114 lines
3.1 KiB
Go
114 lines
3.1 KiB
Go
package ssdp
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import (
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"context"
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"log"
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"net/http"
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"net/url"
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"strconv"
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"time"
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)
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const (
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ssdpDiscover = `"ssdp:discover"`
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ntsAlive = `ssdp:alive`
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ntsByebye = `ssdp:byebye`
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ntsUpdate = `ssdp:update`
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ssdpUDP4Addr = "239.255.255.250:1900"
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ssdpSearchPort = 1900
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methodSearch = "M-SEARCH"
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methodNotify = "NOTIFY"
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// SSDPAll is a value for searchTarget that searches for all devices and services.
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SSDPAll = "ssdp:all"
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// UPNPRootDevice is a value for searchTarget that searches for all root devices.
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UPNPRootDevice = "upnp:rootdevice"
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)
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// HTTPUClient is the interface required to perform HTTP-over-UDP requests.
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type HTTPUClient interface {
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Do(req *http.Request, numSends int) ([]*http.Response, error)
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}
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func max(a, b int64) int64 {
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if a > b {
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return a
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}
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return b
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}
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// SSDPRawSearch performs a fairly raw SSDP search request, and returns the
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// unique response(s) that it receives. Each response has the requested
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// searchTarget, a USN, and a valid location. maxWaitSeconds states how long to
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// wait for responses in seconds, and must be a minimum of 1 (the
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// implementation waits an additional 100ms for responses to arrive), 2 is a
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// reasonable value for this. numSends is the number of requests to send - 3 is
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// a reasonable value for this.
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func SSDPRawSearch(
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ctx context.Context,
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httpu HTTPUClient,
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searchTarget string,
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numSends int,
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) ([]*http.Response, error) {
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// Must specify at least 1 second according to the spec.
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var wait int64 = 1
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// https://openconnectivity.org/upnp-specs/UPnP-arch-DeviceArchitecture-v2.0-20200417.pdf
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if deadline, ok := ctx.Deadline(); ok {
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wait = max(wait, int64(time.Until(deadline).Seconds()))
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}
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header := http.Header{
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// Putting headers in here avoids them being title-cased.
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// (The UPnP discovery protocol uses case-sensitive headers)
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"HOST": []string{ssdpUDP4Addr},
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"MAN": []string{ssdpDiscover},
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"MX": []string{strconv.FormatInt(wait, 10)},
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"ST": []string{searchTarget},
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}
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req := &http.Request{
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Method: methodSearch,
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// TODO: Support both IPv4 and IPv6.
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Host: ssdpUDP4Addr,
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URL: &url.URL{Opaque: "*"},
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Header: header,
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}
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ctx, cancel := context.WithTimeout(ctx, time.Duration(wait)*time.Second)
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defer cancel()
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req = req.WithContext(ctx)
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allResponses, err := httpu.Do(req, numSends)
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if err != nil {
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return nil, err
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}
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isExactSearch := searchTarget != SSDPAll && searchTarget != UPNPRootDevice
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seenUSNs := make(map[string]bool)
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var responses []*http.Response
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for _, response := range allResponses {
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if response.StatusCode != 200 {
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log.Printf("ssdp: got response status code %q in search response", response.Status)
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continue
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}
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if st := response.Header.Get("ST"); isExactSearch && st != searchTarget {
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continue
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}
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usn := response.Header.Get("USN")
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if usn == "" {
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// Empty/missing USN in search response - using location instead.
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location, err := response.Location()
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if err != nil {
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// No usable location in search response - discard.
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continue
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}
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usn = location.String()
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}
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if _, alreadySeen := seenUSNs[usn]; !alreadySeen {
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seenUSNs[usn] = true
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responses = append(responses, response)
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}
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}
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return responses, nil
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}
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