Since we're using byte streamed Unix sockets for the IPC protocols,
it's possible for the kernel to run out of socket buffer space with
a partial message near the end of the buffer.
Handle this situation in IPC::Connection by buffering the bytes of
what may be a partial message, and prepending them to the incoming
data next time we receive from the peer.
This fixes WindowServer asserting when a peer is spamming it hard.
Writing to the socket may trigger a close of the socket descriptor
if a disconnect was detected. We need to check if it is still valid
when waiting for a response after attempting to send a synchronous
message.
Fixes#3515
Because we're closing a file descriptor, we need to disable any
Notifier that is using it so that the EventLoop does not use invalid
file descriptors.
Fixes#3508
This patch introduces IPC::Connection which becomes the new base class
of ClientConnection and ServerConnection. Most of the functionality
has been hoisted up to the base class since almost all of it is useful
on both sides.
This gives us the ability to send synchronous messages in both
directions, which is needed for the WebContent server process.
Unlike other servers, WebContent does not mind blocking on a response
from its client.
