135 lines
3.6 KiB
Go
135 lines
3.6 KiB
Go
package httpu
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import (
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"bufio"
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"bytes"
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"errors"
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"fmt"
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"log"
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"net"
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"net/http"
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"sync"
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"time"
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)
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// HTTPUClient is a client for dealing with HTTPU (HTTP over UDP). Its typical
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// function is for HTTPMU, and particularly SSDP.
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type HTTPUClient struct {
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connLock sync.Mutex // Protects use of conn.
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conn net.PacketConn
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}
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// NewHTTPUClient creates a new HTTPUClient, opening up a new UDP socket for the
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// purpose.
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func NewHTTPUClient() (*HTTPUClient, error) {
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conn, err := net.ListenPacket("udp", ":0")
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if err != nil {
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return nil, err
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}
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return &HTTPUClient{conn: conn}, nil
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}
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// NewHTTPUClientAddr creates a new HTTPUClient which will broadcast packets
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// from the specified address, opening up a new UDP socket for the purpose
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func NewHTTPUClientAddr(addr string) (*HTTPUClient, error) {
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ip := net.ParseIP(addr)
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if ip == nil {
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return nil, errors.New("Invalid listening address")
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}
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conn, err := net.ListenPacket("udp", ip.String()+":0")
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if err != nil {
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return nil, err
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}
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return &HTTPUClient{conn: conn}, nil
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}
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// Close shuts down the client. The client will no longer be useful following
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// this.
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func (httpu *HTTPUClient) Close() error {
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httpu.connLock.Lock()
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defer httpu.connLock.Unlock()
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return httpu.conn.Close()
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}
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// Do performs a request. The timeout is how long to wait for before returning
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// the responses that were received. An error is only returned for failing to
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// send the request. Failures in receipt simply do not add to the resulting
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// responses.
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//
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// Note that at present only one concurrent connection will happen per
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// HTTPUClient.
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func (httpu *HTTPUClient) Do(req *http.Request, timeout time.Duration, numSends int) ([]*http.Response, error) {
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httpu.connLock.Lock()
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defer httpu.connLock.Unlock()
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// Create the request. This is a subset of what http.Request.Write does
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// deliberately to avoid creating extra fields which may confuse some
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// devices.
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var requestBuf bytes.Buffer
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method := req.Method
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if method == "" {
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method = "GET"
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}
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if _, err := fmt.Fprintf(&requestBuf, "%s %s HTTP/1.1\r\n", method, req.URL.RequestURI()); err != nil {
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return nil, err
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}
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if err := req.Header.Write(&requestBuf); err != nil {
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return nil, err
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}
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if _, err := requestBuf.Write([]byte{'\r', '\n'}); err != nil {
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return nil, err
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}
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destAddr, err := net.ResolveUDPAddr("udp", req.Host)
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if err != nil {
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return nil, err
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}
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if err = httpu.conn.SetDeadline(time.Now().Add(timeout)); err != nil {
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return nil, err
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}
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// Send request.
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for i := 0; i < numSends; i++ {
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if n, err := httpu.conn.WriteTo(requestBuf.Bytes(), destAddr); err != nil {
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return nil, err
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} else if n < len(requestBuf.Bytes()) {
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return nil, fmt.Errorf("httpu: wrote %d bytes rather than full %d in request",
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n, len(requestBuf.Bytes()))
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}
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time.Sleep(5 * time.Millisecond)
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}
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// Await responses until timeout.
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var responses []*http.Response
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responseBytes := make([]byte, 2048)
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for {
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// 2048 bytes should be sufficient for most networks.
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n, _, err := httpu.conn.ReadFrom(responseBytes)
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if err != nil {
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if err, ok := err.(net.Error); ok {
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if err.Timeout() {
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break
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}
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if err.Temporary() {
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// Sleep in case this is a persistent error to avoid pegging CPU until deadline.
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time.Sleep(10 * time.Millisecond)
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continue
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}
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}
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return nil, err
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}
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// Parse response.
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response, err := http.ReadResponse(bufio.NewReader(bytes.NewBuffer(responseBytes[:n])), req)
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if err != nil {
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log.Printf("httpu: error while parsing response: %v", err)
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continue
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}
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responses = append(responses, response)
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}
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// Timeout reached - return discovered responses.
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return responses, nil
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}
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