Constant MAX_MESSAGE_SIZE 

const MAX_MESSAGE_SIZE: usize = _; // 4_194_304usize

The largest WebSocket message and frame a client of exec or attach may send. Clients send stdin, which kubectl reads in 32 KiB chunks and the attach sockets take in packets of up to 33 KiB, and small resize events. The Python client sends all stdin of a write in one message, 1 MiB at a time for k8s_cp of Ansible, a third more in base64. The defaults of 64 MiB per message, or the 32 MiB of Kubernetes, would let a client make the server buffer that much per message. A client which sends more fails its session with a status and a close which tell why.