From: Ammar Faizi <ammarfaizi2@xxxxxxxxxxx>
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/918facd1-78ba-2de7-693a-5f8c65ea2fcd@xxxxxxxxxxx
Cc: Dylan Yudaken <dylany@xxxxxx>
Cc: Facebook Kernel Team <kernel-team@xxxxxx>
Cc: Pavel Begunkov <asml.silence@xxxxxxxxx>
Signed-off-by: Ammar Faizi <ammarfaizi2@xxxxxxxxxxx>
---
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
@@ -19,24 +19,42 @@
/*
* Helper for allocating memory in tests.
*/
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);
assert(!ret);
}
/*
* Helper for allocating space for an array of nmemb elements
diff --git a/test/helpers.h b/test/helpers.h
index 6d5726c..9ad9947 100644
--- a/test/helpers.h
+++ b/test/helpers.h
@@ -13,24 +13,31 @@ extern "C" {
enum t_setup_ret {
T_SETUP_OK = 0,
T_SETUP_SKIP,
};
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);
/*
* Helper for allocating size bytes aligned on a boundary.
*/
void t_posix_memalign(void **memptr, size_t alignment, size_t size);
--
Ammar Faizi
