docs: networking: convert tuntap.txt to ReST

- add SPDX header;
- use copyright symbol;
- adjust titles and chapters, adding proper markups;
- mark code blocks and literals as such;
- adjust identation, whitespaces and blank lines where needed;
- add to networking/index.rst.
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

Documentation/networking/index.rst

@@ -111,6 +111,7 @@ Contents:
    team
    timestamping
    tproxy
+   tuntap
 
 .. only::  subproject and html
 

Documentation/networking/tuntap.txt → Documentation/networking/tuntap.rst

-Universal TUN/TAP device driver.
-Copyright (C) 1999-2000 Maxim Krasnyansky <max_mk@yahoo.com>
+.. SPDX-License-Identifier: GPL-2.0
+.. include:: <isonum.txt>
+
+===============================
+Universal TUN/TAP device driver
+===============================
+
+Copyright |copy| 1999-2000 Maxim Krasnyansky <max_mk@yahoo.com>
 
   Linux, Solaris drivers
-  Copyright (C) 1999-2000 Maxim Krasnyansky <max_mk@yahoo.com>
+  Copyright |copy| 1999-2000 Maxim Krasnyansky <max_mk@yahoo.com>
 
   FreeBSD TAP driver
-  Copyright (c) 1999-2000 Maksim Yevmenkin <m_evmenkin@yahoo.com>
+  Copyright |copy| 1999-2000 Maksim Yevmenkin <m_evmenkin@yahoo.com>
 
   Revision of this document 2002 by Florian Thiel <florian.thiel@gmx.net>
 
 1. Description
+==============
+
   TUN/TAP provides packet reception and transmission for user space programs.
   It can be seen as a simple Point-to-Point or Ethernet device, which,
   instead of receiving packets from physical media, receives them from
@@ -34,12 +42,17 @@ Copyright (C) 1999-2000 Maxim Krasnyansky <max_mk@yahoo.com>
   However, the best example is VTun http://vtun.sourceforge.net :))
 
 2. Configuration
-  Create device node:
+================
+
+  Create device node::
+
      mkdir /dev/net (if it doesn't exist already)
      mknod /dev/net/tun c 10 200
 
-  Set permissions:
+  Set permissions::
+
      e.g. chmod 0666 /dev/net/tun
+
   There's no harm in allowing the device to be accessible by non-root users,
   since CAP_NET_ADMIN is required for creating network devices or for
   connecting to network devices which aren't owned by the user in question.
@@ -54,7 +67,9 @@ Copyright (C) 1999-2000 Maxim Krasnyansky <max_mk@yahoo.com>
      first access.
 
   Manual loading
-     insert the module by hand:
+
+     insert the module by hand::
+
 	modprobe tun
 
   If you do it the latter way, you have to load the module every time you
@@ -62,12 +77,15 @@ Copyright (C) 1999-2000 Maxim Krasnyansky <max_mk@yahoo.com>
   /dev/net/tun is being opened.
 
 3. Program interface
-  3.1 Network device allocation:
+====================
+
+3.1 Network device allocation
+-----------------------------
 
-  char *dev should be the name of the device with a format string (e.g.
-  "tun%d"), but (as far as I can see) this can be any valid network device name.
-  Note that the character pointer becomes overwritten with the real device name
-  (e.g. "tun0")
+``char *dev`` should be the name of the device with a format string (e.g.
+"tun%d"), but (as far as I can see) this can be any valid network device name.
+Note that the character pointer becomes overwritten with the real device name
+(e.g. "tun0")::
 
   #include <linux/if.h>
   #include <linux/if_tun.h>
@@ -99,24 +117,30 @@ Copyright (C) 1999-2000 Maxim Krasnyansky <max_mk@yahoo.com>
       return fd;
   }
 
-  3.2 Frame format:
-  If flag IFF_NO_PI is not set each frame format is: 
+3.2 Frame format
+----------------
+
+If flag IFF_NO_PI is not set each frame format is::
+
      Flags [2 bytes]
      Proto [2 bytes]
      Raw protocol(IP, IPv6, etc) frame.
 
-  3.3 Multiqueue tuntap interface:
+3.3 Multiqueue tuntap interface
+-------------------------------
+
+From version 3.8, Linux supports multiqueue tuntap which can uses multiple
+file descriptors (queues) to parallelize packets sending or receiving. The
+device allocation is the same as before, and if user wants to create multiple
+queues, TUNSETIFF with the same device name must be called many times with
+IFF_MULTI_QUEUE flag.
 
-  From version 3.8, Linux supports multiqueue tuntap which can uses multiple
-  file descriptors (queues) to parallelize packets sending or receiving. The
-  device allocation is the same as before, and if user wants to create multiple
-  queues, TUNSETIFF with the same device name must be called many times with
-  IFF_MULTI_QUEUE flag.
+``char *dev`` should be the name of the device, queues is the number of queues
+to be created, fds is used to store and return the file descriptors (queues)
+created to the caller. Each file descriptor were served as the interface of a
+queue which could be accessed by userspace.
 
-  char *dev should be the name of the device, queues is the number of queues to
-  be created, fds is used to store and return the file descriptors (queues)
-  created to the caller. Each file descriptor were served as the interface of a
-  queue which could be accessed by userspace.
+::
 
   #include <linux/if.h>
   #include <linux/if_tun.h>
@@ -157,13 +181,13 @@ Copyright (C) 1999-2000 Maxim Krasnyansky <max_mk@yahoo.com>
       return err;
   }
 
-  A new ioctl(TUNSETQUEUE) were introduced to enable or disable a queue. When
-  calling it with IFF_DETACH_QUEUE flag, the queue were disabled. And when
-  calling it with IFF_ATTACH_QUEUE flag, the queue were enabled. The queue were
-  enabled by default after it was created through TUNSETIFF.
+A new ioctl(TUNSETQUEUE) were introduced to enable or disable a queue. When
+calling it with IFF_DETACH_QUEUE flag, the queue were disabled. And when
+calling it with IFF_ATTACH_QUEUE flag, the queue were enabled. The queue were
+enabled by default after it was created through TUNSETIFF.
 
-  fd is the file descriptor (queue) that we want to enable or disable, when
-  enable is true we enable it, otherwise we disable it
+fd is the file descriptor (queue) that we want to enable or disable, when
+enable is true we enable it, otherwise we disable it::
 
   #include <linux/if.h>
   #include <linux/if_tun.h>
@@ -182,15 +206,19 @@ Copyright (C) 1999-2000 Maxim Krasnyansky <max_mk@yahoo.com>
       return ioctl(fd, TUNSETQUEUE, (void *)&ifr);
   }
 
-Universal TUN/TAP device driver Frequently Asked Question.
+Universal TUN/TAP device driver Frequently Asked Question
+=========================================================
 
 1. What platforms are supported by TUN/TAP driver ?
+
 Currently driver has been written for 3 Unices:
-   Linux kernels 2.2.x, 2.4.x 
-   FreeBSD 3.x, 4.x, 5.x
-   Solaris 2.6, 7.0, 8.0
+
+  - Linux kernels 2.2.x, 2.4.x
+  - FreeBSD 3.x, 4.x, 5.x
+  - Solaris 2.6, 7.0, 8.0
 
 2. What is TUN/TAP driver used for?
+
 As mentioned above, main purpose of TUN/TAP driver is tunneling.
 It is used by VTun (http://vtun.sourceforge.net).
 
@@ -199,6 +227,7 @@ Another interesting application using TUN/TAP is pipsecd
 implementation that can use complete kernel routing (unlike FreeS/WAN).
 
 3. How does Virtual network device actually work ?
+
 Virtual network device can be viewed as a simple Point-to-Point or
 Ethernet device, which instead of receiving packets from a physical
 media, receives them from user space program and instead of sending
@@ -212,16 +241,19 @@ and decrypts the data received and writes the packet to the TAP device,
 the kernel handles the packet like it came from real physical device.
 
 4. What is the difference between TUN driver and TAP driver?
+
 TUN works with IP frames. TAP works with Ethernet frames.
 
 This means that you have to read/write IP packets when you are using tun and
 ethernet frames when using tap.
 
 5. What is the difference between BPF and TUN/TAP driver?
+
 BPF is an advanced packet filter. It can be attached to existing
 network interface. It does not provide a virtual network interface.
 A TUN/TAP driver does provide a virtual network interface and it is possible
 to attach BPF to this interface.
 
 6. Does TAP driver support kernel Ethernet bridging?
+
 Yes. Linux and FreeBSD drivers support Ethernet bridging.

MAINTAINERS

@@ -17161,7 +17161,7 @@ TUN/TAP driver
 M:	Maxim Krasnyansky <maxk@qti.qualcomm.com>
 S:	Maintained
 W:	http://vtun.sourceforge.net/tun
-F:	Documentation/networking/tuntap.txt
+F:	Documentation/networking/tuntap.rst
 F:	arch/um/os-Linux/drivers/
 
 TURBOCHANNEL SUBSYSTEM

drivers/net/Kconfig

@@ -355,7 +355,7 @@ config TUN
 	  devices, driver will automatically delete tunXX or tapXX device and
 	  all routes corresponding to it.
 
-	  Please read <file:Documentation/networking/tuntap.txt> for more
+	  Please read <file:Documentation/networking/tuntap.rst> for more
 	  information.
 
 	  To compile this driver as a module, choose M here: the module