made the minimum announce interval configurable

docs/manual.html

@@ -2915,6 +2915,8 @@ struct session_settings
         int auto_scrape_min_interval;
 
         int max_peerlist_size;
+
+        int min_announce_interval;
 };
 </pre>
 <p><tt class="docutils literal"><span class="pre">user_agent</span></tt> this is the client identification to the tracker.
@@ -3126,6 +3128,10 @@ should be much greater than the maximum number of connected peers.
 Peers are evicted from the cache when the list grows passed 90% of
 this limit, and once the size hits the limit, peers are no longer
 added to the list.</p>
+<p><tt class="docutils literal"><span class="pre">min_announce_interval</span></tt> is the minimum allowed announce interval
+for a tracker. This is specified in seconds, defaults to 5 minutes and
+is used as a sanity check on what is returned from a tracker. It
+mitigates hammering misconfigured trackers.</p>
 </div>
 <div class="section">
 <h1><a id="pe-settings" name="pe-settings">pe_settings</a></h1>

docs/manual.rst

@@ -2899,6 +2899,8 @@ that will be sent to the tracker. The user-agent is a good way to identify your
 		int auto_scrape_min_interval;
 
 		int max_peerlist_size;
+
+		int min_announce_interval;
 	};
 
 ``user_agent`` this is the client identification to the tracker.
@@ -3165,6 +3167,12 @@ Peers are evicted from the cache when the list grows passed 90% of
 this limit, and once the size hits the limit, peers are no longer
 added to the list.
 
+``min_announce_interval`` is the minimum allowed announce interval
+for a tracker. This is specified in seconds, defaults to 5 minutes and
+is used as a sanity check on what is returned from a tracker. It
+mitigates hammering misconfigured trackers.
+
+
 pe_settings
 ===========
 

include/libtorrent/session_settings.hpp

@@ -140,6 +140,7 @@ namespace libtorrent
 			, auto_scrape_interval(1800)
 			, auto_scrape_min_interval(300)
 			, max_peerlist_size(8000)
+			, min_announce_interval(5 * 60)
 		{}
 
 		// this is the user agent that will be sent to the tracker
@@ -430,6 +431,11 @@ namespace libtorrent
 		// per torrent. This is the peers we know
 		// about, not necessarily connected to.
 		int max_peerlist_size;
+
+		// any announce intervals reported from a tracker
+		// that is lower than this, will be clamped to this
+		// value. It's specified in seconds
+		int min_announce_interval;
 	};
 
 #ifndef TORRENT_DISABLE_DHT

src/torrent.cpp

@@ -962,9 +962,9 @@ namespace libtorrent
 			m_complete_sent = true;
 
 		m_failed_trackers = 0;
-		// announce intervals less than 5 minutes
-		// are insane.
-		if (interval < 60 * 5) interval = 60 * 5;
+
+		if (interval < m_ses.settings().min_announce_interval)
+			interval = m_ses.settings().min_announce_interval;
 
 		m_last_working_tracker
 			= prioritize_tracker(m_currently_trying_tracker);