Re: [PATCH RFC net-next v5 07/14] virtio/vsock: add common datagram send path
From: Arseniy Krasnov <hidden>
Date: 2023-07-22 08:16:16
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bpf, kvm, linux-hyperv, lkml
On 19.07.2023 03:50, Bobby Eshleman wrote:
quoted hunk ↗ jump to hunk
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> --- net/vmw_vsock/virtio_transport_common.c | 76 ++++++++++++++++++++++++++++++++- 1 file changed, 75 insertions(+), 1 deletion(-)diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c index ffcbdd77feaa..3bfaff758433 100644 --- a/net/vmw_vsock/virtio_transport_common.c +++ b/net/vmw_vsock/virtio_transport_common.c@@ -819,7 +819,81 @@ virtio_transport_dgram_enqueue(struct vsock_sock *vsk, 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_stack = { + .op = VIRTIO_VSOCK_OP_RW, + .msg = msg, + .vsk = vsk, + .type = VIRTIO_VSOCK_TYPE_DGRAM, + }; + const struct virtio_transport *t_ops; + struct virtio_vsock_pkt_info *info; + struct sock *sk = sk_vsock(vsk); + struct virtio_vsock_hdr *hdr; + u32 src_cid, src_port; + struct sk_buff *skb; + void *payload; + int noblock; + int err; + + info = &info_stack;
I think 'info' assignment could be moved below, to the place where it is used first time.
+ + if (dgram_len > VIRTIO_VSOCK_MAX_PKT_BUF_SIZE) + return -EMSGSIZE; + + t_ops = virtio_transport_get_ops(vsk); + if (unlikely(!t_ops)) + return -EFAULT; + + /* Unlike some of our other sending functions, this function is not + * intended for use without a msghdr. + */ + if (WARN_ONCE(!msg, "vsock dgram bug: no msghdr found for dgram enqueue\n")) + return -EFAULT;
Sorry, but is that possible? I thought 'msg' is always provided by general socket layer (e.g. before af_vsock.c code) and can't be NULL for DGRAM. Please correct me if i'm wrong. Also I see, that in af_vsock.c , 'vsock_dgram_sendmsg()' dereferences 'msg' for checking MSG_OOB without any checks (before calling transport callback - this function in case of virtio). So I think if we want to keep this type of check - such check must be placed in af_vsock.c or somewhere before first dereference of this pointer.
+ + noblock = 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, dgram_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; + + 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(remote_addr->svm_cid); + hdr->src_port = cpu_to_le32(src_port); + hdr->dst_port = cpu_to_le32(remote_addr->svm_port); + hdr->flags = cpu_to_le32(info->flags); + hdr->len = cpu_to_le32(dgram_len); + + skb_set_owner_w(skb, sk); + + payload = skb_put(skb, dgram_len); + err = memcpy_from_msg(payload, msg, dgram_len); + if (err) + return err;
Do we need free allocated skb here ?
+ + trace_virtio_transport_alloc_pkt(src_cid, src_port, + remote_addr->svm_cid, + remote_addr->svm_port, + dgram_len, + info->type, + info->op, + 0); + + return t_ops->send_pkt(skb); } EXPORT_SYMBOL_GPL(virtio_transport_dgram_enqueue);
Thanks, Arseniy