This is needed for Send/Recieve to correctly handle borders between
the messages.
The framing uses a single 32bit uint32 length for each frame, of which
the high bit is used to indicate whether the message contains a file
descriptor or not. This is enough to separate out each message sent
and to decide to which message each file descriptors belongs, even
though multiple Sends may be coalesced into a single read, and/or one
Send can be split into multiple writes.
Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)
Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)
Instead of calling syscall.Close() on the fds in sendUnix() we call
Close() on the *os.File in Send(). Otherwise the fd will be closed, but
the *os.File will continue to live, and when it is finalized the
fd will be closed (which by then may be reused and can be anything).
This also adds a note to Send() the the file is closed.
Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)
Grab forklock to make sure no forks accidentally inherit the new fds
before they are made CLOEXEC There is a slight race condition between
ReadMsgUnix returns and when we grap the lock, so this is not
perfect. Unfortunately There is no way to pass MSG_CMSG_CLOEXEC to
recvmsg() nor any way to implement non-blocking i/o in go, so this is
hard to fix.
Docker-DCO-1.1-Signed-off-by: Alexander Larsson <alexl@redhat.com> (github: alexlarsson)
This inserts low-level hooks for interactive step-by-step debugging.
Hooks are triggered by setting the *TEST* environment variable.
This is particularly useful for tracking down file descriptor leaks,
double-closing, or other issues which are difficult to debug with
the usual toolbox.
Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)
* Close all file descriptors successfully sent as attachment
* Close duplicate file descriptors created by net.FileCon and net.UnixConn.File
Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)
These convenience functions expose a familiar face to the unknown and bizarre world of beam networking.
Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)
This patch includes a stripped down implementation with a bare minimum
unix socket transport. It relies on fd passing for stream multiplexing.
The purpose of this first patch is to allow implementation of dynamic
linking, which will allow advanced service discovery.
Docker-DCO-1.1-Signed-off-by: Solomon Hykes <solomon@docker.com> (github: shykes)
