linux-kernel - Re: [PATCH net-next v2 4/4] af_vsock: Assign the vsock transport considering the vsock address flags

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Date:   Mon, 7 Dec 2020 11:00:16 +0100
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     Andra Paraschiv <andraprs@...zon.com>
Cc:     netdev <netdev@...r.kernel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        "David S . Miller" <davem@...emloft.net>,
        David Duncan <davdunc@...zon.com>,
        Dexuan Cui <decui@...rosoft.com>,
        Alexander Graf <graf@...zon.de>,
        Jorgen Hansen <jhansen@...are.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>
Subject: Re: [PATCH net-next v2 4/4] af_vsock: Assign the vsock transport
 considering the vsock address flags

On Fri, Dec 04, 2020 at 07:02:35PM +0200, Andra Paraschiv wrote:
>The vsock flags field can be set in the connect and (listen) receive
>paths.
>
>When the vsock transport is assigned, the remote CID is used to
>distinguish between types of connection.
>
>Use the vsock flags value (in addition to the CID) from the remote
>address to decide which vsock transport to assign. For the sibling VMs
>use case, all the vsock packets need to be forwarded to the host, so
>always assign the guest->host transport if the VMADDR_FLAG_TO_HOST flag
>is set. For the other use cases, the vsock transport assignment logic is
>not changed.
>
>Changelog
>
>v1 -> v2
>
>* Use bitwise operator to check the vsock flag.
>* Use the updated "VMADDR_FLAG_TO_HOST" flag naming.
>* Merge the checks for the g2h transport assignment in one "if" block.
>
>Signed-off-by: Andra Paraschiv <andraprs@...zon.com>
>---
> net/vmw_vsock/af_vsock.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
>diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
>index 83d035eab0b05..66e643c3b5f85 100644
>--- a/net/vmw_vsock/af_vsock.c
>+++ b/net/vmw_vsock/af_vsock.c
>@@ -421,7 +421,8 @@ static void vsock_deassign_transport(struct vsock_sock *vsk)
>  * The vsk->remote_addr is used to decide which transport to use:
>  *  - remote CID == VMADDR_CID_LOCAL or g2h->local_cid or VMADDR_CID_HOST if
>  *    g2h is not loaded, will use local transport;
>- *  - remote CID <= VMADDR_CID_HOST will use guest->host transport;
>+ *  - remote CID <= VMADDR_CID_HOST or h2g is not loaded or remote flags field
>+ *    includes VMADDR_FLAG_TO_HOST flag value, will use guest->host transport;
>  *  - remote CID > VMADDR_CID_HOST will use host->guest transport;
>  */
> int vsock_assign_transport(struct vsock_sock *vsk, struct vsock_sock *psk)
>@@ -429,6 +430,7 @@ int vsock_assign_transport(struct vsock_sock *vsk, struct vsock_sock *psk)
> 	const struct vsock_transport *new_transport;
> 	struct sock *sk = sk_vsock(vsk);
> 	unsigned int remote_cid = vsk->remote_addr.svm_cid;
>+	unsigned short remote_flags;
> 	int ret;
>
> 	/* If the packet is coming with the source and destination CIDs higher
>@@ -443,6 +445,8 @@ int vsock_assign_transport(struct vsock_sock *vsk, struct vsock_sock *psk)
> 	    vsk->remote_addr.svm_cid > VMADDR_CID_HOST)
> 		vsk->remote_addr.svm_flags |= VMADDR_FLAG_TO_HOST;
>
>+	remote_flags = vsk->remote_addr.svm_flags;
>+
> 	switch (sk->sk_type) {
> 	case SOCK_DGRAM:
> 		new_transport = transport_dgram;
>@@ -450,7 +454,8 @@ int vsock_assign_transport(struct vsock_sock *vsk, struct vsock_sock *psk)
> 	case SOCK_STREAM:
> 		if (vsock_use_local_transport(remote_cid))
> 			new_transport = transport_local;
>-		else if (remote_cid <= VMADDR_CID_HOST || !transport_h2g)
>+		else if (remote_cid <= VMADDR_CID_HOST || !transport_h2g ||
>+			 (remote_flags & VMADDR_FLAG_TO_HOST) == VMADDR_FLAG_TO_HOST)

Maybe "remote_flags & VMADDR_FLAG_TO_HOST" should be enough, but the 
patch is okay:

Reviewed-by: Stefano Garzarella <sgarzare@...hat.com>

> 			new_transport = transport_g2h;
> 		else
> 			new_transport = transport_h2g;
>-- 
>2.20.1 (Apple Git-117)
>
>
>
>
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