Subject: Re: [PATCH bpf v7 11/13] bpf: sockmap, test shutdown() correctly exits epoll and recv()=0

From: John Fastabend <[email-masked]>
Date: Mon, 15 May 2023 18:51:20 -0700

Jakub Sitnicki wrote:
> On Tue, May 02, 2023 at 08:51 AM -07, John Fastabend wrote:
> > When session gracefully shutdowns epoll needs to wake up and any recv()
> > readers should return 0 not the -EAGAIN they previously returned.
> >
> > Note we use epoll instead of select to test the epoll wake on shutdown
> > event as well.
> >
> > Signed-off-by: John Fastabend <[email-masked]>
> > ---
> >  .../selftests/bpf/prog_tests/sockmap_basic.c  | 68 +++++++++++++++++++
> >  .../bpf/progs/test_sockmap_pass_prog.c        | 32 +++++++++
> >  2 files changed, 100 insertions(+)
> >  create mode 100644 tools/testing/selftests/bpf/progs/test_sockmap_pass_prog.c
> >
> > diff --git a/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c b/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c
> > index 0ce25a967481..f9f611618e45 100644
> > --- a/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c
> > +++ b/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c
> > @@ -2,6 +2,7 @@
> >  // Copyright (c) 2020 Cloudflare
> >  #include <error.h>
> >  #include <netinet/tcp.h>
> > +#include <sys/epoll.h>
> >  
> >  #include "test_progs.h"
> >  #include "test_skmsg_load_helpers.skel.h"
> > @@ -9,8 +10,11 @@
> >  #include "test_sockmap_invalid_update.skel.h"
> >  #include "test_sockmap_skb_verdict_attach.skel.h"
> >  #include "test_sockmap_progs_query.skel.h"
> > +#include "test_sockmap_pass_prog.skel.h"
> >  #include "bpf_iter_sockmap.skel.h"
> >  
> > +#include "sockmap_helpers.h"
> > +
> >  #define TCP_REPAIR		19	/* TCP sock is under repair right now */
> >  
> >  #define TCP_REPAIR_ON		1
> > @@ -350,6 +354,68 @@ static void test_sockmap_progs_query(enum bpf_attach_type attach_type)
> >  	test_sockmap_progs_query__destroy(skel);
> >  }
> >  
> > +#define MAX_EVENTS 10
> > +static void test_sockmap_skb_verdict_shutdown(void)
> > +{
> > +	int n, err, map, verdict, s, c0, c1, p0, p1;
> > +	struct epoll_event ev, events[MAX_EVENTS];
> > +	struct test_sockmap_pass_prog *skel;
> > +	int epollfd;
> > +	int zero = 0;
> > +	char b;
> > +
> > +	skel = test_sockmap_pass_prog__open_and_load();
> > +	if (!ASSERT_OK_PTR(skel, "open_and_load"))
> > +		return;
> > +
> > +	verdict = bpf_program__fd(skel->progs.prog_skb_verdict);
> > +	map = bpf_map__fd(skel->maps.sock_map_rx);
> > +
> > +	err = bpf_prog_attach(verdict, map, BPF_SK_SKB_STREAM_VERDICT, 0);
> > +	if (!ASSERT_OK(err, "bpf_prog_attach"))
> > +		goto out;
> > +
> > +	s = socket_loopback(AF_INET, SOCK_STREAM);
> > +	if (s < 0)
> > +		goto out;
> > +	err = create_socket_pairs(s, AF_INET, SOCK_STREAM, &c0, &c1, &p0, &p1);
> > +	if (err < 0)
> > +		goto out;
> > +
> > +	err = bpf_map_update_elem(map, &zero, &c1, BPF_NOEXIST);
> > +	if (err < 0)
> > +		goto out_close;
> > +
> > +	shutdown(c0, SHUT_RDWR);
> > +	shutdown(p1, SHUT_WR);
> > +
> > +	ev.events = EPOLLIN;
> > +	ev.data.fd = c1;
> > +
> > +	epollfd = epoll_create1(0);
> > +	if (!ASSERT_GT(epollfd, -1, "epoll_create(0)"))
> > +		goto out_close;
> > +	err = epoll_ctl(epollfd, EPOLL_CTL_ADD, c1, &ev);
> > +	if (!ASSERT_OK(err, "epoll_ctl(EPOLL_CTL_ADD)"))
> > +		goto out_close;
> > +	err = epoll_wait(epollfd, events, MAX_EVENTS, -1);
> > +	if (!ASSERT_EQ(err, 1, "epoll_wait(fd)"))
> > +		goto out_close;
> > +
> > +	n = recv(c1, &b, 1, SOCK_NONBLOCK);
> > +	ASSERT_EQ(n, 0, "recv_timeout(fin)");
> > +	n = recv(p0, &b, 1, SOCK_NONBLOCK);
> > +	ASSERT_EQ(n, 0, "recv_timeout(fin)");
> > +
> > +out_close:
> > +	close(c0);
> > +	close(p0);
> > +	close(c1);
> > +	close(p1);
> > +out:
> > +	test_sockmap_pass_prog__destroy(skel);
> > +}
> > +
> 
> This test has me scratching my head. I don't grasp what we're testing
> with (c0, p0) socket pair, since c0 is not in any sockmap?

Yeah the test is on (c1,p1) I was just lazy and using the API as is
I can fix the API to allow single set c1,p1.