| Message ID | 20220902011548.2506938-2-ammar.faizi@intel.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Introducing t_bind_ephemeral_port() function | expand |
On Fri, Sep 2, 2022 at 8:18 AM Ammar Faizi wrote: > From: Ammar Faizi <ammarfaizi2@gnuweeb.org> > > 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@gnuweeb.org > Cc: Dylan Yudaken <dylany@fb.com> > Cc: Facebook Kernel Team <kernel-team@fb.com> > Cc: Pavel Begunkov <asml.silence@gmail.com> > Signed-off-by: Ammar Faizi <ammarfaizi2@gnuweeb.org> Reviewed-by: Alviro Iskandar Setiawan <alviro.iskandar@gnuweeb.org> tq -- Viro
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);