[PATCH net-next 01/15] net: define IPPROTO_QUIC and SOL_QUIC constants

[Xin Long <lucien.xin@gmail.com>]

This patch adds IPPROTO_QUIC and SOL_QUIC constants to the networking
subsystem. These definitions are essential for applications to set
socket options and protocol identifiers related to the QUIC protocol.

QUIC does not possess a protocol number allocated from IANA, and like
IPPROTO_MPTCP, IPPROTO_QUIC is merely a value used when opening a QUIC
socket with:

  socket(AF_INET, SOCK_STREAM, IPPROTO_QUIC);

Note we did not opt for UDP ULP for QUIC implementation due to several
considerations:

- QUIC's connection Migration requires at least 2 UDP sockets for one
  QUIC connection at the same time, not to mention the multipath
  feature in one of its draft RFCs.

- In-Kernel QUIC, as a Transport Protocol, wants to provide users with
  the TCP or SCTP like Socket APIs, like connect()/listen()/accept()...
  Note that a single UDP socket might even be used for multiple QUIC
  connections.

The use of IPPROTO_QUIC type sockets over UDP tunnel will effectively
address these challenges and provides a more flexible and scalable
solution.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
---
 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 3b262487ec06..a7c05b064583 100644
--- a/include/linux/socket.h
+++ b/include/linux/socket.h
@@ -386,6 +386,7 @@ struct ucred {
 #define SOL_MCTP	285
 #define SOL_SMC		286
 #define SOL_VSOCK	287
+#define SOL_QUIC	288
 
 /* IPX options */
 #define IPX_TYPE	1
diff --git a/include/uapi/linux/in.h b/include/uapi/linux/in.h
index ced0fc3c3aa5..34becd90d3a6 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_QUIC = 261,		/* A UDP-Based Multiplexed and Secure Transport	*/
+#define IPPROTO_QUIC		IPPROTO_QUIC
   IPPROTO_MPTCP = 262,		/* Multipath TCP connection		*/
 #define IPPROTO_MPTCP		IPPROTO_MPTCP
   IPPROTO_MAX
-- 
2.47.1