This new implementation of the UDS service is built on top of the
libsockevent library. It thereby inherits all the advantages that
libsockevent brings. However, the fundamental restructuring
required for that change also paved the way for resolution of a
number of other important open issues with the old UDS code. Most
importantly, the rewrite brings the behavior of the service much
closer to POSIX compliance and NetBSD compatibility. These are the
most important changes:
- due to the use of libsockevent, UDS now supports multiple suspending
calls per socket and a large number of standard socket flags and
options;
- socket address matching is now based on <device,inode> lookups
instead of canonized path names, and socket addresses are no longer
altered either due to canonization or at connect time;
- the socket state machine is now well defined, most importantly
resolving the erroneous reset-on-EOF semantics of the old UDS, but
also allowing socket reuse;
- sockets are now connected before being accepted instead of being
held in connecting state, unless the LOCAL_CONNWAIT option is set
on either the connecting or the listening socket;
- connect(2) on datagram sockets is now supported (needed by syslog),
and proper datagram socket disconnect notification is provided;
- the receive queue now supports segmentation, associating ancillary
data (in-flight file descriptors and credentials) with each segment
instead of being kept fully separately; this is a POSIX requirement
(and needed by tmux);
- as part of the segmentation support, the receive queue can now hold
as many packets as can fit, instead of one;
- in addition to the flags supported by libsockevent, the MSG_PEEK,
MSG_WAITALL, MSG_CMSG_CLOEXEC, MSG_TRUNC, and MSG_CTRUNC send and
receive flags are now supported;
- the SO_PASSCRED and SO_PEERCRED socket options are replaced by
LOCAL_CREDS and LOCAL_PEEREID respectively, now following NetBSD
semantics and allowing use of NetBSD libc's getpeereid(3);
- memory usage is reduced by about 250 KB due to centralized in-flight
file descriptor tracking, with a limit of OPEN_MAX total rather than
of OPEN_MAX per socket;
- memory usage is reduced by another ~50 KB due to removal of state
redundancy, despite the fact that socket path names may now be up to
253 bytes rather than the previous 104 bytes;
- compared to the old UDS, there is now very little direct indexing on
the static array of sockets, thus allowing dynamic allocation of
sockets more easily in the future;
- the UDS service now has RMIB support for the net.local sysctl tree,
implementing preliminary support for NetBSD netstat(1).
Change-Id: I4a9b6fe4aaeef0edf2547eee894e6c14403fcb32
The flag is supported only when copying out file descriptors (i.e.
COPYFD_TO). It will be used by UDS to support MSG_CMSG_CLOEXEC.
Change-Id: I46bfd04b5f28e22ec48938e43e42f78d3931220d
This patch stops a socket driver from using copyfd(2) to copy in a
file descriptor that is a reference to a socket owned by that socket
driver, returning EDEADLK instead. In effect, this will stop deadlock
and resource exhaustion issues with UDS once it has been converted to
a socket driver. See the comment in the patch for details.
Change-Id: I5728a405eabda207725618231a6ff7be2d517146
This change effectively adds the VFS side of support for the SO_LINGER
socket option, by allowing file descriptor close operations to be
suspended (and later resumed) by socket drivers. Currently, support
is limited to the close(2) system call--in all other cases where file
descriptors are closed (dup2, close-on-exec, process exit..), the
close operation still completes instantly. As a general policy, the
close(2) return value will always indicate that the file descriptor
has been closed: either 0, or -1 with errno set to EINPROGRESS. The
latter error may be thrown only when a suspended close is interrupted
by a signal.
As necessary for UDS, this change also introduces a closenb(2) system
call extension, allowing the caller to bypass blocking SO_LINGER close
behavior. This extension allows UDS to avoid blocking on closing the
last reference to an in-flight file descriptor, in an atomic fashion.
The extension is currently part of libsys, but there is no reason why
userland would not be allowed to make this call, so it is deliberately
not protected from use by userland.
Change-Id: Iec77d6665232110346180017fc1300b1614910b7
This patch adds the implementation of the BSD socket system calls
which have been introduced in an earlier patch. At the same time, it
adds support for communication with socket drivers, using a new
"socket device" (SDEV_) protocol. These two parts, implemented in
socket.c and sdev.c respectively, form the upper and lower halves of
the new BSD socket support in VFS. New mapping functionality for
socket domains and drivers is added as well, implemented in smap.c.
The rest of the changes mainly facilitate the separation of character
and socket driver calls, and do not make any fundamental alterations.
For example, while this patch changes VFS's select.c rather heavily,
the new select logic for socket drivers is the exact same as for
character drivers; the changes mainly separate the driver type
specific parts from the generic select logic further than before.
Change-Id: I2f13084dd3c8d3a68bfc69da0621120c8291f707
The remapping from /dev/tty to the real controlling terminal in the
device code was confusing the select code. The latter is now aware
of this case and should handle it properly, at the cost of one extra
field in the filp structure.
There is a nasty, hopefully sufficiently rare case of /dev/tty being
kept open while controlling terminals are changing, that we are still
not handling. Doing so would require more than just a few changes,
but the code should at least detect and cleanly fail on this case.
Test77 now has a basic test set for selecting on /dev/tty.
Change-Id: Iaedea449cdb728d0e66a9de8faacdfd9638dfe92
