prevent peer flooding request queue for an inv

mapAlreadyAskedFor does not keep track of which peer has a request queued for a
particular tx. As a result, a peer can blind a node to a tx indefinitely by
sending many invs for the same tx, and then never replying to getdatas for it.
Each inv received will be placed 2 minutes farther back in mapAlreadyAskedFor,
so a short message containing 10 invs would render that tx unavailable for 20
minutes.

This is fixed by disallowing a peer from having more than one entry for a
particular inv in mapAlreadyAskedFor at a time.

1 files changed, 1 insertions, 0 deletions

diff --git a/src/net.h b/src/net.h
index 559cdf0878..046811d54c 100644
--- a/src/net.h
+++ b/src/net.h
@@ -382,6 +382,7 @@ public:
     mruset<CInv> setInventoryKnown;
     std::vector<CInv> vInventoryToSend;
     CCriticalSection cs_inventory;
+    std::set<uint256> setAskFor;
     std::multimap<int64_t, CInv> mapAskFor;
 
     // Ping time measurement: