt, err
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}
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// ReadMsg reads a message from the connection co.
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// If the received message contains a TSIG record the transaction
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// signature is verified.
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func (co *Conn) ReadMsg() (*Msg, error) {
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var p []byte
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m := new(Msg)
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if _, ok := co.Conn.(*net.TCPConn); ok {
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p = make([]byte, MaxMsgSize)
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} else {
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if co.UDPSize >= 512 {
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p = make([]byte, co.UDPSize)
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} else {
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p = make([]byte, MinMsgSize)
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}
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}
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n, err := co.Read(p)
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if err != nil && n == 0 {
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return nil, err
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}
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p = p[:n]
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if err := m.Unpack(p); err != nil {
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return nil, err
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}
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co.rtt = time.Since(co.t)
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if t := m.IsTsig(); t != nil {
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if _, ok := co.TsigSecret[t.Hdr.Name]; !ok {
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return m, ErrSecret
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}
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// Need to work on the original message p, as that was used to calculate the tsig.
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err = TsigVerify(p, co.TsigSecret[t.Hdr.Name], co.tsigRequestMAC, false)
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}
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return m, err
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}
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// Read implements the net.Conn read method.
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func (co *Conn) Read(p []byte) (n int, err error) {
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if co.Conn == nil {
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return 0, ErrConnEmpty
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}
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if len(p) < 2 {
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return 0, io.ErrShortBuffer
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}
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if t, ok := co.Conn.(*net.TCPConn); ok {
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n, err = t.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 = t.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 := t.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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return n, err
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}
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// assume udp connection
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n, err = co.Conn.Read(p)
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if err != nil {
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return n, err
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}
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return n, err
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}
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// WriteMsg sends a message throught the connection co.
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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 (co *Conn) WriteMsg(m *Msg) (err error) {
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var out []byte
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if t := m.IsTsig(); t != nil {
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mac := ""
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if _, ok := co.TsigSecret[t.Hdr.Name]; !ok {
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return ErrSecret
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}
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out, mac, err = TsigGenerate(m, co.TsigSecret[t.Hdr.Name], co.tsigRequestMAC, false)
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// Set for the next read, allthough only used in zone transfers
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co.tsigRequestMAC = mac
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} else {
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out, err = m.Pack()
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}
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if err != nil {
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return err
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}
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co.t = time.Now()
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if _, err = co.Write(out); 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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// Write implements the net.Conn Write method.
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func (co *Conn) Write(p []byte) (n int, err error) {
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if t, ok := co.Conn.(*net.TCPConn); ok {
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if len(p) < 2 {
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return 0, io.ErrShortBuffer
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}
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l := make([]byte, 2)
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l[0], l[1] = packUint16(uint16(len(p)))
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p = append(l, p...)
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n, err := t.Write(p)
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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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if i < len(p) {
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j, err := t.Write(p[i:len(p)])
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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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return n, err
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}
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n, err = co.Conn.(*net.UDPConn).Write(p)
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return n, err
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}
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// Dial connects to the address on the named network.
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func Dial(network, address string) (conn *Conn, err error) {
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conn.Conn, err = net.Dial(network, address)
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if err != nil {
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return nil, err
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}
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return conn, nil
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}
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// Dialtimeout acts like Dial but takes a timeout.
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func DialTimeout(network, address string, timeout time.Duration) (conn *Conn, err error) {
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conn.Conn, err = net.DialTimeout(network, address, timeout)
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if err != nil {
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return nil, err
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}
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return conn, nil
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}
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// Close implements the net.Conn Close method.
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func (co *Conn) Close() error { return co.Conn.Close() }
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// LocalAddr implements the net.Conn LocalAddr method.
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func (co *Conn) LocalAddr() net.Addr { return co.Conn.LocalAddr() }
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// RemoteAddr implements the net.Conn RemoteAddr method.
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func (co *Conn) RemoteAddr() net.Addr { return co.Conn.RemoteAddr() }
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// SetDeadline implements the net.Conn SetDeadline method.
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func (co *Conn) SetDeadline(t time.Time) error { return co.Conn.SetDeadline(t) }
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// SetReadDeadline implements the net.Conn SetReadDeadline method.
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func (co *Conn) SetReadDeadline(t time.Time) error { return co.Conn.SetReadDeadline(t) }
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// SetWriteDeadline implements the net.Conn SetWriteDeadline method.
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func (co *Conn) SetWriteDeadline(t time.Time) error { return co.Conn.SetWriteDeadline(t) }
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