BACKPORT [FROMLIST] New getsockopt option to get socket cookie

Cherry-pick from linux net-next branch commit
http://patchwork.ozlabs.org/patch/747590/

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/

Test: Unit test added in kernel/tests

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>
diff --git a/arch/alpha/include/uapi/asm/socket.h b/arch/alpha/include/uapi/asm/socket.h
index 9e46d6e..fa47df6a 100644
--- a/arch/alpha/include/uapi/asm/socket.h
+++ b/arch/alpha/include/uapi/asm/socket.h
@@ -97,4 +97,6 @@
 
 #define SO_CNX_ADVICE		53
 
+#define SO_COOKIE		57
+
 #endif /* _UAPI_ASM_SOCKET_H */
diff --git a/arch/avr32/include/uapi/asm/socket.h b/arch/avr32/include/uapi/asm/socket.h
index 1fd147f..5f10f9b 100644
--- a/arch/avr32/include/uapi/asm/socket.h
+++ b/arch/avr32/include/uapi/asm/socket.h
@@ -90,4 +90,6 @@
 
 #define SO_CNX_ADVICE		53
 
+#define SO_COOKIE		57
+
 #endif /* _UAPI__ASM_AVR32_SOCKET_H */
diff --git a/arch/frv/include/uapi/asm/socket.h b/arch/frv/include/uapi/asm/socket.h
index afbc98f0..ed960d3 100644
--- a/arch/frv/include/uapi/asm/socket.h
+++ b/arch/frv/include/uapi/asm/socket.h
@@ -90,5 +90,7 @@
 
 #define SO_CNX_ADVICE		53
 
+#define SO_COOKIE		57
+
 #endif /* _ASM_SOCKET_H */
 
diff --git a/arch/ia64/include/uapi/asm/socket.h b/arch/ia64/include/uapi/asm/socket.h
index 0018fad..9790d13 100644
--- a/arch/ia64/include/uapi/asm/socket.h
+++ b/arch/ia64/include/uapi/asm/socket.h
@@ -99,4 +99,6 @@
 
 #define SO_CNX_ADVICE		53
 
+#define SO_COOKIE		57
+
 #endif /* _ASM_IA64_SOCKET_H */
diff --git a/arch/m32r/include/uapi/asm/socket.h b/arch/m32r/include/uapi/asm/socket.h
index 5fe42fc..ad25676 100644
--- a/arch/m32r/include/uapi/asm/socket.h
+++ b/arch/m32r/include/uapi/asm/socket.h
@@ -90,4 +90,6 @@
 
 #define SO_CNX_ADVICE		53
 
+#define SO_COOKIE		57
+
 #endif /* _ASM_M32R_SOCKET_H */
diff --git a/arch/mips/include/uapi/asm/socket.h b/arch/mips/include/uapi/asm/socket.h
index 2027240a..2f106d0 100644
--- a/arch/mips/include/uapi/asm/socket.h
+++ b/arch/mips/include/uapi/asm/socket.h
@@ -108,4 +108,6 @@
 
 #define SO_CNX_ADVICE		53
 
+#define SO_COOKIE		57
+
 #endif /* _UAPI_ASM_SOCKET_H */
diff --git a/arch/mn10300/include/uapi/asm/socket.h b/arch/mn10300/include/uapi/asm/socket.h
index 5129f23..69f9618 100644
--- a/arch/mn10300/include/uapi/asm/socket.h
+++ b/arch/mn10300/include/uapi/asm/socket.h
@@ -90,4 +90,6 @@
 
 #define SO_CNX_ADVICE		53
 
+#define SO_COOKIE		57
+
 #endif /* _ASM_SOCKET_H */
diff --git a/arch/parisc/include/uapi/asm/socket.h b/arch/parisc/include/uapi/asm/socket.h
index 9c935d7..b96a193 100644
--- a/arch/parisc/include/uapi/asm/socket.h
+++ b/arch/parisc/include/uapi/asm/socket.h
@@ -89,4 +89,6 @@
 
 #define SO_CNX_ADVICE		0x402E
 
+#define SO_COOKIE		0x4032
+
 #endif /* _UAPI_ASM_SOCKET_H */
diff --git a/arch/powerpc/include/uapi/asm/socket.h b/arch/powerpc/include/uapi/asm/socket.h
index 1672e33..e78550f 100644
--- a/arch/powerpc/include/uapi/asm/socket.h
+++ b/arch/powerpc/include/uapi/asm/socket.h
@@ -97,4 +97,6 @@
 
 #define SO_CNX_ADVICE		53
 
+#define SO_COOKIE		57
+
 #endif	/* _ASM_POWERPC_SOCKET_H */
diff --git a/arch/s390/include/uapi/asm/socket.h b/arch/s390/include/uapi/asm/socket.h
index 41b51c2..04fe908 100644
--- a/arch/s390/include/uapi/asm/socket.h
+++ b/arch/s390/include/uapi/asm/socket.h
@@ -96,4 +96,6 @@
 
 #define SO_CNX_ADVICE		53
 
+#define SO_COOKIE		57
+
 #endif /* _ASM_SOCKET_H */
diff --git a/arch/sparc/include/uapi/asm/socket.h b/arch/sparc/include/uapi/asm/socket.h
index 31aede3..de15f0a 100644
--- a/arch/sparc/include/uapi/asm/socket.h
+++ b/arch/sparc/include/uapi/asm/socket.h
@@ -86,6 +86,8 @@
 
 #define SO_CNX_ADVICE		0x0037
 
+#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
diff --git a/arch/xtensa/include/uapi/asm/socket.h b/arch/xtensa/include/uapi/asm/socket.h
index 81435d9..fc7ca28 100644
--- a/arch/xtensa/include/uapi/asm/socket.h
+++ b/arch/xtensa/include/uapi/asm/socket.h
@@ -101,4 +101,6 @@
 
 #define SO_CNX_ADVICE		53
 
+#define SO_COOKIE		57
+
 #endif	/* _XTENSA_SOCKET_H */
diff --git a/include/uapi/asm-generic/socket.h b/include/uapi/asm-generic/socket.h
index 67d632f..2d078c20 100644
--- a/include/uapi/asm-generic/socket.h
+++ b/include/uapi/asm-generic/socket.h
@@ -92,4 +92,6 @@
 
 #define SO_CNX_ADVICE		53
 
+#define SO_COOKIE		57
+
 #endif /* __ASM_GENERIC_SOCKET_H */
diff --git a/net/core/sock.c b/net/core/sock.c
index 19562f7..facffab 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -1034,6 +1034,7 @@
 
 	union {
 		int val;
+		u64 val64;
 		struct linger ling;
 		struct timeval tm;
 	} v;
@@ -1264,6 +1265,13 @@
 		v.val = sk->sk_incoming_cpu;
 		break;
 
+
+	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).