tracing: add inbound connection tracepoint

doc/tracing.md

@@ -93,6 +93,18 @@ to user-space in full. Messages longer than a 32kb might be cut off. This can
 be detected in tracing scripts by comparing the message size to the length of
 the passed message.
 
+#### Tracepoint `net:inbound_connection`
+
+Is called when a new inbound connection is opened to us. Passes information about
+the peer and the number of inbound connections including the newly opened connection.
+
+Arguments passed:
+1. Peer ID as `int64`
+2. Peer address and port (IPv4, IPv6, Tor v3, I2P, ...) as `pointer to C-style String` (max. length 68 characters)
+3. Connection Type (inbound, feeler, outbound-full-relay, ...) as `pointer to C-style String` (max. length 20 characters)
+4. Network the peer connects from as `uint32` (1 = IPv4, 2 = IPv6, 3 = Onion, 4 = I2P, 5 = CJDNS). See `Network` enum in `netaddress.h`.
+5. Number of existing inbound connections as `uint64` including the newly opened inbound connection.
+
 ### Context `validation`
 
 #### Tracepoint `validation:block_connected`

src/net.cpp

@@ -53,6 +53,7 @@
 #include <optional>
 #include <unordered_map>
 
+TRACEPOINT_SEMAPHORE(net, inbound_connection);
 TRACEPOINT_SEMAPHORE(net, outbound_message);
 
 /** Maximum number of block-relay-only anchor connections */
@@ -1833,6 +1834,12 @@ void CConnman::CreateNodeFromAcceptedSocket(std::unique_ptr<Sock>&& sock,
         m_nodes.push_back(pnode);
     }
     LogDebug(BCLog::NET, "connection from %s accepted\n", addr.ToStringAddrPort());
+    TRACEPOINT(net, inbound_connection,
+        pnode->GetId(),
+        pnode->m_addr_name.c_str(),
+        pnode->ConnectionTypeAsString().c_str(),
+        pnode->ConnectedThroughNetwork(),
+        GetNodeCount(ConnectionDirection::In));
 
     // We received a new connection, harvest entropy from the time (and our peer count)
     RandAddEvent((uint32_t)id);

test/functional/interface_usdt_net.py

@@ -27,6 +27,9 @@ MAX_MSG_TYPE_LENGTH = 20
 # larger messanges see contrib/tracing/log_raw_p2p_msgs.py
 MAX_MSG_DATA_LENGTH = 150
 
+# from net_address.h
+NETWORK_TYPE_UNROUTABLE = 0
+
 net_tracepoints_program = """
 #include <uapi/linux/ptrace.h>
 
@@ -53,6 +56,20 @@ struct p2p_message
     u8      msg[MAX_MSG_DATA_LENGTH];
 };
 
+struct Connection
+{
+    u64     id;
+    char    addr[MAX_PEER_ADDR_LENGTH];
+    char    type[MAX_PEER_CONN_TYPE_LENGTH];
+    u32     network;
+};
+
+struct NewConnection
+{
+    struct Connection   conn;
+    u64                 existing;
+};
+
 BPF_PERF_OUTPUT(inbound_messages);
 int trace_inbound_message(struct pt_regs *ctx) {
     struct p2p_message msg = {};
@@ -78,9 +95,46 @@ int trace_outbound_message(struct pt_regs *ctx) {
     outbound_messages.perf_submit(ctx, &msg, sizeof(msg));
     return 0;
 };
+
+BPF_PERF_OUTPUT(inbound_connections);
+int trace_inbound_connection(struct pt_regs *ctx) {
+    struct NewConnection inbound = {};
+    void *conn_type_pointer = NULL, *address_pointer = NULL;
+    bpf_usdt_readarg(1, ctx, &inbound.conn.id);
+    bpf_usdt_readarg(2, ctx, &address_pointer);
+    bpf_usdt_readarg(3, ctx, &conn_type_pointer);
+    bpf_usdt_readarg(4, ctx, &inbound.conn.network);
+    bpf_usdt_readarg(5, ctx, &inbound.existing);
+    bpf_probe_read_user_str(&inbound.conn.addr, sizeof(inbound.conn.addr), address_pointer);
+    bpf_probe_read_user_str(&inbound.conn.type, sizeof(inbound.conn.type), conn_type_pointer);
+    inbound_connections.perf_submit(ctx, &inbound, sizeof(inbound));
+    return 0;
+};
+
 """
 
 
+class Connection(ctypes.Structure):
+    _fields_ = [
+        ("id", ctypes.c_uint64),
+        ("addr", ctypes.c_char * MAX_PEER_ADDR_LENGTH),
+        ("conn_type", ctypes.c_char * MAX_PEER_CONN_TYPE_LENGTH),
+        ("network", ctypes.c_uint32),
+    ]
+
+    def __repr__(self):
+        return f"Connection(peer={self.id}, addr={self.addr.decode('utf-8')}, conn_type={self.conn_type.decode('utf-8')}, network={self.network})"
+
+
+class NewConnection(ctypes.Structure):
+    _fields_ = [
+        ("conn", Connection),
+        ("existing", ctypes.c_uint64),
+    ]
+
+    def __repr__(self):
+        return f"NewConnection(conn={self.conn}, existing={self.existing})"
+
 class NetTracepointTest(BitcoinTestFramework):
     def set_test_params(self):
         self.num_nodes = 1
@@ -92,6 +146,10 @@ class NetTracepointTest(BitcoinTestFramework):
         self.skip_if_no_bpf_permissions()
 
     def run_test(self):
+        self.p2p_message_tracepoint_test()
+        self.inbound_conn_tracepoint_test()
+
+    def p2p_message_tracepoint_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
 
@@ -166,7 +224,44 @@ class NetTracepointTest(BitcoinTestFramework):
 
 
         bpf.cleanup()
+        test_node.peer_disconnect()
 
+    def inbound_conn_tracepoint_test(self):
+        self.log.info("hook into the net:inbound_connection tracepoint")
+        ctx = USDT(pid=self.nodes[0].process.pid)
+        ctx.enable_probe(probe="net:inbound_connection",
+                         fn_name="trace_inbound_connection")
+        bpf = BPF(text=net_tracepoints_program, usdt_contexts=[ctx], debug=0, cflags=["-Wno-error=implicit-function-declaration"])
+
+        inbound_connections = []
+        EXPECTED_INBOUND_CONNECTIONS = 2
+
+        def handle_inbound_connection(_, data, __):
+            nonlocal inbound_connections
+            event = ctypes.cast(data, ctypes.POINTER(NewConnection)).contents
+            self.log.info(f"handle_inbound_connection(): {event}")
+            inbound_connections.append(event)
+
+        bpf["inbound_connections"].open_perf_buffer(handle_inbound_connection)
+
+        self.log.info("connect two P2P test nodes to our bitcoind node")
+        testnodes = list()
+        for _ in range(EXPECTED_INBOUND_CONNECTIONS):
+            testnode = P2PInterface()
+            self.nodes[0].add_p2p_connection(testnode)
+            testnodes.append(testnode)
+        bpf.perf_buffer_poll(timeout=200)
+
+        assert_equal(EXPECTED_INBOUND_CONNECTIONS, len(inbound_connections))
+        for inbound_connection in inbound_connections:
+            assert inbound_connection.conn.id > 0
+            assert inbound_connection.existing > 0
+            assert_equal(b'inbound', inbound_connection.conn.conn_type)
+            assert_equal(NETWORK_TYPE_UNROUTABLE, inbound_connection.conn.network)
+
+        bpf.cleanup()
+        for node in testnodes:
+            node.peer_disconnect()
 
 if __name__ == '__main__':
     NetTracepointTest(__file__).main()