Change Details

The purpose and scope of this feature is intentionally limited. It answers a question anyone new to Bitcoin's P2P protocol has had: "Can I see what messages my node is sending and receiving?". When a new debug-only command line argument `capturemessages` is set, any message that the node receives or sends is captured. The capture occurs in the `MessageHandler` thread. When receiving a message, it is captured as soon as the `MessageHandler` thread takes the message off of the `vProcessMsg` queue. When sending, the message is captured just before the message is pushed onto the `vSendMsg` queue. The message capture is as minimal as possible to reduce the performance impact on the node. Messages are captured to a new message_capture folder in the datadir. Each node has their own subfolder named with their IP address and port. Inside, received and sent messages are captured into two binary files, msgs_recv.dat and msgs_sent.dat, like so: ``` message_capture/203.0.113.7:56072/msgs_recv.dat message_capture/203.0.113.7:56072/msgs_sent.dat ``` Because the messages are raw binary dumps, included in this PR is a Python parsing tool to convert the binary files into human-readable JSON. This script has been placed on its own and out of the way in the new contrib/message-capture folder. Its usage is simple and easily discovered by the autogenerated -h option. This is a backport of [[https://github.com/bitcoin/bitcoin/pull/19509 | core#19509]]

The purpose and scope of this feature is intentionally limited. It answers a question anyone new to Bitcoin's P2P protocol has had: "Can I see what messages my node is sending and receiving?". When a new debug-only command line argument `capturemessages` is set, any message that the node receives or sends is captured. The capture occurs in the `MessageHandler` thread. When receiving a message, it is captured as soon as the `MessageHandler` thread takes the message off of the `vProcessMsg` queue. When sending, the message is captured just before the message is pushed onto the `vSendMsg` queue. The message capture is as minimal as possible to reduce the performance impact on the node. Messages are captured to a new message_capture folder in the datadir. Each node has their own subfolder named with their IP address and port. Inside, received and sent messages are captured into two binary files, msgs_recv.dat and msgs_sent.dat, like so: ``` message_capture/203.0.113.7:56072/msgs_recv.dat message_capture/203.0.113.7:56072/msgs_sent.dat ``` Because the messages are raw binary dumps, included in this PR is a Python parsing tool to convert the binary files into human-readable JSON. This script has been placed on its own and out of the way in the new contrib/message-capture folder. Its usage is simple and easily discovered by the autogenerated -h option. This is a backport of [[https://github.com/bitcoin/bitcoin/pull/19509 | core#19509]]

The purpose and scope of this feature is intentionally limited. It answers a question anyone new to Bitcoin's P2P protocol has had: "Can I see what messages my node is sending and receiving?". When a new debug-only command line argument `capturemessages` is set, any message that the node receives or sends is captured. The capture occurs in the `MessageHandler` thread. When receiving a message, it is captured as soon as the `MessageHandler` thread takes the message off of the `vProcessMsg` queue. When sending, the message is captured just before the message is pushed onto the `vSendMsg` queue. The message capture is as minimal as possible to reduce the performance impact on the node. Messages are captured to a new message_capture folder in the datadir. Each node has their own subfolder named with their IP address and port. Inside, received and sent messages are captured into two binary files, msgs_recv.dat and msgs_sent.dat, like so: ``` message_capture/203.0.113.7:56072/msgs_recv.dat message_capture/203.0.113.7:56072/msgs_sent.dat ``` Because the messages are raw binary dumps, included in this PR is a Python parsing tool to convert the binary files into human-readable JSON. This script has been placed on its own and out of the way in the new contrib/message-capture folder. Its usage is simple and easily discovered by the autogenerated -h option. This is a backport of [[https://github.com/bitcoin/bitcoin/pull/19509 | core#19509]]