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[79.18.148.79]) by smtp.gmail.com with ESMTPSA id w1sm6577646eds.37.2021.06.07.05.28.17 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 07 Jun 2021 05:28:18 -0700 (PDT) Date: Mon, 7 Jun 2021 14:28:16 +0200 From: Stefano Garzarella To: Arseny Krasnov Cc: Stefan Hajnoczi , "Michael S. Tsirkin" , Jason Wang , "David S. Miller" , Jakub Kicinski , Jorgen Hansen , Colin Ian King , Andra Paraschiv , Norbert Slusarek , "kvm@vger.kernel.org" , "virtualization@lists.linux-foundation.org" , "netdev@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "oxffffaa@gmail.com" Subject: Re: [MASSMAIL KLMS] Re: [PATCH v10 04/18] af_vsock: implement SEQPACKET receive loop Message-ID: <20210607122816.yas4fpfmtvlrbfku@steredhat> References: <20210520191357.1270473-1-arseny.krasnov@kaspersky.com> <20210520191611.1271204-1-arseny.krasnov@kaspersky.com> <20210604150638.rmx262k4wjmp2zob@steredhat> <93254e99-1cf9-3135-f1c8-d60336bf41b5@kaspersky.com> <20210607104816.fgudxa5a6pldkqts@steredhat> <95a11b19-8266-7fc0-9426-edccd4512a2d@kaspersky.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <95a11b19-8266-7fc0-9426-edccd4512a2d@kaspersky.com> Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Mon, Jun 07, 2021 at 02:29:28PM +0300, Arseny Krasnov wrote: > >On 07.06.2021 13:48, Stefano Garzarella wrote: >> On Fri, Jun 04, 2021 at 09:00:14PM +0300, Arseny Krasnov wrote: >>> On 04.06.2021 18:06, Stefano Garzarella wrote: >>>> On Thu, May 20, 2021 at 10:16:08PM +0300, Arseny Krasnov wrote: >>>>> Add receive loop for SEQPACKET. It looks like receive loop for >>>>> STREAM, but there are differences: >>>>> 1) It doesn't call notify callbacks. >>>>> 2) It doesn't care about 'SO_SNDLOWAT' and 'SO_RCVLOWAT' values, because >>>>> there is no sense for these values in SEQPACKET case. >>>>> 3) It waits until whole record is received or error is found during >>>>> receiving. >>>>> 4) It processes and sets 'MSG_TRUNC' flag. >>>>> >>>>> So to avoid extra conditions for two types of socket inside one loop, two >>>>> independent functions were created. >>>>> >>>>> Signed-off-by: Arseny Krasnov >>>>> --- >>>>> v9 -> v10: >>>>> 1) Use 'msg_data_left()' instead of direct access to 'msg_hdr'. >>>>> >>>>> include/net/af_vsock.h | 4 +++ >>>>> net/vmw_vsock/af_vsock.c | 72 +++++++++++++++++++++++++++++++++++++++- >>>>> 2 files changed, 75 insertions(+), 1 deletion(-) >>>>> >>>>> diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h >>>>> index b1c717286993..5175f5a52ce1 100644 >>>>> --- a/include/net/af_vsock.h >>>>> +++ b/include/net/af_vsock.h >>>>> @@ -135,6 +135,10 @@ struct vsock_transport { >>>>> bool (*stream_is_active)(struct vsock_sock *); >>>>> bool (*stream_allow)(u32 cid, u32 port); >>>>> >>>>> + /* SEQ_PACKET. */ >>>>> + ssize_t (*seqpacket_dequeue)(struct vsock_sock *vsk, struct msghdr *msg, >>>>> + int flags, bool *msg_ready); >>>>> + >>>>> /* Notification. */ >>>>> int (*notify_poll_in)(struct vsock_sock *, size_t, bool *); >>>>> int (*notify_poll_out)(struct vsock_sock *, size_t, bool *); >>>>> diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c >>>>> index c4f6bfa1e381..aede474343d1 100644 >>>>> --- a/net/vmw_vsock/af_vsock.c >>>>> +++ b/net/vmw_vsock/af_vsock.c >>>>> @@ -1974,6 +1974,73 @@ static int __vsock_stream_recvmsg(struct sock *sk, struct msghdr *msg, >>>>> return err; >>>>> } >>>>> >>>>> +static int __vsock_seqpacket_recvmsg(struct sock *sk, struct msghdr *msg, >>>>> + size_t len, int flags) >>>>> +{ >>>>> + const struct vsock_transport *transport; >>>>> + bool msg_ready; >>>>> + struct vsock_sock *vsk; >>>>> + ssize_t record_len; >>>>> + long timeout; >>>>> + int err = 0; >>>>> + DEFINE_WAIT(wait); >>>>> + >>>>> + vsk = vsock_sk(sk); >>>>> + transport = vsk->transport; >>>>> + >>>>> + timeout = sock_rcvtimeo(sk, flags & MSG_DONTWAIT); >>>>> + msg_ready = false; >>>>> + record_len = 0; >>>>> + >>>>> + while (1) { >>>>> + ssize_t fragment_len; >>>>> + >>>>> + if (vsock_wait_data(sk, &wait, timeout, NULL, 0) <= 0) { >>>>> + /* In case of any loop break(timeout, signal >>>>> + * interrupt or shutdown), we report user that >>>>> + * nothing was copied. >>>>> + */ >>>>> + err = 0; >>>> Why we report that nothing was copied? >>>> >>>> What happen to the bytes already copied in `msg`? >>> Seems i need to return result of vsock_wait_data()... >> I'm not sure. >> >> My biggest concern is if we reach timeout or get a signal while waiting >> for the other pieces of a message. >> I believe that we should not start copying a message if we have not >> received all the fragments. Otherwise we have this problem. >> >> When we are sure that we have all the pieces, then we should copy them >> without interrupting. >> >> IIRC this was done in previous versions. > >As i remember, previous versions also returned 0, because i thought, >that for interrupted read we can copy piece of data to user's buffer, >but we must return that nothing copied or error. In this way user This can also be fine, but we should remove packet form the rx_queue only when we are sure that we delivered the entire message. > >won't read part of message, because syscall returned that there is >nothing to copy. So as i understand, it is not enough - user's buffer >must be touched only when whole message is copied? The important thing is to not remove packets from the rx_queue unless we are sure that everything went well and we are returning the entire message to the user. Stefano