kcm: Add memory limit for receive message construction
Message assembly is performed on the TCP socket. This is logically
equivalent of an application that performs a peek on the socket to find
out how much memory is needed for a receive buffer. The receive socket
buffer also provides the maximum message size which is checked.
The receive algorithm is something like:
1) Receive the first skbuf for a message (or skbufs if multiple are
needed to determine message length).
2) Check the message length against the number of bytes in the TCP
receive queue (tcp_inq()).
- If all the bytes of the message are in the queue (incluing the
skbuf received), then proceed with message assembly (it should
complete with the tcp_read_sock)
- Else, mark the psock with the number of bytes needed to
complete the message.
3) In TCP data ready function, if the psock indicates that we are
waiting for the rest of the bytes of a messages, check the number
of queued bytes against that.
- If there are still not enough bytes for the message, just
return
- Else, clear the waiting bytes and proceed to receive the
skbufs. The message should now be received in one
tcp_read_sock
Signed-off-by: Tom Herbert <tom@herbertland.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
3 files changed