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Date: Thu, 22 Jun 2023 17:19:08 +0200
From: Stefano Garzarella <sgarzare@...hat.com>
To: Bobby Eshleman <bobby.eshleman@...edance.com>
Cc: Stefan Hajnoczi <stefanha@...hat.com>,
"Michael S. Tsirkin" <mst@...hat.com>,
Jason Wang <jasowang@...hat.com>,
Xuan Zhuo <xuanzhuo@...ux.alibaba.com>,
"David S. Miller" <davem@...emloft.net>,
Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>,
"K. Y. Srinivasan" <kys@...rosoft.com>,
Haiyang Zhang <haiyangz@...rosoft.com>,
Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
Bryan Tan <bryantan@...are.com>,
Vishnu Dasa <vdasa@...are.com>,
VMware PV-Drivers Reviewers <pv-drivers@...are.com>,
Dan Carpenter <dan.carpenter@...aro.org>,
Simon Horman <simon.horman@...igine.com>,
Krasnov Arseniy <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
Subject: Re: [PATCH RFC net-next v4 3/8] vsock: support multi-transport
datagrams
On Sat, Jun 10, 2023 at 12:58:30AM +0000, Bobby Eshleman wrote:
>This patch adds support for multi-transport datagrams.
>
>This includes:
>- Per-packet lookup of transports when using sendto(sockaddr_vm)
>- Selecting H2G or G2H transport using VMADDR_FLAG_TO_HOST and CID in
> sockaddr_vm
>
>To preserve backwards compatibility with VMCI, some important changes
>were made. The "transport_dgram" / VSOCK_TRANSPORT_F_DGRAM is changed to
>be used for dgrams iff there is not yet a g2h or h2g transport that has
s/iff/if
>been registered that can transmit the packet. If there is a g2h/h2g
>transport for that remote address, then that transport will be used and
>not "transport_dgram". This essentially makes "transport_dgram" a
>fallback transport for when h2g/g2h has not yet gone online, which
>appears to be the exact use case for VMCI.
>
>This design makes sense, because there is no reason that the
>transport_{g2h,h2g} cannot also service datagrams, which makes the role
>of transport_dgram difficult to understand outside of the VMCI context.
>
>The logic around "transport_dgram" had to be retained to prevent
>breaking VMCI:
>
>1) VMCI datagrams appear to function outside of the h2g/g2h
> paradigm. When the vmci transport becomes online, it registers itself
> with the DGRAM feature, but not H2G/G2H. Only later when the
> transport has more information about its environment does it register
> H2G or G2H. In the case that a datagram socket becomes active
> after DGRAM registration but before G2H/H2G registration, the
> "transport_dgram" transport needs to be used.
IIRC we did this, because at that time only VMCI supported DGRAM. Now
that there are more transports, maybe DGRAM can follow the h2g/g2h
paradigm.
>
>2) VMCI seems to require special message be sent by the transport when a
> datagram socket calls bind(). Under the h2g/g2h model, the transport
> is selected using the remote_addr which is set by connect(). At
> bind time there is no remote_addr because often no connect() has been
> called yet: the transport is null. Therefore, with a null transport
> there doesn't seem to be any good way for a datagram socket a tell the
> VMCI transport that it has just had bind() called upon it.
@Vishnu, @Bryan do you think we can avoid this in some way?
>
>Only transports with a special datagram fallback use-case such as VMCI
>need to register VSOCK_TRANSPORT_F_DGRAM.
Maybe we should rename it in VSOCK_TRANSPORT_F_DGRAM_FALLBACK or
something like that.
In any case, we definitely need to update the comment in
include/net/af_vsock.h on top of VSOCK_TRANSPORT_F_DGRAM mentioning
this.
>
>Signed-off-by: Bobby Eshleman <bobby.eshleman@...edance.com>
>---
> drivers/vhost/vsock.c | 1 -
> include/linux/virtio_vsock.h | 2 -
> net/vmw_vsock/af_vsock.c | 78 +++++++++++++++++++++++++--------
> net/vmw_vsock/hyperv_transport.c | 6 ---
> net/vmw_vsock/virtio_transport.c | 1 -
> net/vmw_vsock/virtio_transport_common.c | 7 ---
> net/vmw_vsock/vsock_loopback.c | 1 -
> 7 files changed, 60 insertions(+), 36 deletions(-)
>
>diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
>index c8201c070b4b..8f0082da5e70 100644
>--- a/drivers/vhost/vsock.c
>+++ b/drivers/vhost/vsock.c
>@@ -410,7 +410,6 @@ static struct virtio_transport vhost_transport = {
> .cancel_pkt = vhost_transport_cancel_pkt,
>
> .dgram_enqueue = virtio_transport_dgram_enqueue,
>- .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,
>diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
>index 23521a318cf0..73afa09f4585 100644
>--- a/include/linux/virtio_vsock.h
>+++ b/include/linux/virtio_vsock.h
>@@ -216,8 +216,6 @@ void virtio_transport_notify_buffer_size(struct vsock_sock *vsk, u64 *val);
> u64 virtio_transport_stream_rcvhiwat(struct vsock_sock *vsk);
> bool virtio_transport_stream_is_active(struct vsock_sock *vsk);
> 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);
>diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>index 74358f0b47fa..ef86765f3765 100644
>--- a/net/vmw_vsock/af_vsock.c
>+++ b/net/vmw_vsock/af_vsock.c
>@@ -438,6 +438,18 @@ vsock_connectible_lookup_transport(unsigned int cid, __u8 flags)
> return transport;
> }
>
>+static const struct vsock_transport *
>+vsock_dgram_lookup_transport(unsigned int cid, __u8 flags)
>+{
>+ const struct vsock_transport *transport;
>+
>+ transport = vsock_connectible_lookup_transport(cid, flags);
>+ if (transport)
>+ return transport;
>+
>+ return transport_dgram;
>+}
>+
> /* Assign a transport to a socket and call the .init transport callback.
> *
> * Note: for connection oriented socket this must be called when vsk->remote_addr
>@@ -474,7 +486,8 @@ int vsock_assign_transport(struct vsock_sock *vsk, struct vsock_sock *psk)
>
> switch (sk->sk_type) {
> case SOCK_DGRAM:
>- new_transport = transport_dgram;
>+ new_transport = vsock_dgram_lookup_transport(remote_cid,
>+ remote_flags);
> break;
> case SOCK_STREAM:
> case SOCK_SEQPACKET:
>@@ -691,6 +704,9 @@ static int __vsock_bind_connectible(struct vsock_sock *vsk,
> static int __vsock_bind_dgram(struct vsock_sock *vsk,
> struct sockaddr_vm *addr)
> {
>+ if (!vsk->transport || !vsk->transport->dgram_bind)
>+ return -EINVAL;
>+
> return vsk->transport->dgram_bind(vsk, addr);
> }
>
>@@ -1172,19 +1188,24 @@ static int vsock_dgram_sendmsg(struct socket *sock, struct msghdr *msg,
>
> lock_sock(sk);
>
>- transport = vsk->transport;
>-
>- err = vsock_auto_bind(vsk);
>- if (err)
>- goto out;
>-
>-
> /* If the provided message contains an address, use that. Otherwise
> * fall back on the socket's remote handle (if it has been connected).
> */
> if (msg->msg_name &&
> vsock_addr_cast(msg->msg_name, msg->msg_namelen,
> &remote_addr) == 0) {
>+ transport = vsock_dgram_lookup_transport(remote_addr->svm_cid,
>+ remote_addr->svm_flags);
>+ if (!transport) {
>+ err = -EINVAL;
>+ goto out;
>+ }
>+
>+ if (!try_module_get(transport->module)) {
>+ err = -ENODEV;
>+ goto out;
>+ }
>+
> /* Ensure this address is of the right type and is a valid
> * destination.
> */
>@@ -1193,11 +1214,27 @@ static int vsock_dgram_sendmsg(struct socket *sock, struct msghdr *msg,
> remote_addr->svm_cid = transport->get_local_cid();
>
From here ...
> if (!vsock_addr_bound(remote_addr)) {
>+ module_put(transport->module);
>+ err = -EINVAL;
>+ goto out;
>+ }
>+
>+ if (!transport->dgram_allow(remote_addr->svm_cid,
>+ remote_addr->svm_port)) {
>+ module_put(transport->module);
> err = -EINVAL;
> goto out;
> }
>+
>+ err = transport->dgram_enqueue(vsk, remote_addr, msg, len);
... to here, looks like duplicate code, can we get it out of the if
block?
>+ module_put(transport->module);
> } else if (sock->state == SS_CONNECTED) {
> remote_addr = &vsk->remote_addr;
>+ transport = vsk->transport;
>+
>+ err = vsock_auto_bind(vsk);
>+ if (err)
>+ goto out;
>
> if (remote_addr->svm_cid == VMADDR_CID_ANY)
> remote_addr->svm_cid = transport->get_local_cid();
>@@ -1205,23 +1242,23 @@ static int vsock_dgram_sendmsg(struct socket *sock, struct msghdr *msg,
> /* XXX Should connect() or this function ensure remote_addr is
> * bound?
> */
>- if (!vsock_addr_bound(&vsk->remote_addr)) {
>+ if (!vsock_addr_bound(remote_addr)) {
> err = -EINVAL;
> goto out;
> }
>- } else {
>- err = -EINVAL;
>- goto out;
>- }
>
>- if (!transport->dgram_allow(remote_addr->svm_cid,
>- remote_addr->svm_port)) {
>+ if (!transport->dgram_allow(remote_addr->svm_cid,
>+ remote_addr->svm_port)) {
>+ err = -EINVAL;
>+ goto out;
>+ }
>+
>+ err = transport->dgram_enqueue(vsk, remote_addr, msg, len);
>+ } else {
> err = -EINVAL;
> goto out;
> }
>
>- err = transport->dgram_enqueue(vsk, remote_addr, msg, len);
>-
> out:
> release_sock(sk);
> return err;
>@@ -1255,13 +1292,18 @@ static int vsock_dgram_connect(struct socket *sock,
> if (err)
> goto out;
>
>+ memcpy(&vsk->remote_addr, remote_addr, sizeof(vsk->remote_addr));
>+
>+ err = vsock_assign_transport(vsk, NULL);
>+ if (err)
>+ goto out;
>+
> if (!vsk->transport->dgram_allow(remote_addr->svm_cid,
> remote_addr->svm_port)) {
> err = -EINVAL;
> goto out;
> }
>
>- memcpy(&vsk->remote_addr, remote_addr, sizeof(vsk->remote_addr));
> sock->state = SS_CONNECTED;
>
> /* sock map disallows redirection of non-TCP sockets with sk_state !=
>diff --git a/net/vmw_vsock/hyperv_transport.c b/net/vmw_vsock/hyperv_transport.c
>index ff6e87e25fa0..c00bc5da769a 100644
>--- a/net/vmw_vsock/hyperv_transport.c
>+++ b/net/vmw_vsock/hyperv_transport.c
>@@ -551,11 +551,6 @@ static void hvs_destruct(struct vsock_sock *vsk)
> kfree(hvs);
> }
>
>-static int hvs_dgram_bind(struct vsock_sock *vsk, struct sockaddr_vm *addr)
>-{
>- return -EOPNOTSUPP;
>-}
>-
> static int hvs_dgram_get_cid(struct sk_buff *skb, unsigned int *cid)
> {
> return -EOPNOTSUPP;
>@@ -841,7 +836,6 @@ static struct vsock_transport hvs_transport = {
> .connect = hvs_connect,
> .shutdown = hvs_shutdown,
>
>- .dgram_bind = hvs_dgram_bind,
> .dgram_get_cid = hvs_dgram_get_cid,
> .dgram_get_port = hvs_dgram_get_port,
> .dgram_get_length = hvs_dgram_get_length,
>diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
>index 5763cdf13804..1b7843a7779a 100644
>--- a/net/vmw_vsock/virtio_transport.c
>+++ b/net/vmw_vsock/virtio_transport.c
>@@ -428,7 +428,6 @@ static struct virtio_transport virtio_transport = {
> .shutdown = virtio_transport_shutdown,
> .cancel_pkt = virtio_transport_cancel_pkt,
>
>- .dgram_bind = virtio_transport_dgram_bind,
> .dgram_enqueue = virtio_transport_dgram_enqueue,
> .dgram_allow = virtio_transport_dgram_allow,
> .dgram_get_cid = virtio_transport_dgram_get_cid,
>diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
>index e6903c719964..d5a3c8efe84b 100644
>--- a/net/vmw_vsock/virtio_transport_common.c
>+++ b/net/vmw_vsock/virtio_transport_common.c
>@@ -790,13 +790,6 @@ bool virtio_transport_stream_allow(u32 cid, u32 port)
> }
> EXPORT_SYMBOL_GPL(virtio_transport_stream_allow);
>
>-int virtio_transport_dgram_bind(struct vsock_sock *vsk,
>- struct sockaddr_vm *addr)
>-{
>- return -EOPNOTSUPP;
>-}
>-EXPORT_SYMBOL_GPL(virtio_transport_dgram_bind);
>-
> int virtio_transport_dgram_get_cid(struct sk_buff *skb, unsigned int *cid)
> {
> return -EOPNOTSUPP;
>diff --git a/net/vmw_vsock/vsock_loopback.c b/net/vmw_vsock/vsock_loopback.c
>index 2f3cabc79ee5..e9de45a26fbd 100644
>--- a/net/vmw_vsock/vsock_loopback.c
>+++ b/net/vmw_vsock/vsock_loopback.c
>@@ -61,7 +61,6 @@ static struct virtio_transport loopback_transport = {
> .shutdown = virtio_transport_shutdown,
> .cancel_pkt = vsock_loopback_cancel_pkt,
>
>- .dgram_bind = virtio_transport_dgram_bind,
> .dgram_enqueue = virtio_transport_dgram_enqueue,
> .dgram_allow = virtio_transport_dgram_allow,
> .dgram_get_cid = virtio_transport_dgram_get_cid,
>
>--
>2.30.2
>
The rest LGTM!
Stefano
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