Thanks Kuniyuki, will fold this into v3. Your approach of checking epoll right around shutdown() is much better. I didn't think to put the check inside migrate_dance(). With my original placement, the test still passed without patch 1 — I should have called this out in the cover letter instead of settling for what was effectively just a smoke test.
On Tue, Apr 21, 2026 at 3:20 PM Kuniyuki Iwashima <[email protected]> wrote: > > From: Zhenzhong Wu <[email protected]> > Date: Sun, 19 Apr 2026 02:13:33 +0800 > > After migrate_dance() moves established children to the target > > listener, add it to an epoll set and verify that epoll_wait(..., 0) > > reports it ready before accept(). > > > > This adds epoll coverage for the TCP_ESTABLISHED reuseport migration > > case in migrate_reuseport. > > > > Keep the check limited to TCP_ESTABLISHED cases. TCP_SYN_RECV and > > TCP_NEW_SYN_RECV still depend on asynchronous handshake completion, > > so a zero-timeout epoll_wait() would race there. > > > > Signed-off-by: Zhenzhong Wu <[email protected]> > > --- > > .../bpf/prog_tests/migrate_reuseport.c | 32 ++++++++++++++++++- > > 1 file changed, 31 insertions(+), 1 deletion(-) > > > > diff --git a/tools/testing/selftests/bpf/prog_tests/migrate_reuseport.c > > b/tools/testing/selftests/bpf/prog_tests/migrate_reuseport.c > > index 653b0a20f..580a53424 100644 > > --- a/tools/testing/selftests/bpf/prog_tests/migrate_reuseport.c > > +++ b/tools/testing/selftests/bpf/prog_tests/migrate_reuseport.c > > @@ -18,13 +18,16 @@ > > * 9. 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. > > + * 10. for TCP_ESTABLISHED cases, call epoll_wait(..., 0) > > + * for the last server socket. > > + * 11. call accept() for the last server socket. > > * > > * Author: Kuniyuki Iwashima <[email protected]> > > */ > > > > #include <bpf/bpf.h> > > #include <bpf/libbpf.h> > > +#include <sys/epoll.h> > > > > #include "test_progs.h" > > #include "test_migrate_reuseport.skel.h" > > @@ -522,6 +525,33 @@ static void run_test(struct > > migrate_reuseport_test_case *test_case, > > goto close_clients; > > } > > > > + /* Only TCP_ESTABLISHED has already-migrated accept-queue entries > > + * here. Later states still depend on follow-up handshake work. > > + */ > > + if (test_case->state == BPF_TCP_ESTABLISHED) { > > + struct epoll_event ev = { > > + .events = EPOLLIN, > > + }; > > + int epfd; > > + int nfds; > > + > > + epfd = epoll_create1(EPOLL_CLOEXEC); > > + if (!ASSERT_NEQ(epfd, -1, "epoll_create1")) > > + goto close_clients; > > + > > + ev.data.fd = test_case->servers[MIGRATED_TO]; > > + if (!ASSERT_OK(epoll_ctl(epfd, EPOLL_CTL_ADD, > > + test_case->servers[MIGRATED_TO], > > &ev), > > + "epoll_ctl")) > > + goto close_epfd; > > + > > + nfds = epoll_wait(epfd, &ev, 1, 0); > > + ASSERT_EQ(nfds, 1, "epoll_wait"); > > Thanks for the update, but the test passes without patch 1. > > I think it would be best to test just after shutdown() > where migration happens. > > Also, TCP_SYN_RECV should be covered in the same way. > > ---8<--- > diff --git a/tools/testing/selftests/bpf/prog_tests/migrate_reuseport.c > b/tools/testing/selftests/bpf/prog_tests/migrate_reuseport.c > index 580a534249a7..66fea936649e 100644 > --- a/tools/testing/selftests/bpf/prog_tests/migrate_reuseport.c > +++ b/tools/testing/selftests/bpf/prog_tests/migrate_reuseport.c > @@ -353,8 +353,29 @@ 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, 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. > */ > @@ -368,6 +389,15 @@ static int migrate_dance(struct > migrate_reuseport_test_case *test_case) > 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: > + close(epoll); > + return -1; > + } > + > + close(epoll); > + > /* Note that we use the second listener instead of the > * first one here. > * > @@ -525,33 +555,6 @@ static void run_test(struct migrate_reuseport_test_case > *test_case, > goto close_clients; > } > > - /* Only TCP_ESTABLISHED has already-migrated accept-queue entries > - * here. Later states still depend on follow-up handshake work. > - */ > - if (test_case->state == BPF_TCP_ESTABLISHED) { > - struct epoll_event ev = { > - .events = EPOLLIN, > - }; > - int epfd; > - int nfds; > - > - epfd = epoll_create1(EPOLL_CLOEXEC); > - if (!ASSERT_NEQ(epfd, -1, "epoll_create1")) > - goto close_clients; > - > - ev.data.fd = test_case->servers[MIGRATED_TO]; > - if (!ASSERT_OK(epoll_ctl(epfd, EPOLL_CTL_ADD, > - test_case->servers[MIGRATED_TO], > &ev), > - "epoll_ctl")) > - goto close_epfd; > - > - nfds = epoll_wait(epfd, &ev, 1, 0); > - ASSERT_EQ(nfds, 1, "epoll_wait"); > - > -close_epfd: > - close(epfd); > - } > - > count_requests(test_case, skel); > > close_clients: > ---8<---
