Re: [PATCH] reintroduce accept4

quoted

Andrew, you noted a lack of explanation accompanying the original
patch.  Here's something to fill the gap, and which may be suitable
for the changelog.

==
Introduce a new accept4() system call.  The addition of this system
call matches analogous changes in 2.6.27 (dup3(), evenfd2(),
signalfd4(), inotify_init1(), epoll_create1(), pipe2()) which added
new system calls that differed from analogous traditional system calls
in adding a flags argument that can be used to access additional
functionality. The accept4() system call is exactly the same as
accept(), except that it adds a flags bit-mask argument.  Two flags
are initially implemented.  (Most of the new system calls in 2.6.27
also had both of these flags.)  SOCK_CLOEXEC causes the close-on-exec
(FD_CLOEXEC) flag to be enabled for the new file descriptor returned
by accept4().  This is a useful security feature to avoid leaking
information in a multithreaded program where one thread is doing an
accept() at the same time as another thread is doing a fork() plus
exec().  (More details here:
http://udrepper.livejournal.com/20407.html "Secure File Descriptor
Handling", Ulrich Drepper)  The other flag is SOCK_NONBLOCK, which
causes the O_NONBLOCK flag to be enabled on the new open file
description created by accept4().  (This flag is merely a convenience,
saving the use of additional calls fcntl(F_GETFL) and fcntl (F_SETFL)
to achieve the same result.)

I replaced the existing changelog with the above (plus some paragraph
breaks ;)).  Will add the new test app when it comes along.

Git allows paragraph breaks in changelogs?!  You gotta love technology ;-).

-- 
Michael Kerrisk Linux man-pages maintainer;
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