[trackerscraper] Add custom DNS lookup function

config.go

@@ -90,6 +90,9 @@ type ClientConfig struct {
 	// Defines proxy for HTTP requests, such as for trackers. It's commonly set from the result of
 	// "net/http".ProxyURL(HTTPProxy).
 	HTTPProxy func(*http.Request) (*url.URL, error)
+	// Takes a tracker's hostname and requests DNS A and AAAA records.
+	// Used in case DNS lookups require a special setup (i.e., dns-over-https)
+	TrackerIpFetcher func(*url.URL) ([]net.IP, error)
 	// HTTPUserAgent changes default UserAgent for HTTP requests
 	HTTPUserAgent string
 	// Updated occasionally to when there's been some changes to client

torrent.go

@@ -1579,6 +1579,7 @@ func (t *Torrent) startScrapingTracker(_url string) {
 		newAnnouncer := &trackerScraper{
 			u:         *u,
 			t:         t,
+			ipFetcher: t.cl.config.TrackerIpFetcher,
 		}
 		go newAnnouncer.Run()
 		return newAnnouncer

tracker_scraper.go

@@ -21,6 +21,7 @@ type trackerScraper struct {
 	u            url.URL
 	t            *Torrent
 	lastAnnounce trackerAnnounceResult
+	ipFetcher    func(*url.URL) ([]net.IP, error)
 }
 
 type torrentTrackerAnnouncer interface {
@@ -66,7 +67,13 @@ type trackerAnnounceResult struct {
 }
 
 func (me *trackerScraper) getIp() (ip net.IP, err error) {
-	ips, err := net.LookupIP(me.u.Hostname())
+	var ips []net.IP
+	if me.ipFetcher != nil {
+		ips, err = me.ipFetcher(&me.u)
+	} else {
+		// Do a regular dns lookup
+		ips, err = net.LookupIP(me.u.Hostname())
+	}
 	if err != nil {
 		return
 	}