Re: [PATCH RFC net-next v4 1/8] vsock/dgram: generalize recvmsg and drop transport->dgram_dequeue
From: Arseniy Krasnov
Date: Thu Jun 22 2023 - 15:23:41 EST
On 22.06.2023 17:51, Stefano Garzarella wrote:
> On Sun, Jun 11, 2023 at 11:43:15PM +0300, Arseniy Krasnov wrote:
>> Hello Bobby! Thanks for this patchset! Small comment below:
>>
>> On 10.06.2023 03:58, Bobby Eshleman wrote:
>>> This commit drops the transport->dgram_dequeue callback and makes
>>> vsock_dgram_recvmsg() generic. It also adds additional transport
>>> callbacks for use by the generic vsock_dgram_recvmsg(), such as for
>>> parsing skbs for CID/port which vary in format per transport.
>>>
>>> Signed-off-by: Bobby Eshleman <bobby.eshleman@xxxxxxxxxxxxx>
>>> ---
>>> drivers/vhost/vsock.c | 4 +-
>>> include/linux/virtio_vsock.h | 3 ++
>>> include/net/af_vsock.h | 13 ++++++-
>>> net/vmw_vsock/af_vsock.c | 51 ++++++++++++++++++++++++-
>>> net/vmw_vsock/hyperv_transport.c | 17 +++++++--
>>> net/vmw_vsock/virtio_transport.c | 4 +-
>>> net/vmw_vsock/virtio_transport_common.c | 18 +++++++++
>>> net/vmw_vsock/vmci_transport.c | 68 +++++++++++++--------------------
>>> net/vmw_vsock/vsock_loopback.c | 4 +-
>>> 9 files changed, 132 insertions(+), 50 deletions(-)
>>>
>>> diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
>>> index 6578db78f0ae..c8201c070b4b 100644
>>> --- a/drivers/vhost/vsock.c
>>> +++ b/drivers/vhost/vsock.c
>>> @@ -410,9 +410,11 @@ static struct virtio_transport vhost_transport = {
>>> .cancel_pkt = vhost_transport_cancel_pkt,
>>>
>>> .dgram_enqueue = virtio_transport_dgram_enqueue,
>>> - .dgram_dequeue = virtio_transport_dgram_dequeue,
>>> .dgram_bind = virtio_transport_dgram_bind,
>>> .dgram_allow = virtio_transport_dgram_allow,
>>> + .dgram_get_cid = virtio_transport_dgram_get_cid,
>>> + .dgram_get_port = virtio_transport_dgram_get_port,
>>> + .dgram_get_length = virtio_transport_dgram_get_length,
>>>
>>> .stream_enqueue = virtio_transport_stream_enqueue,
>>> .stream_dequeue = virtio_transport_stream_dequeue,
>>> diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
>>> index c58453699ee9..23521a318cf0 100644
>>> --- a/include/linux/virtio_vsock.h
>>> +++ b/include/linux/virtio_vsock.h
>>> @@ -219,6 +219,9 @@ bool virtio_transport_stream_allow(u32 cid, u32 port);
>>> int virtio_transport_dgram_bind(struct vsock_sock *vsk,
>>> struct sockaddr_vm *addr);
>>> bool virtio_transport_dgram_allow(u32 cid, u32 port);
>>> +int virtio_transport_dgram_get_cid(struct sk_buff *skb, unsigned int *cid);
>>> +int virtio_transport_dgram_get_port(struct sk_buff *skb, unsigned int *port);
>>> +int virtio_transport_dgram_get_length(struct sk_buff *skb, size_t *len);
>>>
>>> int virtio_transport_connect(struct vsock_sock *vsk);
>>>
>>> diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
>>> index 0e7504a42925..7bedb9ee7e3e 100644
>>> --- a/include/net/af_vsock.h
>>> +++ b/include/net/af_vsock.h
>>> @@ -120,11 +120,20 @@ struct vsock_transport {
>>>
>>> /* DGRAM. */
>>> int (*dgram_bind)(struct vsock_sock *, struct sockaddr_vm *);
>>> - int (*dgram_dequeue)(struct vsock_sock *vsk, struct msghdr *msg,
>>> - size_t len, int flags);
>>> int (*dgram_enqueue)(struct vsock_sock *, struct sockaddr_vm *,
>>> struct msghdr *, size_t len);
>>> bool (*dgram_allow)(u32 cid, u32 port);
>>> + int (*dgram_get_cid)(struct sk_buff *skb, unsigned int *cid);
>>> + int (*dgram_get_port)(struct sk_buff *skb, unsigned int *port);
>>> + int (*dgram_get_length)(struct sk_buff *skb, size_t *length);
>>> +
>>> + /* The number of bytes into the buffer at which the payload starts, as
>>> + * first seen by the receiving socket layer. For example, if the
>>> + * transport presets the skb pointers using skb_pull(sizeof(header))
>>> + * than this would be zero, otherwise it would be the size of the
>>> + * header.
>>> + */
>>> + const size_t dgram_payload_offset;
>>>
>>> /* STREAM. */
>>> /* TODO: stream_bind() */
>>> diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>>> index efb8a0937a13..ffb4dd8b6ea7 100644
>>> --- a/net/vmw_vsock/af_vsock.c
>>> +++ b/net/vmw_vsock/af_vsock.c
>>> @@ -1271,11 +1271,15 @@ static int vsock_dgram_connect(struct socket *sock,
>>> int vsock_dgram_recvmsg(struct socket *sock, struct msghdr *msg,
>>> size_t len, int flags)
>>> {
>>> + const struct vsock_transport *transport;
>>> #ifdef CONFIG_BPF_SYSCALL
>>> const struct proto *prot;
>>> #endif
>>> struct vsock_sock *vsk;
>>> + struct sk_buff *skb;
>>> + size_t payload_len;
>>> struct sock *sk;
>>> + int err;
>>>
>>> sk = sock->sk;
>>> vsk = vsock_sk(sk);
>>> @@ -1286,7 +1290,52 @@ int vsock_dgram_recvmsg(struct socket *sock, struct msghdr *msg,
>>> return prot->recvmsg(sk, msg, len, flags, NULL);
>>> #endif
>>>
>>> - return vsk->transport->dgram_dequeue(vsk, msg, len, flags);
>>> + if (flags & MSG_OOB || flags & MSG_ERRQUEUE)
>>> + return -EOPNOTSUPP;
>>> +
>>> + transport = vsk->transport;
>>> +
>>> + /* Retrieve the head sk_buff from the socket's receive queue. */
>>> + err = 0;
>>> + skb = skb_recv_datagram(sk_vsock(vsk), flags, &err);
>>> + if (!skb)
>>> + return err;
>>> +
>>> + err = transport->dgram_get_length(skb, &payload_len);
>
> What about ssize_t return value here?
>
> Or maybe a single callback that return both length and offset?
>
> .dgram_get_payload_info(skb, &payload_len, &payload_off)
Just architectural question:
May be we can avoid this callback for length? IIUC concept of skbuff is that
current level of network stack already have pointer to its data 'skb->data' and
length of the payload 'skb->len' (both are set by previous stack handler - transport in
this case), so here we can use just 'skb->len' and thats all. There is no need to ask
lower level of network stack for length of payload? I see that VMCI stores metadata
with payload in 'data' buffer, but may be it is more correctly to do 'skb_pull()'
in vmci before inserting skbuff to sockets queue? In this case field with dgram payload
offset could be removed from transport.
Thanks, Arseniy
>
>>> + if (err)
>>> + goto out;
>>> +
>>> + if (payload_len > len) {
>>> + payload_len = len;
>>> + msg->msg_flags |= MSG_TRUNC;
>>> + }
>>> +
>>> + /* Place the datagram payload in the user's iovec. */
>>> + err = skb_copy_datagram_msg(skb, transport->dgram_payload_offset, msg, payload_len);
>>> + if (err)
>>> + goto out;
>>> +
>>> + if (msg->msg_name) {
>>> + /* Provide the address of the sender. */
>>> + DECLARE_SOCKADDR(struct sockaddr_vm *, vm_addr, msg->msg_name);
>>> + unsigned int cid, port;
>>> +
>>> + err = transport->dgram_get_cid(skb, &cid);
>>> + if (err)
>>> + goto out;
>>> +
>>> + err = transport->dgram_get_port(skb, &port);
>>> + if (err)
>>> + goto out;
>>
>> Maybe we can merge 'dgram_get_cid' and 'dgram_get_port' to a single callback? Because I see that this is
>> the only place where both are used (correct me if i'm wrong) and logically both operates with addresses:
>> CID and port. E.g. something like that: dgram_get_cid_n_port().
>
> What about .dgram_addr_init(struct sk_buff *skb, struct sockaddr_vm *addr)
> and the transport can set cid and port?
>
>>
>> Moreover, I'm not sure, but is it good "tradeoff" here: remove transport specific callback for dgram receive
>> where we already have 'msghdr' with both data buffer and buffer for 'sockaddr_vm' and instead of it add new
>> several fields (callbacks) to transports like dgram_get_cid(), dgram_get_port()? I agree, that in each transport
>> specific callback we will have same copying logic by calling 'skb_copy_datagram_msg()' and filling address
>> by using 'vsock_addr_init()', but in this case we don't need to update transports too much. For example HyperV
>> still unchanged as it does not support SOCK_DGRAM. For VMCI You just need to add 'vsock_addr_init()' logic
>> to it's dgram dequeue callback.
>>
>> What do You think?
>
> Honestly, I'd rather avoid duplicate code than reduce changes in
> transports that don't support dgram.
>
> One thing I do agree on though is minimizing the number of callbacks
> to call to reduce the number of indirection (more performance?).
>
> Thanks,
> Stefano
>
>>
>> Thanks, Arseniy
>>
>>> +
>>> + vsock_addr_init(vm_addr, cid, port);
>>> + msg->msg_namelen = sizeof(*vm_addr);
>>> + }
>>> + err = payload_len;
>>> +
>>> +out:
>>> + skb_free_datagram(&vsk->sk, skb);
>>> + return err;
>>> }
>>> EXPORT_SYMBOL_GPL(vsock_dgram_recvmsg);
>>>
>>> diff --git a/net/vmw_vsock/hyperv_transport.c b/net/vmw_vsock/hyperv_transport.c
>>> index 7cb1a9d2cdb4..ff6e87e25fa0 100644
>>> --- a/net/vmw_vsock/hyperv_transport.c
>>> +++ b/net/vmw_vsock/hyperv_transport.c
>>> @@ -556,8 +556,17 @@ static int hvs_dgram_bind(struct vsock_sock *vsk, struct sockaddr_vm *addr)
>>> return -EOPNOTSUPP;
>>> }
>>>
>>> -static int hvs_dgram_dequeue(struct vsock_sock *vsk, struct msghdr *msg,
>>> - size_t len, int flags)
>>> +static int hvs_dgram_get_cid(struct sk_buff *skb, unsigned int *cid)
>>> +{
>>> + return -EOPNOTSUPP;
>>> +}
>>> +
>>> +static int hvs_dgram_get_port(struct sk_buff *skb, unsigned int *port)
>>> +{
>>> + return -EOPNOTSUPP;
>>> +}
>>> +
>>> +static int hvs_dgram_get_length(struct sk_buff *skb, size_t *len)
>>> {
>>> return -EOPNOTSUPP;
>>> }
>>> @@ -833,7 +842,9 @@ static struct vsock_transport hvs_transport = {
>>> .shutdown = hvs_shutdown,
>>>
>>> .dgram_bind = hvs_dgram_bind,
>>> - .dgram_dequeue = hvs_dgram_dequeue,
>>> + .dgram_get_cid = hvs_dgram_get_cid,
>>> + .dgram_get_port = hvs_dgram_get_port,
>>> + .dgram_get_length = hvs_dgram_get_length,
>>> .dgram_enqueue = hvs_dgram_enqueue,
>>> .dgram_allow = hvs_dgram_allow,
>>>
>>> diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
>>> index e95df847176b..5763cdf13804 100644
>>> --- a/net/vmw_vsock/virtio_transport.c
>>> +++ b/net/vmw_vsock/virtio_transport.c
>>> @@ -429,9 +429,11 @@ static struct virtio_transport virtio_transport = {
>>> .cancel_pkt = virtio_transport_cancel_pkt,
>>>
>>> .dgram_bind = virtio_transport_dgram_bind,
>>> - .dgram_dequeue = virtio_transport_dgram_dequeue,
>>> .dgram_enqueue = virtio_transport_dgram_enqueue,
>>> .dgram_allow = virtio_transport_dgram_allow,
>>> + .dgram_get_cid = virtio_transport_dgram_get_cid,
>>> + .dgram_get_port = virtio_transport_dgram_get_port,
>>> + .dgram_get_length = virtio_transport_dgram_get_length,
>>>
>>> .stream_dequeue = virtio_transport_stream_dequeue,
>>> .stream_enqueue = virtio_transport_stream_enqueue,
>>> diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
>>> index b769fc258931..e6903c719964 100644
>>> --- a/net/vmw_vsock/virtio_transport_common.c
>>> +++ b/net/vmw_vsock/virtio_transport_common.c
>>> @@ -797,6 +797,24 @@ int virtio_transport_dgram_bind(struct vsock_sock *vsk,
>>> }
>>> EXPORT_SYMBOL_GPL(virtio_transport_dgram_bind);
>>>
>>> +int virtio_transport_dgram_get_cid(struct sk_buff *skb, unsigned int *cid)
>>> +{
>>> + return -EOPNOTSUPP;
>>> +}
>>> +EXPORT_SYMBOL_GPL(virtio_transport_dgram_get_cid);
>>> +
>>> +int virtio_transport_dgram_get_port(struct sk_buff *skb, unsigned int *port)
>>> +{
>>> + return -EOPNOTSUPP;
>>> +}
>>> +EXPORT_SYMBOL_GPL(virtio_transport_dgram_get_port);
>>> +
>>> +int virtio_transport_dgram_get_length(struct sk_buff *skb, size_t *len)
>>> +{
>>> + return -EOPNOTSUPP;
>>> +}
>>> +EXPORT_SYMBOL_GPL(virtio_transport_dgram_get_length);
>>> +
>>> bool virtio_transport_dgram_allow(u32 cid, u32 port)
>>> {
>>> return false;
>>> diff --git a/net/vmw_vsock/vmci_transport.c b/net/vmw_vsock/vmci_transport.c
>>> index b370070194fa..bbc63826bf48 100644
>>> --- a/net/vmw_vsock/vmci_transport.c
>>> +++ b/net/vmw_vsock/vmci_transport.c
>>> @@ -1731,57 +1731,40 @@ static int vmci_transport_dgram_enqueue(
>>> return err - sizeof(*dg);
>>> }
>>>
>>> -static int vmci_transport_dgram_dequeue(struct vsock_sock *vsk,
>>> - struct msghdr *msg, size_t len,
>>> - int flags)
>>> +static int vmci_transport_dgram_get_cid(struct sk_buff *skb, unsigned int *cid)
>>> {
>>> - int err;
>>> struct vmci_datagram *dg;
>>> - size_t payload_len;
>>> - struct sk_buff *skb;
>>>
>>> - if (flags & MSG_OOB || flags & MSG_ERRQUEUE)
>>> - return -EOPNOTSUPP;
>>> + dg = (struct vmci_datagram *)skb->data;
>>> + if (!dg)
>>> + return -EINVAL;
>>>
>>> - /* Retrieve the head sk_buff from the socket's receive queue. */
>>> - err = 0;
>>> - skb = skb_recv_datagram(&vsk->sk, flags, &err);
>>> - if (!skb)
>>> - return err;
>>> + *cid = dg->src.context;
>>> + return 0;
>>> +}
>>> +
>>> +static int vmci_transport_dgram_get_port(struct sk_buff *skb, unsigned int *port)
>>> +{
>>> + struct vmci_datagram *dg;
>>>
>>> dg = (struct vmci_datagram *)skb->data;
>>> if (!dg)
>>> - /* err is 0, meaning we read zero bytes. */
>>> - goto out;
>>> -
>>> - payload_len = dg->payload_size;
>>> - /* Ensure the sk_buff matches the payload size claimed in the packet. */
>>> - if (payload_len != skb->len - sizeof(*dg)) {
>>> - err = -EINVAL;
>>> - goto out;
>>> - }
>>> + return -EINVAL;
>>>
>>> - if (payload_len > len) {
>>> - payload_len = len;
>>> - msg->msg_flags |= MSG_TRUNC;
>>> - }
>>> + *port = dg->src.resource;
>>> + return 0;
>>> +}
>>>
>>> - /* Place the datagram payload in the user's iovec. */
>>> - err = skb_copy_datagram_msg(skb, sizeof(*dg), msg, payload_len);
>>> - if (err)
>>> - goto out;
>>> +static int vmci_transport_dgram_get_length(struct sk_buff *skb, size_t *len)
>>> +{
>>> + struct vmci_datagram *dg;
>>>
>>> - if (msg->msg_name) {
>>> - /* Provide the address of the sender. */
>>> - DECLARE_SOCKADDR(struct sockaddr_vm *, vm_addr, msg->msg_name);
>>> - vsock_addr_init(vm_addr, dg->src.context, dg->src.resource);
>>> - msg->msg_namelen = sizeof(*vm_addr);
>>> - }
>>> - err = payload_len;
>>> + dg = (struct vmci_datagram *)skb->data;
>>> + if (!dg)
>>> + return -EINVAL;
>>>
>>> -out:
>>> - skb_free_datagram(&vsk->sk, skb);
>>> - return err;
>>> + *len = dg->payload_size;
>>> + return 0;
>>> }
>>>
>>> static bool vmci_transport_dgram_allow(u32 cid, u32 port)
>>> @@ -2040,9 +2023,12 @@ static struct vsock_transport vmci_transport = {
>>> .release = vmci_transport_release,
>>> .connect = vmci_transport_connect,
>>> .dgram_bind = vmci_transport_dgram_bind,
>>> - .dgram_dequeue = vmci_transport_dgram_dequeue,
>>> .dgram_enqueue = vmci_transport_dgram_enqueue,
>>> .dgram_allow = vmci_transport_dgram_allow,
>>> + .dgram_get_cid = vmci_transport_dgram_get_cid,
>>> + .dgram_get_port = vmci_transport_dgram_get_port,
>>> + .dgram_get_length = vmci_transport_dgram_get_length,
>>> + .dgram_payload_offset = sizeof(struct vmci_datagram),
>>> .stream_dequeue = vmci_transport_stream_dequeue,
>>> .stream_enqueue = vmci_transport_stream_enqueue,
>>> .stream_has_data = vmci_transport_stream_has_data,
>>> diff --git a/net/vmw_vsock/vsock_loopback.c b/net/vmw_vsock/vsock_loopback.c
>>> index 5c6360df1f31..2f3cabc79ee5 100644
>>> --- a/net/vmw_vsock/vsock_loopback.c
>>> +++ b/net/vmw_vsock/vsock_loopback.c
>>> @@ -62,9 +62,11 @@ static struct virtio_transport loopback_transport = {
>>> .cancel_pkt = vsock_loopback_cancel_pkt,
>>>
>>> .dgram_bind = virtio_transport_dgram_bind,
>>> - .dgram_dequeue = virtio_transport_dgram_dequeue,
>>> .dgram_enqueue = virtio_transport_dgram_enqueue,
>>> .dgram_allow = virtio_transport_dgram_allow,
>>> + .dgram_get_cid = virtio_transport_dgram_get_cid,
>>> + .dgram_get_port = virtio_transport_dgram_get_port,
>>> + .dgram_get_length = virtio_transport_dgram_get_length,
>>>
>>> .stream_dequeue = virtio_transport_stream_dequeue,
>>> .stream_enqueue = virtio_transport_stream_enqueue,
>>>
>>
>