Merge #9058: Fixes for p2p-compactblocks.py test timeouts on travis (#8842)

dac53b5 Modify getblocktxn handler not to drop requests for old blocks (Russell Yanofsky)
55bfddc [qa] Fix stale data bug in test_compactblocks_not_at_tip (Russell Yanofsky)
47e9659 [qa] Fix bug in compactblocks v2 merge (Russell Yanofsky)

qa/rpc-tests/p2p-compactblocks.py

@@ -300,8 +300,8 @@ class CompactBlocksTest(BitcoinTestFramework):
             assert(segwit_tx_generated) # check that our test is not broken
 
         # Wait until we've seen the block announcement for the resulting tip
-        tip = int(self.nodes[0].getbestblockhash(), 16)
-        assert(self.test_node.wait_for_block_announcement(tip))
+        tip = int(node.getbestblockhash(), 16)
+        assert(test_node.wait_for_block_announcement(tip))
 
         # Now mine a block, and look at the resulting compact block.
         test_node.clear_block_announcement()
@@ -589,8 +589,8 @@ class CompactBlocksTest(BitcoinTestFramework):
         assert_equal(int(node.getbestblockhash(), 16), block.sha256)
 
     def test_getblocktxn_handler(self, node, test_node, version):
-        # bitcoind won't respond for blocks whose height is more than 15 blocks
-        # deep.
+        # bitcoind will not send blocktxn responses for blocks whose height is
+        # more than 10 blocks deep.
         MAX_GETBLOCKTXN_DEPTH = 10
         chain_height = node.getblockcount()
         current_height = chain_height
@@ -623,11 +623,17 @@ class CompactBlocksTest(BitcoinTestFramework):
                 test_node.last_blocktxn = None
             current_height -= 1
 
-        # Next request should be ignored, as we're past the allowed depth.
+        # Next request should send a full block response, as we're past the
+        # allowed depth for a blocktxn response.
         block_hash = node.getblockhash(current_height)
         msg.block_txn_request = BlockTransactionsRequest(int(block_hash, 16), [0])
+        with mininode_lock:
+            test_node.last_block = None
+            test_node.last_blocktxn = None
         test_node.send_and_ping(msg)
         with mininode_lock:
+            test_node.last_block.block.calc_sha256()
+            assert_equal(test_node.last_block.block.sha256, int(block_hash, 16))
             assert_equal(test_node.last_blocktxn, None)
 
     def test_compactblocks_not_at_tip(self, node, test_node):
@@ -648,6 +654,8 @@ class CompactBlocksTest(BitcoinTestFramework):
         node.generate(1)
         wait_until(test_node.received_block_announcement, timeout=30)
         test_node.clear_block_announcement()
+        with mininode_lock:
+            test_node.last_block = None
         test_node.send_message(msg_getdata([CInv(4, int(new_blocks[0], 16))]))
         success = wait_until(lambda: test_node.last_block is not None, timeout=30)
         assert(success)

src/main.cpp

@@ -5495,7 +5495,19 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv,
         }
 
         if (it->second->nHeight < chainActive.Height() - MAX_BLOCKTXN_DEPTH) {
+            // If an older block is requested (should never happen in practice,
+            // but can happen in tests) send a block response instead of a
+            // blocktxn response. Sending a full block response instead of a
+            // small blocktxn response is preferable in the case where a peer
+            // might maliciously send lots of getblocktxn requests to trigger
+            // expensive disk reads, because it will require the peer to
+            // actually receive all the data read from disk over the network.
             LogPrint("net", "Peer %d sent us a getblocktxn for a block > %i deep", pfrom->id, MAX_BLOCKTXN_DEPTH);
+            CInv vInv;
+            vInv.type = State(pfrom->GetId())->fWantsCmpctWitness ? MSG_WITNESS_BLOCK : MSG_BLOCK;
+            vInv.hash = req.blockhash;
+            pfrom->vRecvGetData.push_back(vInv);
+            ProcessGetData(pfrom, chainparams.GetConsensus(), connman);
             return true;
         }