[RFC PATCH 5/5] syscall: sys_fbind() introduced

[Stanislav Kinsbursky <skinsbursky@parallels.com>]

This syscall allows to bind socket to specified file descriptor.
Descriptor can be gained by simple open with O_PATH flag.
Socket node can be created by sys_mknod().

Signed-off-by: Stanislav Kinsbursky <skinsbursky@parallels.com>
---
 arch/x86/syscalls/syscall_32.tbl |    1 +
 arch/x86/syscalls/syscall_64.tbl |    1 +
 include/linux/syscalls.h         |    1 +
 kernel/sys_ni.c                  |    3 +++
 net/socket.c                     |   25 +++++++++++++++++++++++++
 5 files changed, 31 insertions(+), 0 deletions(-)

diff --git a/arch/x86/syscalls/syscall_32.tbl b/arch/x86/syscalls/syscall_32.tbl
index 7a35a6e..9594b82 100644
--- a/arch/x86/syscalls/syscall_32.tbl
+++ b/arch/x86/syscalls/syscall_32.tbl
@@ -356,3 +356,4 @@
 347	i386	process_vm_readv	sys_process_vm_readv		compat_sys_process_vm_readv
 348	i386	process_vm_writev	sys_process_vm_writev		compat_sys_process_vm_writev
 349	i386	kcmp			sys_kcmp
+350	i386	fbind			sys_fbind
diff --git a/arch/x86/syscalls/syscall_64.tbl b/arch/x86/syscalls/syscall_64.tbl
index 51171ae..f964df8 100644
--- a/arch/x86/syscalls/syscall_64.tbl
+++ b/arch/x86/syscalls/syscall_64.tbl
@@ -319,6 +319,7 @@
 310	64	process_vm_readv	sys_process_vm_readv
 311	64	process_vm_writev	sys_process_vm_writev
 312	64	kcmp			sys_kcmp
+313	common	fbind			sys_fbind
 
 #
 # x32-specific system call numbers start at 512 to avoid cache impact
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 19439c7..9e78fa4 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -602,6 +602,7 @@ asmlinkage long sys_setsockopt(int fd, int level, int optname,
 asmlinkage long sys_getsockopt(int fd, int level, int optname,
 				char __user *optval, int __user *optlen);
 asmlinkage long sys_bind(int, struct sockaddr __user *, int);
+asmlinkage long sys_fbind(int, int);
 asmlinkage long sys_connect(int, struct sockaddr __user *, int);
 asmlinkage long sys_accept(int, struct sockaddr __user *, int __user *);
 asmlinkage long sys_accept4(int, struct sockaddr __user *, int __user *, int);
diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
index dbff751..30c393a 100644
--- a/kernel/sys_ni.c
+++ b/kernel/sys_ni.c
@@ -206,3 +206,6 @@ cond_syscall(compat_sys_open_by_handle_at);
 
 /* compare kernel pointers */
 cond_syscall(sys_kcmp);
+
+cond_syscall(sys_fbind);
+
diff --git a/net/socket.c b/net/socket.c
index 6e0ccc0..67d9795 100644
--- a/net/socket.c
+++ b/net/socket.c
@@ -1432,6 +1432,31 @@ out:
 	return err;
 }
 
+SYSCALL_DEFINE2(fbind, int, fd, int, sk_fd)
+{
+	struct socket *sock;
+	int err, fput_sk, fput_fd;
+	struct file *file;
+
+	sock = sockfd_lookup_light(sk_fd, &err, &fput_sk);
+	if (!sock)
+		return err;
+
+	err = -EBADF;
+	file = fget_raw_light(fd, &fput_fd);
+	if (!file)
+		goto out_put_sk;
+
+	err = -EINVAL;
+	if (sock->ops->fbind)
+		err = sock->ops->fbind(file, sock);
+
+	fput_light(file, fput_fd);
+out_put_sk:
+	fput_light(sock->file, fput_sk);
+	return err;
+}
+
 /*
  *	Bind a name to a socket. Nothing much to do here since it's
  *	the protocol's responsibility to handle the local address.