Re: [PATCH bpf v4 1/2] selftests/bpf: Add F_SETFL for fcntl in test_sockmap

[Geliang Tang <geliang@kernel.org>]

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Hi Martin,

On Thu, Apr 11, 2024 at 11:10:49AM -0700, Martin KaFai Lau wrote:
> On 4/8/24 10:18 PM, Geliang Tang wrote:
> > From: Geliang Tang <tanggeliang@kylinos.cn>
> > 
> > Incorrect arguments are passed to fcntl() in test_sockmap.c when invoking
> > it to set file status flags. If O_NONBLOCK is used as 2nd argument and
> > passed into fcntl, -EINVAL will be returned (See do_fcntl() in fs/fcntl.c).
> > The correct approach is to use F_SETFL as 2nd argument, and O_NONBLOCK as
> > 3rd one.
> > 
> > In nonblock mode, if EWOULDBLOCK is received, continue receiving, otherwise
> > some subtests of test_sockmap fail.
> > 
> > Fixes: 16962b2404ac ("bpf: sockmap, add selftests")
> > Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
> > Acked-by: Yonghong Song <yonghong.song@linux.dev>
> > ---
> >   tools/testing/selftests/bpf/test_sockmap.c | 5 ++++-
> >   1 file changed, 4 insertions(+), 1 deletion(-)
> > 
> > diff --git a/tools/testing/selftests/bpf/test_sockmap.c b/tools/testing/selftests/bpf/test_sockmap.c
> > index 024a0faafb3b..4feed253fca2 100644
> > --- a/tools/testing/selftests/bpf/test_sockmap.c
> > +++ b/tools/testing/selftests/bpf/test_sockmap.c
> > @@ -603,7 +603,9 @@ static int msg_loop(int fd, int iov_count, int iov_length, int cnt,
> >   		struct timeval timeout;
> >   		fd_set w;
> > -		fcntl(fd, fd_flags);
> > +		if (fcntl(fd, F_SETFL, fd_flags))
> > +			goto out_errno;
> > +
> >   		/* Account for pop bytes noting each iteration of apply will
> >   		 * call msg_pop_data helper so we need to account for this
> >   		 * by calculating the number of apply iterations. Note user
> > @@ -678,6 +680,7 @@ static int msg_loop(int fd, int iov_count, int iov_length, int cnt,
> >   					perror("recv failed()");
> >   					goto out_errno;
> >   				}
> > +				continue;
> 
> From looking at it again, there is a select() earlier, so it should not hit
> EWOULDBLOCK.

Can the patch in the attachment be accepted? It can work, but I'm not sure
if it has changed the behavior of this test. Anyway, I would like to hear
your opinion.

Thanks,
-Geliang

> 
> Patch 2 looks good. Only patch 2 is applied. Thanks.
> 
> >   			}
> >   			s->bytes_recvd += recv;

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From d20ac7e06d9e869094f452d8c2dcdc316508dcc8 Mon Sep 17 00:00:00 2001
Message-Id: <d20ac7e06d9e869094f452d8c2dcdc316508dcc8.1713340686.git.tanggeliang@kylinos.cn>
From: Geliang Tang <tanggeliang@kylinos.cn>
Date: Wed, 3 Apr 2024 16:08:21 +0800
Subject: [PATCH] selftests/bpf: Add F_SETFL for fcntl in test_sockmap

Incorrect arguments are passed to fcntl() in test_sockmap.c when invoking
it to set file status flags. If O_NONBLOCK is used as 2nd argument and
passed into fcntl, -EINVAL will be returned (See do_fcntl() in fs/fcntl.c).
The correct approach is to use F_SETFL as 2nd argument, and O_NONBLOCK as
3rd one.

In nonblock mode, if EWOULDBLOCK is received, continue receiving, otherwise
some subtests of test_sockmap fail.

Fixes: 16962b2404ac ("bpf: sockmap, add selftests")
Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
Acked-by: Yonghong Song <yonghong.song@linux.dev>
---
 tools/testing/selftests/bpf/test_sockmap.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/bpf/test_sockmap.c b/tools/testing/selftests/bpf/test_sockmap.c
index 024a0faafb3b..8130f465afb9 100644
--- a/tools/testing/selftests/bpf/test_sockmap.c
+++ b/tools/testing/selftests/bpf/test_sockmap.c
@@ -603,7 +603,9 @@ static int msg_loop(int fd, int iov_count, int iov_length, int cnt,
 		struct timeval timeout;
 		fd_set w;
 
-		fcntl(fd, fd_flags);
+		if (fcntl(fd, F_SETFL, fd_flags))
+			goto out_errno;
+
 		/* Account for pop bytes noting each iteration of apply will
 		 * call msg_pop_data helper so we need to account for this
 		 * by calculating the number of apply iterations. Note user
@@ -1531,10 +1533,10 @@ static void test_txmsg_skb(int cgrp, struct sockmap_options *opt)
 	txmsg_ktls_skb_drop = 1;
 	test_exec(cgrp, opt);
 
-	txmsg_ktls_skb_drop = 0;
 	txmsg_ktls_skb_redir = 1;
 	test_exec(cgrp, opt);
 	txmsg_ktls_skb_redir = 0;
+	txmsg_ktls_skb_drop = 0;
 
 	/* Tests that omit skb_parser */
 	txmsg_omit_skb_parser = 1;
-- 
2.40.1