Documentation/networking/kcm.rst

8 interface over TCP for generic application protocols. With KCM an application
9 can efficiently send and receive application protocol messages over TCP using
31     | TCP sock |  | TCP sock |  | TCP sock |  | TCP sock | | TCP sock |
46 written on a KCM socket are sent atomically on an appropriate TCP socket.
47 Similarly, in the receive path, messages are constructed on each TCP socket
50 TCP sockets & Psocks
53 TCP sockets may be bound to a KCM multiplexor. A Psock structure is allocated
54 for each bound TCP socket, this structure holds the state for constructing
60 Each multiplexor assumes that all attached TCP connections are to the same
73 Messages are sent over a TCP stream with some application protocol message
78 A TCP stream must be parsed to determine message boundaries. Berkeley Packet
79 Filter (BPF) is used for this. When attaching a TCP socket to a multiplexor a
86 TCP socket management
89 When a TCP socket is attached to a KCM multiplexor data ready (POLLIN) and
91 is a state change (disconnection) or other error on a TCP socket, an error is
92 posted on the TCP socket so that a POLLERR event happens and KCM discontinues
94 TCP socket, it should unattach the socket from KCM and then handle the error
99 socket buffer on the attached TCP socket (the socket buffer size can be set by
101 greater than this limit a corresponding error (EMSGSIZE) is posted on the TCP
106 value is taken from the receive timeout of the attached TCP socket (this is set
167   - fd: file descriptor for TCP socket being attached
227 in mapping a message based protocol onto the TCP stream. KCM also make
236 to the same TCP connection. This allows parallelism between in I/O
237 operations on the TCP socket (for instance copyin and copyout of data is
251 message to a different TCP socket, can negatively impact performance
265 same KCM socket during each TCP ready callback. The targeted KCM socket
273 the TCP connection. Normally, this will be done by placing each
274 TCP socket attached to a KCM multiplexor in epoll set for POLLERR
275 event. If an error occurs on an attached TCP socket, KCM sets an EPIPE
279 posted on the TCP socket the data stream is unrecoverable (i.e. an error
282 TCP connection monitoring
285 In KCM there is no means to correlate a message to the TCP socket that
287 only one attached TCP socket). However, the application does retain