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>

1 files changed, 120 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
+```