tcp: don't ever return ECONNRESET on close(2)

The SUS doesn't mention this error code as a possible one [1]. The FreeBSD
manual page specifies a possible ECONNRESET for close(2):

[ECONNRESET] The u

tcp: don't ever return ECONNRESET on close(2)

The SUS doesn't mention this error code as a possible one [1]. The FreeBSD
manual page specifies a possible ECONNRESET for close(2):

[ECONNRESET] The underlying object was a stream socket that was
shut down by the peer before all pending data was
delivered.

In the past it had been EINVAL (see 21367f630d72), and this EINVAL was
added as a safety measure in 623dce13c64ef. After conversion to
ECONNRESET it had been documented in the manual page in 78e3a7fdd51e6, but
I bet wasn't ever tested to actually be ever returned, cause the
tcp-testsuite[2] didn't exist back then. So documentation is incorrect
since 2006, if my bet wins. Anyway, in the modern FreeBSD the condition
described above doesn't end up with ECONNRESET error code from close(2).
The error condition is reported via SO_ERROR socket option, though. This
can be checked using the tcp-testsuite, temporarily disabling the
getsockopt(SO_ERROR) lines using sed command [3]. Most of these
getsockopt(2)s are followed by '+0.00 close(3) = 0', which will confirm
that close(2) doesn't return ECONNRESET even on a socket that has the
error stored, neither it is returned in the case described in the manual
page. The latter case is covered by multiple tests residing in tcp-
testsuite/state-event-engine/rcv-rst-*.

However, the deleted block of code could be entered in a race condition
between close(2) and processing of incoming packet, when connection had
already been half-closed with shutdown(SHUT_WR) and sits in TCPS_LAST_ACK.
This was reported in the bug 146845. With the block deleted, we will
continue into tcp_disconnect() which has proper handling of INP_DROPPED.

The race explanation follows. The connection is in TCPS_LAST_ACK. The
network input thread acquires the tcpcb lock first, sets INP_DROPPED,
acquires the socket lock in soisdisconnected() and clears SS_ISCONNECTED.
Meanwhile, the syscall thread goes through sodisconnect() which checks for
SS_ISCONNECTED locklessly(!). The check passes and the thread blocks on
the tcpcb lock in tcp_usr_disconnect(). Once input thread releases the
lock, the syscall thread observes INP_DROPPED and returns ECONNRESET.

- Thread 1: tcp_do_segment()->tcp_close()->in_pcbdrop(),soisdisconnected()
- Thread 2: sys_close()...->soclose()->sodisconnect()->tcp_usr_disconnect()

Note that the lockless operation in sodisconnect() isn't correct, but
enforcing the socket lock there will not fix the problem.

[1] https://pubs.opengroup.org/onlinepubs/9799919799/
[2] https://github.com/freebsd-net/tcp-testsuite
[3] sed -i "" -Ee '/\+0\.00 getsockopt\(3, SOL_SOCKET, SO_ERROR, \[ECONNRESET\]/d' $(grep -lr ECONNRESET tcp-testsuite)

PR: 146845
Reviewed by: tuexen, rrs, imp
Differential Revision: https://reviews.freebsd.org/D48148

show more ...

libsys: relocate implementations and manpages

Remove core system call implementations and documentation to lib/libsys
and lib/libsys/<arch> from lib/libc/sys and lib/libc/<arch>/<sys>.
Update paths

libsys: relocate implementations and manpages

Remove core system call implementations and documentation to lib/libsys
and lib/libsys/<arch> from lib/libc/sys and lib/libc/<arch>/<sys>.
Update paths to allow libc to find them in their new home.

Reviewed by: kib, emaste, imp
Pull Request: https://github.com/freebsd/freebsd-src/pull/908

show more ...

lib: Remove ancient SCCS tags.

Remove ancient SCCS tags from the tree, automated scripting, with two
minor fixup to keep things compiling. All the common forms in the tree
were removed with a perl s

lib: Remove ancient SCCS tags.

Remove ancient SCCS tags from the tree, automated scripting, with two
minor fixup to keep things compiling. All the common forms in the tree
were removed with a perl script.

Sponsored by: Netflix

show more ...

Remove $FreeBSD$: one-line nroff pattern

Remove /^\.\\"\s*\$FreeBSD\$$\n/

Mark all the system calls that were in 1st Edition Unix as such in the
HISTORY section. Note: Any system calls that were added prior to v7,
but after v1 weren't changed.

Obtained from: http://www.tu

Mark all the system calls that were in 1st Edition Unix as such in the
HISTORY section. Note: Any system calls that were added prior to v7,
but after v1 weren't changed.

Obtained from: http://www.tuhs.org/cgi-bin/utree.pl?file=V1/man/man2

show more ...

Renumber copyright clause 4

Renumber cluase 4 to 3, per what everybody else did when BSD granted
them permission to remove clause 3. My insistance on keeping the same
numbering for legal reasons is

Renumber copyright clause 4

Renumber cluase 4 to 3, per what everybody else did when BSD granted
them permission to remove clause 3. My insistance on keeping the same
numbering for legal reasons is too pedantic, so give up on that point.

Submitted by: Jan Schaumann <jschauma@stevens.edu>
Pull Request: https://github.com/freebsd/freebsd/pull/96

show more ...

Consistently reference file descriptors as "fd". 55 other manpages
used "fd", while these used "d" and "filedes".

MFC after: 1 week
Approved by: gjb
Approved by: re (delphij)

Clarify the implementation-defined behaviour in case of close(2)
returning error.

MFC after: 1 week

Add a new 'void closefrom(int lowfd)' system call. When called, it closes
any open file descriptors >= 'lowfd'. It is largely identical to the same
function on other operating systems such as Solar

Add a new 'void closefrom(int lowfd)' system call. When called, it closes
any open file descriptors >= 'lowfd'. It is largely identical to the same
function on other operating systems such as Solaris, DFly, NetBSD, and
OpenBSD. One difference from other *BSD is that this closefrom() does not
fail with any errors. In practice, while the manpages for NetBSD and
OpenBSD claim that they return EINTR, they ignore internal errors from
close() and never return EINTR. DFly does return EINTR, but for the common
use case (closing fd's prior to execve()), the caller really wants all
fd's closed and returning EINTR just forces callers to call closefrom() in
a loop until it stops failing.

Note that this implementation of closefrom(2) does not make any effort to
resolve userland races with open(2) in other threads. As such, it is not
multithread safe.

Submitted by: rwatson (initial version)
Reviewed by: rwatson
MFC after: 2 weeks

show more ...

Per Regents of the University of Calfornia letter, remove advertising
clause.

# If I've done so improperly on a file, please let me know.

Grammar.

OK'ed by: sam

document recent change to return ECONNRESET for tcp sockets

MFC after: 1 month

Mechanically kill hard sentence breaks.

Document ENOSPC.

PR: 52612
Submitted by: Marc Olzheim <marcolz@ilse.nl>

mdoc(7) police: "The .Fa argument.".

mdoc(7) police: Tidy up the syscall language.

Stop calling system calls "function calls".

Use "The .Fn system call" a-la "The .Nm utility".

When referring to a non-BSD implementation in
the HISTOR

mdoc(7) police: Tidy up the syscall language.

Stop calling system calls "function calls".

Use "The .Fn system call" a-la "The .Nm utility".

When referring to a non-BSD implementation in
the HISTORY section, call syscall a function,
to be safe.

show more ...

The .Fn function.

Correct a call to fcntl(F_SETFD) to use `FD_CLOEXEC' instead of `1'.

Remove the internal implementation details of wrapping syscalls,
which do not match the reality anyway.

Approved by: deischen, bde

mdoc(7) police: Use the new .In macro for #include statements.

Use the ``.Rv -std'' mdoc(7) macro in appropriate cases.

Reviewed by: ru

Remove whitespace at EOL.

mdoc(7) police: removed HISTORY info from the .Os call.

mdoc(7) police: remove extraneous .Pp before and/or after .Sh.

Replace .Va, .Ar and .Nm with .Fa or .Va where necessary, examples:
``.Ar errno'' -> ``.Va errno''
``.Nm ops'' -> ``.Fa ops''
``.Va fd'' -> ``.Fa fd''