net: implement a SO_PROTOCOL getsockoption

Similar to SO_TYPE returning the socket type, SO_PROTOCOL allows to
retrieve the protocol used with a given socket.

I am not quite sure why we have that-many copies of socket.h, and why
the values are not the same on all arches either, but for where hex
numbers dominate, I use 0x1029 for SO_PROTOCOL as that seems to be
the next free unused number across a bunch of operating systems, or
so Google results make me want to believe. SO_PROTOCOL for others
just uses the next free Linux number, 38.
Signed-off-by: Jan Engelhardt <jengelh@medozas.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

arch/alpha/include/asm/socket.h

@@ -32,6 +32,7 @@
 #define	SO_RCVTIMEO	0x1012
 #define	SO_SNDTIMEO	0x1013
 #define SO_ACCEPTCONN	0x1014
+#define SO_PROTOCOL	0x1028
 
 /* linux-specific, might as well be the same as on i386 */
 #define SO_NO_CHECK	11

arch/arm/include/asm/socket.h

@@ -57,4 +57,6 @@
 #define SO_TIMESTAMPING		37
 #define SCM_TIMESTAMPING	SO_TIMESTAMPING
 
+#define SO_PROTOCOL		38
+
 #endif /* _ASM_SOCKET_H */

arch/avr32/include/asm/socket.h

@@ -57,4 +57,6 @@
 #define SO_TIMESTAMPING		37
 #define SCM_TIMESTAMPING	SO_TIMESTAMPING
 
+#define SO_PROTOCOL		38
+
 #endif /* __ASM_AVR32_SOCKET_H */

arch/cris/include/asm/socket.h

@@ -59,6 +59,8 @@
 #define SO_TIMESTAMPING		37
 #define SCM_TIMESTAMPING	SO_TIMESTAMPING
 
+#define SO_PROTOCOL		38
+
 #endif /* _ASM_SOCKET_H */
 
 

arch/frv/include/asm/socket.h

@@ -57,5 +57,7 @@
 #define SO_TIMESTAMPING		37
 #define SCM_TIMESTAMPING	SO_TIMESTAMPING
 
+#define SO_PROTOCOL		38
+
 #endif /* _ASM_SOCKET_H */
 

arch/h8300/include/asm/socket.h

@@ -57,4 +57,6 @@
 #define SO_TIMESTAMPING		37
 #define SCM_TIMESTAMPING	SO_TIMESTAMPING
 
+#define SO_PROTOCOL		38
+
 #endif /* _ASM_SOCKET_H */

arch/ia64/include/asm/socket.h

@@ -66,4 +66,6 @@
 #define SO_TIMESTAMPING		37
 #define SCM_TIMESTAMPING	SO_TIMESTAMPING
 
+#define SO_PROTOCOL		38
+
 #endif /* _ASM_IA64_SOCKET_H */

arch/m32r/include/asm/socket.h

@@ -57,4 +57,6 @@
 #define SO_TIMESTAMPING		37
 #define SCM_TIMESTAMPING	SO_TIMESTAMPING
 
+#define SO_PROTOCOL		38
+
 #endif /* _ASM_M32R_SOCKET_H */

arch/m68k/include/asm/socket.h

@@ -57,4 +57,6 @@
 #define SO_TIMESTAMPING		37
 #define SCM_TIMESTAMPING	SO_TIMESTAMPING
 
+#define SO_PROTOCOL		38
+
 #endif /* _ASM_SOCKET_H */

arch/microblaze/include/asm/socket.h

@@ -66,4 +66,6 @@
 #define SO_TIMESTAMPING		37
 #define SCM_TIMESTAMPING	SO_TIMESTAMPING
 
+#define SO_PROTOCOL		38
+
 #endif /* _ASM_MICROBLAZE_SOCKET_H */

arch/mips/include/asm/socket.h

@@ -42,6 +42,7 @@ To add: #define SO_REUSEPORT 0x0200	/* Allow local address and port reuse.  */
 #define SO_SNDTIMEO	0x1005	/* send timeout */
 #define SO_RCVTIMEO 	0x1006	/* receive timeout */
 #define SO_ACCEPTCONN	0x1009
+#define SO_PROTOCOL	0x1028	/* protocol type */
 
 /* linux-specific, might as well be the same as on i386 */
 #define SO_NO_CHECK	11

arch/mn10300/include/asm/socket.h

@@ -57,4 +57,6 @@
 #define SO_TIMESTAMPING		37
 #define SCM_TIMESTAMPING	SO_TIMESTAMPING
 
+#define SO_PROTOCOL		38
+
 #endif /* _ASM_SOCKET_H */

arch/parisc/include/asm/socket.h

@@ -24,6 +24,7 @@
 #define SO_RCVTIMEO	0x1006
 #define SO_ERROR	0x1007
 #define SO_TYPE		0x1008
+#define SO_PROTOCOL	0x1028
 #define SO_PEERNAME	0x2000
 
 #define SO_NO_CHECK	0x400b

arch/powerpc/include/asm/socket.h

@@ -64,4 +64,6 @@
 #define SO_TIMESTAMPING		37
 #define SCM_TIMESTAMPING	SO_TIMESTAMPING
 
+#define SO_PROTOCOL		38
+
 #endif	/* _ASM_POWERPC_SOCKET_H */

arch/s390/include/asm/socket.h

@@ -65,4 +65,6 @@
 #define SO_TIMESTAMPING		37
 #define SCM_TIMESTAMPING	SO_TIMESTAMPING
 
+#define SO_PROTOCOL		38
+
 #endif /* _ASM_SOCKET_H */

arch/sparc/include/asm/socket.h

@@ -29,6 +29,8 @@
 #define SO_RCVBUFFORCE	0x100b
 #define SO_ERROR	0x1007
 #define SO_TYPE		0x1008
+#define SO_PROTOCOL	0x1028
+
 
 /* Linux specific, keep the same. */
 #define SO_NO_CHECK	0x000b

arch/x86/include/asm/socket.h

@@ -57,4 +57,6 @@
 #define SO_TIMESTAMPING		37
 #define SCM_TIMESTAMPING	SO_TIMESTAMPING
 
+#define SO_PROTOCOL		38
+
 #endif /* _ASM_X86_SOCKET_H */

arch/xtensa/include/asm/socket.h

@@ -68,4 +68,6 @@
 #define SO_TIMESTAMPING		37
 #define SCM_TIMESTAMPING	SO_TIMESTAMPING
 
+#define SO_PROTOCOL		38
+
 #endif	/* _XTENSA_SOCKET_H */

include/asm-generic/socket.h

@@ -60,4 +60,6 @@
 #define SO_TIMESTAMPING		37
 #define SCM_TIMESTAMPING	SO_TIMESTAMPING
 
+#define SO_PROTOCOL		38
+
 #endif /* __ASM_GENERIC_SOCKET_H */

net/core/sock.c

@@ -482,6 +482,7 @@ int sock_setsockopt(struct socket *sock, int level, int optname,
 		sk->sk_reuse = valbool;
 		break;
 	case SO_TYPE:
+	case SO_PROTOCOL:
 	case SO_ERROR:
 		ret = -ENOPROTOOPT;
 		break;
@@ -764,6 +765,10 @@ int sock_getsockopt(struct socket *sock, int level, int optname,
 		v.val = sk->sk_type;
 		break;
 
+	case SO_PROTOCOL:
+		v.val = sk->sk_protocol;
+		break;
+
 	case SO_ERROR:
 		v.val = -sock_error(sk);
 		if (v.val == 0)