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client_dialer.go
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client_dialer.go
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package fastdns
import (
"context"
"crypto/tls"
"fmt"
"io"
"net"
"net/http"
"net/url"
"reflect"
"sync"
"time"
"unsafe"
)
// UDPDialer is a custom dialer for creating UDP connections.
// It manages a pool of connections to optimize performance in scenarios
// where multiple UDP connections to the same server are required.
type UDPDialer struct {
// Addr specifies the remote UDP address that the dialer will connect to.
Addr *net.UDPAddr
// Timeout specifies the maximum duration for a query to complete.
// If a query exceeds this duration, it will result in a timeout error.
Timeout time.Duration
// MaxConns limits the maximum number of UDP connections that can be created
// and reused. Once this limit is reached, no new connections will be made.
// If not set, use 64 as default.
MaxConns uint16
once sync.Once
conns chan net.Conn
}
func (d *UDPDialer) DialContext(ctx context.Context, network, addr string) (conn net.Conn, err error) {
return d.get()
}
func (d *UDPDialer) get() (_ net.Conn, err error) {
d.once.Do(func() {
if d.MaxConns == 0 {
d.MaxConns = 64
}
d.conns = make(chan net.Conn, d.MaxConns)
for range d.MaxConns {
var c *net.UDPConn
c, err = net.DialUDP("udp", nil, d.Addr)
if err != nil {
break
}
d.conns <- c
}
})
if err != nil {
return
}
c := <-d.conns
return c, nil
}
func (d *UDPDialer) put(conn net.Conn) {
d.conns <- conn
}
// TCPDialer is a custom dialer for creating TLS connections.
// It manages a pool of connections to optimize performance in scenarios
// where multiple TLS connections to the same server are required.
type TCPDialer struct {
// Addr specifies the remote TLS address that the dialer will connect to.
Addr *net.TCPAddr
// TLSConfig specifies the *tls.Config for TLS handshakes.
// If set, use DoT instead of TCP protocol.
TLSConfig *tls.Config
// Timeout specifies the maximum duration for a query to complete.
// If a query exceeds this duration, it will result in a timeout error.
Timeout time.Duration
// MaxConns limits the maximum number of TLS connections that can be created
// and reused. Once this limit is reached, no new connections will be made.
// If not set, use 8 as default.
MaxConns uint16
once sync.Once
conns chan net.Conn
}
func (d *TCPDialer) DialContext(ctx context.Context, network, addr string) (conn net.Conn, err error) {
return d.get()
}
func (d *TCPDialer) get() (_ net.Conn, err error) {
d.once.Do(func() {
if d.MaxConns == 0 {
d.MaxConns = 8
}
d.conns = make(chan net.Conn, d.MaxConns)
for range d.MaxConns {
d.conns <- &tcpConn{nil, d, make([]byte, 0, 1024)}
}
})
if err != nil {
return
}
c := <-d.conns
return c, nil
}
func (d *TCPDialer) put(conn net.Conn) {
d.conns <- conn
}
type tcpConn struct {
net.Conn
dialer *TCPDialer
buffer []byte
}
func (c *tcpConn) Write(b []byte) (int, error) {
if c.Conn == nil {
var err error
if c.dialer.TLSConfig != nil {
c.Conn, err = tls.DialWithDialer(&net.Dialer{Timeout: c.dialer.Timeout}, "tcp", c.dialer.Addr.String(), c.dialer.TLSConfig)
} else {
c.Conn, err = (&net.Dialer{Timeout: c.dialer.Timeout}).Dial("tcp", c.dialer.Addr.String())
}
if err != nil {
return 0, err
}
}
n := len(b)
c.buffer = append(c.buffer[:0], byte(n>>8), byte(n&0xFF))
c.buffer = append(c.buffer, b...)
_, err := c.Conn.Write(c.buffer)
return n, err
}
func (c *tcpConn) Read(b []byte) (n int, err error) {
c.buffer = c.buffer[:cap(c.buffer)]
n, err = c.Conn.Read(c.buffer)
if err != nil {
return
}
m := int(c.buffer[0])<<8 | int(c.buffer[1])
if m+2 != n {
return 0, ErrInvalidAnswer
}
copy(b, c.buffer[2:n])
return n - 2, nil
}
// HTTPDialer is a custom dialer for creating HTTP connections.
// It allows sending HTTP requests with a specified endpoint, user agent, and transport configuration.
type HTTPDialer struct {
// Endpoint specifies the HTTP server's URL that the dialer will connect to.
// This is the base address used for sending HTTP requests.
Endpoint *url.URL
// Transport allows for customizing the underlying transport mechanism used
// for making HTTP requests. If set, it overrides the default RoundTripper behavior.
Transport http.RoundTripper
// Header defines the request header that will be sent in the HTTP requests.
// It can be customized for specific needs, E.g. User-Agent.
Header http.Header
once sync.Once
pool sync.Pool
}
func (d *HTTPDialer) DialContext(ctx context.Context, network, addr string) (net.Conn, error) {
d.once.Do(func() {
if d.Header == nil {
d.Header = http.Header{
"content-type": {"application/dns-message"},
"user-agent": {"fastdns/1.0"},
}
}
d.pool = sync.Pool{
New: func() any {
return &httpConn{
req: &http.Request{
Method: http.MethodPost,
URL: d.Endpoint,
Host: d.Endpoint.Host,
Header: d.Header,
},
reader: new(bufferreader),
writer: new(bufferwriter),
}
},
}
})
c := d.pool.Get().(*httpConn)
c.dialer = d
c.ctx = ctx
c.writer.B = c.writer.B[:0]
c.reader.B = nil
c.resp = nil
return c, nil
}
func (d *HTTPDialer) put(conn net.Conn) {
if c, _ := conn.(*httpConn); c != nil {
d.pool.Put(c)
}
}
type httpConn struct {
dialer *HTTPDialer
ctx context.Context
req *http.Request
reader *bufferreader
writer *bufferwriter
resp []byte
}
func (c *httpConn) Read(b []byte) (n int, err error) {
if c.resp == nil {
err = io.EOF
return
}
n = copy(b, c.resp)
if n < len(c.resp) {
c.resp = c.resp[n:]
} else {
c.resp = nil
}
return n, nil
}
func (c *httpConn) Write(b []byte) (n int, err error) {
var tr = c.dialer.Transport
if tr == nil {
tr = http.DefaultTransport
}
c.reader.B = b
c.req.Body = c.reader
c.req.ContentLength = int64(len(b))
// c.req.ctx = c.ctx
*(*context.Context)(unsafe.Pointer(uintptr(unsafe.Pointer(c.req)) + httpctxoffset)) = c.ctx
resp, err := tr.RoundTrip(c.req)
if err != nil {
return 0, fmt.Errorf("fastdns: roundtrip %s error: %w", c.dialer.Endpoint, err)
}
defer resp.Body.Close()
_, err = io.Copy(c.writer, resp.Body)
if err != nil {
return 0, fmt.Errorf("fastdns: read from %s error: %w", c.dialer.Endpoint, err)
}
if resp.StatusCode != http.StatusOK || resp.ContentLength <= 0 {
return 0, fmt.Errorf("fastdns: read from %s error: %s: %s", c.dialer.Endpoint, resp.Status, c.writer.B)
}
c.resp = c.writer.B
return len(b), nil
}
func (c *httpConn) Close() (err error) {
return
}
func (c *httpConn) LocalAddr() net.Addr {
return &net.TCPAddr{}
}
func (c *httpConn) RemoteAddr() net.Addr {
return &net.TCPAddr{}
}
func (c *httpConn) SetDeadline(t time.Time) error {
return nil
}
func (c *httpConn) SetReadDeadline(t time.Time) error {
return nil
}
func (c *httpConn) SetWriteDeadline(t time.Time) error {
return nil
}
var httpctxoffset = func() uintptr {
var req http.Request
v := reflect.TypeOf(req)
for i := 0; i < v.NumField(); i++ {
field := v.Field(i)
if field.Name == "ctx" {
return field.Offset
}
}
panic("unsupported go version, please upgrade fastdns")
}()
type bufferwriter struct {
B []byte
}
func (b *bufferwriter) Write(p []byte) (int, error) {
b.B = append(b.B, p...)
return len(p), nil
}
type bufferreader struct {
B []byte
}
func (r *bufferreader) Read(b []byte) (int, error) {
if r.B == nil {
return 0, io.EOF
}
n := copy(b, r.B)
if n < len(r.B) {
r.B = r.B[n:]
} else {
r.B = nil
}
return n, nil
}
func (r *bufferreader) Close() error {
r.B = nil
return nil
}
func (r *bufferreader) WriteTo(w io.Writer) (int64, error) {
n, err := w.Write(r.B)
return int64(n), err
}
var _ io.Writer = (*bufferwriter)(nil)
var _ io.ReadCloser = (*bufferreader)(nil)
var _ io.WriterTo = (*bufferreader)(nil)