[PATCH] net: define IPPROTO_SMBDIRECT and SOL_SMBDIRECT constants

[Stefan Metzmacher]

This patch adds IPPROTO_SMBDIRECT and SOL_SMBDIRECT constants to the
networking subsystem. These definitions are essential for applications
to set socket options and protocol identifiers related to the SMBDIRECT
protocol, defined in [MS-SMBD] by Microsoft. It is used as wrapper
around RDMA in order to provide a transport for SMB3, but Microsoft also
uses it as transport for other protocols.

SMBDIRECT works over Infiniband, RoCE and iWarp.
RoCEv2 is based on IP/UDP and iWarp is based on IP/TCP,
so these use IP addresses natively.
Infiniband and RoCEv1 require IPOIB in order to be used for
SMBDIRECT.

So instead of adding a PF_SMBDIRECT, which would only use AF_INET[6],
we use IPPROTO_SMBDIRECT instead, this uses a number not
allocated from IANA, as it would not appear in an IP header.

This is similar to IPPROTO_SMC, IPPROTO_MPTCP and IPPROTO_QUIC,
which are linux specific values for the socket() syscall.

  socket(AF_INET, SOCK_STREAM, IPPROTO_SMBDIRECT);
  socket(AF_INET6, SOCK_STREAM, IPPROTO_SMBDIRECT);

This will allow the existing smbdirect code used by
cifs.ko and ksmbd.ko to be moved behind the socket layer [1],
so that there's less special handling. Only sock_sendmsg()
sock_recvmsg() are used, so that the main stream handling
is done all the same for tcp, smbdirect and later also quic.

The special RDMA read/write handling will be via direct
function calls as they are currently done for the in kernel
consumers.

As a start __sock_create(kern=0)/sk->sk_kern_sock == 0 will
still cause a -EPROTONOSUPPORT. So only in kernel consumers
will be supported for now.

Once I have developed a stable interface for the RDMA read/write
handling using sendmsg/recvmsg with MSG_OOB and msg_control,
it will also exposed to userspace in order to allow Samba to
use it.

[1]
https://git.samba.org/?p=metze/linux/wip.git;a=shortlog;h=refs/heads/master-ipproto-smbdirect

Cc: David S. Miller <davem at davemloft.net>
Cc: Eric Dumazet <edumazet at google.com>
Cc: Jakub Kicinski <kuba at kernel.org>
Cc: Paolo Abeni <pabeni at redhat.com>
Cc: Simon Horman <horms at kernel.org>
Cc: Kuniyuki Iwashima <kuniyu at google.com>
Cc: Willem de Bruijn <willemb at google.com>
Cc: Steve French <smfrench at gmail.com>
Cc: Tom Talpey <tom at talpey.com>
Cc: Long Li <longli at microsoft.com>
Cc: Namjae Jeon <linkinjeon at kernel.org>
Cc: Xin Long <lucien.xin at gmail.com>
Cc: netdev at vger.kernel.org
Cc: linux-kernel at vger.kernel.org
Cc: linux-cifs at vger.kernel.org
Cc: samba-technical at lists.samba.org
Cc: linux-rdma at vger.kernel.org
Signed-off-by: Stefan Metzmacher <metze at samba.org>

---

In order to avoid conflicts with the addition of IPPROTO_QUIC,
the patch is based on netdev-next/main + the patch adding
IPPROTO_QUIC and SOL_QUIC [2].

[2]
https://lore.kernel.org/quic/0cb58f6fcf35ac988660e42704dae9960744a0a7.1763994509.git.lucien.xin@gmail.com/T/#u

As the numbers of IPPROTO_QUIC and SOL_QUIC are already used
in various userspace applications it would be good to have
this merged to netdev-next/main even if the actual
implementation is still waiting for review.

Having IPPROTO_SMBDIRECT+SOL_SMBDIRECT merged would also make
thinks easier for me.
---
 include/linux/socket.h  | 1 +
 include/uapi/linux/in.h | 2 ++
 2 files changed, 3 insertions(+)

diff --git a/include/linux/socket.h b/include/linux/socket.h
index b4563ffe552b..350a579a87da 100644
--- a/include/linux/socket.h
+++ b/include/linux/socket.h
@@ -402,6 +402,7 @@ struct ucred {
 #define SOL_SMC		286
 #define SOL_VSOCK	287
 #define SOL_QUIC	288
+#define SOL_SMBDIRECT	289
 
 /* IPX options */
 #define IPX_TYPE	1
diff --git a/include/uapi/linux/in.h b/include/uapi/linux/in.h
index 34becd90d3a6..b30caa6db8ca 100644
--- a/include/uapi/linux/in.h
+++ b/include/uapi/linux/in.h
@@ -85,6 +85,8 @@ enum {
 #define IPPROTO_RAW		IPPROTO_RAW
   IPPROTO_SMC = 256,		/* Shared Memory Communications		*/
 #define IPPROTO_SMC		IPPROTO_SMC
+  IPPROTO_SMBDIRECT = 257,	/* RDMA based transport (mostly used by SMB3) */
+#define IPPROTO_SMBDIRECT	IPPROTO_SMBDIRECT
   IPPROTO_QUIC = 261,		/* A UDP-Based Multiplexed and Secure Transport	*/
 #define IPPROTO_QUIC		IPPROTO_QUIC
   IPPROTO_MPTCP = 262,		/* Multipath TCP connection		*/
-- 
2.43.0