sock: Introduce the SO_PEEK_OFF sock option

This one specifies where to start MSG_PEEK-ing queue data from. When
set to negative value means that MSG_PEEK works as ususally -- peeks
from the head of the queue always.

When some bytes are peeked from queue and the peeking offset is non
negative it is moved forward so that the next peek will return next
portion of data.

When non-peeking recvmsg occurs and the peeking offset is non negative
is is moved backward so that the next peek will still peek the proper
data (i.e. the one that would have been picked if there were no non
peeking recv in between).

The offset is set using per-proto opteration to let the protocol handle
the locking issues and to check whether the peeking offset feature is
supported by the protocol the socket belongs to.

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

20 files changed, 56 insertions, 0 deletions

diff --git a/arch/alpha/include/asm/socket.h b/arch/alpha/include/asm/socket.h
index 082355f159e6..16449d330dae 100644
--- a/arch/alpha/include/asm/socket.h
+++ b/arch/alpha/include/asm/socket.h
@@ -71,6 +71,7 @@
 
 #define SO_WIFI_STATUS          41
 #define SCM_WIFI_STATUS         SO_WIFI_STATUS
+#define SO_PEEK_OFF             42
 
 /* O_NONBLOCK clashes with the bits used for socket types.  Therefore we
  * have to define SOCK_NONBLOCK to a different value here.
diff --git a/arch/arm/include/asm/socket.h b/arch/arm/include/asm/socket.h
index dec6f9afb3cf..d958c74e5260 100644
--- a/arch/arm/include/asm/socket.h
+++ b/arch/arm/include/asm/socket.h
@@ -64,5 +64,6 @@
 
 #define SO_WIFI_STATUS          41
 #define SCM_WIFI_STATUS         SO_WIFI_STATUS
+#define SO_PEEK_OFF             42
 
 #endif /* _ASM_SOCKET_H */
diff --git a/arch/avr32/include/asm/socket.h b/arch/avr32/include/asm/socket.h
index 247b88c760be..30078f98b3ab 100644
--- a/arch/avr32/include/asm/socket.h
+++ b/arch/avr32/include/asm/socket.h
@@ -64,5 +64,6 @@
 
 #define SO_WIFI_STATUS          41
 #define SCM_WIFI_STATUS         SO_WIFI_STATUS
+#define SO_PEEK_OFF             42
 
 #endif /* __ASM_AVR32_SOCKET_H */
diff --git a/arch/cris/include/asm/socket.h b/arch/cris/include/asm/socket.h
index e269264df7c4..048aba64600c 100644
--- a/arch/cris/include/asm/socket.h
+++ b/arch/cris/include/asm/socket.h
@@ -66,6 +66,7 @@
 
 #define SO_WIFI_STATUS          41
 #define SCM_WIFI_STATUS         SO_WIFI_STATUS
+#define SO_PEEK_OFF             42
 
 #endif /* _ASM_SOCKET_H */
 
diff --git a/arch/frv/include/asm/socket.h b/arch/frv/include/asm/socket.h
index ce80fdadcce5..7a361810f3cc 100644
--- a/arch/frv/include/asm/socket.h
+++ b/arch/frv/include/asm/socket.h
@@ -64,6 +64,7 @@
 
 #define SO_WIFI_STATUS          41
 #define SCM_WIFI_STATUS         SO_WIFI_STATUS
+#define SO_PEEK_OFF             42
 
 #endif /* _ASM_SOCKET_H */
 
diff --git a/arch/h8300/include/asm/socket.h b/arch/h8300/include/asm/socket.h
index cf1daab6f27e..e7bbfcee5b99 100644
--- a/arch/h8300/include/asm/socket.h
+++ b/arch/h8300/include/asm/socket.h
@@ -64,5 +64,6 @@
 
 #define SO_WIFI_STATUS          41
 #define SCM_WIFI_STATUS         SO_WIFI_STATUS
+#define SO_PEEK_OFF             42
 
 #endif /* _ASM_SOCKET_H */
diff --git a/arch/ia64/include/asm/socket.h b/arch/ia64/include/asm/socket.h
index 4b03664e3fb5..ced62de9d5a9 100644
--- a/arch/ia64/include/asm/socket.h
+++ b/arch/ia64/include/asm/socket.h
@@ -73,5 +73,6 @@
 
 #define SO_WIFI_STATUS          41
 #define SCM_WIFI_STATUS         SO_WIFI_STATUS
+#define SO_PEEK_OFF             42
 
 #endif /* _ASM_IA64_SOCKET_H */
diff --git a/arch/m32r/include/asm/socket.h b/arch/m32r/include/asm/socket.h
index e8b8c5bb053c..696cb4c7ca4e 100644
--- a/arch/m32r/include/asm/socket.h
+++ b/arch/m32r/include/asm/socket.h
@@ -64,5 +64,6 @@
 
 #define SO_WIFI_STATUS          41
 #define SCM_WIFI_STATUS         SO_WIFI_STATUS
+#define SO_PEEK_OFF             42
 
 #endif /* _ASM_M32R_SOCKET_H */
diff --git a/arch/m68k/include/asm/socket.h b/arch/m68k/include/asm/socket.h
index d4708ce466e0..e8b41a6775f9 100644
--- a/arch/m68k/include/asm/socket.h
+++ b/arch/m68k/include/asm/socket.h
@@ -64,5 +64,6 @@
 
 #define SO_WIFI_STATUS          41
 #define SCM_WIFI_STATUS         SO_WIFI_STATUS
+#define SO_PEEK_OFF             42
 
 #endif /* _ASM_SOCKET_H */
diff --git a/arch/mips/include/asm/socket.h b/arch/mips/include/asm/socket.h
index ad5c0a7a02a7..52104872e9e3 100644
--- a/arch/mips/include/asm/socket.h
+++ b/arch/mips/include/asm/socket.h
@@ -84,6 +84,7 @@ To add: #define SO_REUSEPORT 0x0200	/* Allow local address and port reuse.  */
 
 #define SO_WIFI_STATUS          41
 #define SCM_WIFI_STATUS         SO_WIFI_STATUS
+#define SO_PEEK_OFF             42
 
 #ifdef __KERNEL__
 
diff --git a/arch/mn10300/include/asm/socket.h b/arch/mn10300/include/asm/socket.h
index 876356d78522..013fcc51698f 100644
--- a/arch/mn10300/include/asm/socket.h
+++ b/arch/mn10300/include/asm/socket.h
@@ -64,5 +64,6 @@
 
 #define SO_WIFI_STATUS          41
 #define SCM_WIFI_STATUS         SO_WIFI_STATUS
+#define SO_PEEK_OFF             42
 
 #endif /* _ASM_SOCKET_H */
diff --git a/arch/parisc/include/asm/socket.h b/arch/parisc/include/asm/socket.h
index d28c51b61067..f717c9bec16f 100644
--- a/arch/parisc/include/asm/socket.h
+++ b/arch/parisc/include/asm/socket.h
@@ -63,6 +63,7 @@
 
 #define SO_WIFI_STATUS          0x4022
 #define SCM_WIFI_STATUS         SO_WIFI_STATUS
+#define SO_PEEK_OFF             0x4023
 
 /* O_NONBLOCK clashes with the bits used for socket types.  Therefore we
  * have to define SOCK_NONBLOCK to a different value here.
diff --git a/arch/powerpc/include/asm/socket.h b/arch/powerpc/include/asm/socket.h
index 2fc2af8fbf59..fe1c0b478fd7 100644
--- a/arch/powerpc/include/asm/socket.h
+++ b/arch/powerpc/include/asm/socket.h
@@ -71,5 +71,6 @@
 
 #define SO_WIFI_STATUS          41
 #define SCM_WIFI_STATUS         SO_WIFI_STATUS
+#define SO_PEEK_OFF             42
 
 #endif  /* _ASM_POWERPC_SOCKET_H */
diff --git a/arch/s390/include/asm/socket.h b/arch/s390/include/asm/socket.h
index 67b5c1b14b51..581702fa1b0c 100644
--- a/arch/s390/include/asm/socket.h
+++ b/arch/s390/include/asm/socket.h
@@ -72,5 +72,6 @@
 
 #define SO_WIFI_STATUS          41
 #define SCM_WIFI_STATUS         SO_WIFI_STATUS
+#define SO_PEEK_OFF             42
 
 #endif /* _ASM_SOCKET_H */
diff --git a/arch/sparc/include/asm/socket.h b/arch/sparc/include/asm/socket.h
index 8af1b64168b3..68e2e2746f6f 100644
--- a/arch/sparc/include/asm/socket.h
+++ b/arch/sparc/include/asm/socket.h
@@ -60,6 +60,7 @@
 
 #define SO_WIFI_STATUS          0x0025
 #define SCM_WIFI_STATUS         SO_WIFI_STATUS
+#define SO_PEEK_OFF             0x0026
 
 /* Security levels - as per NRL IPv6 - don't actually do anything */
 #define SO_SECURITY_AUTHENTICATION              0x5001
diff --git a/arch/xtensa/include/asm/socket.h b/arch/xtensa/include/asm/socket.h
index bb06968be227..74818b161362 100644
--- a/arch/xtensa/include/asm/socket.h
+++ b/arch/xtensa/include/asm/socket.h
@@ -75,5 +75,6 @@
 
 #define SO_WIFI_STATUS          41
 #define SCM_WIFI_STATUS         SO_WIFI_STATUS
+#define SO_PEEK_OFF             42
 
 #endif  /* _XTENSA_SOCKET_H */
diff --git a/include/asm-generic/socket.h b/include/asm-generic/socket.h
index 49c1704173e7..d9aaac0c36d4 100644
--- a/include/asm-generic/socket.h
+++ b/include/asm-generic/socket.h
@@ -67,4 +67,5 @@
 
 #define SO_WIFI_STATUS          41
 #define SCM_WIFI_STATUS SO_WIFI_STATUS
+#define SO_PEEK_OFF             42
 #endif /* __ASM_GENERIC_SOCKET_H */
diff --git a/include/linux/net.h b/include/linux/net.h
index b29923006b11..be60c7f5e145 100644
--- a/include/linux/net.h
+++ b/include/linux/net.h
@@ -206,6 +206,7 @@ struct proto_ops {
                                       int offset, size_t size, int flags);
         ssize_t         (*splice_read)(struct socket *sock,  loff_t *ppos,
                                        struct pipe_inode_info *pipe, size_t len, unsigned int flags);
+        void            (*set_peek_off)(struct sock *sk, int val);
 };
 
 #define DECLARE_SOCKADDR(type, dst, src)        \
diff --git a/include/net/sock.h b/include/net/sock.h
index 91c1c8baf020..9c0553b9e451 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -357,6 +357,7 @@ struct sock {
         struct page             *sk_sndmsg_page;
         struct sk_buff          *sk_send_head;
         __u32                   sk_sndmsg_off;
+        __s32                   sk_peek_off;
         int                     sk_write_pending;
 #ifdef CONFIG_SECURITY
         void                    *sk_security;
@@ -373,6 +374,30 @@ struct sock {
         void                    (*sk_destruct)(struct sock *sk);
 };
 
+static inline int sk_peek_offset(struct sock *sk, int flags)
+{
+        if ((flags & MSG_PEEK) && (sk->sk_peek_off >= 0))
+                return sk->sk_peek_off;
+        else
+                return 0;
+}
+
+static inline void sk_peek_offset_bwd(struct sock *sk, int val)
+{
+        if (sk->sk_peek_off >= 0) {
+                if (sk->sk_peek_off >= val)
+                        sk->sk_peek_off -= val;
+                else
+                        sk->sk_peek_off = 0;
+        }
+}
+
+static inline void sk_peek_offset_fwd(struct sock *sk, int val)
+{
+        if (sk->sk_peek_off >= 0)
+                sk->sk_peek_off += val;
+}
+
 /*
  * Hashed lists helper routines
  */
diff --git a/net/core/sock.c b/net/core/sock.c
index 02f8dfe320b7..19942d4bb6e6 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -793,6 +793,12 @@ set_rcvbuf:
                 sock_valbool_flag(sk, SOCK_WIFI_STATUS, valbool);
                 break;
 
+        case SO_PEEK_OFF:
+                if (sock->ops->set_peek_off)
+                        sock->ops->set_peek_off(sk, val);
+                else
+                        ret = -EOPNOTSUPP;
+                break;
         default:
                 ret = -ENOPROTOOPT;
                 break;
@@ -1018,6 +1024,12 @@ int sock_getsockopt(struct socket *sock, int level, int optname,
                 v.val = !!sock_flag(sk, SOCK_WIFI_STATUS);
                 break;
 
+        case SO_PEEK_OFF:
+                if (!sock->ops->set_peek_off)
+                        return -EOPNOTSUPP;
+
+                v.val = sk->sk_peek_off;
+                break;
         default:
                 return -ENOPROTOOPT;
         }
@@ -2092,6 +2104,7 @@ void sock_init_data(struct socket *sock, struct sock *sk)
 
         sk->sk_sndmsg_page      =       NULL;
         sk->sk_sndmsg_off       =       0;
+        sk->sk_peek_off         =       -1;
 
         sk->sk_peer_pid         =       NULL;
         sk->sk_peer_cred        =       NULL;