1 files changed, 506 insertions, 0 deletions
diff --git a/vendor/github.com/miekg/dns/client.go b/vendor/github.com/miekg/dns/client.go
new file mode 100644
index 0000000..856b169
--- /dev/null
+++ b/vendor/github.com/miekg/dns/client.go
@@ -0,0 +1,506 @@
+package dns
+
+// A client implementation.
+
+import (
+	"bytes"
+	"context"
+	"crypto/tls"
+	"encoding/binary"
+	"io"
+	"net"
+	"strings"
+	"time"
+)
+
+const dnsTimeout time.Duration = 2 * time.Second
+const tcpIdleTimeout time.Duration = 8 * time.Second
+
+// A Conn represents a connection to a DNS server.
+type Conn struct {
+	net.Conn                         // a net.Conn holding the connection
+	UDPSize        uint16            // minimum receive buffer for UDP messages
+	TsigSecret     map[string]string // secret(s) for Tsig map[<zonename>]<base64 secret>, zonename must be in canonical form (lowercase, fqdn, see RFC 4034 Section 6.2)
+	rtt            time.Duration
+	t              time.Time
+	tsigRequestMAC string
+}
+
+// A Client defines parameters for a DNS client.
+type Client struct {
+	Net       string      // if "tcp" or "tcp-tls" (DNS over TLS) a TCP query will be initiated, otherwise an UDP one (default is "" for UDP)
+	UDPSize   uint16      // minimum receive buffer for UDP messages
+	TLSConfig *tls.Config // TLS connection configuration
+	Dialer    *net.Dialer // a net.Dialer used to set local address, timeouts and more
+	// Timeout is a cumulative timeout for dial, write and read, defaults to 0 (disabled) - overrides DialTimeout, ReadTimeout,
+	// WriteTimeout when non-zero. Can be overridden with net.Dialer.Timeout (see Client.ExchangeWithDialer and
+	// Client.Dialer) or context.Context.Deadline (see the deprecated ExchangeContext)
+	Timeout        time.Duration
+	DialTimeout    time.Duration     // net.DialTimeout, defaults to 2 seconds, or net.Dialer.Timeout if expiring earlier - overridden by Timeout when that value is non-zero
+	ReadTimeout    time.Duration     // net.Conn.SetReadTimeout value for connections, defaults to 2 seconds - overridden by Timeout when that value is non-zero
+	WriteTimeout   time.Duration     // net.Conn.SetWriteTimeout value for connections, defaults to 2 seconds - overridden by Timeout when that value is non-zero
+	TsigSecret     map[string]string // secret(s) for Tsig map[<zonename>]<base64 secret>, zonename must be in canonical form (lowercase, fqdn, see RFC 4034 Section 6.2)
+	SingleInflight bool              // if true suppress multiple outstanding queries for the same Qname, Qtype and Qclass
+	group          singleflight
+}
+
+// Exchange performs a synchronous UDP query. It sends the message m to the address
+// contained in a and waits for a reply. Exchange does not retry a failed query, nor
+// will it fall back to TCP in case of truncation.
+// See client.Exchange for more information on setting larger buffer sizes.
+func Exchange(m *Msg, a string) (r *Msg, err error) {
+	client := Client{Net: "udp"}
+	r, _, err = client.Exchange(m, a)
+	return r, err
+}
+
+func (c *Client) dialTimeout() time.Duration {
+	if c.Timeout != 0 {
+		return c.Timeout
+	}
+	if c.DialTimeout != 0 {
+		return c.DialTimeout
+	}
+	return dnsTimeout
+}
+
+func (c *Client) readTimeout() time.Duration {
+	if c.ReadTimeout != 0 {
+		return c.ReadTimeout
+	}
+	return dnsTimeout
+}
+
+func (c *Client) writeTimeout() time.Duration {
+	if c.WriteTimeout != 0 {
+		return c.WriteTimeout
+	}
+	return dnsTimeout
+}
+
+// Dial connects to the address on the named network.
+func (c *Client) Dial(address string) (conn *Conn, err error) {
+	// create a new dialer with the appropriate timeout
+	var d net.Dialer
+	if c.Dialer == nil {
+		d = net.Dialer{}
+	} else {
+		d = net.Dialer(*c.Dialer)
+	}
+	d.Timeout = c.getTimeoutForRequest(c.writeTimeout())
+
+	network := "udp"
+	useTLS := false
+
+	switch c.Net {
+	case "tcp-tls":
+		network = "tcp"
+		useTLS = true
+	case "tcp4-tls":
+		network = "tcp4"
+		useTLS = true
+	case "tcp6-tls":
+		network = "tcp6"
+		useTLS = true
+	default:
+		if c.Net != "" {
+			network = c.Net
+		}
+	}
+
+	conn = new(Conn)
+	if useTLS {
+		conn.Conn, err = tls.DialWithDialer(&d, network, address, c.TLSConfig)
+	} else {
+		conn.Conn, err = d.Dial(network, address)
+	}
+	if err != nil {
+		return nil, err
+	}
+	return conn, nil
+}
+
+// Exchange performs a synchronous query. It sends the message m to the address
+// contained in a and waits for a reply. Basic use pattern with a *dns.Client:
+//
+//	c := new(dns.Client)
+//	in, rtt, err := c.Exchange(message, "127.0.0.1:53")
+//
+// Exchange does not retry a failed query, nor will it fall back to TCP in
+// case of truncation.
+// It is up to the caller to create a message that allows for larger responses to be
+// returned. Specifically this means adding an EDNS0 OPT RR that will advertise a larger
+// buffer, see SetEdns0. Messages without an OPT RR will fallback to the historic limit
+// of 512 bytes
+// To specify a local address or a timeout, the caller has to set the `Client.Dialer`
+// attribute appropriately
+func (c *Client) Exchange(m *Msg, address string) (r *Msg, rtt time.Duration, err error) {
+	if !c.SingleInflight {
+		return c.exchange(m, address)
+	}
+
+	t := "nop"
+	if t1, ok := TypeToString[m.Question[0].Qtype]; ok {
+		t = t1
+	}
+	cl := "nop"
+	if cl1, ok := ClassToString[m.Question[0].Qclass]; ok {
+		cl = cl1
+	}
+	r, rtt, err, shared := c.group.Do(m.Question[0].Name+t+cl, func() (*Msg, time.Duration, error) {
+		return c.exchange(m, address)
+	})
+	if r != nil && shared {
+		r = r.Copy()
+	}
+	return r, rtt, err
+}
+
+func (c *Client) exchange(m *Msg, a string) (r *Msg, rtt time.Duration, err error) {
+	var co *Conn
+
+	co, err = c.Dial(a)
+
+	if err != nil {
+		return nil, 0, err
+	}
+	defer co.Close()
+
+	opt := m.IsEdns0()
+	// If EDNS0 is used use that for size.
+	if opt != nil && opt.UDPSize() >= MinMsgSize {
+		co.UDPSize = opt.UDPSize()
+	}
+	// Otherwise use the client's configured UDP size.
+	if opt == nil && c.UDPSize >= MinMsgSize {
+		co.UDPSize = c.UDPSize
+	}
+
+	co.TsigSecret = c.TsigSecret
+	// write with the appropriate write timeout
+	co.SetWriteDeadline(time.Now().Add(c.getTimeoutForRequest(c.writeTimeout())))
+	if err = co.WriteMsg(m); err != nil {
+		return nil, 0, err
+	}
+
+	co.SetReadDeadline(time.Now().Add(c.getTimeoutForRequest(c.readTimeout())))
+	r, err = co.ReadMsg()
+	if err == nil && r.Id != m.Id {
+		err = ErrId
+	}
+	return r, co.rtt, err
+}
+
+// ReadMsg reads a message from the connection co.
+// If the received message contains a TSIG record the transaction signature
+// is verified. This method always tries to return the message, however if an
+// error is returned there are no guarantees that the returned message is a
+// valid representation of the packet read.
+func (co *Conn) ReadMsg() (*Msg, error) {
+	p, err := co.ReadMsgHeader(nil)
+	if err != nil {
+		return nil, err
+	}
+
+	m := new(Msg)
+	if err := m.Unpack(p); err != nil {
+		// If an error was returned, we still want to allow the user to use
+		// the message, but naively they can just check err if they don't want
+		// to use an erroneous message
+		return m, err
+	}
+	if t := m.IsTsig(); t != nil {
+		if _, ok := co.TsigSecret[t.Hdr.Name]; !ok {
+			return m, ErrSecret
+		}
+		// Need to work on the original message p, as that was used to calculate the tsig.
+		err = TsigVerify(p, co.TsigSecret[t.Hdr.Name], co.tsigRequestMAC, false)
+	}
+	return m, err
+}
+
+// ReadMsgHeader reads a DNS message, parses and populates hdr (when hdr is not nil).
+// Returns message as a byte slice to be parsed with Msg.Unpack later on.
+// Note that error handling on the message body is not possible as only the header is parsed.
+func (co *Conn) ReadMsgHeader(hdr *Header) ([]byte, error) {
+	var (
+		p   []byte
+		n   int
+		err error
+	)
+
+	switch t := co.Conn.(type) {
+	case *net.TCPConn, *tls.Conn:
+		r := t.(io.Reader)
+
+		// First two bytes specify the length of the entire message.
+		l, err := tcpMsgLen(r)
+		if err != nil {
+			return nil, err
+		}
+		p = make([]byte, l)
+		n, err = tcpRead(r, p)
+		co.rtt = time.Since(co.t)
+	default:
+		if co.UDPSize > MinMsgSize {
+			p = make([]byte, co.UDPSize)
+		} else {
+			p = make([]byte, MinMsgSize)
+		}
+		n, err = co.Read(p)
+		co.rtt = time.Since(co.t)
+	}
+
+	if err != nil {
+		return nil, err
+	} else if n < headerSize {
+		return nil, ErrShortRead
+	}
+
+	p = p[:n]
+	if hdr != nil {
+		dh, _, err := unpackMsgHdr(p, 0)
+		if err != nil {
+			return nil, err
+		}
+		*hdr = dh
+	}
+	return p, err
+}
+
+// tcpMsgLen is a helper func to read first two bytes of stream as uint16 packet length.
+func tcpMsgLen(t io.Reader) (int, error) {
+	p := []byte{0, 0}
+	n, err := t.Read(p)
+	if err != nil {
+		return 0, err
+	}
+
+	// As seen with my local router/switch, returns 1 byte on the above read,
+	// resulting a a ShortRead. Just write it out (instead of loop) and read the
+	// other byte.
+	if n == 1 {
+		n1, err := t.Read(p[1:])
+		if err != nil {
+			return 0, err
+		}
+		n += n1
+	}
+
+	if n != 2 {
+		return 0, ErrShortRead
+	}
+	l := binary.BigEndian.Uint16(p)
+	if l == 0 {
+		return 0, ErrShortRead
+	}
+	return int(l), nil
+}
+
+// tcpRead calls TCPConn.Read enough times to fill allocated buffer.
+func tcpRead(t io.Reader, p []byte) (int, error) {
+	n, err := t.Read(p)
+	if err != nil {
+		return n, err
+	}
+	for n < len(p) {
+		j, err := t.Read(p[n:])
+		if err != nil {
+			return n, err
+		}
+		n += j
+	}
+	return n, err
+}
+
+// Read implements the net.Conn read method.
+func (co *Conn) Read(p []byte) (n int, err error) {
+	if co.Conn == nil {
+		return 0, ErrConnEmpty
+	}
+	if len(p) < 2 {
+		return 0, io.ErrShortBuffer
+	}
+	switch t := co.Conn.(type) {
+	case *net.TCPConn, *tls.Conn:
+		r := t.(io.Reader)
+
+		l, err := tcpMsgLen(r)
+		if err != nil {
+			return 0, err
+		}
+		if l > len(p) {
+			return int(l), io.ErrShortBuffer
+		}
+		return tcpRead(r, p[:l])
+	}
+	// UDP connection
+	n, err = co.Conn.Read(p)
+	if err != nil {
+		return n, err
+	}
+	return n, err
+}
+
+// WriteMsg sends a message through the connection co.
+// If the message m contains a TSIG record the transaction
+// signature is calculated.
+func (co *Conn) WriteMsg(m *Msg) (err error) {
+	var out []byte
+	if t := m.IsTsig(); t != nil {
+		mac := ""
+		if _, ok := co.TsigSecret[t.Hdr.Name]; !ok {
+			return ErrSecret
+		}
+		out, mac, err = TsigGenerate(m, co.TsigSecret[t.Hdr.Name], co.tsigRequestMAC, false)
+		// Set for the next read, although only used in zone transfers
+		co.tsigRequestMAC = mac
+	} else {
+		out, err = m.Pack()
+	}
+	if err != nil {
+		return err
+	}
+	co.t = time.Now()
+	if _, err = co.Write(out); err != nil {
+		return err
+	}
+	return nil
+}
+
+// Write implements the net.Conn Write method.
+func (co *Conn) Write(p []byte) (n int, err error) {
+	switch t := co.Conn.(type) {
+	case *net.TCPConn, *tls.Conn:
+		w := t.(io.Writer)
+
+		lp := len(p)
+		if lp < 2 {
+			return 0, io.ErrShortBuffer
+		}
+		if lp > MaxMsgSize {
+			return 0, &Error{err: "message too large"}
+		}
+		l := make([]byte, 2, lp+2)
+		binary.BigEndian.PutUint16(l, uint16(lp))
+		p = append(l, p...)
+		n, err := io.Copy(w, bytes.NewReader(p))
+		return int(n), err
+	}
+	n, err = co.Conn.Write(p)
+	return n, err
+}
+
+// Return the appropriate timeout for a specific request
+func (c *Client) getTimeoutForRequest(timeout time.Duration) time.Duration {
+	var requestTimeout time.Duration
+	if c.Timeout != 0 {
+		requestTimeout = c.Timeout
+	} else {
+		requestTimeout = timeout
+	}
+	// net.Dialer.Timeout has priority if smaller than the timeouts computed so
+	// far
+	if c.Dialer != nil && c.Dialer.Timeout != 0 {
+		if c.Dialer.Timeout < requestTimeout {
+			requestTimeout = c.Dialer.Timeout
+		}
+	}
+	return requestTimeout
+}
+
+// Dial connects to the address on the named network.
+func Dial(network, address string) (conn *Conn, err error) {
+	conn = new(Conn)
+	conn.Conn, err = net.Dial(network, address)
+	if err != nil {
+		return nil, err
+	}
+	return conn, nil
+}
+
+// ExchangeContext performs a synchronous UDP query, like Exchange. It
+// additionally obeys deadlines from the passed Context.
+func ExchangeContext(ctx context.Context, m *Msg, a string) (r *Msg, err error) {
+	client := Client{Net: "udp"}
+	r, _, err = client.ExchangeContext(ctx, m, a)
+	// ignorint rtt to leave the original ExchangeContext API unchanged, but
+	// this function will go away
+	return r, err
+}
+
+// ExchangeConn performs a synchronous query. It sends the message m via the connection
+// c and waits for a reply. The connection c is not closed by ExchangeConn.
+// This function is going away, but can easily be mimicked:
+//
+//	co := &dns.Conn{Conn: c} // c is your net.Conn
+//	co.WriteMsg(m)
+//	in, _  := co.ReadMsg()
+//	co.Close()
+//
+func ExchangeConn(c net.Conn, m *Msg) (r *Msg, err error) {
+	println("dns: ExchangeConn: this function is deprecated")
+	co := new(Conn)
+	co.Conn = c
+	if err = co.WriteMsg(m); err != nil {
+		return nil, err
+	}
+	r, err = co.ReadMsg()
+	if err == nil && r.Id != m.Id {
+		err = ErrId
+	}
+	return r, err
+}
+
+// DialTimeout acts like Dial but takes a timeout.
+func DialTimeout(network, address string, timeout time.Duration) (conn *Conn, err error) {
+	client := Client{Net: network, Dialer: &net.Dialer{Timeout: timeout}}
+	conn, err = client.Dial(address)
+	if err != nil {
+		return nil, err
+	}
+	return conn, nil
+}
+
+// DialWithTLS connects to the address on the named network with TLS.
+func DialWithTLS(network, address string, tlsConfig *tls.Config) (conn *Conn, err error) {
+	if !strings.HasSuffix(network, "-tls") {
+		network += "-tls"
+	}
+	client := Client{Net: network, TLSConfig: tlsConfig}
+	conn, err = client.Dial(address)
+
+	if err != nil {
+		return nil, err
+	}
+	return conn, nil
+}
+
+// DialTimeoutWithTLS acts like DialWithTLS but takes a timeout.
+func DialTimeoutWithTLS(network, address string, tlsConfig *tls.Config, timeout time.Duration) (conn *Conn, err error) {
+	if !strings.HasSuffix(network, "-tls") {
+		network += "-tls"
+	}
+	client := Client{Net: network, Dialer: &net.Dialer{Timeout: timeout}, TLSConfig: tlsConfig}
+	conn, err = client.Dial(address)
+	if err != nil {
+		return nil, err
+	}
+	return conn, nil
+}
+
+// ExchangeContext acts like Exchange, but honors the deadline on the provided
+// context, if present. If there is both a context deadline and a configured
+// timeout on the client, the earliest of the two takes effect.
+func (c *Client) ExchangeContext(ctx context.Context, m *Msg, a string) (r *Msg, rtt time.Duration, err error) {
+	var timeout time.Duration
+	if deadline, ok := ctx.Deadline(); !ok {
+		timeout = 0
+	} else {
+		timeout = deadline.Sub(time.Now())
+	}
+	// not passing the context to the underlying calls, as the API does not support
+	// context. For timeouts you should set up Client.Dialer and call Client.Exchange.
+	c.Dialer = &net.Dialer{Timeout: timeout}
+	return c.Exchange(m, a)
+}