test: Add test for coinselection tracepoints

2 files changed, 209 insertions, 0 deletions

diff --git a/test/functional/interface_usdt_coinselection.py b/test/functional/interface_usdt_coinselection.py
new file mode 100755
index 0000000000..ef32feda99
--- /dev/null
+++ b/test/functional/interface_usdt_coinselection.py
@@ -0,0 +1,208 @@
+#!/usr/bin/env python3
+# Copyright (c) 2022 The Bitcoin Core developers
+# Distributed under the MIT software license, see the accompanying
+# file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+"""  Tests the coin_selection:* tracepoint API interface.
+     See https://github.com/bitcoin/bitcoin/blob/master/doc/tracing.md#context-coin_selection
+"""
+
+# Test will be skipped if we don't have bcc installed
+try:
+    from bcc import BPF, USDT # type: ignore[import]
+except ImportError:
+    pass
+from test_framework.test_framework import BitcoinTestFramework
+from test_framework.util import (
+    assert_equal,
+    assert_greater_than,
+    assert_raises_rpc_error,
+)
+
+coinselection_tracepoints_program = """
+#include <uapi/linux/ptrace.h>
+
+#define WALLET_NAME_LENGTH 16
+#define ALGO_NAME_LENGTH 16
+
+struct event_data
+{
+    u8 type;
+    char wallet_name[WALLET_NAME_LENGTH];
+
+    // selected coins event
+    char algo[ALGO_NAME_LENGTH];
+    s64 target;
+    s64 waste;
+    s64 selected_value;
+
+    // create tx event
+    bool success;
+    s64 fee;
+    s32 change_pos;
+
+    // aps create tx event
+    bool use_aps;
+};
+
+BPF_QUEUE(coin_selection_events, struct event_data, 1024);
+
+int trace_selected_coins(struct pt_regs *ctx) {
+    struct event_data data;
+    __builtin_memset(&data, 0, sizeof(data));
+    data.type = 1;
+    bpf_usdt_readarg_p(1, ctx, &data.wallet_name, WALLET_NAME_LENGTH);
+    bpf_usdt_readarg_p(2, ctx, &data.algo, ALGO_NAME_LENGTH);
+    bpf_usdt_readarg(3, ctx, &data.target);
+    bpf_usdt_readarg(4, ctx, &data.waste);
+    bpf_usdt_readarg(5, ctx, &data.selected_value);
+    coin_selection_events.push(&data, 0);
+    return 0;
+}
+
+int trace_normal_create_tx(struct pt_regs *ctx) {
+    struct event_data data;
+    __builtin_memset(&data, 0, sizeof(data));
+    data.type = 2;
+    bpf_usdt_readarg_p(1, ctx, &data.wallet_name, WALLET_NAME_LENGTH);
+    bpf_usdt_readarg(2, ctx, &data.success);
+    bpf_usdt_readarg(3, ctx, &data.fee);
+    bpf_usdt_readarg(4, ctx, &data.change_pos);
+    coin_selection_events.push(&data, 0);
+    return 0;
+}
+
+int trace_attempt_aps(struct pt_regs *ctx) {
+    struct event_data data;
+    __builtin_memset(&data, 0, sizeof(data));
+    data.type = 3;
+    bpf_usdt_readarg_p(1, ctx, &data.wallet_name, WALLET_NAME_LENGTH);
+    coin_selection_events.push(&data, 0);
+    return 0;
+}
+
+int trace_aps_create_tx(struct pt_regs *ctx) {
+    struct event_data data;
+    __builtin_memset(&data, 0, sizeof(data));
+    data.type = 4;
+    bpf_usdt_readarg_p(1, ctx, &data.wallet_name, WALLET_NAME_LENGTH);
+    bpf_usdt_readarg(2, ctx, &data.use_aps);
+    bpf_usdt_readarg(3, ctx, &data.success);
+    bpf_usdt_readarg(4, ctx, &data.fee);
+    bpf_usdt_readarg(5, ctx, &data.change_pos);
+    coin_selection_events.push(&data, 0);
+    return 0;
+}
+"""
+
+
+class CoinSelectionTracepointTest(BitcoinTestFramework):
+    def set_test_params(self):
+        self.num_nodes = 1
+        self.setup_clean_chain = True
+
+    def skip_test_if_missing_module(self):
+        self.skip_if_platform_not_linux()
+        self.skip_if_no_bitcoind_tracepoints()
+        self.skip_if_no_python_bcc()
+        self.skip_if_no_bpf_permissions()
+        self.skip_if_no_wallet()
+
+    def get_tracepoints(self, expected_types):
+        events = []
+        try:
+            for i in range(0, len(expected_types) + 1):
+                event = self.bpf["coin_selection_events"].pop()
+                assert_equal(event.wallet_name.decode(), self.default_wallet_name)
+                assert_equal(event.type, expected_types[i])
+                events.append(event)
+            else:
+                # If the loop exits successfully instead of throwing a KeyError, then we have had
+                # more events than expected. There should be no more than len(expected_types) events.
+                assert False
+        except KeyError:
+            assert_equal(len(events), len(expected_types))
+            return events
+
+
+    def determine_selection_from_usdt(self, events):
+        success = None
+        use_aps = None
+        algo = None
+        waste = None
+        change_pos = None
+
+        is_aps = False
+        sc_events = []
+        for event in events:
+            if event.type == 1:
+                if not is_aps:
+                    algo = event.algo.decode()
+                    waste = event.waste
+                sc_events.append(event)
+            elif event.type == 2:
+                success = event.success
+                if not is_aps:
+                    change_pos = event.change_pos
+            elif event.type == 3:
+                is_aps = True
+            elif event.type == 4:
+                assert is_aps
+                if event.use_aps:
+                    use_aps = True
+                    assert_equal(len(sc_events), 2)
+                    algo = sc_events[1].algo.decode()
+                    waste = sc_events[1].waste
+                    change_pos = event.change_pos
+        return success, use_aps, algo, waste, change_pos
+
+    def run_test(self):
+        self.log.info("hook into the coin_selection tracepoints")
+        ctx = USDT(pid=self.nodes[0].process.pid)
+        ctx.enable_probe(probe="coin_selection:selected_coins", fn_name="trace_selected_coins")
+        ctx.enable_probe(probe="coin_selection:normal_create_tx_internal", fn_name="trace_normal_create_tx")
+        ctx.enable_probe(probe="coin_selection:attempting_aps_create_tx", fn_name="trace_attempt_aps")
+        ctx.enable_probe(probe="coin_selection:aps_create_tx_internal", fn_name="trace_aps_create_tx")
+        self.bpf = BPF(text=coinselection_tracepoints_program, usdt_contexts=[ctx], debug=0)
+
+        self.log.info("Prepare wallets")
+        self.generate(self.nodes[0], 101)
+        wallet = self.nodes[0].get_wallet_rpc(self.default_wallet_name)
+
+        self.log.info("Sending a transaction should result in all tracepoints")
+        # We should have 5 tracepoints in the order:
+        # 1. selected_coins (type 1)
+        # 2. normal_create_tx_internal (type 2)
+        # 3. attempting_aps_create_tx (type 3)
+        # 4. selected_coins (type 1)
+        # 5. aps_create_tx_internal (type 4)
+        wallet.sendtoaddress(wallet.getnewaddress(), 10)
+        events = self.get_tracepoints([1, 2, 3, 1, 4])
+        success, use_aps, algo, waste, change_pos = self.determine_selection_from_usdt(events)
+        assert_equal(success, True)
+        assert_greater_than(change_pos, -1)
+
+        self.log.info("Failing to fund results in 1 tracepoint")
+        # We should have 1 tracepoints in the order
+        # 1. normal_create_tx_internal (type 2)
+        assert_raises_rpc_error(-6, "Insufficient funds", wallet.sendtoaddress, wallet.getnewaddress(), 102 * 50)
+        events = self.get_tracepoints([2])
+        success, use_aps, algo, waste, change_pos = self.determine_selection_from_usdt(events)
+        assert_equal(success, False)
+
+        self.log.info("Explicitly enabling APS results in 2 tracepoints")
+        # We should have 2 tracepoints in the order
+        # 1. selected_coins (type 1)
+        # 2. normal_create_tx_internal (type 2)
+        wallet.setwalletflag("avoid_reuse")
+        wallet.sendtoaddress(address=wallet.getnewaddress(), amount=10, avoid_reuse=True)
+        events = self.get_tracepoints([1, 2])
+        success, use_aps, algo, waste, change_pos = self.determine_selection_from_usdt(events)
+        assert_equal(success, True)
+        assert_equal(use_aps, None)
+
+        self.bpf.cleanup()
+
+
+if __name__ == '__main__':
+    CoinSelectionTracepointTest().main()
diff --git a/test/functional/test_runner.py b/test/functional/test_runner.py
index 1f0f806d91..7a1d1a9776 100755
--- a/test/functional/test_runner.py
+++ b/test/functional/test_runner.py
@@ -168,6 +168,7 @@ BASE_SCRIPTS = [
     'wallet_reorgsrestore.py',
     'interface_http.py',
     'interface_rpc.py',
+    'interface_usdt_coinselection.py',
     'interface_usdt_net.py',
     'interface_usdt_utxocache.py',
     'interface_usdt_validation.py',