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From: Ammar Faizi <[email protected]>
To: Jens Axboe <[email protected]>
Cc: Ammar Faizi <[email protected]>,
	Dylan Yudaken <[email protected]>,
	Facebook Kernel Team <[email protected]>,
	Pavel Begunkov <[email protected]>,
	io-uring Mailing List <[email protected]>,
	GNU/Weeb Mailing List <[email protected]>,
	Kanna Scarlet <[email protected]>,
	Muhammad Rizki <[email protected]>,
	Alviro Iskandar Setiawan <[email protected]>
Subject: [PATCH liburing v2 01/12] test/helpers: Add `t_bind_ephemeral_port()` function
Date: Fri,  2 Sep 2022 14:14:54 +0700	[thread overview]
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>

From: Ammar Faizi <[email protected]>

This is a prep patch to fix an intermittent issue with the port number.

We have many places where we need to bind() a socket to any unused port
number. To achieve that, the current approach does one of the following
mechanisms:

  1) Randomly brute force the port number until the bind() syscall
     succeeds.

  2) Use a static port at compile time (randomly chosen too).

This is not reliable and it results in an intermittent issue (test
fails when the selected port is in use).

Setting @addr->sin_port to zero on a bind() syscall lets the kernel
choose a port number that is not in use. The caller then can know the
port number to be bound by invoking a getsockname() syscall after
bind() succeeds.

Wrap this procedure in a new function called t_bind_ephemeral_port().
The selected port will be returned into @addr->sin_port, the caller
can use it later to connect() or whatever they need.

Link: https://lore.kernel.org/r/[email protected]
Cc: Dylan Yudaken <[email protected]>
Cc: Facebook Kernel Team <[email protected]>
Cc: Pavel Begunkov <[email protected]>
Reviewed-by: Alviro Iskandar Setiawan <[email protected]>
Tested-by: Alviro Iskandar Setiawan <[email protected]>
Signed-off-by: Ammar Faizi <[email protected]>
---
 test/helpers.c | 18 ++++++++++++++++++
 test/helpers.h |  7 +++++++
 2 files changed, 25 insertions(+)

diff --git a/test/helpers.c b/test/helpers.c
index 0146533..4d5c402 100644
--- a/test/helpers.c
+++ b/test/helpers.c
@@ -24,14 +24,32 @@ void *t_malloc(size_t size)
 {
 	void *ret;
 	ret = malloc(size);
 	assert(ret);
 	return ret;
 }
 
+/*
+ * Helper for binding socket to an ephemeral port.
+ * The port number to be bound is returned in @addr->sin_port.
+ */
+int t_bind_ephemeral_port(int fd, struct sockaddr_in *addr)
+{
+	socklen_t addrlen;
+
+	addr->sin_port = 0;
+	if (bind(fd, (struct sockaddr *)addr, sizeof(*addr)))
+		return -errno;
+
+	addrlen = sizeof(*addr);
+	assert(!getsockname(fd, (struct sockaddr *)addr, &addrlen));
+	assert(addr->sin_port != 0);
+	return 0;
+}
+
 /*
  * Helper for allocating size bytes aligned on a boundary.
  */
 void t_posix_memalign(void **memptr, size_t alignment, size_t size)
 {
 	int ret;
 	ret = posix_memalign(memptr, alignment, size);
diff --git a/test/helpers.h b/test/helpers.h
index 6d5726c..9ad9947 100644
--- a/test/helpers.h
+++ b/test/helpers.h
@@ -18,14 +18,21 @@ enum t_setup_ret {
 
 enum t_test_result {
 	T_EXIT_PASS   = 0,
 	T_EXIT_FAIL   = 1,
 	T_EXIT_SKIP   = 77,
 };
 
+/*
+ * Helper for binding socket to an ephemeral port.
+ * The port number to be bound is returned in @addr->sin_port.
+ */
+int t_bind_ephemeral_port(int fd, struct sockaddr_in *addr);
+
+
 /*
  * Helper for allocating memory in tests.
  */
 void *t_malloc(size_t size);
 
 
 /*
-- 
Ammar Faizi


  reply	other threads:[~2022-09-02  7:15 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-09-02  7:14 [PATCH liburing v2 00/12] Introducing t_bind_ephemeral_port() function Ammar Faizi
2022-09-02  7:14 ` Ammar Faizi [this message]
2022-09-02  7:14 ` [PATCH liburing v2 02/12] t/poll-link: Don't brute force the port number Ammar Faizi
2022-09-02  7:14 ` [PATCH liburing v2 03/12] t/socket-rw: " Ammar Faizi
2022-09-02  7:14 ` [PATCH liburing v2 04/12] t/socket-rw-eagain: " Ammar Faizi
2022-09-02  7:14 ` [PATCH liburing v2 05/12] t/socket-rw-offset: " Ammar Faizi
2022-09-02  7:14 ` [PATCH liburing v2 06/12] t/files-exit-hang-poll: " Ammar Faizi
2022-09-02  7:15 ` [PATCH liburing v2 07/12] t/socket: Don't use a static " Ammar Faizi
2022-09-02  7:15 ` [PATCH liburing v2 08/12] t/connect: " Ammar Faizi
2022-09-02  7:15 ` [PATCH liburing v2 09/12] t/shutdown: " Ammar Faizi
2022-09-02  7:15 ` [PATCH liburing v2 10/12] t/recv-msgall: " Ammar Faizi
2022-09-02  7:15 ` [PATCH liburing v2 11/12] t/232c93d07b74: " Ammar Faizi
2022-09-02  7:15 ` [PATCH liburing v2 12/12] t/recv-msgall-stream: " Ammar Faizi
2022-09-02 11:57 ` [PATCH liburing v2 00/12] Introducing t_bind_ephemeral_port() function Jens Axboe

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