Re: [PATCH net v4 2/2] selftests/bpf: check epoll readiness during reuseport migration

Kuniyuki Iwashima
2026-04-22T06:40:34Z

On Tue, Apr 21, 2026 at 11:34 PM Zhenzhong Wu <jt26wzz@gmail.com> wrote:
>
> Thanks Tamir, I will fold this into v5 - there's already a precedent
> in socket_helpers.h, so I will just include it from there.

The test does not use cleanup in other places,
no need to mix them up.

>
> On Wed, Apr 22, 2026 at 11:04 AM Tamir Duberstein <tamird@kernel.org> wrote:
> >
> > On Tue, Apr 21, 2026 at 7:46 PM Zhenzhong Wu <jt26wzz@gmail.com> wrote:
> > >
> > > Inside migrate_dance(), add epoll checks around shutdown() to
> > > verify that the target listener is not ready before shutdown()
> > > and becomes ready immediately after shutdown() triggers migration.
> > >
> > > Cover TCP_ESTABLISHED and TCP_SYN_RECV. Exclude TCP_NEW_SYN_RECV
> > > as it depends on later handshake completion.
> > >
> > > Suggested-by: Kuniyuki Iwashima <kuniyu@google.com>
> > > Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
> > > Signed-off-by: Zhenzhong Wu <jt26wzz@gmail.com>
> > > ---
> > > .../bpf/prog_tests/migrate_reuseport.c | 49 ++++++++++++++++---
> > > 1 file changed, 42 insertions(+), 7 deletions(-)
> > >
> > > diff --git a/tools/testing/selftests/bpf/prog_tests/migrate_reuseport.c b/tools/testing/selftests/bpf/prog_tests/migrate_reuseport.c
> > > index 653b0a20f..c62907732 100644
> > > --- a/tools/testing/selftests/bpf/prog_tests/migrate_reuseport.c
> > > +++ b/tools/testing/selftests/bpf/prog_tests/migrate_reuseport.c
> > > @@ -7,24 +7,29 @@
> > > * 3. call listen() for 1 server socket. (migration target)
> > > * 4. update a map to migrate all child sockets
> > > * to the last server socket (migrate_map[cookie] = 4)
> > > - * 5. call shutdown() for first 4 server sockets
> > > + * 5. for TCP_ESTABLISHED and TCP_SYN_RECV cases, verify via epoll
> > > + * that the last server socket is not ready before migration.
> > > + * 6. call shutdown() for first 4 server sockets
> > > * and migrate the requests in the accept queue
> > > * to the last server socket.
> > > - * 6. call listen() for the second server socket.
> > > - * 7. call shutdown() for the last server
> > > + * 7. for TCP_ESTABLISHED and TCP_SYN_RECV cases, verify via epoll
> > > + * that the last server socket is ready after migration.
> > > + * 8. call listen() for the second server socket.
> > > + * 9. call shutdown() for the last server
> > > * and migrate the requests in the accept queue
> > > * to the second server socket.
> > > - * 8. call listen() for the last server.
> > > - * 9. call shutdown() for the second server
> > > + * 10. call listen() for the last server.
> > > + * 11. call shutdown() for the second server
> > > * and migrate the requests in the accept queue
> > > * to the last server socket.
> > > - * 10. call accept() for the last server socket.
> > > + * 12. call accept() for the last server socket.
> > > *
> > > * Author: Kuniyuki Iwashima <kuniyu@amazon.co.jp>
> > > */
> > >
> > > #include <bpf/bpf.h>
> > > #include <bpf/libbpf.h>
> > > +#include <sys/epoll.h>
> > >
> > > #include "test_progs.h"
> > > #include "test_migrate_reuseport.skel.h"
> > > @@ -350,21 +355,51 @@ static int update_maps(struct migrate_reuseport_test_case *test_case,
> > >
> > > static int migrate_dance(struct migrate_reuseport_test_case *test_case)
> > > {
> > > + struct epoll_event ev = {
> > > + .events = EPOLLIN,
> > > + };
> > > + int epoll = -1, nfds;
> > > int i, err;
> > >
> > > + if (test_case->state != BPF_TCP_NEW_SYN_RECV) {
> > > + epoll = epoll_create1(0);
> > > + if (!ASSERT_NEQ(epoll, -1, "epoll_create1"))
> > > + return -1;
> > > +
> > > + ev.data.fd = test_case->servers[MIGRATED_TO];
> > > + if (!ASSERT_OK(epoll_ctl(epoll, EPOLL_CTL_ADD,
> > > + test_case->servers[MIGRATED_TO], &ev),
> > > + "epoll_ctl"))
> > > + goto close_epoll;
> > > +
> > > + nfds = epoll_wait(epoll, &ev, 1, 0);
> > > + if (!ASSERT_EQ(nfds, 0, "epoll_wait 1"))
> > > + goto close_epoll;
> > > + }
> > > +
> > > /* Migrate TCP_ESTABLISHED and TCP_SYN_RECV requests
> > > * to the last listener based on eBPF.
> > > */
> > > for (i = 0; i < MIGRATED_TO; i++) {
> > > err = shutdown(test_case->servers[i], SHUT_RDWR);
> > > if (!ASSERT_OK(err, "shutdown"))
> > > - return -1;
> > > + goto close_epoll;
> > > }
> > >
> > > /* No dance for TCP_NEW_SYN_RECV to migrate based on eBPF */
> > > if (test_case->state == BPF_TCP_NEW_SYN_RECV)
> > > return 0;
> > >
> > > + nfds = epoll_wait(epoll, &ev, 1, 0);
> > > + if (!ASSERT_EQ(nfds, 1, "epoll_wait 2")) {
> > > +close_epoll:
> > > + if (epoll >= 0)
> > > + close(epoll);
> > > + return -1;
> > > + }
> >
> > I think you can avoid this goto using `__attribute__((cleanup(...))`:
> >
> > static void close_fd(int *fd)
> > {
> > if (*fd >= 0)
> > close(*fd);
> > }
> >
> > #define __close_fd __attribute__((cleanup(close_fd)))
> >
> > then in the test:
> >
> > __close_fd int epoll = -1;
> >
> > there's an example of this in
> > tools/testing/selftests/bpf/prog_tests/socket_helpers.h.