On Tue, Jul 23, 2024 at 7:42 AM Stefano Garzarella [off-list ref] wrote:

On Wed, Jul 10, 2024 at 09:25:48PM GMT, Amery Hung wrote:

quoted

From: Bobby Eshleman <redacted>

This commit implements the common function
virtio_transport_dgram_enqueue for enqueueing datagrams. It does not add
usage in either vhost or virtio yet.

Signed-off-by: Bobby Eshleman <redacted>
Signed-off-by: Amery Hung <redacted>
---
include/linux/virtio_vsock.h            |  1 +
include/net/af_vsock.h                  |  2 +
net/vmw_vsock/af_vsock.c                |  2 +-
net/vmw_vsock/virtio_transport_common.c | 87 ++++++++++++++++++++++++-
4 files changed, 90 insertions(+), 2 deletions(-)

diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
index f749a066af46..4408749febd2 100644
--- a/include/linux/virtio_vsock.h
+++ b/include/linux/virtio_vsock.h

@@ -152,6 +152,7 @@ struct virtio_vsock_pkt_info {
      u16 op;
      u32 flags;
      bool reply;
+      u8 remote_flags;

};

struct virtio_transport {

diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
index 44db8f2c507d..6e97d344ac75 100644
--- a/include/net/af_vsock.h
+++ b/include/net/af_vsock.h

@@ -216,6 +216,8 @@ void vsock_for_each_connected_socket(struct vsock_transport *transport,
                                   void (*fn)(struct sock *sk));

int vsock_assign_transport(struct vsock_sock *vsk, struct vsock_sock *psk);
bool vsock_find_cid(unsigned int cid);
+const struct vsock_transport *vsock_dgram_lookup_transport(unsigned int cid,
+                                                         __u8 flags);

Why __u8 and not just u8?

Will change to u8.

quoted

struct vsock_skb_cb {
      unsigned int src_cid;

diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
index ab08cd81720e..f83b655fdbe9 100644
--- a/net/vmw_vsock/af_vsock.c
+++ b/net/vmw_vsock/af_vsock.c

@@ -487,7 +487,7 @@ vsock_connectible_lookup_transport(unsigned int cid, __u8 flags)
      return transport;

}

-static const struct vsock_transport *
+const struct vsock_transport *
vsock_dgram_lookup_transport(unsigned int cid, __u8 flags)
{
      const struct vsock_transport *transport;

diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
index a1c76836d798..46cd1807f8e3 100644
--- a/net/vmw_vsock/virtio_transport_common.c
+++ b/net/vmw_vsock/virtio_transport_common.c

@@ -1040,13 +1040,98 @@ int virtio_transport_shutdown(struct vsock_sock *vsk, int mode)

}
EXPORT_SYMBOL_GPL(virtio_transport_shutdown);

+static int virtio_transport_dgram_send_pkt_info(struct vsock_sock *vsk,
+                                              struct virtio_vsock_pkt_info *info)
+{
+      u32 src_cid, src_port, dst_cid, dst_port;
+      const struct vsock_transport *transport;
+      const struct virtio_transport *t_ops;
+      struct sock *sk = sk_vsock(vsk);
+      struct virtio_vsock_hdr *hdr;
+      struct sk_buff *skb;
+      void *payload;
+      int noblock = 0;
+      int err;
+
+      info->type = virtio_transport_get_type(sk_vsock(vsk));
+
+      if (info->pkt_len > VIRTIO_VSOCK_MAX_PKT_BUF_SIZE)
+              return -EMSGSIZE;
+
+      transport = vsock_dgram_lookup_transport(info->remote_cid, info->remote_flags);

Can `transport` be null?

I don't understand why we are calling vsock_dgram_lookup_transport()
again. Didn't we already do that in vsock_dgram_sendmsg()?

transport should be valid here since we null-checked it in
vsock_dgram_sendmsg(). The reason vsock_dgram_lookup_transport() is
called again here is we don't have the transport when we called into
transport->dgram_enqueue(). I can also instead add transport to the
argument of dgram_enqueue() to eliminate this redundant lookup.

Also should we add a comment mentioning that we can't use
virtio_transport_get_ops()? IIUC becuase the vsk can be not assigned
to a specific transport, right?

Correct. For virtio dgram socket, transport is not assigned unless
vsock_dgram_connect() is called. I will add a comment here explaining
this.

quoted

+      t_ops = container_of(transport, struct virtio_transport, transport);
+      if (unlikely(!t_ops))
+              return -EFAULT;
+
+      if (info->msg)
+              noblock = info->msg->msg_flags & MSG_DONTWAIT;
+
+      /* Use sock_alloc_send_skb to throttle by sk_sndbuf. This helps avoid
+       * triggering the OOM.
+       */
+      skb = sock_alloc_send_skb(sk, info->pkt_len + VIRTIO_VSOCK_SKB_HEADROOM,
+                                noblock, &err);
+      if (!skb)
+              return err;
+
+      skb_reserve(skb, VIRTIO_VSOCK_SKB_HEADROOM);
+
+      src_cid = t_ops->transport.get_local_cid();
+      src_port = vsk->local_addr.svm_port;
+      dst_cid = info->remote_cid;
+      dst_port = info->remote_port;
+
+      hdr = virtio_vsock_hdr(skb);
+      hdr->type       = cpu_to_le16(info->type);
+      hdr->op         = cpu_to_le16(info->op);
+      hdr->src_cid    = cpu_to_le64(src_cid);
+      hdr->dst_cid    = cpu_to_le64(dst_cid);
+      hdr->src_port   = cpu_to_le32(src_port);
+      hdr->dst_port   = cpu_to_le32(dst_port);
+      hdr->flags      = cpu_to_le32(info->flags);
+      hdr->len        = cpu_to_le32(info->pkt_len);
+
+      if (info->msg && info->pkt_len > 0) {
+              payload = skb_put(skb, info->pkt_len);
+              err = memcpy_from_msg(payload, info->msg, info->pkt_len);
+              if (err)
+                      goto out;
+      }
+
+      trace_virtio_transport_alloc_pkt(src_cid, src_port,
+                                       dst_cid, dst_port,
+                                       info->pkt_len,
+                                       info->type,
+                                       info->op,
+                                       info->flags,
+                                       false);
+
+      return t_ops->send_pkt(skb);
+out:
+      kfree_skb(skb);
+      return err;
+}
+
int
virtio_transport_dgram_enqueue(struct vsock_sock *vsk,
                             struct sockaddr_vm *remote_addr,
                             struct msghdr *msg,
                             size_t dgram_len)
{
-      return -EOPNOTSUPP;
+      /* Here we are only using the info struct to retain style uniformity
+       * and to ease future refactoring and merging.
+       */
+      struct virtio_vsock_pkt_info info = {
+              .op = VIRTIO_VSOCK_OP_RW,
+              .remote_cid = remote_addr->svm_cid,
+              .remote_port = remote_addr->svm_port,
+              .remote_flags = remote_addr->svm_flags,
+              .msg = msg,
+              .vsk = vsk,
+              .pkt_len = dgram_len,
+      };
+
+      return virtio_transport_dgram_send_pkt_info(vsk, &info);
}
EXPORT_SYMBOL_GPL(virtio_transport_dgram_enqueue);

--
2.20.1