Disable bloom filtering by default.

BIP 37 bloom filters have been well-known to be a significant DoS
target for some time. However, in order to provide continuity for
SPV clients relying on it, the NODE_BLOOM service flag was added,
and left as a default, to ensure sufficient nodes exist with such a
flag.

NODE_BLOOM is, at this point, well-established and, as long as
there exist 0.18 nodes with default config (which I'd anticipate
will be true for many years), will be available from some peers. By
that time, the continued slowdown of BIP 37-based filtering will
likely have rendered it useless (though this is already largely the
case). Further, BIP 37 was deliberately never updated to support
witness-based filtering as newer wallets are expected to migrate to
some yet-to-be-network-exposed filters.

src/validation.h

@@ -127,7 +127,7 @@ static const unsigned int MAX_BLOCKS_TO_ANNOUNCE = 8;
 /** Maximum number of unconnecting headers announcements before DoS score */
 static const int MAX_UNCONNECTING_HEADERS = 10;
 
-static const bool DEFAULT_PEERBLOOMFILTERS = true;
+static const bool DEFAULT_PEERBLOOMFILTERS = false;
 
 /** Default for -stopatheight */
 static const int DEFAULT_STOPATHEIGHT = 0;

test/functional/p2p_node_network_limited.py

@@ -8,7 +8,7 @@ Tests that a node configured with -prune=550 signals NODE_NETWORK_LIMITED correc
 and that it responds to getdata requests for blocks correctly:
     - send a block within 288 + 2 of the tip
     - disconnect peers who request blocks older than that."""
-from test_framework.messages import CInv, msg_getdata, msg_verack, NODE_BLOOM, NODE_NETWORK_LIMITED, NODE_WITNESS
+from test_framework.messages import CInv, msg_getdata, msg_verack, NODE_NETWORK_LIMITED, NODE_WITNESS
 from test_framework.mininode import P2PInterface, mininode_lock
 from test_framework.test_framework import BitcoinTestFramework
 from test_framework.util import (
@@ -55,7 +55,7 @@ class NodeNetworkLimitedTest(BitcoinTestFramework):
     def run_test(self):
         node = self.nodes[0].add_p2p_connection(P2PIgnoreInv())
 
-        expected_services = NODE_BLOOM | NODE_WITNESS | NODE_NETWORK_LIMITED
+        expected_services = NODE_WITNESS | NODE_NETWORK_LIMITED
 
         self.log.info("Check that node has signalled expected services.")
         assert_equal(node.nServices, expected_services)
@@ -83,7 +83,7 @@ class NodeNetworkLimitedTest(BitcoinTestFramework):
 
         node1.wait_for_addr()
         #must relay address with NODE_NETWORK_LIMITED
-        assert_equal(node1.firstAddrnServices, 1036)
+        assert_equal(node1.firstAddrnServices, expected_services)
 
         self.nodes[0].disconnect_p2ps()
         node1.wait_for_disconnect()

test/functional/test_framework/messages.py

@@ -44,7 +44,7 @@ BIP125_SEQUENCE_NUMBER = 0xfffffffd  # Sequence number that is BIP 125 opt-in an
 
 NODE_NETWORK = (1 << 0)
 # NODE_GETUTXO = (1 << 1)
-NODE_BLOOM = (1 << 2)
+# NODE_BLOOM = (1 << 2)
 NODE_WITNESS = (1 << 3)
 NODE_NETWORK_LIMITED = (1 << 10)