Linux Kernel Programming - TUNTAP Source-code - ioctl handlers
Linux Kernel Programming - TUNTAP Source-code - ioctl handlers

I was doing a general code walk of Tun/Tap drivers in /drivers/net/tun.c and /drivers/net/tap.c, which is when I stumbled across its ioctl handlers/implementation and then started comparing with generic /net/core/dev_ioctl.c. Network port ioctl support is pretty vital so that whenever we control/configure any network ports (physical or virtual ports, such as tun/tap, veth, lo, dummy, so on), the configuration is passed on from user-space to kernel-space port drivers via ioctl (also known as IO control) APIs.

There are various ioctl commands/instructions which these kernel network drivers support which you can find in /include/uapi/linux/sockios.h as shown below:

/* SPDX-License-Identifier: GPL-2.0+ WITH Linux-syscall-note */
/*
 * INET		An implementation of the TCP/IP protocol suite for the LINUX
 *		operating system.  INET is implemented using the  BSD Socket
 *		interface as the means of communication with the user level.
 *
 *		Definitions of the socket-level I/O control calls.
 *
 * Version:	@(#)sockios.h	1.0.2	03/09/93
 *
 * Authors:	Ross Biro
 *		Fred N. van Kempen, <[email protected]>
 *
 *		This program is free software; you can redistribute it and/or
 *		modify it under the terms of the GNU General Public License
 *		as published by the Free Software Foundation; either version
 *		2 of the License, or (at your option) any later version.
 */
#ifndef _LINUX_SOCKIOS_H
#define _LINUX_SOCKIOS_H

#include <asm/bitsperlong.h>
#include <asm/sockios.h>

/* Linux-specific socket ioctls */
#define SIOCINQ		FIONREAD
#define SIOCOUTQ	TIOCOUTQ        /* output queue size (not sent + not acked) */

#define SOCK_IOC_TYPE	0x89

/*
 * the timeval/timespec data structure layout is defined by libc,
 * so we need to cover both possible versions on 32-bit.
 */
/* Get stamp (timeval) */
#define SIOCGSTAMP_NEW	 _IOR(SOCK_IOC_TYPE, 0x06, long long[2])
/* Get stamp (timespec) */
#define SIOCGSTAMPNS_NEW _IOR(SOCK_IOC_TYPE, 0x07, long long[2])

#if __BITS_PER_LONG == 64 || (defined(__x86_64__) && defined(__ILP32__))
/* on 64-bit and x32, avoid the ?: operator */
#define SIOCGSTAMP	SIOCGSTAMP_OLD
#define SIOCGSTAMPNS	SIOCGSTAMPNS_OLD
#else
#define SIOCGSTAMP	((sizeof(struct timeval))  == 8 ? \
			 SIOCGSTAMP_OLD   : SIOCGSTAMP_NEW)
#define SIOCGSTAMPNS	((sizeof(struct timespec)) == 8 ? \
			 SIOCGSTAMPNS_OLD : SIOCGSTAMPNS_NEW)
#endif

/* Routing table calls. */
#define SIOCADDRT	0x890B		/* add routing table entry	*/
#define SIOCDELRT	0x890C		/* delete routing table entry	*/
#define SIOCRTMSG	0x890D		/* unused			*/

/* Socket configuration controls. */
#define SIOCGIFNAME	0x8910		/* get iface name		*/
#define SIOCSIFLINK	0x8911		/* set iface channel		*/
#define SIOCGIFCONF	0x8912		/* get iface list		*/
#define SIOCGIFFLAGS	0x8913		/* get flags			*/
#define SIOCSIFFLAGS	0x8914		/* set flags			*/
#define SIOCGIFADDR	0x8915		/* get PA address		*/
#define SIOCSIFADDR	0x8916		/* set PA address		*/
#define SIOCGIFDSTADDR	0x8917		/* get remote PA address	*/
#define SIOCSIFDSTADDR	0x8918		/* set remote PA address	*/
#define SIOCGIFBRDADDR	0x8919		/* get broadcast PA address	*/
#define SIOCSIFBRDADDR	0x891a		/* set broadcast PA address	*/
#define SIOCGIFNETMASK	0x891b		/* get network PA mask		*/
#define SIOCSIFNETMASK	0x891c		/* set network PA mask		*/
#define SIOCGIFMETRIC	0x891d		/* get metric			*/
#define SIOCSIFMETRIC	0x891e		/* set metric			*/
#define SIOCGIFMEM	0x891f		/* get memory address (BSD)	*/
#define SIOCSIFMEM	0x8920		/* set memory address (BSD)	*/
#define SIOCGIFMTU	0x8921		/* get MTU size			*/
#define SIOCSIFMTU	0x8922		/* set MTU size			*/
#define SIOCSIFNAME	0x8923		/* set interface name */
#define	SIOCSIFHWADDR	0x8924		/* set hardware address 	*/
#define SIOCGIFENCAP	0x8925		/* get/set encapsulations       */
#define SIOCSIFENCAP	0x8926		
#define SIOCGIFHWADDR	0x8927		/* Get hardware address		*/
#define SIOCGIFSLAVE	0x8929		/* Driver slaving support	*/
#define SIOCSIFSLAVE	0x8930
#define SIOCADDMULTI	0x8931		/* Multicast address lists	*/
#define SIOCDELMULTI	0x8932
#define SIOCGIFINDEX	0x8933		/* name -> if_index mapping	*/
#define SIOGIFINDEX	SIOCGIFINDEX	/* misprint compatibility :-)	*/
#define SIOCSIFPFLAGS	0x8934		/* set/get extended flags set	*/
#define SIOCGIFPFLAGS	0x8935
#define SIOCDIFADDR	0x8936		/* delete PA address		*/
#define	SIOCSIFHWBROADCAST	0x8937	/* set hardware broadcast addr	*/
#define SIOCGIFCOUNT	0x8938		/* get number of devices */

#define SIOCGIFBR	0x8940		/* Bridging support		*/
#define SIOCSIFBR	0x8941		/* Set bridging options 	*/

#define SIOCGIFTXQLEN	0x8942		/* Get the tx queue length	*/
#define SIOCSIFTXQLEN	0x8943		/* Set the tx queue length 	*/

/* SIOCGIFDIVERT was:	0x8944		Frame diversion support */
/* SIOCSIFDIVERT was:	0x8945		Set frame diversion options */

#define SIOCETHTOOL	0x8946		/* Ethtool interface		*/

#define SIOCGMIIPHY	0x8947		/* Get address of MII PHY in use. */
#define SIOCGMIIREG	0x8948		/* Read MII PHY register.	*/
#define SIOCSMIIREG	0x8949		/* Write MII PHY register.	*/

#define SIOCWANDEV	0x894A		/* get/set netdev parameters	*/

#define SIOCOUTQNSD	0x894B		/* output queue size (not sent only) */
#define SIOCGSKNS	0x894C		/* get socket network namespace */

/* ARP cache control calls. */
		    /*  0x8950 - 0x8952  * obsolete calls, don't re-use */
#define SIOCDARP	0x8953		/* delete ARP table entry	*/
#define SIOCGARP	0x8954		/* get ARP table entry		*/
#define SIOCSARP	0x8955		/* set ARP table entry		*/

/* RARP cache control calls. */
#define SIOCDRARP	0x8960		/* delete RARP table entry	*/
#define SIOCGRARP	0x8961		/* get RARP table entry		*/
#define SIOCSRARP	0x8962		/* set RARP table entry		*/

/* Driver configuration calls */

#define SIOCGIFMAP	0x8970		/* Get device parameters	*/
#define SIOCSIFMAP	0x8971		/* Set device parameters	*/

/* DLCI configuration calls */

#define SIOCADDDLCI	0x8980		/* Create new DLCI device	*/
#define SIOCDELDLCI	0x8981		/* Delete DLCI device		*/

#define SIOCGIFVLAN	0x8982		/* 802.1Q VLAN support		*/
#define SIOCSIFVLAN	0x8983		/* Set 802.1Q VLAN options 	*/

/* bonding calls */

#define SIOCBONDENSLAVE	0x8990		/* enslave a device to the bond */
#define SIOCBONDRELEASE 0x8991		/* release a slave from the bond*/
#define SIOCBONDSETHWADDR      0x8992	/* set the hw addr of the bond  */
#define SIOCBONDSLAVEINFOQUERY 0x8993   /* rtn info about slave state   */
#define SIOCBONDINFOQUERY      0x8994	/* rtn info about bond state    */
#define SIOCBONDCHANGEACTIVE   0x8995   /* update to a new active slave */
			
/* bridge calls */
#define SIOCBRADDBR     0x89a0		/* create new bridge device     */
#define SIOCBRDELBR     0x89a1		/* remove bridge device         */
#define SIOCBRADDIF	0x89a2		/* add interface to bridge      */
#define SIOCBRDELIF	0x89a3		/* remove interface from bridge */

/* hardware time stamping: parameters in linux/net_tstamp.h */
#define SIOCSHWTSTAMP	0x89b0		/* set and get config		*/
#define SIOCGHWTSTAMP	0x89b1		/* get config			*/

/* Device private ioctl calls */

/*
 *	These 16 ioctls are available to devices via the do_ioctl() device
 *	vector. Each device should include this file and redefine these names
 *	as their own. Because these are device dependent it is a good idea
 *	_NOT_ to issue them to random objects and hope.
 *
 *	THESE IOCTLS ARE _DEPRECATED_ AND WILL DISAPPEAR IN 2.5.X -DaveM
 */
 
#define SIOCDEVPRIVATE	0x89F0	/* to 89FF */

/*
 *	These 16 ioctl calls are protocol private
 */
 
#define SIOCPROTOPRIVATE 0x89E0 /* to 89EF */
#endif	/* _LINUX_SOCKIOS_H */

So you can find some of the ioctl commands are supported in the Tun/Tap driver source, vs the general implementation you can find in the /net/core/dev_ioctl.c. Here is a video episode in which I cover about the same in depth:

Refer:
Linux (user-space) RAW Socket Programming – Generate Layer-3 IP multicast OSPF Packets ↗
Linux (user-space) RAW Socket Programming – Generate Layer-2 multicast STP Packets ↗
Net-Tools Package – Source Code Walk – ifconfig Command – Part 1 ↗
The Linux Channel Videos ↗
ifconfig source-code ↗
net-tools github ↗
ifconfig commands ↗

Refer Linux Kernel source:
/drivers/net/tap.c ↗
/drivers/net/tun.c ↗
/net/core/dev_ioctl.c ↗
/include/uapi/linux/sockios.h ↗