From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.3.2 (2011-06-06) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS47066 71.19.144.0/20 X-Spam-Status: No, score=-0.4 required=3.0 tests=BAYES_00,DATE_IN_PAST_06_12, MSGID_FROM_MTA_HEADER shortcircuit=no autolearn=no version=3.3.2 Path: news.gmane.org!not-for-mail From: Christopher Lord Newsgroups: gmane.comp.lang.ruby.posix-mq.general Subject: [PATCH] Ability to adopt file descriptors Date: Sat, 3 Jan 2015 10:15:58 -0700 Message-ID: <1420305358-21019-1-git-send-email-christopher@lord.ac> References: <1420305358-21019-1-git-send-email-christopher@lord.ac> NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit X-Trace: ger.gmane.org 1420330560 20043 80.91.229.3 (4 Jan 2015 00:16:00 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Sun, 4 Jan 2015 00:16:00 +0000 (UTC) To: ruby.posix.mq@librelist.com Original-X-From: ruby.posix.mq@librelist.com Sun Jan 04 01:15:55 2015 Return-path: Envelope-to: gclrpg-ruby.posix.mq@m.gmane.org In-Reply-To: <1420305358-21019-1-git-send-email-christopher@lord.ac> List-Archive: List-Help: List-Id: List-Post: List-Subscribe: List-Unsubscribe: Precedence: list Original-Sender: ruby.posix.mq@librelist.com Xref: news.gmane.org gmane.comp.lang.ruby.posix-mq.general:120 Archived-At: Received: from zedshaw2.xen.prgmr.com ([71.19.156.177]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1Y7YrL-0007WD-7J for gclrpg-ruby.posix.mq@m.gmane.org; Sun, 04 Jan 2015 01:15:55 +0100 Received: from zedshaw2.xen.prgmr.com (unknown [IPv6:::1]) by zedshaw2.xen.prgmr.com (Postfix) with ESMTP id 26DAA74DF4 for ; Sun, 4 Jan 2015 00:16:57 +0000 (UTC) This patch adds support for adopting an existing file descriptor, together with testcases. The need for this comes up when we use systemd with the ListenMessageQueue directive. For socket activation, systemd opens the POSIX message queue and expects user code to begin using the file descriptor without opening it in-process. To support the systemd model in the `posix_mq` gem, this patch suggests imitating the behavior on the Socket class, which uses `#for_fd` to create a socket class from a descriptor. One confounding factor exists. POSIX queues have a name but it is difficult to get access to this name in a safe manner from the file descriptor. One option would be to `readlink(2)` on `/proc/self/fd/N` to get the name[1], but note that if the descriptor is unlinked we wouldn't get anything usable. Rather than risk incorrect behavior and extra complexity, I've decided to just raise an `ArgumentError` if `#name` is called on adopted descriptors. Typically one wouldn't need the actual name in a systemd socket-activated situation, anyway. [1]: http://stackoverflow.com/questions/1188757/getting-filename-from-file-descriptor-in-c --- ext/posix_mq/posix_mq.c | 63 ++++++++++++++++++++++++++++++++++++++++++++++++- test/test_posix_mq.rb | 13 ++++++++++ 2 files changed, 75 insertions(+), 1 deletion(-) diff --git a/ext/posix_mq/posix_mq.c b/ext/posix_mq/posix_mq.c index cbc32b9..901b6ce 100644 --- a/ext/posix_mq/posix_mq.c +++ b/ext/posix_mq/posix_mq.c @@ -26,6 +26,7 @@ #if defined(__linux__) # define MQD_TO_FD(mqd) (int)(mqd) +# define FD_TO_MQD(fd) (mqd_t)(fd) #elif defined(HAVE___MQ_OSHANDLE) /* FreeBSD */ # define MQD_TO_FD(mqd) __mq_oshandle(mqd) #else @@ -66,7 +67,7 @@ static int MQ_IO_CLOSE(struct posix_mq *mq) # define PMQ_TRY (1<<1) static VALUE cAttr; -static ID id_new, id_kill, id_fileno, id_divmod; +static ID id_new, id_kill, id_fileno, id_divmod, id_to_i; static ID id_flags, id_maxmsg, id_msgsize, id_curmsgs; static VALUE sym_r, sym_w, sym_rw; static const mqd_t MQD_INVALID = (mqd_t)-1; @@ -365,6 +366,51 @@ static void rstruct2mqattr(struct mq_attr *attr, VALUE astruct, int all) attr->mq_curmsgs = NUM2LONG(tmp); } +#ifdef FD_TO_MQD + +/* + * call-seq: + * POSIX_MQ.for_fd(socket) => mq + * + * Adopts a socket as a POSIX message queue. Argument will be + * checked to ensure it is a POSIX message queue socket. + * + * This is useful for adopting systemd sockets passed via the + * ListenMessageQueue directive. + * Returns a +POSIX_MQ+ instance. This method is only available + * under Linux and FreeBSD and is not intended to be portable. + * + */ +static VALUE for_fd(VALUE klass, VALUE socket) +{ + VALUE mqv = alloc(klass); + struct posix_mq *mq = get(mqv, 0); + + mq->name = Qnil; + + if (rb_respond_to(socket, id_to_i)) { + VALUE fd_num = rb_funcall(socket, id_to_i, 0); + mq->des = FD_TO_MQD(NUM2INT(fd_num)); + } + else { + rb_raise(rb_eArgError, "provided argument must be (or convertable to) an integer file descriptor"); + } + + if (mq->des < 0) { + rb_raise(rb_eArgError, "provided argument must be a valid file descriptor"); + } + + if (mq_getattr(mq->des, &mq->attr) < 0) { + if (errno) { + rb_raise(rb_eArgError, "provided file descriptor is not a POSIX message queue"); + } + } + return mqv; +} + + +#endif + /* * call-seq: * POSIX_MQ.new(name [, flags [, mode [, mq_attr]]) => mq @@ -507,6 +553,10 @@ static VALUE _unlink(VALUE self) struct posix_mq *mq = get(self, 0); int rv; + if (NIL_P(mq->name)) { + rb_raise(rb_eArgError, "can not unlink an adopted socket"); + } + assert(TYPE(mq->name) == T_STRING && "mq->name is not a string"); rv = mq_unlink(RSTRING_PTR(mq->name)); @@ -807,6 +857,12 @@ static VALUE name(VALUE self) { struct posix_mq *mq = get(self, 0); + if (NIL_P(mq->name)) { + /* We could use readlink(2) on /proc/self/fd/N, but lots of care required. + * http://stackoverflow.com/questions/1188757/getting-filename-from-file-descriptor-in-c */ + rb_raise(rb_eArgError, "can not get name of an adopted socket"); + } + return rb_str_dup(mq->name); } @@ -1114,6 +1170,10 @@ void Init_posix_mq_ext(void) rb_define_method(cPOSIX_MQ, "to_io", to_io, 0); #endif +#ifdef FD_TO_MQD + rb_define_module_function(cPOSIX_MQ, "for_fd", for_fd, 1); +#endif + id_new = rb_intern("new"); id_kill = rb_intern("kill"); id_fileno = rb_intern("fileno"); @@ -1122,6 +1182,7 @@ void Init_posix_mq_ext(void) id_maxmsg = rb_intern("maxmsg"); id_msgsize = rb_intern("msgsize"); id_curmsgs = rb_intern("curmsgs"); + id_to_i = rb_intern("to_i"); sym_r = ID2SYM(rb_intern("r")); sym_w = ID2SYM(rb_intern("w")); sym_rw = ID2SYM(rb_intern("rw")); diff --git a/test/test_posix_mq.rb b/test/test_posix_mq.rb index 1cc24aa..ceb9f7c 100644 --- a/test/test_posix_mq.rb +++ b/test/test_posix_mq.rb @@ -17,6 +17,8 @@ class Test_POSIX_MQ < Test::Unit::TestCase warn "POSIX_MQ#to_io not supported on this platform: #{RUBY_PLATFORM}" POSIX_MQ.method_defined?(:notify) or warn "POSIX_MQ#notify not supported on this platform: #{RUBY_PLATFORM}" + POSIX_MQ.class.method_defined?(:for_fd) or + warn "POSIX_MQ::for_fd not supported on this platform: #{RUBY_PLATFORM}" def setup @mq = nil @@ -244,6 +246,17 @@ class Test_POSIX_MQ < Test::Unit::TestCase assert_nothing_raised { IO.select([@mq], nil, nil, 0) } end if POSIX_MQ.method_defined?(:to_io) + def test_for_fd + @mq = POSIX_MQ.new @path, IO::CREAT|IO_RDWR, 0666 + @alt = POSIX_MQ.for_fd(@mq.to_io.to_i) + assert_equal true, @mq.send("hello", 0) + assert_equal [ "hello", 0 ], @alt.receive(buf) + assert_equal "hello", buf + assert_equal @mq.to_io.to_i, @alt.to_io.to_i + assert_raises(ArgumentError) { @alt.name } + assert_raises(ArgumentError) { POSIX_MQ.for_fd(1) } + end if POSIX_MQ.class.method_defined?(:for_fd) && POSIX_MQ.method_defined(:to_io) + def test_notify rd, wr = IO.pipe orig = trap(:USR1) { wr.syswrite('.') } -- 1.8.3.1