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    SubjectRe: [PATCH RFC 1/3] vsock: support sockmap
    On Wed, Jan 18, 2023 at 12:27:39PM -0800, Bobby Eshleman wrote:
    >This patch adds sockmap support for vsock sockets. It is intended to be
    >usable by all transports, but only the virtio transport is implemented.
    >
    >Signed-off-by: Bobby Eshleman <bobby.eshleman@bytedance.com>
    >---
    > drivers/vhost/vsock.c | 1 +
    > include/linux/virtio_vsock.h | 1 +
    > include/net/af_vsock.h | 17 +++
    > net/vmw_vsock/Makefile | 1 +
    > net/vmw_vsock/af_vsock.c | 59 +++++++++--
    > net/vmw_vsock/virtio_transport.c | 2 +
    > net/vmw_vsock/virtio_transport_common.c | 22 ++++
    > net/vmw_vsock/vsock_bpf.c | 180 ++++++++++++++++++++++++++++++++
    > net/vmw_vsock/vsock_loopback.c | 2 +
    > 9 files changed, 279 insertions(+), 6 deletions(-)

    ./scripts/checkpatch.pl --strict prints some simple warnings/checks that
    I suggest to fix :-)

    >
    >diff --git a/drivers/vhost/vsock.c b/drivers/vhost/vsock.c
    >index 1f3b89c885cca..3c6dc036b9044 100644
    >--- a/drivers/vhost/vsock.c
    >+++ b/drivers/vhost/vsock.c
    >@@ -439,6 +439,7 @@ static struct virtio_transport vhost_transport = {
    > .notify_send_post_enqueue = virtio_transport_notify_send_post_enqueue,
    > .notify_buffer_size = virtio_transport_notify_buffer_size,
    >
    >+ .read_skb = virtio_transport_read_skb,
    > },
    >
    > .send_pkt = vhost_transport_send_pkt,
    >diff --git a/include/linux/virtio_vsock.h b/include/linux/virtio_vsock.h
    >index 3f9c166113063..c58453699ee98 100644
    >--- a/include/linux/virtio_vsock.h
    >+++ b/include/linux/virtio_vsock.h
    >@@ -245,4 +245,5 @@ u32 virtio_transport_get_credit(struct virtio_vsock_sock *vvs, u32 wanted);
    > void virtio_transport_put_credit(struct virtio_vsock_sock *vvs, u32 credit);
    > void virtio_transport_deliver_tap_pkt(struct sk_buff *skb);
    > int virtio_transport_purge_skbs(void *vsk, struct sk_buff_head *list);
    >+int virtio_transport_read_skb(struct vsock_sock *vsk, skb_read_actor_t read_actor);
    > #endif /* _LINUX_VIRTIO_VSOCK_H */
    >diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
    >index 568a87c5e0d0f..a73f5fbd296af 100644
    >--- a/include/net/af_vsock.h
    >+++ b/include/net/af_vsock.h
    >@@ -75,6 +75,7 @@ struct vsock_sock {
    > void *trans;
    > };
    >
    >+s64 vsock_connectible_has_data(struct vsock_sock *vsk);
    > s64 vsock_stream_has_data(struct vsock_sock *vsk);
    > s64 vsock_stream_has_space(struct vsock_sock *vsk);
    > struct sock *vsock_create_connected(struct sock *parent);
    >@@ -173,6 +174,9 @@ struct vsock_transport {
    >
    > /* Addressing. */
    > u32 (*get_local_cid)(void);
    >+
    >+ /* Read a single skb */
    >+ int (*read_skb)(struct vsock_sock *, skb_read_actor_t);
    > };
    >
    > /**** CORE ****/
    >@@ -225,5 +229,18 @@ int vsock_init_tap(void);
    > int vsock_add_tap(struct vsock_tap *vt);
    > int vsock_remove_tap(struct vsock_tap *vt);
    > void vsock_deliver_tap(struct sk_buff *build_skb(void *opaque), void *opaque);
    >+int vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
    >+ int flags);
    >+int vsock_dgram_recvmsg(struct socket *sock, struct msghdr *msg,
    >+ size_t len, int flags);
    >+
    >+#ifdef CONFIG_BPF_SYSCALL
    >+extern struct proto vsock_proto;
    >+int vsock_bpf_update_proto(struct sock *sk, struct sk_psock *psock, bool restore);
    >+void __init vsock_bpf_build_proto(void);
    >+#else
    >+static inline void __init vsock_bpf_build_proto(void)
    >+{}
    >+#endif
    >
    > #endif /* __AF_VSOCK_H__ */
    >diff --git a/net/vmw_vsock/Makefile b/net/vmw_vsock/Makefile
    >index 6a943ec95c4a5..5da74c4a9f1d1 100644
    >--- a/net/vmw_vsock/Makefile
    >+++ b/net/vmw_vsock/Makefile
    >@@ -8,6 +8,7 @@ obj-$(CONFIG_HYPERV_VSOCKETS) += hv_sock.o
    > obj-$(CONFIG_VSOCKETS_LOOPBACK) += vsock_loopback.o
    >
    > vsock-y += af_vsock.o af_vsock_tap.o vsock_addr.o
    >+vsock-$(CONFIG_BPF_SYSCALL) += vsock_bpf.o
    >
    > vsock_diag-y += diag.o
    >
    >diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
    >index d593d5b6d4b15..7081b3a992c1e 100644
    >--- a/net/vmw_vsock/af_vsock.c
    >+++ b/net/vmw_vsock/af_vsock.c
    >@@ -116,10 +116,13 @@ static void vsock_sk_destruct(struct sock *sk);
    > static int vsock_queue_rcv_skb(struct sock *sk, struct sk_buff *skb);
    >
    > /* Protocol family. */
    >-static struct proto vsock_proto = {
    >+struct proto vsock_proto = {
    > .name = "AF_VSOCK",
    > .owner = THIS_MODULE,
    > .obj_size = sizeof(struct vsock_sock),
    >+#ifdef CONFIG_BPF_SYSCALL
    >+ .psock_update_sk_prot = vsock_bpf_update_proto,
    >+#endif
    > };
    >
    > /* The default peer timeout indicates how long we will wait for a peer response
    >@@ -865,7 +868,7 @@ s64 vsock_stream_has_data(struct vsock_sock *vsk)
    > }
    > EXPORT_SYMBOL_GPL(vsock_stream_has_data);
    >
    >-static s64 vsock_connectible_has_data(struct vsock_sock *vsk)
    >+s64 vsock_connectible_has_data(struct vsock_sock *vsk)
    > {
    > struct sock *sk = sk_vsock(vsk);
    >
    >@@ -874,6 +877,7 @@ static s64 vsock_connectible_has_data(struct vsock_sock *vsk)
    > else
    > return vsock_stream_has_data(vsk);
    > }
    >+EXPORT_SYMBOL_GPL(vsock_connectible_has_data);
    >
    > s64 vsock_stream_has_space(struct vsock_sock *vsk)
    > {
    >@@ -1131,6 +1135,19 @@ static __poll_t vsock_poll(struct file *file, struct socket *sock,
    > return mask;
    > }
    >
    >+static int vsock_read_skb(struct sock *sk, skb_read_actor_t read_actor)
    >+{
    >+ struct vsock_sock *vsk = vsock_sk(sk);
    >+
    >+ if (!vsk->transport)
    >+ return -ENODEV;
    >+
    >+ if (!vsk->transport->read_skb)
    >+ return -EOPNOTSUPP;
    >+
    >+ return vsk->transport->read_skb(vsk, read_actor);
    >+}
    >+
    > static int vsock_dgram_sendmsg(struct socket *sock, struct msghdr *msg,
    > size_t len)
    > {
    >@@ -1241,19 +1258,32 @@ static int vsock_dgram_connect(struct socket *sock,
    >
    > memcpy(&vsk->remote_addr, remote_addr, sizeof(vsk->remote_addr));
    > sock->state = SS_CONNECTED;
    >+ sk->sk_state = TCP_ESTABLISHED;

    Why we need this change?
    If it's a fix, we should put it in another patch.

    >
    > out:
    > release_sock(sk);
    > return err;
    > }
    >
    >-static int vsock_dgram_recvmsg(struct socket *sock, struct msghdr *msg,
    >- size_t len, int flags)
    >+int vsock_dgram_recvmsg(struct socket *sock, struct msghdr *msg,
    >+ size_t len, int flags)
    > {
    >- struct vsock_sock *vsk = vsock_sk(sock->sk);
    >+ const struct proto *prot;

    We should use the guard for this statement as in
    vsock_connectible_recvmsg().

    >+ struct vsock_sock *vsk;
    >+ struct sock *sk;
    >+
    >+ sk = sock->sk;
    >+ vsk = vsock_sk(sk);
    >+
    >+#ifdef CONFIG_BPF_SYSCALL
    >+ prot = READ_ONCE(sk->sk_prot);
    >+ if (prot != &vsock_proto)
    >+ return prot->recvmsg(sk, msg, len, flags, NULL);
    >+#endif
    >
    > return vsk->transport->dgram_dequeue(vsk, msg, len, flags);
    > }
    >+EXPORT_SYMBOL_GPL(vsock_dgram_recvmsg);
    >
    > static const struct proto_ops vsock_dgram_ops = {
    > .family = PF_VSOCK,
    >@@ -1272,6 +1302,7 @@ static const struct proto_ops vsock_dgram_ops = {
    > .recvmsg = vsock_dgram_recvmsg,
    > .mmap = sock_no_mmap,
    > .sendpage = sock_no_sendpage,
    >+ .read_skb = vsock_read_skb,
    > };
    >
    > static int vsock_transport_cancel_pkt(struct vsock_sock *vsk)
    >@@ -2085,13 +2116,16 @@ static int __vsock_seqpacket_recvmsg(struct sock *sk, struct msghdr *msg,
    > return err;
    > }
    >
    >-static int
    >+int
    > vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
    > int flags)
    > {
    > struct sock *sk;
    > struct vsock_sock *vsk;
    > const struct vsock_transport *transport;
    >+#ifdef CONFIG_BPF_SYSCALL
    >+ const struct proto *prot;
    >+#endif
    > int err;
    >
    > sk = sock->sk;
    >@@ -2138,6 +2172,14 @@ vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
    > goto out;
    > }
    >
    >+#ifdef CONFIG_BPF_SYSCALL
    >+ prot = READ_ONCE(sk->sk_prot);
    >+ if (prot != &vsock_proto) {
    >+ release_sock(sk);
    >+ return prot->recvmsg(sk, msg, len, flags, NULL);
    >+ }
    >+#endif
    >+
    > if (sk->sk_type == SOCK_STREAM)
    > err = __vsock_stream_recvmsg(sk, msg, len, flags);
    > else
    >@@ -2147,6 +2189,7 @@ vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
    > release_sock(sk);
    > return err;
    > }
    >+EXPORT_SYMBOL_GPL(vsock_connectible_recvmsg);
    >
    > static int vsock_set_rcvlowat(struct sock *sk, int val)
    > {
    >@@ -2187,6 +2230,7 @@ static const struct proto_ops vsock_stream_ops = {
    > .mmap = sock_no_mmap,
    > .sendpage = sock_no_sendpage,
    > .set_rcvlowat = vsock_set_rcvlowat,
    >+ .read_skb = vsock_read_skb,
    > };
    >
    > static const struct proto_ops vsock_seqpacket_ops = {
    >@@ -2208,6 +2252,7 @@ static const struct proto_ops vsock_seqpacket_ops = {
    > .recvmsg = vsock_connectible_recvmsg,
    > .mmap = sock_no_mmap,
    > .sendpage = sock_no_sendpage,
    >+ .read_skb = vsock_read_skb,
    > };
    >
    > static int vsock_create(struct net *net, struct socket *sock,
    >@@ -2347,6 +2392,8 @@ static int __init vsock_init(void)
    > goto err_unregister_proto;
    > }
    >
    >+ vsock_bpf_build_proto();
    >+
    > return 0;
    >
    > err_unregister_proto:
    >diff --git a/net/vmw_vsock/virtio_transport.c b/net/vmw_vsock/virtio_transport.c
    >index 28b5a8e8e0948..e95df847176b6 100644
    >--- a/net/vmw_vsock/virtio_transport.c
    >+++ b/net/vmw_vsock/virtio_transport.c
    >@@ -457,6 +457,8 @@ static struct virtio_transport virtio_transport = {
    > .notify_send_pre_enqueue =
    > virtio_transport_notify_send_pre_enqueue,
    > .notify_send_post_enqueue = virtio_transport_notify_send_post_enqueue,
    > .notify_buffer_size = virtio_transport_notify_buffer_size,
    >+
    >+ .read_skb = virtio_transport_read_skb,
    > },
    >
    > .send_pkt = virtio_transport_send_pkt,
    >diff --git a/net/vmw_vsock/virtio_transport_common.c b/net/vmw_vsock/virtio_transport_common.c
    >index a1581c77cf84a..9a87ead5b1fc5 100644
    >--- a/net/vmw_vsock/virtio_transport_common.c
    >+++ b/net/vmw_vsock/virtio_transport_common.c
    >@@ -1388,6 +1388,28 @@ int virtio_transport_purge_skbs(void *vsk, struct sk_buff_head *queue)
    > }
    > EXPORT_SYMBOL_GPL(virtio_transport_purge_skbs);
    >
    >+int virtio_transport_read_skb(struct vsock_sock *vsk, skb_read_actor_t recv_actor)
    >+{
    >+ struct virtio_vsock_sock *vvs = vsk->trans;
    >+ struct sock *sk = sk_vsock(vsk);
    >+ struct sk_buff *skb;
    >+ int copied = 0;

    We could avoid initializing `copied`, since it is overwritten later.

    >+ int off = 0;
    >+ int err;
    >+
    >+ spin_lock_bh(&vvs->rx_lock);
    >+ skb = __skb_recv_datagram(sk, &vvs->rx_queue, MSG_DONTWAIT, &off, &err);

    Will this work also for STREAM and SEQPACKET sockets?

    >+ spin_unlock_bh(&vvs->rx_lock);
    >+
    >+ if (!skb)
    >+ return err;
    >+
    >+ copied = recv_actor(sk, skb);
    >+ kfree_skb(skb);

    I would have moved these steps to vsock_read_skb() to avoid duplicating
    these steps in each transport. Perhaps not all transports want to pass
    skb ownership to the caller, though, so maybe we can leave it that
    way for now.

    >+ return copied;
    >+}
    >+EXPORT_SYMBOL_GPL(virtio_transport_read_skb);
    >+
    > MODULE_LICENSE("GPL v2");
    > MODULE_AUTHOR("Asias He");
    > MODULE_DESCRIPTION("common code for virtio vsock");
    >diff --git a/net/vmw_vsock/vsock_bpf.c b/net/vmw_vsock/vsock_bpf.c
    >new file mode 100644
    >index 0000000000000..9e11282d3bc1f
    >--- /dev/null
    >+++ b/net/vmw_vsock/vsock_bpf.c
    >@@ -0,0 +1,180 @@
    >+// SPDX-License-Identifier: GPL-2.0
    >+/* Copyright (c) 2022 Bobby Eshleman <bobby.eshleman@bytedance.com>
    >+ *
    >+ * Based off of net/unix/unix_bpf.c
    >+ */
    >+
    >+#include <linux/bpf.h>
    >+#include <linux/module.h>
    >+#include <linux/skmsg.h>
    >+#include <linux/socket.h>
    >+#include <net/af_vsock.h>
    >+#include <net/sock.h>
    >+
    >+#define vsock_sk_has_data(__sk, __psock) \
    >+ ({ !skb_queue_empty(&__sk->sk_receive_queue) || \
    >+ !skb_queue_empty(&__psock->ingress_skb) || \
    >+ !list_empty(&__psock->ingress_msg); \
    >+ })
    >+
    >+static struct proto *vsock_dgram_prot_saved __read_mostly;
    >+static DEFINE_SPINLOCK(vsock_dgram_prot_lock);
    >+static struct proto vsock_dgram_bpf_prot;
    >+
    >+static bool vsock_has_data(struct vsock_sock *vsk, struct sk_psock *psock)
    >+{
    >+ struct sock *sk = sk_vsock(vsk);
    >+ s64 ret;
    >+
    >+ ret = vsock_connectible_has_data(vsk);
    >+ if (ret > 0)
    >+ return true;
    >+
    >+ return vsock_sk_has_data(sk, psock);
    >+}
    >+
    >+static int vsock_msg_wait_data(struct sock *sk, struct sk_psock *psock, long timeo)
    >+{
    >+ struct vsock_sock *vsk;
    >+ int err;
    >+
    >+ DEFINE_WAIT(wait);
    >+
    >+ vsk = vsock_sk(sk);
    >+ err = 0;
    >+
    >+ while (vsock_has_data(vsk, psock)) {
    >+ prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
    >+
    >+ if (sk->sk_err != 0 ||
    >+ (sk->sk_shutdown & RCV_SHUTDOWN) ||
    >+ (vsk->peer_shutdown & SEND_SHUTDOWN)) {
    >+ break;
    >+ }
    >+
    >+ if (timeo == 0) {
    >+ err = -EAGAIN;
    >+ break;
    >+ }
    >+
    >+ release_sock(sk);
    >+ timeo = schedule_timeout(timeo);
    >+ lock_sock(sk);
    >+
    >+ if (signal_pending(current)) {
    >+ err = sock_intr_errno(timeo);
    >+ break;
    >+ } else if (timeo == 0) {
    >+ err = -EAGAIN;
    >+ break;
    >+ }
    >+ }
    >+
    >+ finish_wait(sk_sleep(sk), &wait);
    >+
    >+ if (err)
    >+ return err;
    >+
    >+ return 0;
    >+}
    >+
    >+static int vsock_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int flags)
    >+{
    >+ int err;
    >+ struct socket *sock = sk->sk_socket;
    >+
    >+ if (sk->sk_type == SOCK_STREAM || sk->sk_type == SOCK_SEQPACKET)
    >+ err = vsock_connectible_recvmsg(sock, msg, len, flags);
    >+ else

    Could it happen that it is not DGRAM and we should return an error in
    this case?

    Thanks,
    Stefano

    >+ err = vsock_dgram_recvmsg(sock, msg, len, flags);
    >+
    >+ return err;
    >+}
    >+
    >+static int vsock_bpf_recvmsg(struct sock *sk, struct msghdr *msg,
    >+ size_t len, int flags, int *addr_len)
    >+{
    >+ int copied;
    >+ struct sk_psock *psock;
    >+
    >+ lock_sock(sk);
    >+ psock = sk_psock_get(sk);
    >+ if (unlikely(!psock)) {
    >+ release_sock(sk);
    >+ return vsock_recvmsg(sk, msg, len, flags);
    >+ }
    >+
    >+ if (vsock_has_data(vsock_sk(sk), psock) && sk_psock_queue_empty(psock)) {
    >+ sk_psock_put(sk, psock);
    >+ release_sock(sk);
    >+ return vsock_recvmsg(sk, msg, len, flags);
    >+ }
    >+
    >+msg_bytes_ready:
    >+ copied = sk_msg_recvmsg(sk, psock, msg, len, flags);
    >+ if (!copied) {
    >+ long timeo;
    >+ int data;
    >+
    >+ timeo = sock_rcvtimeo(sk, flags & MSG_DONTWAIT);
    >+ data = vsock_msg_wait_data(sk, psock, timeo);
    >+ if (data) {
    >+ if (!sk_psock_queue_empty(psock))
    >+ goto msg_bytes_ready;
    >+ sk_psock_put(sk, psock);
    >+ release_sock(sk);
    >+ return vsock_recvmsg(sk, msg, len, flags);
    >+ }
    >+ copied = -EAGAIN;
    >+ }
    >+ sk_psock_put(sk, psock);
    >+ release_sock(sk);
    >+
    >+ return copied;
    >+}
    >+
    >+/* Copy of original proto with updated sock_map methods */
    >+static struct proto vsock_dgram_bpf_prot = {
    >+ .close = sock_map_close,
    >+ .recvmsg = vsock_bpf_recvmsg,
    >+ .sock_is_readable = sk_msg_is_readable,
    >+ .unhash = sock_map_unhash,
    >+};
    >+
    >+static void vsock_dgram_bpf_rebuild_protos(struct proto *prot, const struct proto *base)
    >+{
    >+ *prot = *base;
    >+ prot->close = sock_map_close;
    >+ prot->recvmsg = vsock_bpf_recvmsg;
    >+ prot->sock_is_readable = sk_msg_is_readable;
    >+}
    >+
    >+static void vsock_dgram_bpf_check_needs_rebuild(struct proto *ops)
    >+{
    >+ if (unlikely(ops != smp_load_acquire(&vsock_dgram_prot_saved))) {
    >+ spin_lock_bh(&vsock_dgram_prot_lock);
    >+ if (likely(ops != vsock_dgram_prot_saved)) {
    >+ vsock_dgram_bpf_rebuild_protos(&vsock_dgram_bpf_prot, ops);
    >+ smp_store_release(&vsock_dgram_prot_saved, ops);
    >+ }
    >+ spin_unlock_bh(&vsock_dgram_prot_lock);
    >+ }
    >+}
    >+
    >+int vsock_bpf_update_proto(struct sock *sk, struct sk_psock *psock, bool restore)
    >+{
    >+ if (restore) {
    >+ sk->sk_write_space = psock->saved_write_space;
    >+ sock_replace_proto(sk, psock->sk_proto);
    >+ return 0;
    >+ }
    >+
    >+ vsock_dgram_bpf_check_needs_rebuild(psock->sk_proto);
    >+ sock_replace_proto(sk, &vsock_dgram_bpf_prot);
    >+ return 0;
    >+}
    >+
    >+void __init vsock_bpf_build_proto(void)
    >+{
    >+ vsock_dgram_bpf_rebuild_protos(&vsock_dgram_bpf_prot, &vsock_proto);
    >+}
    >diff --git a/net/vmw_vsock/vsock_loopback.c b/net/vmw_vsock/vsock_loopback.c
    >index 671e03240fc52..40753b661c135 100644
    >--- a/net/vmw_vsock/vsock_loopback.c
    >+++ b/net/vmw_vsock/vsock_loopback.c
    >@@ -94,6 +94,8 @@ static struct virtio_transport loopback_transport = {
    > .notify_send_pre_enqueue = virtio_transport_notify_send_pre_enqueue,
    > .notify_send_post_enqueue = virtio_transport_notify_send_post_enqueue,
    > .notify_buffer_size = virtio_transport_notify_buffer_size,
    >+
    >+ .read_skb = virtio_transport_read_skb,
    > },
    >
    > .send_pkt = vsock_loopback_send_pkt,
    >
    >--
    >2.30.2
    >

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