public inbox for netdev@vger.kernel.org 
 help / color / mirror / Atom feed

From: Jakub Kicinski <kuba@kernel•org>
To: Tetsuo Handa <penguin-kernel@I-love•SAKURA.ne.jp>
Cc: David Howells <dhowells@redhat•com>,
	David Ahern <dsahern@kernel•org>, Jens Axboe <axboe@kernel•dk>,
	Matthew Wilcox <willy@infradead•org>,
	Network Development <netdev@vger•kernel.org>
Subject: Re: [possible regression in 6.5-rc1] sendmsg()/splice() returns EBADMSG
Date: Fri, 7 Jul 2023 18:09:01 -0700	[thread overview]
Message-ID: <20230707180901.34c17465@kernel.org> (raw)
In-Reply-To: <b9b17f87-007f-3ef9-d9e3-3080749cf01f@I-love.SAKURA.ne.jp>

On Sat, 8 Jul 2023 08:45:50 +0900 Tetsuo Handa wrote:
> (Branched from https://lkml.kernel.org/r/63006262-f808-50ab-97b8-c2193c7a9ba1@I-love.SAKURA.ne.jp .)
> 
> I found that the following program started returning EBADMSG. Bisection for sendmsg() reached
> commit c5c37af6ecad ("tcp: Convert do_tcp_sendpages() to use MSG_SPLICE_PAGES") and bisection
> for splice() reached commit 2dc334f1a63a ("splice, net: Use sendmsg(MSG_SPLICE_PAGES) rather
> than ->sendpage()"). Is this program doing something wrong?
> 
>   6.4.0-rc5-00892-g2dc334f1a63a-dirty    argc==1 ? splice()=EBADMSG, sendmsg()=EBADMSG : sendmsg()=success, splice()=EBADMSG
>   6.4.0-rc5-00891-g81840b3b91aa-dirty    argc==1 ? splice()=success, sendmsg()=EBADMSG : sendmsg()=success, splice()=success
> 
>   6.4.0-rc2-00520-gc5c37af6ecad-dirty    argc==1 ? splice()=success, sendmsg()=EBADMSG : sendmsg()=success, splice()=success
>   6.4.0-rc2-00519-g270a1c3de47e-dirty    argc==1 ? splice()=success, sendmsg()=success : sendmsg()=success, splice()=success

> 	setsockopt(fd, SOL_TCP, TCP_REPAIR, &one, sizeof(one));

I think it's just because the repro puts the socket in repair mode, 
and the current code doesn't want to play with repair mode as nicely.

I added:
	// needs #include <linux/tcp.h>
        int val = TCP_SEND_QUEUE;                                                   
        setsockopt(fd, SOL_TCP, TCP_REPAIR_QUEUE, &val, sizeof(val)); 

here (i.e. after putting the socket in repair mode), and I don't get 
the EBADMSG any more. Both sendmsg and splice succeed.

Can you check if we're back to the KMSAN problem with those lines added?


FWIW you can also try to repro with real tls sockets (not in repair
mode) by adding cases to tools/testing/selftests/net/tls.c for example:

TEST_F(tls, bla_bla)
{
	struct iovec iov = {
		.iov_base = "@@@@@@@@@@@@@@@@",
		.iov_len = 16
	};
	struct msghdr hdr = {
		.msg_iov = &iov,
		.msg_iovlen = 1,
		.msg_flags = MSG_FASTOPEN
	};
	int pipe_fds[2] = { -1, -1 };
	static char buf[32768] = { };
	int ret;

	ret = pipe(pipe_fds);
	ASSERT_EQ(ret, 0);

	EXPECT_EQ(write(pipe_fds[1], buf, 2432), 2432);
	EXPECT_EQ(write(pipe_fds[1], buf, 10676), 10676);
	EXPECT_EQ(write(pipe_fds[1], buf, 17996), 17996);

	EXPECT_EQ(splice(pipe_fds[0], NULL, self->fd, NULL, 1048576,
			 SPLICE_F_MORE), 17996 + 10676 + 2432);
	EXPECT_EQ(sendmsg(self->fd, &hdr, MSG_DONTWAIT | MSG_MORE), 16);
}

Then compiling:

make -C tools/testing/selftests/net/

And running:

tools/testing/selftests/net/tls -r tls.13_aes_gcm_256.bla_bla

     prev parent reply	other threads:[~2023-07-08  1:09 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-07-07 23:45 [possible regression in 6.5-rc1] sendmsg()/splice() returns EBADMSG Tetsuo Handa
2023-07-08  1:09 ` Jakub Kicinski [this message]

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20230707180901.34c17465@kernel.org \
    --to=kuba@kernel$(echo .)org \
    --cc=axboe@kernel$(echo .)dk \
    --cc=dhowells@redhat$(echo .)com \
    --cc=dsahern@kernel$(echo .)org \
    --cc=netdev@vger$(echo .)kernel.org \
    --cc=penguin-kernel@I-love$(echo .)SAKURA.ne.jp \
    --cc=willy@infradead$(echo .)org \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox