Re: [PATCH net-next v1 02/12] vsock: read from socket's error queue

[Stefano Garzarella]

On Tue, Sep 26, 2023 at 10:36:58PM +0300, Arseniy Krasnov wrote:
> On 26.09.2023 15:55, Stefano Garzarella wrote:
> > On Fri, Sep 22, 2023 at 08:24:18AM +0300, Arseniy Krasnov wrote:
> > > This adds handling of MSG_ERRQUEUE input flag in receive call. This flag
> > > is used to read socket's error queue instead of data queue. Possible
> > > scenario of error queue usage is receiving completions for transmission
> > > with MSG_ZEROCOPY flag. This patch also adds new defines: 'SOL_VSOCK'
> > > and 'VSOCK_RECVERR'.
> > >
> > > Signed-off-by: Arseniy Krasnov <avkrasnov@xxxxxxxxxxxxxxxxx>
> > > ---
> > > Changelog:
> > > v5(big patchset) -> v1:
> > >  * R-b tag removed, due to added defines to 'include/uapi/linux/vsock.h'.
> > >    Both 'SOL_VSOCK' and 'VSOCK_RECVERR' are needed by userspace, so
> > >    they were placed to 'include/uapi/linux/vsock.h'. At the same time,
> > >    the same define for 'SOL_VSOCK' was placed to 'include/linux/socket.h'.
> > >    This is needed because this file contains SOL_XXX defines for different
> > >    types of socket, so it prevents situation when another new SOL_XXX
> > >    will use constant 287.
> > >
> > > include/linux/socket.h     | 1 +
> > > include/uapi/linux/vsock.h | 9 +++++++++
> > > net/vmw_vsock/af_vsock.c   | 6 ++++++
> > > 3 files changed, 16 insertions(+)
> > > create mode 100644 include/uapi/linux/vsock.h
> > >
> > > diff --git a/include/linux/socket.h b/include/linux/socket.h
> > > index 39b74d83c7c4..cfcb7e2c3813 100644
> > > --- a/include/linux/socket.h
> > > +++ b/include/linux/socket.h
> > > @@ -383,6 +383,7 @@ struct ucred {
> > > #define SOL_MPTCP    284
> > > #define SOL_MCTP    285
> > > #define SOL_SMC        286
> > > +#define SOL_VSOCK    287
> > >
> > > /* IPX options */
> > > #define IPX_TYPE    1
> > > diff --git a/include/uapi/linux/vsock.h b/include/uapi/linux/vsock.h
> > > new file mode 100644
> > > index 000000000000..b25c1347a3b8
> > > --- /dev/null
> > > +++ b/include/uapi/linux/vsock.h
> >
> > We already have include/uapi/linux/vm_sockets.h
> >
> > Should we include these changes there instead of creating a new header?
> >
> > > @@ -0,0 +1,9 @@
> > > +/* SPDX-License-Identifier: GPL-2.0 WITH Linux-syscall-note */
> > > +#ifndef _UAPI_LINUX_VSOCK_H
> > > +#define _UAPI_LINUX_VSOCK_H
> > > +
> > > +#define SOL_VSOCK    287
> >
> > Why we need to re-define this also here?
>
> Reason of this re-define is that SOL_VSOCK must be exported to userspace, so
> i place it to include/uapi/XXX. At the same time include/linux/socket.h contains
> constants for SOL_XXX and they goes sequentially in this file (e.g. one by one,
> each new value is +1 to the previous). So if I add SOL_VSOCK to include/uapi/XXX
> only, it is possible that someone will add new SOL_VERY_NEW_SOCKET == 287 to
> include/linux/socket.h in future. I think it is not good that two SOL_XXX will
> have same value.
>
> For example SOL_RDS and SOL_TIPS uses the same approach - there are two same defines:
> one in include/uapi/ and another is in include/linux/socket.h

Okay, I was confused, I though socket.h was the uapi one.
If others do the same, it's fine.

But why adding a new vsock.h instead of reusing vm_sockets.h?

> > In that case, should we protect with some guards to avoid double
> > defines?
>
> May be:
>
> in include/linux/socket.h
>
> #ifndef SOL_VSOCK
> #define SOL_VSOCK 287
> #endif
>
> But not sure...

Nope, let's follow others definition.

Sorry for the confusion ;-)

> > > +
> > > +#define VSOCK_RECVERR    1
> > > +
> > > +#endif /* _UAPI_LINUX_VSOCK_H */
> > > diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
> > > index d841f4de33b0..4fd11bf34bc7 100644
> > > --- a/net/vmw_vsock/af_vsock.c
> > > +++ b/net/vmw_vsock/af_vsock.c
> > > @@ -110,6 +110,8 @@
> > > #include <linux/workqueue.h>
> > > #include <net/sock.h>
> > > #include <net/af_vsock.h>
> > > +#include <linux/errqueue.h>
> > > +#include <uapi/linux/vsock.h>
> > >
> > > static int __vsock_bind(struct sock *sk, struct sockaddr_vm *addr);
> > > static void vsock_sk_destruct(struct sock *sk);
> > > @@ -2137,6 +2139,10 @@ vsock_connectible_recvmsg(struct socket *sock, struct msghdr *msg, size_t len,
> > >     int err;
> > >
> > >     sk = sock->sk;
> > > +
> > > +    if (unlikely(flags & MSG_ERRQUEUE))
> > > +        return sock_recv_errqueue(sk, msg, len, SOL_VSOCK, 
> > > VSOCK_RECVERR);
> > > +
> > >     vsk = vsock_sk(sk);
> > >     err = 0;
> > >
> > > -- 
> > > 2.25.1