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Diffstat (limited to 'Documentation/networking/tuntap.txt')
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diff --git a/Documentation/networking/tuntap.txt b/Documentation/networking/tuntap.txt deleted file mode 100644 index 0104830d5075..000000000000 --- a/Documentation/networking/tuntap.txt +++ /dev/null @@ -1,227 +0,0 @@ -Universal TUN/TAP device driver. -Copyright (C) 1999-2000 Maxim Krasnyansky <max_mk@yahoo.com> - - Linux, Solaris drivers - Copyright (C) 1999-2000 Maxim Krasnyansky <max_mk@yahoo.com> - - FreeBSD TAP driver - Copyright (c) 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 - user space program and instead of sending packets via physical media - writes them to the user space program. - - In order to use the driver a program has to open /dev/net/tun and issue a - corresponding ioctl() to register a network device with the kernel. A network - device will appear as tunXX or tapXX, depending on the options chosen. When - the program closes the file descriptor, the network device and all - corresponding routes will disappear. - - Depending on the type of device chosen the userspace program has to read/write - IP packets (with tun) or ethernet frames (with tap). Which one is being used - depends on the flags given with the ioctl(). - - The package from http://vtun.sourceforge.net/tun contains two simple examples - for how to use tun and tap devices. Both programs work like a bridge between - two network interfaces. - br_select.c - bridge based on select system call. - br_sigio.c - bridge based on async io and SIGIO signal. - However, the best example is VTun http://vtun.sourceforge.net :)) - -2. Configuration - Create device node: - mkdir /dev/net (if it doesn't exist already) - mknod /dev/net/tun c 10 200 - - 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. - If you want to create persistent devices and give ownership of them to - unprivileged users, then you need the /dev/net/tun device to be usable by - those users. - - Driver module autoloading - - Make sure that "Kernel module loader" - module auto-loading - support is enabled in your kernel. The kernel should load it on - first access. - - Manual loading - insert the module by hand: - modprobe tun - - If you do it the latter way, you have to load the module every time you - need it, if you do it the other way it will be automatically loaded when - /dev/net/tun is being opened. - -3. Program interface - 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") - - #include <linux/if.h> - #include <linux/if_tun.h> - - int tun_alloc(char *dev) - { - struct ifreq ifr; - int fd, err; - - if( (fd = open("/dev/net/tun", O_RDWR)) < 0 ) - return tun_alloc_old(dev); - - memset(&ifr, 0, sizeof(ifr)); - - /* Flags: IFF_TUN - TUN device (no Ethernet headers) - * IFF_TAP - TAP device - * - * IFF_NO_PI - Do not provide packet information - */ - ifr.ifr_flags = IFF_TUN; - if( *dev ) - strncpy(ifr.ifr_name, dev, IFNAMSIZ); - - if( (err = ioctl(fd, TUNSETIFF, (void *) &ifr)) < 0 ){ - close(fd); - return err; - } - strcpy(dev, ifr.ifr_name); - return fd; - } - - 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: - - 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. - - #include <linux/if.h> - #include <linux/if_tun.h> - - int tun_alloc_mq(char *dev, int queues, int *fds) - { - struct ifreq ifr; - int fd, err, i; - - if (!dev) - return -1; - - memset(&ifr, 0, sizeof(ifr)); - /* Flags: IFF_TUN - TUN device (no Ethernet headers) - * IFF_TAP - TAP device - * - * IFF_NO_PI - Do not provide packet information - * IFF_MULTI_QUEUE - Create a queue of multiqueue device - */ - ifr.ifr_flags = IFF_TAP | IFF_NO_PI | IFF_MULTI_QUEUE; - strcpy(ifr.ifr_name, dev); - - for (i = 0; i < queues; i++) { - if ((fd = open("/dev/net/tun", O_RDWR)) < 0) - goto err; - err = ioctl(fd, TUNSETIFF, (void *)&ifr); - if (err) { - close(fd); - goto err; - } - fds[i] = fd; - } - - return 0; - err: - for (--i; i >= 0; i--) - close(fds[i]); - 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. - - 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> - - int tun_set_queue(int fd, int enable) - { - struct ifreq ifr; - - memset(&ifr, 0, sizeof(ifr)); - - if (enable) - ifr.ifr_flags = IFF_ATTACH_QUEUE; - else - ifr.ifr_flags = IFF_DETACH_QUEUE; - - return ioctl(fd, TUNSETQUEUE, (void *)&ifr); - } - -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 - -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). - -Another interesting application using TUN/TAP is pipsecd -(http://perso.enst.fr/~beyssac/pipsec/), a userspace IPSec -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 -packets via physical media sends them to the user space program. - -Let's say that you configured IPv6 on the tap0, then whenever -the kernel sends an IPv6 packet to tap0, it is passed to the application -(VTun for example). The application encrypts, compresses and sends it to -the other side over TCP or UDP. The application on the other side decompresses -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. |