[PATCH RFC net-next v4 3/8] vsock: support multi-transport datagrams

From: Bobby Eshleman
Date: Fri Jun 09 2023 - 21:00:09 EST

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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
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.

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.

Only transports with a special datagram fallback use-case such as VMCI
need to register VSOCK_TRANSPORT_F_DGRAM.

Signed-off-by: Bobby Eshleman <bobby.eshleman@xxxxxxxxxxxxx>
---
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();

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);
+ 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

Next message: Bobby Eshleman: "[PATCH RFC net-next v4 5/8] virtio/vsock: add VIRTIO_VSOCK_F_DGRAM feature bit"
Previous message: Bobby Eshleman: "[PATCH RFC net-next v4 7/8] vsock: Add lockless sendmsg() support"
In reply to: Simon Horman: "Re: [PATCH RFC net-next v4 7/8] vsock: Add lockless sendmsg() support"
Next in thread: Bobby Eshleman: "[PATCH RFC net-next v4 5/8] virtio/vsock: add VIRTIO_VSOCK_F_DGRAM feature bit"
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