rpc: Add getblockfilter RPC method.

Retrieves and returns block filter and header from index.

test/functional/rpc_getblockfilter.py

@@ -0,0 +1,59 @@
+#!/usr/bin/env python3
+# Copyright (c) 2018 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+"""Test the getblockfilter RPC."""
+
+from test_framework.test_framework import BitcoinTestFramework
+from test_framework.util import (
+    assert_equal, assert_is_hex_string, assert_raises_rpc_error,
+    connect_nodes, disconnect_nodes, sync_blocks
+    )
+
+FILTER_TYPES = ["basic"]
+
+class GetBlockFilterTest(BitcoinTestFramework):
+    def set_test_params(self):
+        self.setup_clean_chain = True
+        self.num_nodes = 2
+        self.extra_args = [["-blockfilterindex"], []]
+
+    def run_test(self):
+        # Create two chains by disconnecting nodes 0 & 1, mining, then reconnecting
+        disconnect_nodes(self.nodes[0], 1)
+
+        self.nodes[0].generate(3)
+        self.nodes[1].generate(4)
+
+        assert_equal(self.nodes[0].getblockcount(), 3)
+        chain0_hashes = [self.nodes[0].getblockhash(block_height) for block_height in range(4)]
+
+        # Reorg node 0 to a new chain
+        connect_nodes(self.nodes[0], 1)
+        sync_blocks(self.nodes)
+
+        assert_equal(self.nodes[0].getblockcount(), 4)
+        chain1_hashes = [self.nodes[0].getblockhash(block_height) for block_height in range(4)]
+
+        # Test getblockfilter returns a filter for all blocks and filter types on active chain
+        for block_hash in chain1_hashes:
+            for filter_type in FILTER_TYPES:
+                result = self.nodes[0].getblockfilter(block_hash, filter_type)
+                assert_is_hex_string(result['filter'])
+
+        # Test getblockfilter returns a filter for all blocks and filter types on stale chain
+        for block_hash in chain0_hashes:
+            for filter_type in FILTER_TYPES:
+                result = self.nodes[0].getblockfilter(block_hash, filter_type)
+                assert_is_hex_string(result['filter'])
+
+        # Test getblockfilter with unknown block
+        bad_block_hash = "0123456789abcdef" * 4
+        assert_raises_rpc_error(-5, "Block not found", self.nodes[0].getblockfilter, bad_block_hash, "basic")
+
+        # Test getblockfilter with undefined filter type
+        genesis_hash = self.nodes[0].getblockhash(0)
+        assert_raises_rpc_error(-5, "Unknown filtertype", self.nodes[0].getblockfilter, genesis_hash, "unknown")
+
+if __name__ == '__main__':
+    GetBlockFilterTest().main()

test/functional/test_runner.py

@@ -144,6 +144,7 @@ BASE_SCRIPTS = [
     'wallet_txn_doublespend.py',
     'wallet_txn_clone.py --mineblock',
     'feature_notifications.py',
+    'rpc_getblockfilter.py',
     'rpc_invalidateblock.py',
     'feature_rbf.py',
     'mempool_packages.py',