netdev - Re: [RFC PATCH v1 2/3] test/vsock: add big message test

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Date:   Wed, 23 Nov 2022 16:21:59 +0100
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Arseniy Krasnov <AVKrasnov@...rdevices.ru>,
        Bobby Eshleman <bobby.eshleman@...il.com>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        kernel <kernel@...rdevices.ru>,
        Krasnov Arseniy <oxffffaa@...il.com>
Subject: Re: [RFC PATCH v1 2/3] test/vsock: add big message test

On Mon, Nov 21, 2022 at 09:40:39PM +0000, Arseniy Krasnov wrote:
>On 21.11.2022 19:50, Arseniy Krasnov wrote:
>> On 21.11.2022 17:52, Stefano Garzarella wrote:
>>> On Tue, Nov 15, 2022 at 08:52:35PM +0000, Arseniy Krasnov wrote:
>>>> This adds test for sending message, bigger than peer's buffer size.
>>>> For SOCK_SEQPACKET socket it must fail, as this type of socket has
>>>> message size limit.
>>>>
>>>> Signed-off-by: Arseniy Krasnov <AVKrasnov@...rdevices.ru>
>>>> ---
>>>> tools/testing/vsock/vsock_test.c | 62 ++++++++++++++++++++++++++++++++
>>>> 1 file changed, 62 insertions(+)
>>>>
>>>> diff --git a/tools/testing/vsock/vsock_test.c b/tools/testing/vsock/vsock_test.c
>>>> index 107c11165887..bb4e8657f1d6 100644
>>>> --- a/tools/testing/vsock/vsock_test.c
>>>> +++ b/tools/testing/vsock/vsock_test.c
>>>> @@ -560,6 +560,63 @@ static void test_seqpacket_timeout_server(const struct test_opts *opts)
>>>>     close(fd);
>>>> }
>>>>
>>>> +static void test_seqpacket_bigmsg_client(const struct test_opts *opts)
>>>> +{
>>>> +    unsigned long sock_buf_size;
>>>> +    ssize_t send_size;
>>>> +    socklen_t len;
>>>> +    void *data;
>>>> +    int fd;
>>>> +
>>>> +    len = sizeof(sock_buf_size);
>>>> +
>>>> +    fd = vsock_seqpacket_connect(opts->peer_cid, 1234);
>>>
>>> Not for this patch, but someday we should add a macro for this port and maybe even make it configurable :-)
>>>
>>>> +    if (fd < 0) {
>>>> +        perror("connect");
>>>> +        exit(EXIT_FAILURE);
>>>> +    }
>>>> +
>>>> +    if (getsockopt(fd, AF_VSOCK, SO_VM_SOCKETS_BUFFER_SIZE,
>>>> +               &sock_buf_size, &len)) {
>>>> +        perror("getsockopt");
>>>> +        exit(EXIT_FAILURE);
>>>> +    }
>>>> +
>>>> +    sock_buf_size++;
>>>> +
>>>> +    data = malloc(sock_buf_size);
>>>> +    if (!data) {
>>>> +        perror("malloc");
>>>> +        exit(EXIT_FAILURE);
>>>> +    }
>>>> +
>>>> +    send_size = send(fd, data, sock_buf_size, 0);
>>>> +    if (send_size != -1) {
>>>
>>> Can we check also `errno`?
>>> IIUC it should contains EMSGSIZE.
>Hm, seems current implementation is a little bit broken and returns ENOMEM, because any negative value, returned by
>transport callback is always replaced to ENOMEM. I think i need this patch from Bobby:
>https://lore.kernel.org/lkml/d81818b868216c774613dd03641fcfe63cc55a45.1660362668.git.bobby.eshleman@bytedance.com/
>May be i can include it to this patchset also fixing review comments(of course keeping Bobby as author). Or more
>simple way is to check ENOMEM instead of EMSGSIZE in this test(simple, but a little bit dumb i think).

Maybe in this patch you can start checking ENOMEM (with a TODO comment),
and then Bobby can change it when sending his patch.

Or you can repost it (I'm not sure if we should keep the legacy behavior 
for other transports or it was an error, but better to discuss it on 
that patch). However, I think we should merge that patch.

@Bobby, what do you think?

Thanks,
Stefano