Re: [virtio-dev] Re: [PATCH 5/6] virtio/vsock: add support for dgram

[Arseniy Krasnov <AVKrasnov@sberdevices.ru>]

On Tue, 2022-08-16 at 09:57 +0000, Bobby Eshleman wrote:
> On Wed, Aug 17, 2022 at 05:01:00AM +0000, Arseniy Krasnov wrote:
> > On 16.08.2022 05:32, Bobby Eshleman wrote:
> > > CC'ing virtio-dev@lists.oasis-open.org
> > > 
> > > On Mon, Aug 15, 2022 at 10:56:08AM -0700, Bobby Eshleman wrote:
> > > > This patch supports dgram in virtio and on the vhost side.
> > Hello,
> > 
> > sorry, i don't understand, how this maintains message boundaries?
> > Or it
> > is unnecessary for SOCK_DGRAM?
> > 
> > Thanks
> 
> If I understand your question, the length is included in the header,
> so
> receivers always know that header start + header length + payload
> length
> marks the message boundary.

I mean, consider the following case: host sends 5kb packet to guest.
Guest uses 4kb virtio rx buffers, so in drivers/vhost/vsock.c this 5kb
packet(e.g. its payload) will be placed to 2 virtio rx buffers - 4kb
to first buffer and rest 1kb to second buffer. Is it implemented, that
receiver gets whole 5kb piece of data during single 'read()/recv()'
system call?

Thanks

> 
> > > > Signed-off-by: Jiang Wang <jiang.wang@bytedance.com>
> > > > Signed-off-by: Bobby Eshleman <bobby.eshleman@bytedance.com>
> > > > ---
> > > >  drivers/vhost/vsock.c                   |   2 +-
> > > >  include/net/af_vsock.h                  |   2 +
> > > >  include/uapi/linux/virtio_vsock.h       |   1 +
> > > >  net/vmw_vsock/af_vsock.c                |  26 +++-
> > > >  net/vmw_vsock/virtio_transport.c        |   2 +-
> > > >  net/vmw_vsock/virtio_transport_common.c | 173
> > > > ++++++++++++++++++++++--
> > > >  6 files changed, 186 insertions(+), 20 deletions(-)
> > > > 
> > > > diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
> > > > index a5d1bdb786fe..3dc72a5647ca 100644
> > > > --- a/drivers/vhost/vsock.c
> > > > +++ b/drivers/vhost/vsock.c
> > > > @@ -925,7 +925,7 @@ static int __init vhost_vsock_init(void)
> > > >  	int ret;
> > > >  
> > > >  	ret = vsock_core_register(&vhost_transport.transport,
> > > > -				  VSOCK_TRANSPORT_F_H2G);
> > > > +				  VSOCK_TRANSPORT_F_H2G |
> > > > VSOCK_TRANSPORT_F_DGRAM);
> > > >  	if (ret < 0)
> > > >  		return ret;
> > > >  
> > > > diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
> > > > index 1c53c4c4d88f..37e55c81e4df 100644
> > > > --- a/include/net/af_vsock.h
> > > > +++ b/include/net/af_vsock.h
> > > > @@ -78,6 +78,8 @@ struct vsock_sock {
> > > >  s64 vsock_stream_has_data(struct vsock_sock *vsk);
> > > >  s64 vsock_stream_has_space(struct vsock_sock *vsk);
> > > >  struct sock *vsock_create_connected(struct sock *parent);
> > > > +int vsock_bind_stream(struct vsock_sock *vsk,
> > > > +		      struct sockaddr_vm *addr);
> > > >  
> > > >  /**** TRANSPORT ****/
> > > >  
> > > > diff --git a/include/uapi/linux/virtio_vsock.h
> > > > b/include/uapi/linux/virtio_vsock.h
> > > > index 857df3a3a70d..0975b9c88292 100644
> > > > --- a/include/uapi/linux/virtio_vsock.h
> > > > +++ b/include/uapi/linux/virtio_vsock.h
> > > > @@ -70,6 +70,7 @@ struct virtio_vsock_hdr {
> > > >  enum virtio_vsock_type {
> > > >  	VIRTIO_VSOCK_TYPE_STREAM = 1,
> > > >  	VIRTIO_VSOCK_TYPE_SEQPACKET = 2,
> > > > +	VIRTIO_VSOCK_TYPE_DGRAM = 3,
> > > >  };
> > > >  
> > > >  enum virtio_vsock_op {
> > > > diff --git a/net/vmw_vsock/af_vsock.c
> > > > b/net/vmw_vsock/af_vsock.c
> > > > index 1893f8aafa48..87e4ae1866d3 100644
> > > > --- a/net/vmw_vsock/af_vsock.c
> > > > +++ b/net/vmw_vsock/af_vsock.c
> > > > @@ -675,6 +675,19 @@ static int __vsock_bind_connectible(struct
> > > > vsock_sock *vsk,
> > > >  	return 0;
> > > >  }
> > > >  
> > > > +int vsock_bind_stream(struct vsock_sock *vsk,
> > > > +		      struct sockaddr_vm *addr)
> > > > +{
> > > > +	int retval;
> > > > +
> > > > +	spin_lock_bh(&vsock_table_lock);
> > > > +	retval = __vsock_bind_connectible(vsk, addr);
> > > > +	spin_unlock_bh(&vsock_table_lock);
> > > > +
> > > > +	return retval;
> > > > +}
> > > > +EXPORT_SYMBOL(vsock_bind_stream);
> > > > +
> > > >  static int __vsock_bind_dgram(struct vsock_sock *vsk,
> > > >  			      struct sockaddr_vm *addr)
> > > >  {
> > > > @@ -2363,11 +2376,16 @@ int vsock_core_register(const struct
> > > > vsock_transport *t, int features)
> > > >  	}
> > > >  
> > > >  	if (features & VSOCK_TRANSPORT_F_DGRAM) {
> > > > -		if (t_dgram) {
> > > > -			err = -EBUSY;
> > > > -			goto err_busy;
> > > > +		/* TODO: always chose the G2H variant over
> > > > others, support nesting later */
> > > > +		if (features & VSOCK_TRANSPORT_F_G2H) {
> > > > +			if (t_dgram)
> > > > +				pr_warn("virtio_vsock: t_dgram
> > > > already set\n");
> > > > +			t_dgram = t;
> > > > +		}
> > > > +
> > > > +		if (!t_dgram) {
> > > > +			t_dgram = t;
> > > >  		}
> > > > -		t_dgram = t;
> > > >  	}
> > > >  
> > > >  	if (features & VSOCK_TRANSPORT_F_LOCAL) {
> > > > diff --git a/net/vmw_vsock/virtio_transport.c
> > > > b/net/vmw_vsock/virtio_transport.c
> > > > index 073314312683..d4526ca462d2 100644
> > > > --- a/net/vmw_vsock/virtio_transport.c
> > > > +++ b/net/vmw_vsock/virtio_transport.c
> > > > @@ -850,7 +850,7 @@ static int __init virtio_vsock_init(void)
> > > >  		return -ENOMEM;
> > > >  
> > > >  	ret = vsock_core_register(&virtio_transport.transport,
> > > > -				  VSOCK_TRANSPORT_F_G2H);
> > > > +				  VSOCK_TRANSPORT_F_G2H |
> > > > VSOCK_TRANSPORT_F_DGRAM);
> > > >  	if (ret)
> > > >  		goto out_wq;
> > > >  
> > > > diff --git a/net/vmw_vsock/virtio_transport_common.c
> > > > b/net/vmw_vsock/virtio_transport_common.c
> > > > index bdf16fff054f..aedb48728677 100644
> > > > --- a/net/vmw_vsock/virtio_transport_common.c
> > > > +++ b/net/vmw_vsock/virtio_transport_common.c
> > > > @@ -229,7 +229,9 @@
> > > > EXPORT_SYMBOL_GPL(virtio_transport_deliver_tap_pkt);
> > > >  
> > > >  static u16 virtio_transport_get_type(struct sock *sk)
> > > >  {
> > > > -	if (sk->sk_type == SOCK_STREAM)
> > > > +	if (sk->sk_type == SOCK_DGRAM)
> > > > +		return VIRTIO_VSOCK_TYPE_DGRAM;
> > > > +	else if (sk->sk_type == SOCK_STREAM)
> > > >  		return VIRTIO_VSOCK_TYPE_STREAM;
> > > >  	else
> > > >  		return VIRTIO_VSOCK_TYPE_SEQPACKET;
> > > > @@ -287,22 +289,29 @@ static int
> > > > virtio_transport_send_pkt_info(struct vsock_sock *vsk,
> > > >  	vvs = vsk->trans;
> > > >  
> > > >  	/* we can send less than pkt_len bytes */
> > > > -	if (pkt_len > VIRTIO_VSOCK_MAX_PKT_BUF_SIZE)
> > > > -		pkt_len = VIRTIO_VSOCK_MAX_PKT_BUF_SIZE;
> > > > +	if (pkt_len > VIRTIO_VSOCK_MAX_PKT_BUF_SIZE) {
> > > > +		if (info->type != VIRTIO_VSOCK_TYPE_DGRAM)
> > > > +			pkt_len =
> > > > VIRTIO_VSOCK_MAX_PKT_BUF_SIZE;
> > > > +		else
> > > > +			return 0;
> > > > +	}
> > > >  
> > > > -	/* virtio_transport_get_credit might return less than
> > > > pkt_len credit */
> > > > -	pkt_len = virtio_transport_get_credit(vvs, pkt_len);
> > > > +	if (info->type != VIRTIO_VSOCK_TYPE_DGRAM) {
> > > > +		/* virtio_transport_get_credit might return
> > > > less than pkt_len credit */
> > > > +		pkt_len = virtio_transport_get_credit(vvs,
> > > > pkt_len);
> > > >  
> > > > -	/* Do not send zero length OP_RW pkt */
> > > > -	if (pkt_len == 0 && info->op == VIRTIO_VSOCK_OP_RW)
> > > > -		return pkt_len;
> > > > +		/* Do not send zero length OP_RW pkt */
> > > > +		if (pkt_len == 0 && info->op ==
> > > > VIRTIO_VSOCK_OP_RW)
> > > > +			return pkt_len;
> > > > +	}
> > > >  
> > > >  	skb = virtio_transport_alloc_skb(info, pkt_len,
> > > >  					 src_cid, src_port,
> > > >  					 dst_cid, dst_port,
> > > >  					 &err);
> > > >  	if (!skb) {
> > > > -		virtio_transport_put_credit(vvs, pkt_len);
> > > > +		if (info->type != VIRTIO_VSOCK_TYPE_DGRAM)
> > > > +			virtio_transport_put_credit(vvs,
> > > > pkt_len);
> > > >  		return err;
> > > >  	}
> > > >  
> > > > @@ -586,6 +595,61 @@ virtio_transport_seqpacket_dequeue(struct
> > > > vsock_sock *vsk,
> > > >  }
> > > >  EXPORT_SYMBOL_GPL(virtio_transport_seqpacket_dequeue);
> > > >  
> > > > +static ssize_t
> > > > +virtio_transport_dgram_do_dequeue(struct vsock_sock *vsk,
> > > > +				  struct msghdr *msg, size_t
> > > > len)
> > > > +{
> > > > +	struct virtio_vsock_sock *vvs = vsk->trans;
> > > > +	struct sk_buff *skb;
> > > > +	size_t total = 0;
> > > > +	u32 free_space;
> > > > +	int err = -EFAULT;
> > > > +
> > > > +	spin_lock_bh(&vvs->rx_lock);
> > > > +	if (total < len && !skb_queue_empty_lockless(&vvs-
> > > > >rx_queue)) {
> > > > +		skb = __skb_dequeue(&vvs->rx_queue);
> > > > +
> > > > +		total = len;
> > > > +		if (total > skb->len - vsock_metadata(skb)-
> > > > >off)
> > > > +			total = skb->len - vsock_metadata(skb)-
> > > > >off;
> > > > +		else if (total < skb->len -
> > > > vsock_metadata(skb)->off)
> > > > +			msg->msg_flags |= MSG_TRUNC;
> > > > +
> > > > +		/* sk_lock is held by caller so no one else can
> > > > dequeue.
> > > > +		 * Unlock rx_lock since memcpy_to_msg() may
> > > > sleep.
> > > > +		 */
> > > > +		spin_unlock_bh(&vvs->rx_lock);
> > > > +
> > > > +		err = memcpy_to_msg(msg, skb->data +
> > > > vsock_metadata(skb)->off, total);
> > > > +		if (err)
> > > > +			return err;
> > > > +
> > > > +		spin_lock_bh(&vvs->rx_lock);
> > > > +
> > > > +		virtio_transport_dec_rx_pkt(vvs, skb);
> > > > +		consume_skb(skb);
> > > > +	}
> > > > +
> > > > +	free_space = vvs->buf_alloc - (vvs->fwd_cnt - vvs-
> > > > >last_fwd_cnt);
> > > > +
> > > > +	spin_unlock_bh(&vvs->rx_lock);
> > > > +
> > > > +	if (total > 0 && msg->msg_name) {
> > > > +		/* Provide the address of the sender. */
> > > > +		DECLARE_SOCKADDR(struct sockaddr_vm *, vm_addr,
> > > > msg->msg_name);
> > > > +
> > > > +		vsock_addr_init(vm_addr,
> > > > le64_to_cpu(vsock_hdr(skb)->src_cid),
> > > > +				le32_to_cpu(vsock_hdr(skb)-
> > > > >src_port));
> > > > +		msg->msg_namelen = sizeof(*vm_addr);
> > > > +	}
> > > > +	return total;
> > > > +}
> > > > +
> > > > +static s64 virtio_transport_dgram_has_data(struct vsock_sock
> > > > *vsk)
> > > > +{
> > > > +	return virtio_transport_stream_has_data(vsk);
> > > > +}
> > > > +
> > > >  int
> > > >  virtio_transport_seqpacket_enqueue(struct vsock_sock *vsk,
> > > >  				   struct msghdr *msg,
> > > > @@ -611,7 +675,66 @@ virtio_transport_dgram_dequeue(struct
> > > > vsock_sock *vsk,
> > > >  			       struct msghdr *msg,
> > > >  			       size_t len, int flags)
> > > >  {
> > > > -	return -EOPNOTSUPP;
> > > > +	struct sock *sk;
> > > > +	size_t err = 0;
> > > > +	long timeout;
> > > > +
> > > > +	DEFINE_WAIT(wait);
> > > > +
> > > > +	sk = &vsk->sk;
> > > > +	err = 0;
> > > > +
> > > > +	if (flags & MSG_OOB || flags & MSG_ERRQUEUE || flags &
> > > > MSG_PEEK)
> > > > +		return -EOPNOTSUPP;
> > > > +
> > > > +	lock_sock(sk);
> > > > +
> > > > +	if (!len)
> > > > +		goto out;
> > > > +
> > > > +	timeout = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
> > > > +
> > > > +	while (1) {
> > > > +		s64 ready;
> > > > +
> > > > +		prepare_to_wait(sk_sleep(sk), &wait,
> > > > TASK_INTERRUPTIBLE);
> > > > +		ready = virtio_transport_dgram_has_data(vsk);
> > > > +
> > > > +		if (ready == 0) {
> > > > +			if (timeout == 0) {
> > > > +				err = -EAGAIN;
> > > > +				finish_wait(sk_sleep(sk),
> > > > &wait);
> > > > +				break;
> > > > +			}
> > > > +
> > > > +			release_sock(sk);
> > > > +			timeout = schedule_timeout(timeout);
> > > > +			lock_sock(sk);
> > > > +
> > > > +			if (signal_pending(current)) {
> > > > +				err = sock_intr_errno(timeout);
> > > > +				finish_wait(sk_sleep(sk),
> > > > &wait);
> > > > +				break;
> > > > +			} else if (timeout == 0) {
> > > > +				err = -EAGAIN;
> > > > +				finish_wait(sk_sleep(sk),
> > > > &wait);
> > > > +				break;
> > > > +			}
> > > > +		} else {
> > > > +			finish_wait(sk_sleep(sk), &wait);
> > > > +
> > > > +			if (ready < 0) {
> > > > +				err = -ENOMEM;
> > > > +				goto out;
> > > > +			}
> > > > +
> > > > +			err =
> > > > virtio_transport_dgram_do_dequeue(vsk, msg, len);
> > > > +			break;
> > > > +		}
> > > > +	}
> > > > +out:
> > > > +	release_sock(sk);
> > > > +	return err;
> > > >  }
> > > >  EXPORT_SYMBOL_GPL(virtio_transport_dgram_dequeue);
> > > >  
> > > > @@ -819,13 +942,13 @@
> > > > EXPORT_SYMBOL_GPL(virtio_transport_stream_allow);
> > > >  int virtio_transport_dgram_bind(struct vsock_sock *vsk,
> > > >  				struct sockaddr_vm *addr)
> > > >  {
> > > > -	return -EOPNOTSUPP;
> > > > +	return vsock_bind_stream(vsk, addr);
> > > >  }
> > > >  EXPORT_SYMBOL_GPL(virtio_transport_dgram_bind);
> > > >  
> > > >  bool virtio_transport_dgram_allow(u32 cid, u32 port)
> > > >  {
> > > > -	return false;
> > > > +	return true;
> > > >  }
> > > >  EXPORT_SYMBOL_GPL(virtio_transport_dgram_allow);
> > > >  
> > > > @@ -861,7 +984,16 @@ virtio_transport_dgram_enqueue(struct
> > > > vsock_sock *vsk,
> > > >  			       struct msghdr *msg,
> > > >  			       size_t dgram_len)
> > > >  {
> > > > -	return -EOPNOTSUPP;
> > > > +	struct virtio_vsock_pkt_info info = {
> > > > +		.op = VIRTIO_VSOCK_OP_RW,
> > > > +		.msg = msg,
> > > > +		.pkt_len = dgram_len,
> > > > +		.vsk = vsk,
> > > > +		.remote_cid = remote_addr->svm_cid,
> > > > +		.remote_port = remote_addr->svm_port,
> > > > +	};
> > > > +
> > > > +	return virtio_transport_send_pkt_info(vsk, &info);
> > > >  }
> > > >  EXPORT_SYMBOL_GPL(virtio_transport_dgram_enqueue);
> > > >  
> > > > @@ -1165,6 +1297,12 @@ virtio_transport_recv_connected(struct
> > > > sock *sk,
> > > >  	struct virtio_vsock_hdr *hdr = vsock_hdr(skb);
> > > >  	int err = 0;
> > > >  
> > > > +	if (le16_to_cpu(vsock_hdr(skb)->type) ==
> > > > VIRTIO_VSOCK_TYPE_DGRAM) {
> > > > +		virtio_transport_recv_enqueue(vsk, skb);
> > > > +		sk->sk_data_ready(sk);
> > > > +		return err;
> > > > +	}
> > > > +
> > > >  	switch (le16_to_cpu(hdr->op)) {
> > > >  	case VIRTIO_VSOCK_OP_RW:
> > > >  		virtio_transport_recv_enqueue(vsk, skb);
> > > > @@ -1320,7 +1458,8 @@ virtio_transport_recv_listen(struct sock
> > > > *sk, struct sk_buff *skb,
> > > >  static bool virtio_transport_valid_type(u16 type)
> > > >  {
> > > >  	return (type == VIRTIO_VSOCK_TYPE_STREAM) ||
> > > > -	       (type == VIRTIO_VSOCK_TYPE_SEQPACKET);
> > > > +	       (type == VIRTIO_VSOCK_TYPE_SEQPACKET) ||
> > > > +	       (type == VIRTIO_VSOCK_TYPE_DGRAM);
> > > >  }
> > > >  
> > > >  /* We are under the virtio-vsock's vsock->rx_lock or vhost-
> > > > vsock's vq->mutex
> > > > @@ -1384,6 +1523,11 @@ void virtio_transport_recv_pkt(struct
> > > > virtio_transport *t,
> > > >  		goto free_pkt;
> > > >  	}
> > > >  
> > > > +	if (sk->sk_type == SOCK_DGRAM) {
> > > > +		virtio_transport_recv_connected(sk, skb);
> > > > +		goto out;
> > > > +	}
> > > > +
> > > >  	space_available = virtio_transport_space_update(sk,
> > > > skb);
> > > >  
> > > >  	/* Update CID in case it has changed after a transport
> > > > reset event */
> > > > @@ -1415,6 +1559,7 @@ void virtio_transport_recv_pkt(struct
> > > > virtio_transport *t,
> > > >  		break;
> > > >  	}
> > > >  
> > > > +out:
> > > >  	release_sock(sk);
> > > >  
> > > >  	/* Release refcnt obtained when we fetched this socket
> > > > out of the
> > > > -- 
> > > > 2.35.1
> > > > 
> > > 
> > > ---------------------------------------------------------------
> > > ------
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