From: Laurent Vivier <lvivier@redhat.com>
To: Stefano Brivio <sbrivio@redhat.com>,
David Gibson <david@gibson.dropbear.id.au>
Cc: passt-dev@passt.top
Subject: Re: [PATCH v8 7/8] vhost-user: add vhost-user
Date: Wed, 23 Oct 2024 17:27:49 +0200 [thread overview]
Message-ID: <8ac883f3-f1ff-4cb7-85e7-02e590313261@redhat.com> (raw)
In-Reply-To: <c3e382c4-a306-448f-9c0b-5e11979144c3@redhat.com>
On 22/10/2024 14:59, Laurent Vivier wrote:
> On 17/10/2024 02:10, Stefano Brivio wrote:
>> On Wed, 16 Oct 2024 11:41:34 +1100
>> David Gibson <david@gibson.dropbear.id.au> wrote:
>>
>>> On Tue, Oct 15, 2024 at 09:54:38PM +0200, Stefano Brivio wrote:
>>>> [Still partial review]
>>> [snip]
>>>>> + if (peek_offset_cap)
>>>>> + already_sent = 0;
>>>>> +
>>>>> + iov_vu[0].iov_base = tcp_buf_discard;
>>>>> + iov_vu[0].iov_len = already_sent;
>>>>
>>>> I think I had a similar comment to a previous revision. Now, I haven't
>>>> tested this (yet) on a kernel with support for SO_PEEK_OFF on TCP, but
>>>> I think this should eventually follow the same logic as the (updated)
>>>> tcp_buf_data_from_sock(): we should use tcp_buf_discard only if
>>>> (!peek_offset_cap).
>>>>
>>>> It's fine to always initialise VIRTQUEUE_MAX_SIZE iov_vu items,
>>>> starting from 1, for simplicity. But I'm not sure if it's safe to pass a
>>>> zero iov_len if (peek_offset_cap).
>>>
>>>> I'll test that (unless you already did) -- if it works, we can fix this
>>>> up later as well.
>>>
>>> I believe I tested it at some point, and I think we're already using
>>> it somewhere.
>>
>> I tested it again just to be sure on a recent net.git kernel: sometimes
>> the first test in passt_vu_in_ns/tcp, "TCP/IPv4: host to guest: big
>> transfer" hangs on my setup, sometimes it's the "TCP/IPv4: ns to guest
>> (using loopback address): big transfer" test instead.
>>
>> I can reproduce at least one of the two issues consistently (tests
>> stopped 5 times out of 5).
>>
>> The socat client completes the transfer, the server is still waiting
>> for something. I haven't taken captures yet or tried to re-send from
>> the client.
>>
>> It all works (consistently) with an older kernel without support for
>> SO_PEEK_OFF on TCP, but also on this kernel if I force peek_offset_cap
>> to false in tcp_init().
>>
>
> I have a fix for that but there is an error I don't understand:
> when I run twice the test, the second time I have:
>
> guest:
> # socat -u TCP4-LISTEN:10001 OPEN:test_big.bin,create,trunc
> # socat -u TCP4-LISTEN:10001 OPEN:test_big.bin,create,trunc
> 2024/10/22 08:51:58 socat[1485] E bind(5, {AF=2 0.0.0.0:10001}, 16): Address already in use
>
> host:
> $ socat -u OPEN:test/big.bin TCP4:127.0.0.1:10001
>
> If I wait a little it can work again several times and fails again.
>
> Any idea?
>
> The patch is:
> diff --git a/tcp_vu.c b/tcp_vu.c
> index 78884c673215..83e40fb07a03 100644
> --- a/tcp_vu.c
> +++ b/tcp_vu.c
> @@ -379,6 +379,10 @@ int tcp_vu_data_from_sock(const struct ctx *c, struct tcp_tap_conn
> *conn)
> conn->seq_ack_from_tap, conn->seq_to_tap);
> conn->seq_to_tap = conn->seq_ack_from_tap;
> already_sent = 0;
> + if (tcp_set_peek_offset(conn->sock, 0)) {
> + tcp_rst(c, conn);
> + return -1;
> + }
> }
>
> if (!wnd_scaled || already_sent >= wnd_scaled) {
> @@ -389,14 +393,13 @@ int tcp_vu_data_from_sock(const struct ctx *c, struct tcp_tap_conn
> *conn)
>
> /* Set up buffer descriptors we'll fill completely and partially. */
>
> - fillsize = wnd_scaled;
> + fillsize = wnd_scaled - already_sent;
>
> if (peek_offset_cap)
> already_sent = 0;
>
> iov_vu[0].iov_base = tcp_buf_discard;
> iov_vu[0].iov_len = already_sent;
> - fillsize -= already_sent;
>
> /* collect the buffers from vhost-user and fill them with the
> * data from the socket
>
>
For the moment, I can see a behavior change of recvmsg() with the new kernel.
without peek_offset_cap, if no new data is available, it returns "already_sent", so it
enters in (found with tcp_vu.c but code samples from tcp_buf.c):
==> recvmsg() returns already_sent, so len > 0
...
sendlen -= already_sent; ==> here sendlen becomes 0
if (sendlen <= 0) {
conn_flag(c, conn, STALLED);
return 0;
}
With peek_offset, it returns -1, so it enters in:
if (len < 0)
goto err;
...
err:
if (errno != EAGAIN && errno != EWOULDBLOCK) {
ret = -errno;
tcp_rst(c, conn);
}
Thanks,
Laurent
next prev parent reply other threads:[~2024-10-23 15:27 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-10-10 12:28 [PATCH v8 0/8] Add vhost-user support to passt. (part 3) Laurent Vivier
2024-10-10 12:28 ` [PATCH v8 1/8] packet: replace struct desc by struct iovec Laurent Vivier
2024-10-10 12:28 ` [PATCH v8 2/8] vhost-user: introduce virtio API Laurent Vivier
2024-10-10 12:28 ` [PATCH v8 3/8] vhost-user: introduce vhost-user API Laurent Vivier
2024-10-10 12:28 ` [PATCH v8 4/8] udp: Prepare udp.c to be shared with vhost-user Laurent Vivier
2024-10-14 4:29 ` David Gibson
2024-10-10 12:28 ` [PATCH v8 5/8] tcp: Export headers functions Laurent Vivier
2024-10-14 4:29 ` David Gibson
2024-10-10 12:29 ` [PATCH v8 6/8] passt: rename tap_sock_init() to tap_backend_init() Laurent Vivier
2024-10-14 4:30 ` David Gibson
2024-10-14 22:38 ` Stefano Brivio
2024-10-10 12:29 ` [PATCH v8 7/8] vhost-user: add vhost-user Laurent Vivier
2024-10-15 3:23 ` David Gibson
2024-10-16 10:07 ` Laurent Vivier
2024-10-16 16:26 ` Stefano Brivio
2024-10-15 19:54 ` Stefano Brivio
2024-10-16 0:41 ` David Gibson
2024-10-17 0:10 ` Stefano Brivio
2024-10-17 11:25 ` Stefano Brivio
2024-10-17 11:54 ` Laurent Vivier
2024-10-17 17:18 ` Laurent Vivier
2024-10-17 17:25 ` Laurent Vivier
2024-10-17 17:33 ` Stefano Brivio
2024-10-17 21:21 ` Stefano Brivio
2024-10-22 12:59 ` Laurent Vivier
2024-10-22 13:19 ` Stefano Brivio
2024-10-22 18:19 ` Stefano Brivio
2024-10-22 18:22 ` Stefano Brivio
2024-10-23 15:27 ` Laurent Vivier [this message]
2024-10-23 16:23 ` Stefano Brivio
2024-10-17 0:10 ` Stefano Brivio
2024-10-17 7:28 ` Laurent Vivier
2024-10-17 8:33 ` Stefano Brivio
2024-11-14 10:20 ` Laurent Vivier
2024-11-14 14:23 ` Stefano Brivio
2024-11-14 15:16 ` Laurent Vivier
2024-11-14 15:38 ` Stefano Brivio
2024-11-14 10:23 ` Laurent Vivier
2024-11-14 14:23 ` Stefano Brivio
2024-11-15 8:30 ` Laurent Vivier
2024-11-15 10:08 ` Stefano Brivio
2024-11-14 10:29 ` Laurent Vivier
2024-11-14 14:23 ` Stefano Brivio
2024-11-15 11:13 ` Laurent Vivier
2024-11-15 11:23 ` Stefano Brivio
2024-10-10 12:29 ` [PATCH v8 8/8] test: Add tests for passt in vhost-user mode Laurent Vivier
2024-10-15 3:40 ` David Gibson
2024-10-15 19:54 ` Stefano Brivio
2024-10-16 8:06 ` Laurent Vivier
2024-10-16 9:47 ` Stefano Brivio
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