test: net:in/out_message tracepoint tests

This adds tests for the net:inbound_message and net:outbound_message
tracepoint interface.

2 files changed, 172 insertions, 0 deletions

diff --git a/test/functional/interface_usdt_net.py b/test/functional/interface_usdt_net.py
new file mode 100755
index 0000000000..9522cd8c59
--- /dev/null
+++ b/test/functional/interface_usdt_net.py
@@ -0,0 +1,171 @@
+#!/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 net:* tracepoint API interface.
+     See https://github.com/bitcoin/bitcoin/blob/master/doc/tracing.md#context-net
+"""
+
+import ctypes
+from io import BytesIO
+# 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.messages import msg_version
+from test_framework.p2p import P2PInterface
+from test_framework.test_framework import BitcoinTestFramework
+from test_framework.util import assert_equal
+
+# Tor v3 addresses are 62 chars + 6 chars for the port (':12345').
+MAX_PEER_ADDR_LENGTH = 68
+MAX_PEER_CONN_TYPE_LENGTH = 20
+MAX_MSG_TYPE_LENGTH = 20
+# We won't process messages larger than 150 byte in this test. For reading
+# larger messanges see contrib/tracing/log_raw_p2p_msgs.py
+MAX_MSG_DATA_LENGTH = 150
+
+net_tracepoints_program = """
+#include <uapi/linux/ptrace.h>
+
+#define MAX_PEER_ADDR_LENGTH {}
+#define MAX_PEER_CONN_TYPE_LENGTH {}
+#define MAX_MSG_TYPE_LENGTH {}
+#define MAX_MSG_DATA_LENGTH {}
+""".format(
+    MAX_PEER_ADDR_LENGTH,
+    MAX_PEER_CONN_TYPE_LENGTH,
+    MAX_MSG_TYPE_LENGTH,
+    MAX_MSG_DATA_LENGTH
+) + """
+#define MIN(a,b) ({ __typeof__ (a) _a = (a); __typeof__ (b) _b = (b); _a < _b ? _a : _b; })
+
+struct p2p_message
+{
+    u64     peer_id;
+    char    peer_addr[MAX_PEER_ADDR_LENGTH];
+    char    peer_conn_type[MAX_PEER_CONN_TYPE_LENGTH];
+    char    msg_type[MAX_MSG_TYPE_LENGTH];
+    u64     msg_size;
+    u8      msg[MAX_MSG_DATA_LENGTH];
+};
+
+BPF_PERF_OUTPUT(inbound_messages);
+int trace_inbound_message(struct pt_regs *ctx) {
+    struct p2p_message msg = {};
+    bpf_usdt_readarg(1, ctx, &msg.peer_id);
+    bpf_usdt_readarg_p(2, ctx, &msg.peer_addr, MAX_PEER_ADDR_LENGTH);
+    bpf_usdt_readarg_p(3, ctx, &msg.peer_conn_type, MAX_PEER_CONN_TYPE_LENGTH);
+    bpf_usdt_readarg_p(4, ctx, &msg.msg_type, MAX_MSG_TYPE_LENGTH);
+    bpf_usdt_readarg(5, ctx, &msg.msg_size);
+    bpf_usdt_readarg_p(6, ctx, &msg.msg, MIN(msg.msg_size, MAX_MSG_DATA_LENGTH));
+    inbound_messages.perf_submit(ctx, &msg, sizeof(msg));
+    return 0;
+}
+
+BPF_PERF_OUTPUT(outbound_messages);
+int trace_outbound_message(struct pt_regs *ctx) {
+    struct p2p_message msg = {};
+    bpf_usdt_readarg(1, ctx, &msg.peer_id);
+    bpf_usdt_readarg_p(2, ctx, &msg.peer_addr, MAX_PEER_ADDR_LENGTH);
+    bpf_usdt_readarg_p(3, ctx, &msg.peer_conn_type, MAX_PEER_CONN_TYPE_LENGTH);
+    bpf_usdt_readarg_p(4, ctx, &msg.msg_type, MAX_MSG_TYPE_LENGTH);
+    bpf_usdt_readarg(5, ctx, &msg.msg_size);
+    bpf_usdt_readarg_p(6, ctx, &msg.msg, MIN(msg.msg_size, MAX_MSG_DATA_LENGTH));
+    outbound_messages.perf_submit(ctx, &msg, sizeof(msg));
+    return 0;
+};
+"""
+
+
+class NetTracepointTest(BitcoinTestFramework):
+    def set_test_params(self):
+        self.num_nodes = 1
+
+    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()
+
+    def run_test(self):
+        # Tests the net:inbound_message and net:outbound_message tracepoints
+        # See https://github.com/bitcoin/bitcoin/blob/master/doc/tracing.md#context-net
+
+        class P2PMessage(ctypes.Structure):
+            _fields_ = [
+                ("peer_id", ctypes.c_uint64),
+                ("peer_addr", ctypes.c_char * MAX_PEER_ADDR_LENGTH),
+                ("peer_conn_type", ctypes.c_char * MAX_PEER_CONN_TYPE_LENGTH),
+                ("msg_type", ctypes.c_char * MAX_MSG_TYPE_LENGTH),
+                ("msg_size", ctypes.c_uint64),
+                ("msg", ctypes.c_ubyte * MAX_MSG_DATA_LENGTH),
+            ]
+
+            def __repr__(self):
+                return f"P2PMessage(peer={self.peer_id}, addr={self.peer_addr.decode('utf-8')}, conn_type={self.peer_conn_type.decode('utf-8')}, msg_type={self.msg_type.decode('utf-8')}, msg_size={self.msg_size})"
+
+        self.log.info(
+            "hook into the net:inbound_message and net:outbound_message tracepoints")
+        ctx = USDT(path=str(self.options.bitcoind))
+        ctx.enable_probe(probe="net:inbound_message",
+                         fn_name="trace_inbound_message")
+        ctx.enable_probe(probe="net:outbound_message",
+                         fn_name="trace_outbound_message")
+        bpf = BPF(text=net_tracepoints_program, usdt_contexts=[ctx], debug=0)
+
+        # The handle_* function is a ctypes callback function called from C. When
+        # we assert in the handle_* function, the AssertError doesn't propagate
+        # back to Python. The exception is ignored. We manually count and assert
+        # that the handle_* functions succeeded.
+        EXPECTED_INOUTBOUND_VERSION_MSG = 1
+        checked_inbound_version_msg = 0
+        checked_outbound_version_msg = 0
+
+        def check_p2p_message(event, inbound):
+            nonlocal checked_inbound_version_msg, checked_outbound_version_msg
+            if event.msg_type.decode("utf-8") == "version":
+                self.log.info(
+                    f"check_p2p_message(): {'inbound' if inbound else 'outbound'} {event}")
+                peer = self.nodes[0].getpeerinfo()[0]
+                msg = msg_version()
+                msg.deserialize(BytesIO(bytes(event.msg[:event.msg_size])))
+                assert_equal(peer["id"], event.peer_id, peer["id"])
+                assert_equal(peer["addr"], event.peer_addr.decode("utf-8"))
+                assert_equal(peer["connection_type"],
+                             event.peer_conn_type.decode("utf-8"))
+                if inbound:
+                    checked_inbound_version_msg += 1
+                else:
+                    checked_outbound_version_msg += 1
+
+        def handle_inbound(_, data, __):
+            event = ctypes.cast(data, ctypes.POINTER(P2PMessage)).contents
+            check_p2p_message(event, True)
+
+        def handle_outbound(_, data, __):
+            event = ctypes.cast(data, ctypes.POINTER(P2PMessage)).contents
+            check_p2p_message(event, False)
+
+        bpf["inbound_messages"].open_perf_buffer(handle_inbound)
+        bpf["outbound_messages"].open_perf_buffer(handle_outbound)
+
+        self.log.info("connect a P2P test node to our bitcoind node")
+        test_node = P2PInterface()
+        self.nodes[0].add_p2p_connection(test_node)
+        bpf.perf_buffer_poll(timeout=200)
+
+        self.log.info(
+            "check that we got both an inbound and outbound version message")
+        assert_equal(EXPECTED_INOUTBOUND_VERSION_MSG,
+                     checked_inbound_version_msg)
+        assert_equal(EXPECTED_INOUTBOUND_VERSION_MSG,
+                     checked_outbound_version_msg)
+
+        bpf.cleanup()
+
+
+if __name__ == '__main__':
+    NetTracepointTest().main()
diff --git a/test/functional/test_runner.py b/test/functional/test_runner.py
index 516e8be638..86dcf16db1 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_net.py',
     'rpc_psbt.py --legacy-wallet',
     'rpc_psbt.py --descriptors',
     'rpc_users.py',