tracing: Tracepoints for in- and outbound P2P msgs

Can be used to monitor in- and outbound node traffic.

Based on ealier work by jb55.

Co-authored-by: William Casarin <jb55@jb55.com>

4 files changed, 578 insertions, 0 deletions

diff --git a/contrib/tracing/README.md b/contrib/tracing/README.md
index e4da724750..2d81e375dc 100644
--- a/contrib/tracing/README.md
+++ b/contrib/tracing/README.md
@@ -43,3 +43,123 @@ example, to point to release builds if needed. See the
 kernel VM. This means the bpftrace and BCC examples must be executed with root
 privileges. Make sure to carefully review any scripts that you run with root
 privileges first!**
+
+### log_p2p_traffic.bt
+
+A bpftrace script logging information about inbound and outbound P2P network
+messages. Based on the `net:inbound_message` and `net:outbound_message`
+tracepoints.
+
+By default, `bpftrace` limits strings to 64 bytes due to the limited stack size
+in the eBPF VM. For example, Tor v3 addresses exceed the string size limit which
+results in the port being cut off during logging. The string size limit can be
+increased with the `BPFTRACE_STRLEN` environment variable (`BPFTRACE_STRLEN=70`
+works fine).
+
+```
+$ bpftrace contrib/tracing/log_p2p_traffic.bt
+```
+
+Output
+```
+outbound 'ping' msg to peer 11 (outbound-full-relay, [2a02:b10c:f747:1:ef:fake:ipv6:addr]:8333) with 8 bytes
+inbound 'pong' msg from peer 11 (outbound-full-relay, [2a02:b10c:f747:1:ef:fake:ipv6:addr]:8333) with 8 bytes
+inbound 'inv' msg from peer 16 (outbound-full-relay, XX.XX.XXX.121:8333) with 37 bytes
+outbound 'getdata' msg to peer 16 (outbound-full-relay, XX.XX.XXX.121:8333) with 37 bytes
+inbound 'tx' msg from peer 16 (outbound-full-relay, XX.XX.XXX.121:8333) with 222 bytes
+outbound 'inv' msg to peer 9 (outbound-full-relay, faketorv3addressa2ufa6odvoi3s77j4uegey0xb10csyfyve2t33curbyd.onion:8333) with 37 bytes
+outbound 'inv' msg to peer 7 (outbound-full-relay, XX.XX.XXX.242:8333) with 37 bytes
+…
+```
+
+### p2p_monitor.py
+
+A BCC Python script using curses for an interactive P2P message monitor. Based
+on the `net:inbound_message` and `net:outbound_message` tracepoints.
+
+Inbound and outbound traffic is listed for each peer together with information
+about the connection. Peers can be selected individually to view recent P2P
+messages.
+
+```
+$ python3 contrib/tracing/p2p_monitor.py ./src/bitcoind
+```
+
+Lists selectable peers and traffic and connection information.
+```
+ P2P Message Monitor
+ Navigate with UP/DOWN or J/K and select a peer with ENTER or SPACE to see individual P2P messages
+
+ PEER  OUTBOUND              INBOUND               TYPE                   ADDR
+    0  46          398 byte  61      1407590 byte  block-relay-only       XX.XX.XXX.196:8333
+   11  1156     253570 byte  3431    2394924 byte  outbound-full-relay    XXX.X.XX.179:8333
+   13  3425    1809620 byte  1236     305458 byte  inbound                XXX.X.X.X:60380
+   16  1046     241633 byte  1589    1199220 byte  outbound-full-relay    4faketorv2pbfu7x.onion:8333
+   19  577      181679 byte  390      148951 byte  outbound-full-relay    kfake4vctorjv2o2.onion:8333
+   20  11         1248 byte  13         1283 byte  block-relay-only       [2600:fake:64d9:b10c:4436:aaaa:fe:bb]:8333
+   21  11         1248 byte  13         1299 byte  block-relay-only       XX.XXX.X.155:8333
+   22  5           103 byte  1           102 byte  feeler                 XX.XX.XXX.173:8333
+   23  11         1248 byte  12         1255 byte  block-relay-only       XX.XXX.XXX.220:8333
+   24  3           103 byte  1           102 byte  feeler                 XXX.XXX.XXX.64:8333
+…
+```
+
+Showing recent P2P messages between our node and a selected peer.
+
+```
+    ----------------------------------------------------------------------
+    |                PEER 16 (4faketorv2pbfu7x.onion:8333)               |
+    | OUR NODE                outbound-full-relay                   PEER |
+    |                                           <--- sendcmpct (9 bytes) |
+    | inv (37 byte) --->                                                 |
+    |                                                <--- ping (8 bytes) |
+    | pong (8 byte) --->                                                 |
+    | inv (37 byte) --->                                                 |
+    |                                               <--- addr (31 bytes) |
+    | inv (37 byte) --->                                                 |
+    |                                       <--- getheaders (1029 bytes) |
+    | headers (1 byte) --->                                              |
+    |                                           <--- feefilter (8 bytes) |
+    |                                                <--- pong (8 bytes) |
+    |                                            <--- headers (82 bytes) |
+    |                                            <--- addr (30003 bytes) |
+    | inv (1261 byte) --->                                               |
+    |                                 …                                  |
+
+```
+
+### log_raw_p2p_msgs.py
+
+A BCC Python script showcasing eBPF and USDT limitations when passing data
+larger than about 32kb. Based on the `net:inbound_message` and
+`net:outbound_message` tracepoints.
+
+Bitcoin P2P messages can be larger than 32kb (e.g. `tx`, `block`, ...). The
+eBPF VM's stack is limited to 512 bytes, and we can't allocate more than about
+32kb for a P2P message in the eBPF VM. The **message data is cut off** when the
+message is larger than MAX_MSG_DATA_LENGTH (see script). This can be detected
+in user-space by comparing the data length to the message length variable. The
+message is cut off when the data length is smaller than the message length.
+A warning is included with the printed message data.
+
+Data is submitted to user-space (i.e. to this script) via a ring buffer. The
+throughput of the ring buffer is limited. Each p2p_message is about 32kb in
+size. In- or outbound messages submitted to the ring buffer in rapid
+succession fill the ring buffer faster than it can be read. Some messages are
+lost. BCC prints: `Possibly lost 2 samples` on lost messages.
+
+
+```
+$ python3 contrib/tracing/log_raw_p2p_msgs.py ./src/bitcoind
+```
+
+```
+Logging raw P2P messages.
+Messages larger that about 32kb will be cut off!
+Some messages might be lost!
+ outbound msg 'inv' from peer 4 (outbound-full-relay, XX.XXX.XX.4:8333) with 253 bytes: 0705000000be2245c8f844c9f763748e1a7…
+…
+Warning: incomplete message (only 32568 out of 53552 bytes)! inbound msg 'tx' from peer 32 (outbound-full-relay, XX.XXX.XXX.43:8333) with 53552 bytes: 020000000001fd3c01939c85ad6756ed9fc…
+…
+Possibly lost 2 samples
+```
diff --git a/contrib/tracing/log_p2p_traffic.bt b/contrib/tracing/log_p2p_traffic.bt
new file mode 100755
index 0000000000..f62956aa5e
--- /dev/null
+++ b/contrib/tracing/log_p2p_traffic.bt
@@ -0,0 +1,28 @@
+#!/usr/bin/env bpftrace
+
+BEGIN
+{
+  printf("Logging P2P traffic\n")
+}
+
+usdt:./src/bitcoind:net:inbound_message
+{
+  $peer_id = (int64) arg0;
+  $peer_addr = str(arg1);
+  $peer_type = str(arg2);
+  $msg_type = str(arg3);
+  $msg_len = arg4;
+  printf("inbound '%s' msg from peer %d (%s, %s) with %d bytes\n", $msg_type, $peer_id, $peer_type, $peer_addr, $msg_len);
+}
+
+usdt:./src/bitcoind:net:outbound_message
+{
+  $peer_id = (int64) arg0;
+  $peer_addr = str(arg1);
+  $peer_type = str(arg2);
+  $msg_type = str(arg3);
+  $msg_len = arg4;
+
+  printf("outbound '%s' msg to peer %d (%s, %s) with %d bytes\n", $msg_type, $peer_id, $peer_type, $peer_addr, $msg_len);
+}
+
diff --git a/contrib/tracing/log_raw_p2p_msgs.py b/contrib/tracing/log_raw_p2p_msgs.py
new file mode 100755
index 0000000000..b5b5755632
--- /dev/null
+++ b/contrib/tracing/log_raw_p2p_msgs.py
@@ -0,0 +1,180 @@
+#!/usr/bin/env python3
+
+""" Demonstration of eBPF limitations and the effect on USDT with the
+    net:inbound_message and net:outbound_message tracepoints. """
+
+# This script shows a limitation of eBPF when data larger than 32kb is passed to
+# user-space. It uses BCC (https://github.com/iovisor/bcc) to load a sandboxed
+# eBPF program into the Linux kernel (root privileges are required). The eBPF
+# program attaches to two statically defined tracepoints. The tracepoint
+# 'net:inbound_message' is called when a new P2P message is received, and
+# 'net:outbound_message' is called on outbound P2P messages. The eBPF program
+# submits the P2P messages to this script via a BPF ring buffer. The submitted
+# messages are printed.
+
+# eBPF Limitations:
+#
+# Bitcoin P2P messages can be larger than 32kb (e.g. tx, block, ...). The eBPF
+# VM's stack is limited to 512 bytes, and we can't allocate more than about 32kb
+# for a P2P message in the eBPF VM. The message data is cut off when the message
+# is larger than MAX_MSG_DATA_LENGTH (see definition below). This can be detected
+# in user-space by comparing the data length to the message length variable. The
+# message is cut off when the data length is smaller than the message length.
+# A warning is included with the printed message data.
+#
+# Data is submitted to user-space (i.e. to this script) via a ring buffer. The
+# throughput of the ring buffer is limited. Each p2p_message is about 32kb in
+# size. In- or outbound messages submitted to the ring buffer in rapid
+# succession fill the ring buffer faster than it can be read. Some messages are
+# lost.
+#
+# BCC prints: "Possibly lost 2 samples" on lost messages.
+
+import sys
+from bcc import BPF, USDT
+
+# BCC: The C program to be compiled to an eBPF program (by BCC) and loaded into
+# a sandboxed Linux kernel VM.
+program = """
+#include <uapi/linux/ptrace.h>
+
+#define MIN(a,b) ({ __typeof__ (a) _a = (a); __typeof__ (b) _b = (b); _a < _b ? _a : _b; })
+
+// Maximum possible allocation size
+// from include/linux/percpu.h in the Linux kernel
+#define PCPU_MIN_UNIT_SIZE (32 << 10)
+
+// Tor v3 addresses are 62 chars + 6 chars for the port (':12345').
+#define MAX_PEER_ADDR_LENGTH 62 + 6
+#define MAX_PEER_CONN_TYPE_LENGTH 20
+#define MAX_MSG_TYPE_LENGTH 20
+#define MAX_MSG_DATA_LENGTH PCPU_MIN_UNIT_SIZE - 200
+
+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];
+};
+
+// We can't store the p2p_message struct on the eBPF stack as it is limited to
+// 512 bytes and P2P message can be bigger than 512 bytes. However, we can use
+// an BPF-array with a length of 1 to allocate up to 32768 bytes (this is
+// defined by PCPU_MIN_UNIT_SIZE in include/linux/percpu.h in the Linux kernel).
+// Also see https://github.com/iovisor/bcc/issues/2306
+BPF_ARRAY(msg_arr, struct p2p_message, 1);
+
+// Two BPF perf buffers for pushing data (here P2P messages) to user-space.
+BPF_PERF_OUTPUT(inbound_messages);
+BPF_PERF_OUTPUT(outbound_messages);
+
+int trace_inbound_message(struct pt_regs *ctx) {
+    int idx = 0;
+    struct p2p_message *msg = msg_arr.lookup(&idx);
+
+    // lookup() does not return a NULL pointer. However, the BPF verifier
+    // requires an explicit check that that the `msg` pointer isn't a NULL
+    // pointer. See https://github.com/iovisor/bcc/issues/2595
+    if (msg == NULL) return 1;
+
+    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;
+};
+
+int trace_outbound_message(struct pt_regs *ctx) {
+    int idx = 0;
+    struct p2p_message *msg = msg_arr.lookup(&idx);
+
+    // lookup() does not return a NULL pointer. However, the BPF verifier
+    // requires an explicit check that that the `msg` pointer isn't a NULL
+    // pointer. See https://github.com/iovisor/bcc/issues/2595
+    if (msg == NULL) return 1;
+
+    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;
+};
+"""
+
+
+def print_message(event, inbound):
+    print(f"%s %s msg '%s' from peer %d (%s, %s) with %d bytes: %s" %
+          (
+              f"Warning: incomplete message (only %d out of %d bytes)!" % (
+                  len(event.msg), event.msg_size) if len(event.msg) < event.msg_size else "",
+              "inbound" if inbound else "outbound",
+              event.msg_type.decode("utf-8"),
+              event.peer_id,
+              event.peer_conn_type.decode("utf-8"),
+              event.peer_addr.decode("utf-8"),
+              event.msg_size,
+              bytes(event.msg[:event.msg_size]).hex(),
+          )
+          )
+
+
+def main(bitcoind_path):
+    bitcoind_with_usdts = USDT(path=str(bitcoind_path))
+
+    # attaching the trace functions defined in the BPF program to the tracepoints
+    bitcoind_with_usdts.enable_probe(
+        probe="inbound_message", fn_name="trace_inbound_message")
+    bitcoind_with_usdts.enable_probe(
+        probe="outbound_message", fn_name="trace_outbound_message")
+    bpf = BPF(text=program, usdt_contexts=[bitcoind_with_usdts])
+
+    # BCC: perf buffer handle function for inbound_messages
+    def handle_inbound(_, data, size):
+        """ Inbound message handler.
+
+        Called each time a message is submitted to the inbound_messages BPF table."""
+
+        event = bpf["inbound_messages"].event(data)
+        print_message(event, True)
+
+    # BCC: perf buffer handle function for outbound_messages
+
+    def handle_outbound(_, data, size):
+        """ Outbound message handler.
+
+        Called each time a message is submitted to the outbound_messages BPF table."""
+
+        event = bpf["outbound_messages"].event(data)
+        print_message(event, False)
+
+    # BCC: add handlers to the inbound and outbound perf buffers
+    bpf["inbound_messages"].open_perf_buffer(handle_inbound)
+    bpf["outbound_messages"].open_perf_buffer(handle_outbound)
+
+    print("Logging raw P2P messages.")
+    print("Messages larger that about 32kb will be cut off!")
+    print("Some messages might be lost!")
+    while True:
+        try:
+            bpf.perf_buffer_poll()
+        except KeyboardInterrupt:
+            exit()
+
+
+if __name__ == "__main__":
+    if len(sys.argv) < 2:
+        print("USAGE:", sys.argv[0], "path/to/bitcoind")
+        exit()
+    path = sys.argv[1]
+    main(path)
diff --git a/contrib/tracing/p2p_monitor.py b/contrib/tracing/p2p_monitor.py
new file mode 100755
index 0000000000..14e3e3a801
--- /dev/null
+++ b/contrib/tracing/p2p_monitor.py
@@ -0,0 +1,250 @@
+#!/usr/bin/env python3
+
+""" Interactive bitcoind P2P network traffic monitor utilizing USDT and the
+    net:inbound_message and net:outbound_message tracepoints. """
+
+# This script demonstrates what USDT for Bitcoin Core can enable. It uses BCC
+# (https://github.com/iovisor/bcc) to load a sandboxed eBPF program into the
+# Linux kernel (root privileges are required). The eBPF program attaches to two
+# statically defined tracepoints. The tracepoint 'net:inbound_message' is called
+# when a new P2P message is received, and 'net:outbound_message' is called on
+# outbound P2P messages. The eBPF program submits the P2P messages to
+# this script via a BPF ring buffer.
+
+import sys
+import curses
+from curses import wrapper, panel
+from bcc import BPF, USDT
+
+# BCC: The C program to be compiled to an eBPF program (by BCC) and loaded into
+# a sandboxed Linux kernel VM.
+program = """
+#include <uapi/linux/ptrace.h>
+
+// Tor v3 addresses are 62 chars + 6 chars for the port (':12345').
+// I2P addresses are 60 chars + 6 chars for the port (':12345').
+#define MAX_PEER_ADDR_LENGTH 62 + 6
+#define MAX_PEER_CONN_TYPE_LENGTH 20
+#define MAX_MSG_TYPE_LENGTH 20
+
+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;
+};
+
+
+// Two BPF perf buffers for pushing data (here P2P messages) to user space.
+BPF_PERF_OUTPUT(inbound_messages);
+BPF_PERF_OUTPUT(outbound_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);
+
+    inbound_messages.perf_submit(ctx, &msg, sizeof(msg));
+    return 0;
+};
+
+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);
+
+    outbound_messages.perf_submit(ctx, &msg, sizeof(msg));
+    return 0;
+};
+"""
+
+
+class Message:
+    """ A P2P network message. """
+    msg_type = ""
+    size = 0
+    data = bytes()
+    inbound = False
+
+    def __init__(self, msg_type, size, inbound):
+        self.msg_type = msg_type
+        self.size = size
+        self.inbound = inbound
+
+
+class Peer:
+    """ A P2P network peer. """
+    id = 0
+    address = ""
+    connection_type = ""
+    last_messages = list()
+
+    total_inbound_msgs = 0
+    total_inbound_bytes = 0
+    total_outbound_msgs = 0
+    total_outbound_bytes = 0
+
+    def __init__(self, id, address, connection_type):
+        self.id = id
+        self.address = address
+        self.connection_type = connection_type
+        self.last_messages = list()
+
+    def add_message(self, message):
+        self.last_messages.append(message)
+        if len(self.last_messages) > 25:
+            self.last_messages.pop(0)
+        if message.inbound:
+            self.total_inbound_bytes += message.size
+            self.total_inbound_msgs += 1
+        else:
+            self.total_outbound_bytes += message.size
+            self.total_outbound_msgs += 1
+
+
+def main(bitcoind_path):
+    peers = dict()
+
+    bitcoind_with_usdts = USDT(path=str(bitcoind_path))
+
+    # attaching the trace functions defined in the BPF program to the tracepoints
+    bitcoind_with_usdts.enable_probe(
+        probe="inbound_message", fn_name="trace_inbound_message")
+    bitcoind_with_usdts.enable_probe(
+        probe="outbound_message", fn_name="trace_outbound_message")
+    bpf = BPF(text=program, usdt_contexts=[bitcoind_with_usdts])
+
+    # BCC: perf buffer handle function for inbound_messages
+    def handle_inbound(_, data, size):
+        """ Inbound message handler.
+
+        Called each time a message is submitted to the inbound_messages BPF table."""
+        event = bpf["inbound_messages"].event(data)
+        if event.peer_id not in peers:
+            peer = Peer(event.peer_id, event.peer_addr.decode(
+                "utf-8"), event.peer_conn_type.decode("utf-8"))
+            peers[peer.id] = peer
+        peers[event.peer_id].add_message(
+            Message(event.msg_type.decode("utf-8"), event.msg_size, True))
+
+    # BCC: perf buffer handle function for outbound_messages
+    def handle_outbound(_, data, size):
+        """ Outbound message handler.
+
+        Called each time a message is submitted to the outbound_messages BPF table."""
+        event = bpf["outbound_messages"].event(data)
+        if event.peer_id not in peers:
+            peer = Peer(event.peer_id, event.peer_addr.decode(
+                "utf-8"), event.peer_conn_type.decode("utf-8"))
+            peers[peer.id] = peer
+        peers[event.peer_id].add_message(
+            Message(event.msg_type.decode("utf-8"), event.msg_size, False))
+
+    # BCC: add handlers to the inbound and outbound perf buffers
+    bpf["inbound_messages"].open_perf_buffer(handle_inbound)
+    bpf["outbound_messages"].open_perf_buffer(handle_outbound)
+
+    wrapper(loop, bpf, peers)
+
+
+def loop(screen, bpf, peers):
+    screen.nodelay(1)
+    cur_list_pos = 0
+    win = curses.newwin(30, 70, 2, 7)
+    win.erase()
+    win.border(ord("|"), ord("|"), ord("-"), ord("-"),
+               ord("-"), ord("-"), ord("-"), ord("-"))
+    info_panel = panel.new_panel(win)
+    info_panel.hide()
+
+    ROWS_AVALIABLE_FOR_LIST = curses.LINES - 5
+    scroll = 0
+
+    while True:
+        try:
+            # BCC: poll the perf buffers for new events or timeout after 50ms
+            bpf.perf_buffer_poll(timeout=50)
+
+            ch = screen.getch()
+            if (ch == curses.KEY_DOWN or ch == ord("j")) and cur_list_pos < len(
+                    peers.keys()) -1 and info_panel.hidden():
+                cur_list_pos += 1
+                if cur_list_pos >= ROWS_AVALIABLE_FOR_LIST:
+                    scroll += 1
+            if (ch == curses.KEY_UP or ch == ord("k")) and cur_list_pos > 0 and info_panel.hidden():
+                cur_list_pos -= 1
+                if scroll > 0:
+                    scroll -= 1
+            if ch == ord('\n') or ch == ord(' '):
+                if info_panel.hidden():
+                    info_panel.show()
+                else:
+                    info_panel.hide()
+            screen.erase()
+            render(screen, peers, cur_list_pos, scroll, ROWS_AVALIABLE_FOR_LIST, info_panel)
+            curses.panel.update_panels()
+            screen.refresh()
+        except KeyboardInterrupt:
+            exit()
+
+
+def render(screen, peers, cur_list_pos, scroll, ROWS_AVALIABLE_FOR_LIST, info_panel):
+    """ renders the list of peers and details panel
+
+    This code is unrelated to USDT, BCC and BPF.
+    """
+    header_format = "%6s  %-20s  %-20s  %-22s  %-67s"
+    row_format = "%6s  %-5d %9d byte  %-5d %9d byte  %-22s  %-67s"
+
+    screen.addstr(0, 1, (" P2P Message Monitor "), curses.A_REVERSE)
+    screen.addstr(
+        1, 0, (" Navigate with UP/DOWN or J/K and select a peer with ENTER or SPACE to see individual P2P messages"), curses.A_NORMAL)
+    screen.addstr(3, 0,
+                  header_format % ("PEER", "OUTBOUND", "INBOUND", "TYPE", "ADDR"), curses.A_BOLD | curses.A_UNDERLINE)
+    peer_list = sorted(peers.keys())[scroll:ROWS_AVALIABLE_FOR_LIST+scroll]
+    for i, peer_id in enumerate(peer_list):
+        peer = peers[peer_id]
+        screen.addstr(i + 4, 0,
+                      row_format % (peer.id, peer.total_outbound_msgs, peer.total_outbound_bytes,
+                                    peer.total_inbound_msgs, peer.total_inbound_bytes,
+                                    peer.connection_type, peer.address),
+                      curses.A_REVERSE if i + scroll == cur_list_pos else curses.A_NORMAL)
+        if i + scroll == cur_list_pos:
+            info_window = info_panel.window()
+            info_window.erase()
+            info_window.border(
+                ord("|"), ord("|"), ord("-"), ord("-"),
+                ord("-"), ord("-"), ord("-"), ord("-"))
+
+            info_window.addstr(
+                1, 1, f"PEER {peer.id} ({peer.address})".center(68), curses.A_REVERSE | curses.A_BOLD)
+            info_window.addstr(
+                2, 1, f" OUR NODE{peer.connection_type:^54}PEER ",
+                curses.A_BOLD)
+            for i, msg in enumerate(peer.last_messages):
+                if msg.inbound:
+                    info_window.addstr(
+                        i + 3, 1, "%68s" %
+                        (f"<--- {msg.msg_type} ({msg.size} bytes) "), curses.A_NORMAL)
+                else:
+                    info_window.addstr(
+                        i + 3, 1, " %s (%d byte) --->" %
+                        (msg.msg_type, msg.size), curses.A_NORMAL)
+
+
+if __name__ == "__main__":
+    if len(sys.argv) < 2:
+        print("USAGE:", sys.argv[0], "path/to/bitcoind")
+        exit()
+    path = sys.argv[1]
+    main(path)