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Message-ID: <ldyfzp5k2qmhlydflu7biz6bcrekothacitzgbmw2k264zwuxh@hmgoku5kgghp>
Date: Tue, 23 Jul 2024 16:42:41 +0200
From: Stefano Garzarella <sgarzare@...hat.com>
To: Amery Hung <ameryhung@...il.com>
Cc: stefanha@...hat.com, mst@...hat.com, jasowang@...hat.com, 
	xuanzhuo@...ux.alibaba.com, davem@...emloft.net, edumazet@...gle.com, kuba@...nel.org, 
	pabeni@...hat.com, kys@...rosoft.com, haiyangz@...rosoft.com, wei.liu@...nel.org, 
	decui@...rosoft.com, bryantan@...are.com, vdasa@...are.com, pv-drivers@...are.com, 
	dan.carpenter@...aro.org, simon.horman@...igine.com, oxffffaa@...il.com, 
	kvm@...r.kernel.org, virtualization@...ts.linux-foundation.org, 
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org, linux-hyperv@...r.kernel.org, 
	bpf@...r.kernel.org, bobby.eshleman@...edance.com, jiang.wang@...edance.com, 
	amery.hung@...edance.com, xiyou.wangcong@...il.com
Subject: Re: [RFC PATCH net-next v6 09/14] virtio/vsock: add common datagram
 recv path

On Wed, Jul 10, 2024 at 09:25:50PM GMT, Amery Hung wrote:
>From: Bobby Eshleman <bobby.eshleman@...edance.com>
>
>This commit adds the common datagram receive functionality for virtio
>transports. It does not add the vhost/virtio users of that
>functionality.
>
>This functionality includes:
>- changes to the virtio_transport_recv_pkt() path for finding the
>  bound socket receiver for incoming packets
>- virtio_transport_recv_pkt() saves the source cid and port to the
>  control buffer for recvmsg() to initialize sockaddr_vm structure
>  when using datagram
>
>Signed-off-by: Bobby Eshleman <bobby.eshleman@...edance.com>
>Signed-off-by: Amery Hung <amery.hung@...edance.com>
>---
> net/vmw_vsock/virtio_transport_common.c | 79 +++++++++++++++++++++----
> 1 file changed, 66 insertions(+), 13 deletions(-)
>
>diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
>index 46cd1807f8e3..a571b575fde9 100644
>--- a/net/vmw_vsock/virtio_transport_common.c
>+++ b/net/vmw_vsock/virtio_transport_common.c
>@@ -235,7 +235,9 @@ 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;
>@@ -1422,6 +1424,33 @@ virtio_transport_recv_enqueue(struct vsock_sock *vsk,
> 		kfree_skb(skb);
> }
>
>+static void
>+virtio_transport_dgram_kfree_skb(struct sk_buff *skb, int err)
>+{
>+	if (err == -ENOMEM)
>+		kfree_skb_reason(skb, SKB_DROP_REASON_SOCKET_RCVBUFF);
>+	else if (err == -ENOBUFS)
>+		kfree_skb_reason(skb, SKB_DROP_REASON_PROTO_MEM);
>+	else
>+		kfree_skb(skb);
>+}
>+
>+/* This function takes ownership of the skb.
>+ *
>+ * It either places the skb on the sk_receive_queue or frees it.
>+ */
>+static void
>+virtio_transport_recv_dgram(struct sock *sk, struct sk_buff *skb)
>+{
>+	int err;
>+
>+	err = sock_queue_rcv_skb(sk, skb);
>+	if (err) {
>+		virtio_transport_dgram_kfree_skb(skb, err);
>+		return;
>+	}
>+}
>+
> static int
> virtio_transport_recv_connected(struct sock *sk,
> 				struct sk_buff *skb)
>@@ -1591,7 +1620,8 @@ 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
>@@ -1601,44 +1631,57 @@ void virtio_transport_recv_pkt(struct virtio_transport *t,
> 			       struct sk_buff *skb)
> {
> 	struct virtio_vsock_hdr *hdr = virtio_vsock_hdr(skb);
>+	struct vsock_skb_cb *vsock_cb;

This can be defined in the block where it's used.

> 	struct sockaddr_vm src, dst;
> 	struct vsock_sock *vsk;
> 	struct sock *sk;
> 	bool space_available;
>+	u16 type;
>
> 	vsock_addr_init(&src, le64_to_cpu(hdr->src_cid),
> 			le32_to_cpu(hdr->src_port));
> 	vsock_addr_init(&dst, le64_to_cpu(hdr->dst_cid),
> 			le32_to_cpu(hdr->dst_port));
>
>+	type = le16_to_cpu(hdr->type);
>+
> 	trace_virtio_transport_recv_pkt(src.svm_cid, src.svm_port,
> 					dst.svm_cid, dst.svm_port,
> 					le32_to_cpu(hdr->len),
>-					le16_to_cpu(hdr->type),
>+					type,
> 					le16_to_cpu(hdr->op),
> 					le32_to_cpu(hdr->flags),
> 					le32_to_cpu(hdr->buf_alloc),
> 					le32_to_cpu(hdr->fwd_cnt));
>
>-	if (!virtio_transport_valid_type(le16_to_cpu(hdr->type))) {
>+	if (!virtio_transport_valid_type(type)) {
> 		(void)virtio_transport_reset_no_sock(t, skb);
> 		goto free_pkt;
> 	}
>
>-	/* The socket must be in connected or bound table
>-	 * otherwise send reset back
>+	/* For stream/seqpacket, the socket must be in connected or bound table
>+	 * otherwise send reset back.
>+	 *
>+	 * For datagrams, no reset is sent back.
> 	 */
> 	sk = vsock_find_connected_socket(&src, &dst);
> 	if (!sk) {
>-		sk = vsock_find_bound_socket(&dst);
>-		if (!sk) {
>-			(void)virtio_transport_reset_no_sock(t, skb);
>-			goto free_pkt;
>+		if (type == VIRTIO_VSOCK_TYPE_DGRAM) {
>+			sk = vsock_find_bound_dgram_socket(&dst);
>+			if (!sk)
>+				goto free_pkt;
>+		} else {
>+			sk = vsock_find_bound_socket(&dst);
>+			if (!sk) {
>+				(void)virtio_transport_reset_no_sock(t, skb);
>+				goto free_pkt;
>+			}
> 		}
> 	}
>
>-	if (virtio_transport_get_type(sk) != le16_to_cpu(hdr->type)) {
>-		(void)virtio_transport_reset_no_sock(t, skb);
>+	if (virtio_transport_get_type(sk) != type) {
>+		if (type != VIRTIO_VSOCK_TYPE_DGRAM)
>+			(void)virtio_transport_reset_no_sock(t, skb);
> 		sock_put(sk);
> 		goto free_pkt;
> 	}
>@@ -1654,12 +1697,21 @@ void virtio_transport_recv_pkt(struct virtio_transport *t,
>
> 	/* Check if sk has been closed before lock_sock */
> 	if (sock_flag(sk, SOCK_DONE)) {
>-		(void)virtio_transport_reset_no_sock(t, skb);
>+		if (type != VIRTIO_VSOCK_TYPE_DGRAM)
>+			(void)virtio_transport_reset_no_sock(t, skb);
> 		release_sock(sk);
> 		sock_put(sk);
> 		goto free_pkt;
> 	}
>
>+	if (sk->sk_type == SOCK_DGRAM) {
>+		vsock_cb = vsock_skb_cb(skb);
>+		vsock_cb->src_cid = src.svm_cid;
>+		vsock_cb->src_port = src.svm_port;
>+		virtio_transport_recv_dgram(sk, skb);


What about adding an API that transports can use to hide this?

I mean something that hide vsock_cb creation and queue packet in the 
socket receive queue. I'd also not expose vsock_skb_cb in an header, but 
I'd handle it internally in af_vsock.c. So I'd just expose API to 
queue/dequeue them.

Also why VMCI is using sk_receive_skb(), while we are using 
sock_queue_rcv_skb()?

Thanks,
Stefano

>+		goto out;
>+	}
>+
> 	space_available = virtio_transport_space_update(sk, skb);
>
> 	/* Update CID in case it has changed after a transport reset event */
>@@ -1691,6 +1743,7 @@ 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
>-- 
>2.20.1
>


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