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Re: [RFC PATCH 4/4] socket: Add a test for MSG_CMSG_CLOEXEC
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From: |
Sergey Bugaev |
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Subject: |
Re: [RFC PATCH 4/4] socket: Add a test for MSG_CMSG_CLOEXEC |
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Date: |
Tue, 18 Apr 2023 18:37:53 +0300 |
Hello,
On Tue, Apr 18, 2023 at 3:13 PM Adhemerval Zanella Netto wrote:
> On 17/04/23 10:39, Sergey Bugaev via Libc-alpha wrote:
> > Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
>
> Add some description of what the test is accomplishing here.
Do you mean in the commit message? Done.
Also changed:
* in send_fd, memset the cmsg_storage to zero before filling it
* in send_fd, set msg_controllen to sizeof (cmsg_storage) (aka
CMSG_SPACE (sizeof (fd))), not CMSG_LEN (sizeof (fd))
* dropped the /* const */
And here's the test passing on x86_64-linux:
socketpair(AF_UNIX, SOCK_DGRAM|SOCK_CLOEXEC, 0, [3, 4]) = 0
sendmsg(4, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="hello\0",
iov_len=6}], msg_iovlen=1, msg_control=[{cmsg_len=20, cmsg_level=SOL_SOCKET,
cmsg_type=SCM_RIGHTS, cmsg_data=[0]}], msg_controllen=24, msg_flags=0}, 0) = 6
recvmsg(3, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="hello\0",
iov_len=100}], msg_iovlen=1, msg_control=[{cmsg_len=20, cmsg_level=SOL_SOCKET,
cmsg_type=SCM_RIGHTS, cmsg_data=[5]}], msg_controllen=24, msg_flags=0}, 0) = 6
fcntl(5, F_GETFD) = 0
close(5) = 0
sendmsg(4, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="hello\0",
iov_len=6}], msg_iovlen=1, msg_control=[{cmsg_len=20, cmsg_level=SOL_SOCKET,
cmsg_type=SCM_RIGHTS, cmsg_data=[0]}], msg_controllen=24, msg_flags=0}, 0) = 6
recvmsg(3, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="hello\0",
iov_len=100}], msg_iovlen=1, msg_control=[{cmsg_len=20, cmsg_level=SOL_SOCKET,
cmsg_type=SCM_RIGHTS, cmsg_data=[5]}], msg_controllen=24,
msg_flags=MSG_CMSG_CLOEXEC}, MSG_CMSG_CLOEXEC) = 6
fcntl(5, F_GETFD) = 0x1 (flags FD_CLOEXEC)
close(5) = 0
close(3) = 0
close(4) = 0
Sergey
---- >8 ----
>From 256a774a16e1bb3d721e2be82dc4bbab119bf6ea Mon Sep 17 00:00:00 2001
From: Sergey Bugaev <bugaevc@gmail.com>
Date: Mon, 17 Apr 2023 16:28:35 +0300
Subject: [RFC PATCH v3 4/4] socket: Add a test for MSG_CMSG_CLOEXEC
This checks that:
* We can send and receive fds over Unix domain sockets using SCM_RIGHTS;
* msg_controllen, cmsg_level, cmsg_type, cmsg_len are all filled in
correctly on receive;
* Most importantly, the received fd has or has not the close-on-exec
flag set depending on whether we pass MSG_CMSG_CLOEXEC to recvmsg ().
Signed-off-by: Sergey Bugaev <bugaevc@gmail.com>
---
socket/Makefile | 1 +
socket/tst-cmsg_cloexec.c | 126 ++++++++++++++++++++++++++++++++++++++
2 files changed, 127 insertions(+)
create mode 100644 socket/tst-cmsg_cloexec.c
diff --git a/socket/Makefile b/socket/Makefile
index fffed7dd..94951ae3 100644
--- a/socket/Makefile
+++ b/socket/Makefile
@@ -35,6 +35,7 @@ tests := \
tst-accept4 \
tst-sockopt \
tst-cmsghdr \
+ tst-cmsg_cloexec \
# tests
tests-internal := \
diff --git a/socket/tst-cmsg_cloexec.c b/socket/tst-cmsg_cloexec.c
new file mode 100644
index 00000000..a18f4912
--- /dev/null
+++ b/socket/tst-cmsg_cloexec.c
@@ -0,0 +1,126 @@
+/* Smoke test for MSG_CMSG_CLOEXEC.
+ Copyright (C) 2021-2023 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <https://www.gnu.org/licenses/>. */
+
+#include <support/xunistd.h>
+#include <support/check.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <string.h>
+#include <fcntl.h>
+
+static void
+send_fd (int sockfd, int fd)
+{
+ char data[] = "hello";
+ struct iovec iov = { .iov_base = data, .iov_len = sizeof (data) };
+
+ union
+ {
+ struct cmsghdr header;
+ char bytes[CMSG_SPACE (sizeof (fd))];
+ } cmsg_storage;
+
+ struct msghdr msg =
+ {
+ .msg_iov = &iov,
+ .msg_iovlen = 1,
+ .msg_control = cmsg_storage.bytes,
+ .msg_controllen = sizeof (cmsg_storage)
+ };
+
+ memset (&cmsg_storage, 0, sizeof (cmsg_storage));
+
+ struct cmsghdr *cmsg = CMSG_FIRSTHDR (&msg);
+ cmsg->cmsg_level = SOL_SOCKET;
+ cmsg->cmsg_type = SCM_RIGHTS;
+ cmsg->cmsg_len = CMSG_LEN (sizeof (fd));
+ memcpy (CMSG_DATA (cmsg), &fd, sizeof (fd));
+
+ ssize_t nsent = sendmsg (sockfd, &msg, 0);
+ if (nsent < 0)
+ FAIL_EXIT1 ("sendmsg (%d): %m", sockfd);
+ TEST_COMPARE (nsent, sizeof (data));
+}
+
+static int
+recv_fd (int sockfd, int flags)
+{
+ char buffer[100];
+ struct iovec iov = { .iov_base = buffer, .iov_len = sizeof (buffer) };
+
+ union
+ {
+ struct cmsghdr header;
+ char bytes[100];
+ } cmsg_storage;
+
+ struct msghdr msg =
+ {
+ .msg_iov = &iov,
+ .msg_iovlen = 1,
+ .msg_control = cmsg_storage.bytes,
+ .msg_controllen = sizeof (cmsg_storage)
+ };
+
+ ssize_t nrecv = recvmsg (sockfd, &msg, flags);
+ if (nrecv < 0)
+ FAIL_EXIT1 ("recvmsg (%d): %m", sockfd);
+
+ TEST_COMPARE (msg.msg_controllen, CMSG_SPACE (sizeof (int)));
+ struct cmsghdr *cmsg = CMSG_FIRSTHDR (&msg);
+ TEST_COMPARE (cmsg->cmsg_level, SOL_SOCKET);
+ TEST_COMPARE (cmsg->cmsg_type, SCM_RIGHTS);
+ TEST_COMPARE (cmsg->cmsg_len, CMSG_LEN (sizeof (int)));
+
+ int fd;
+ memcpy (&fd, CMSG_DATA (cmsg), sizeof (fd));
+ return fd;
+}
+
+static int
+do_test (void)
+{
+ int sockfd[2];
+ int newfd;
+ int flags;
+ int rc = socketpair (AF_UNIX, SOCK_DGRAM | SOCK_CLOEXEC, 0, sockfd);
+ if (rc < 0)
+ FAIL_EXIT1 ("socketpair: %m");
+
+ send_fd (sockfd[1], STDIN_FILENO);
+ newfd = recv_fd (sockfd[0], 0);
+ TEST_VERIFY_EXIT (newfd > 0);
+ flags = fcntl (newfd, F_GETFD, 0);
+ TEST_VERIFY_EXIT (flags != -1);
+ TEST_VERIFY (!(flags & FD_CLOEXEC));
+ xclose (newfd);
+
+ send_fd (sockfd[1], STDIN_FILENO);
+ newfd = recv_fd (sockfd[0], MSG_CMSG_CLOEXEC);
+ TEST_VERIFY_EXIT (newfd > 0);
+ flags = fcntl (newfd, F_GETFD, 0);
+ TEST_VERIFY_EXIT (flags != -1);
+ TEST_VERIFY (flags & FD_CLOEXEC);
+ xclose (newfd);
+
+ xclose (sockfd[0]);
+ xclose (sockfd[1]);
+ return 0;
+}
+
+#include <support/test-driver.c>
--
2.39.2