From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from ws5-mx01.kavi.com (ws5-mx01.kavi.com [34.193.7.191]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 3EC79CA0FFC for ; Sat, 2 Sep 2023 08:35:38 +0000 (UTC) Received: from lists.oasis-open.org (oasis.ws5.connectedcommunity.org [10.110.1.242]) by ws5-mx01.kavi.com (Postfix) with ESMTP id 90670C6253 for ; Sat, 2 Sep 2023 08:35:37 +0000 (UTC) Received: from lists.oasis-open.org (oasis-open.org [10.110.1.242]) by lists.oasis-open.org (Postfix) with ESMTP id 834439865C8 for ; Sat, 2 Sep 2023 08:35:37 +0000 (UTC) Received: from host09.ws5.connectedcommunity.org (host09.ws5.connectedcommunity.org [10.110.1.97]) by lists.oasis-open.org (Postfix) with QMQP id 74D82983E52; Sat, 2 Sep 2023 08:35:37 +0000 (UTC) Mailing-List: contact virtio-dev-help@lists.oasis-open.org; run by ezmlm List-ID: Sender: Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: Received: from lists.oasis-open.org (oasis-open.org [10.110.1.242]) by lists.oasis-open.org (Postfix) with ESMTP id 64800986595 for ; Sat, 2 Sep 2023 08:35:34 +0000 (UTC) X-Virus-Scanned: amavisd-new at kavi.com X-MC-Unique: QKibJICEPJy7H-nJ8gdkfQ-1 X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1693643730; x=1694248530; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=Tx/R4Ypx48aYWYb22H8fWrmat8EAEjJNpuQqM8wuIOk=; b=VBFnbLEFot3BvrC8jkUM58PYOVKsD15Wxn3fAWUGkXDgUnA/776delGXMDSVVNRMfI nQVDTia5XLU2Hya90HJ6SsO8SNhGBlfKjkBpvG8MJCqejQtfRAzmkDqjs01g9gzfmzNy IWUnjbVRE/MUlawO21I1m/Vv7NXl4kvTVt/6CoZdaRIZVM8IvGCIYyvAROFpV/zDWxfy c5epcHCACf55gCLRYqADpculJu74eZ4ywEUlD23lr8rWzT3exACMOTBAszHqpcS7wj/Z NdsxEE4Y3Mey3LY7Sf1gxKOZSvXc7VC+dCon4eUmF7EiJ3YJm7POAFgfWmtKt3MQ4pA7 8dig== X-Gm-Message-State: AOJu0YzB7eZwVRBpeN0O12iNZCRnEznA/R7BD7b03kvJxdByPM0asXn1 a2NRi2rtQlEytXZPcAyls+WE35hnjYvHlDQ8Z/kxdDcKmJXr90GcdjjBqp50PhhglpXD7ct0/Ey i1PDcDppwtJ/iCvoKwbfZMwTzJT3A X-Received: by 2002:a2e:9a8e:0:b0:2bc:b0ae:a9e5 with SMTP id p14-20020a2e9a8e000000b002bcb0aea9e5mr3448380lji.42.1693643730054; Sat, 02 Sep 2023 01:35:30 -0700 (PDT) X-Google-Smtp-Source: AGHT+IE3zcbVZ6d3LCJHvU3yrSQgputZFAf847TTrPCn81lmpiszvcgxiC7s0VltNhGdY9owoKzF9w== X-Received: by 2002:a2e:9a8e:0:b0:2bc:b0ae:a9e5 with SMTP id p14-20020a2e9a8e000000b002bcb0aea9e5mr3448365lji.42.1693643729668; Sat, 02 Sep 2023 01:35:29 -0700 (PDT) Date: Sat, 2 Sep 2023 04:35:25 -0400 From: "Michael S. Tsirkin" To: Bobby Eshleman Cc: Stefano Garzarella , Bobby Eshleman , virtio-dev@lists.oasis-open.org, cong.wang@bytedance.com, jiang.wang@bytedance.com, cohuck@redhat.com, virtualization@lists.linux-foundation.org, stefanha@redhat.com, virtio-comment@lists.oasis-open.org, arseny.krasnov@kaspersky.com Message-ID: <20230902043334-mutt-send-email-mst@kernel.org> References: <20230829212945.3420727-1-bobby.eshleman@bytedance.com> MIME-Version: 1.0 In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Subject: [virtio-dev] Re: [PATCH] virtio-vsock: add VIRTIO_VSOCK_F_DGRAM feature bit On Sat, Sep 02, 2023 at 04:56:42AM +0000, Bobby Eshleman wrote: > On Fri, Sep 01, 2023 at 02:45:14PM +0200, Stefano Garzarella wrote: > > On Tue, Aug 29, 2023 at 09:29:45PM +0000, Bobby Eshleman wrote: > > > This adds support for datagrams to the virtio-vsock device. > > > > > > virtio-vsock already supports stream and seqpacket types. The existing > > > message types and header fields are extended to support datagrams. > > > Semantic differences between the flow types are stated, as well as any > > > additional requirements for devices and drivers implementing this > > > feature. > > > > > > Signed-off-by: Bobby Eshleman > > > --- > > > device-types/vsock/description.tex | 95 +++++++++++++++++++++++++++--- > > > 1 file changed, 88 insertions(+), 7 deletions(-) > > > > > > diff --git a/device-types/vsock/description.tex b/device-types/vsock/description.tex > > > index 7d91d159872f..638dca8e5da1 100644 > > > --- a/device-types/vsock/description.tex > > > +++ b/device-types/vsock/description.tex > > > @@ -20,6 +20,7 @@ \subsection{Feature bits}\label{sec:Device Types / Socket Device / Feature bits} > > > \item[VIRTIO_VSOCK_F_STREAM (0)] stream socket type is supported. > > > \item[VIRTIO_VSOCK_F_SEQPACKET (1)] seqpacket socket type is supported. > > > \item[VIRTIO_VSOCK_F_NO_IMPLIED_STREAM (2)] stream socket type is not implied. > > > +\item[VIRTIO_VSOCK_F_DGRAM (3)] datagram socket type is supported. > > > \end{description} > > > > > > \drivernormative{\subsubsection}{Feature bits}{Device Types / Socket Device / Feature bits} > > > @@ -167,17 +168,22 @@ \subsubsection{Addressing}\label{sec:Device Types / Socket Device / Device Opera > > > consists of a (cid, port number) tuple. The header fields used for this are > > > \field{src_cid}, \field{src_port}, \field{dst_cid}, and \field{dst_port}. > > > > > > -Currently stream and seqpacket sockets are supported. \field{type} is 1 (VIRTIO_VSOCK_TYPE_STREAM) > > > -for stream socket types, and 2 (VIRTIO_VSOCK_TYPE_SEQPACKET) for seqpacket socket types. > > > + > > > +Currently stream, seqpacket, and datagram sockets are supported. \field{type} is > > > +1 (VIRTIO_VSOCK_TYPE_STREAM) for stream socket types, 2 (VIRTIO_VSOCK_TYPE_SEQPACKET) for > > > +seqpacket socket types, and 3 (VIRTIO_VSOCK_TYPE_DGRAM) for datagram socket types. > > > > > > \begin{lstlisting} > > > #define VIRTIO_VSOCK_TYPE_STREAM 1 > > > #define VIRTIO_VSOCK_TYPE_SEQPACKET 2 > > > +#define VIRTIO_VSOCK_TYPE_DGRAM 3 > > > \end{lstlisting} > > > > > > Stream sockets provide in-order, guaranteed, connection-oriented delivery > > > without message boundaries. Seqpacket sockets provide in-order, guaranteed, > > > -connection-oriented delivery with message and record boundaries. > > > +connection-oriented delivery with message and record boundaries. Datagram > > > +sockets provide connection-less, best-effort delivery of messages, with no > > > +order or reliability guarantees. > > > > > > \subsubsection{Buffer Space Management}\label{sec:Device Types / Socket Device / Device Operation / Buffer Space Management} > > > \field{buf_alloc} and \field{fwd_cnt} are used for buffer space management of > > > @@ -203,16 +209,19 @@ \subsubsection{Buffer Space Management}\label{sec:Device Types / Socket Device / > > > previously receiving a VIRTIO_VSOCK_OP_CREDIT_REQUEST packet. This allows > > > communicating updates any time a change in buffer space occurs. > > > > > > +\field{buf_alloc} and \field{fwd_cnt} are reserved for future use by datagram > > > +sockets. These fields are not used for datagram buffer space management. > > > + > > > \drivernormative{\paragraph}{Device Operation: Buffer Space Management}{Device Types / Socket Device / Device Operation / Buffer Space Management} > > > -VIRTIO_VSOCK_OP_RW data packets MUST only be transmitted when the peer has > > > -sufficient free buffer space for the payload. > > > +For stream and seqpacket flows, VIRTIO_VSOCK_OP_RW data packets MUST only be > > > +transmitted when the peer has sufficient free buffer space for the payload. > > > > > > All packets associated with a stream flow MUST contain valid information in > > > \field{buf_alloc} and \field{fwd_cnt} fields. > > > > > > \devicenormative{\paragraph}{Device Operation: Buffer Space > > > Management}{Device Types / Socket Device / Device Operation / Buffer > > > Space Management} > > > -VIRTIO_VSOCK_OP_RW data packets MUST only be transmitted when the peer has > > > -sufficient free buffer space for the payload. > > > +For stream and seqpacket flows, VIRTIO_VSOCK_OP_RW data packets MUST only be > > > +transmitted when the peer has sufficient free buffer space for the payload. > > > > > > All packets associated with a stream flow MUST contain valid information in > > > \field{buf_alloc} and \field{fwd_cnt} fields. > > > @@ -299,6 +308,78 @@ \subsubsection{Seqpacket Sockets}\label{sec:Device Types / Socket Device / Devic > > > #define VIRTIO_VSOCK_SEQ_EOR (1 << 1) > > > \end{lstlisting} > > > > > > +\subsubsection{Datagram Sockets}\label{sec:Device Types / Socket Device / Device Operation / Datagram Sockets} > > > + > > > +\drivernormative{\paragraph}{Device Operation: Packet Fragmentation}{Device Types / Socket Device / Datagram Sockets / Fragmentation} > > > + > > > +Drivers MAY disassemble packets into smaller fragments. If drivers fragment a > > > +packet, they MUST follow the fragmentation rules described in section > > > +\ref{sec:Device Types / Socket Device / Device Operation / Datagram Sockets / Fragmentation}. > > > + > > > +Drivers MUST support assembly of received packet fragments according to the > > > +fragmentation rules described in section > > > +\ref{sec:Device Types / Socket Device / Device Operation / Datagram > > > Sockets / Fragmentation}. > > > + > > > +\devicenormative{\paragraph}{Device Operation: Packet Fragmentation}{Device Types / Socket Device / Datagram Sockets / Fragmentation} > > > + > > > +Devices MAY disassemble packets into smaller fragments. If devices fragment a > > > +packet, they MUST follow the fragmentation rules described in section > > > +\ref{sec:Device Types / Socket Device / Device Operation / Datagram Sockets / Fragmentation}. > > > + > > > +Devices MUST support assembly of received packet fragments according to the > > > +fragmentation rules described in section > > > +\ref{sec:Device Types / Socket Device / Device Operation / Datagram Sockets / Fragmentation}. > > > + > > > +\drivernormative{\paragraph}{Device Operation: Packet Dropping}{Device Types / Socket Device / Datagram Sockets / Dropping} > > > + > > > +The driver MAY drop received packets with no notification to the device. This > > > +can happen if, for example, there are insufficient resources or no socket > > > +exists for the destination address. > > > + > > > +\devicenormative{\paragraph}{Device Operation: Packet Dropping}{Device Types / Socket Device / Datagram Sockets / Dropping} > > > + > > > +The device MAY drop received packets with no notification to the driver. This > > > +can happen if, for example, there are insufficient resources or no socket > > > +exists for the destination address. > > > > Should we provide some notification if the socket does not exist at the > > destination? > > > > Yes, I think so. I believe a start/stop congestion notification scheme > actually manages this issue well. > > For example, the source begins sending packets to a destination. > > The destination finds that there exists no socket for that destination > address. The destination sends a "stop" notification to the source that > contains the address in question. Meanwhile, packets are still coming in > but they are being dropped. > > The source receives the "stop" notification with the address and adds it > to the "stopped destinations" list. Any new packet destination address > will be compared to that list. Any matches will be dropped before > sending (and ideally, before wasting time allocating the packet). > > Only when a socket is bound to an address that matches a "stopped" > address does the destination send a "start" notification to any source > it has previusly sent a "stop" notification to. > > Once "start" is received, flow may resume as normal. Again, dropping as control flow tactic has a bunch of problems. Blocking senders sounds more reasonable. > > > + > > > +\paragraph{Datagram Fragmentation}\label{sec:Device Types / Socket Device / Device Operation / Datagram Sockets / Fragmentation} > > > + > > > +\field{flags} may have the following bit set: > > > + > > > +\begin{lstlisting} > > > +#define VIRTIO_VSOCK_DGRAM_EOM (1 << 0) > > > +\end{lstlisting} > > > + > > > +When the header \field{flags} field bit VIRTIO_VSOCK_DGRAM_EOM (bit 0) is set, > > > +it indicates that the current payload is the end of a datagram fragment > > > OR that > > > +the current payload is an entire datagram packet. > > > > In the destination, if we discard some fragments, then could we > > reconstruct a different datagram from the one sent? > > > > Is that anything acceptable? > > > > Dropping fragments should be explicitly disallowed. The sender is > explicitly disallowed from NOT placing fragments on the virtqueue, but I > see that I am missing the piece that states that they may not be dropped > on the receive side. > > I think it is worth mentioning that implicit in this spec is that > socket-to-socket dgram communication is unreliable, but device-to-driver > (and vice versa) is still reliable. That is, we can rely at least on the > virtqueues to work... and if they fail then the device/driver can simply > requeue (think send_pkt_queue in Linux)... so there is some reliability > at the lowest layer. Well you have this weird timeout thing for some reason. > > Thanks, > > Stefano > > > > Thanks! > Bobby --------------------------------------------------------------------- To unsubscribe, e-mail: virtio-dev-unsubscribe@lists.oasis-open.org For additional commands, e-mail: virtio-dev-help@lists.oasis-open.org