New getsockopt option to get socket cookie

Introduce a new getsockopt operation to retrieve the socket cookie
for a specific socket based on the socket fd.  It returns a unique
non-decreasing cookie for each socket.
Tested: https://android-review.googlesource.com/#/c/358163/

Acked-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Chenbo Feng <fengc@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

arch/alpha/include/uapi/asm/socket.h

@@ -103,4 +103,6 @@
 
 #define SO_INCOMING_NAPI_ID	56
 
+#define SO_COOKIE		57
+
 #endif /* _UAPI_ASM_SOCKET_H */

arch/avr32/include/uapi/asm/socket.h

@@ -96,4 +96,6 @@
 
 #define SO_INCOMING_NAPI_ID	56
 
+#define SO_COOKIE		57
+
 #endif /* _UAPI__ASM_AVR32_SOCKET_H */

arch/frv/include/uapi/asm/socket.h

@@ -96,5 +96,7 @@
 
 #define SO_INCOMING_NAPI_ID	56
 
+#define SO_COOKIE		57
+
 #endif /* _ASM_SOCKET_H */
 

arch/ia64/include/uapi/asm/socket.h

@@ -105,4 +105,6 @@
 
 #define SO_INCOMING_NAPI_ID	56
 
+#define SO_COOKIE		57
+
 #endif /* _ASM_IA64_SOCKET_H */

arch/m32r/include/uapi/asm/socket.h

@@ -96,4 +96,6 @@
 
 #define SO_INCOMING_NAPI_ID	56
 
+#define SO_COOKIE		57
+
 #endif /* _ASM_M32R_SOCKET_H */

arch/mips/include/uapi/asm/socket.h

@@ -114,4 +114,6 @@
 
 #define SO_INCOMING_NAPI_ID	56
 
+#define SO_COOKIE		57
+
 #endif /* _UAPI_ASM_SOCKET_H */

arch/mn10300/include/uapi/asm/socket.h

@@ -96,4 +96,6 @@
 
 #define SO_INCOMING_NAPI_ID	56
 
+#define SO_COOKIE		57
+
 #endif /* _ASM_SOCKET_H */

arch/parisc/include/uapi/asm/socket.h

@@ -95,4 +95,6 @@
 
 #define SO_INCOMING_NAPI_ID	0x4031
 
+#define SO_COOKIE		0x4032
+
 #endif /* _UAPI_ASM_SOCKET_H */

arch/powerpc/include/uapi/asm/socket.h

@@ -103,4 +103,6 @@
 
 #define SO_INCOMING_NAPI_ID	56
 
+#define SO_COOKIE		57
+
 #endif	/* _ASM_POWERPC_SOCKET_H */

arch/s390/include/uapi/asm/socket.h

@@ -102,4 +102,6 @@
 
 #define SO_INCOMING_NAPI_ID	56
 
+#define SO_COOKIE		57
+
 #endif /* _ASM_SOCKET_H */

arch/sparc/include/uapi/asm/socket.h

@@ -92,6 +92,8 @@
 
 #define SO_INCOMING_NAPI_ID	0x003a
 
+#define SO_COOKIE		0x003b
+
 /* Security levels - as per NRL IPv6 - don't actually do anything */
 #define SO_SECURITY_AUTHENTICATION		0x5001
 #define SO_SECURITY_ENCRYPTION_TRANSPORT	0x5002

arch/xtensa/include/uapi/asm/socket.h

@@ -107,4 +107,6 @@
 
 #define SO_INCOMING_NAPI_ID	56
 
+#define SO_COOKIE		57
+
 #endif	/* _XTENSA_SOCKET_H */

include/uapi/asm-generic/socket.h

@@ -98,4 +98,6 @@
 
 #define SO_INCOMING_NAPI_ID	56
 
+#define SO_COOKIE		57
+
 #endif /* __ASM_GENERIC_SOCKET_H */

net/core/sock.c

@@ -1083,6 +1083,7 @@ int sock_getsockopt(struct socket *sock, int level, int optname,
 
 	union {
 		int val;
+		u64 val64;
 		struct linger ling;
 		struct timeval tm;
 	} v;
@@ -1340,6 +1341,13 @@ int sock_getsockopt(struct socket *sock, int level, int optname,
 		break;
 #endif
 
+	case SO_COOKIE:
+		lv = sizeof(u64);
+		if (len < lv)
+			return -EINVAL;
+		v.val64 = sock_gen_cookie(sk);
+		break;
+
 	default:
 		/* We implement the SO_SNDLOWAT etc to not be settable
 		 * (1003.1g 7).