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      1 /*-
      2  * Copyright (c) 2012 The NetBSD Foundation, Inc.
      3  * All rights reserved.
      4  *
      5  * Redistribution and use in source and binary forms, with or without
      6  * modification, are permitted provided that the following conditions
      7  * are met:
      8  * 1. Redistributions of source code must retain the above copyright
      9  *    notice, this list of conditions and the following disclaimer.
     10  * 2. Redistributions in binary form must reproduce the above copyright
     11  *    notice, this list of conditions and the following disclaimer in the
     12  *    documentation and/or other materials provided with the distribution.
     13  *
     14  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     15  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     16  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     17  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     18  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     19  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     20  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     21  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     22  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     23  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     24  * POSSIBILITY OF SUCH DAMAGE.
     25  */
     26 
     27 /*
     28  * NPF random blocking extension - kernel module.
     29  * This is also a demo extension.
     30  */
     31 
     32 #ifdef _KERNEL
     33 #include <sys/cdefs.h>
     34 __KERNEL_RCSID(0, "$NetBSD: npf_ext_rndblock.c,v 1.9 2020/05/30 14:16:56 rmind Exp $");
     35 
     36 #include <sys/types.h>
     37 #include <sys/cprng.h>
     38 #include <sys/atomic.h>
     39 #include <sys/module.h>
     40 #include <sys/kmem.h>
     41 #endif
     42 
     43 #include "npf_impl.h"
     44 
     45 /*
     46  * NPF extension module definition and the identifier.
     47  */
     48 NPF_EXT_MODULE(npf_ext_rndblock, "");
     49 
     50 #define	NPFEXT_RNDBLOCK_VER		1
     51 
     52 static void *		npf_ext_rndblock_id;
     53 
     54 #define	PERCENTAGE_BASE	10000
     55 
     56 /*
     57  * Meta-data structure, containing parameters.
     58  */
     59 typedef struct {
     60 	unsigned int	mod;
     61 	unsigned long	counter;
     62 	unsigned int	percentage;
     63 } npf_ext_rndblock_t;
     64 
     65 /*
     66  * npf_ext_rndblock_ctor: a constructor to parse and store any parameters
     67  * associated with a rule procedure, which is being newly created.
     68  */
     69 static int
     70 npf_ext_rndblock_ctor(npf_rproc_t *rp, const nvlist_t *params)
     71 {
     72 	npf_ext_rndblock_t *meta;
     73 
     74 	/*
     75 	 * Allocate and a associate a structure for the parameter
     76 	 * and our meta-data.
     77 	 */
     78 	meta = kmem_zalloc(sizeof(npf_ext_rndblock_t), KM_SLEEP);
     79 	meta->mod = dnvlist_get_number(params, "mod", 0);
     80 	meta->percentage = dnvlist_get_number(params, "percentage", 0);
     81 	npf_rproc_assign(rp, meta);
     82 
     83 	return 0;
     84 }
     85 
     86 /*
     87  * npf_ext_rndblock_dtor: a destructor for our rule procedure.
     88  */
     89 static void
     90 npf_ext_rndblock_dtor(npf_rproc_t *rp, void *meta)
     91 {
     92 	/* Free our meta-data, associated with the procedure. */
     93 	kmem_free(meta, sizeof(npf_ext_rndblock_t));
     94 }
     95 
     96 /*
     97  * npf_ext_rndblock: main routine implementing the extension functionality.
     98  */
     99 static bool
    100 npf_ext_rndblock(npf_cache_t *npc, void *meta, const npf_match_info_t *mi,
    101     int *decision)
    102 {
    103 	npf_ext_rndblock_t *rndblock = meta;
    104 	unsigned long c;
    105 
    106 	/* Skip, if already blocking. */
    107 	if (*decision == NPF_DECISION_BLOCK) {
    108 		return true;
    109 	}
    110 
    111 	/*
    112 	 * Sample demo:
    113 	 *
    114 	 * Drop the packets according to the given module or percentage.
    115 	 *
    116 	 * Rule procedures may be executed concurrently in an SMP system.
    117 	 * Use atomic operation to increment the counter.
    118 	 */
    119 	c = atomic_inc_ulong_nv(&rndblock->counter);
    120 
    121 	if (rndblock->mod) {
    122 		if ((c % rndblock->mod) == 0) {
    123 			*decision = NPF_DECISION_BLOCK;
    124 		}
    125 	}
    126 
    127 	if (rndblock->percentage) {
    128 		uint32_t w = cprng_fast32() % PERCENTAGE_BASE;
    129 		if (w <= rndblock->percentage) {
    130 			*decision = NPF_DECISION_BLOCK;
    131 		}
    132 	}
    133 
    134 	return true;
    135 }
    136 
    137 __dso_public int
    138 npf_ext_rndblock_init(npf_t *npf)
    139 {
    140 	static const npf_ext_ops_t npf_rndblock_ops = {
    141 		.version	= NPFEXT_RNDBLOCK_VER,
    142 		.ctx		= NULL,
    143 		.ctor		= npf_ext_rndblock_ctor,
    144 		.dtor		= npf_ext_rndblock_dtor,
    145 		.proc		= npf_ext_rndblock
    146 	};
    147 
    148 	/*
    149 	 * Initialize the NPF extension.  Register the "rndblock" extension
    150 	 * calls (constructor, destructor, the processing routine, etc).
    151 	 */
    152 	npf_ext_rndblock_id = npf_ext_register(npf, "rndblock",
    153 	    &npf_rndblock_ops);
    154 	return npf_ext_rndblock_id ? 0 : EEXIST;
    155 }
    156 
    157 __dso_public int
    158 npf_ext_rndblock_fini(npf_t *npf)
    159 {
    160 	/*
    161 	 * Remove the rndblock extension.  NPF may return an if there
    162 	 * are active references and it cannot drain them.
    163 	 */
    164 	return npf_ext_unregister(npf, npf_ext_rndblock_id);
    165 }
    166 
    167 #ifdef _KERNEL
    168 /*
    169  * Kernel module interface.
    170  */
    171 static int
    172 npf_ext_rndblock_modcmd(modcmd_t cmd, void *arg)
    173 {
    174 	npf_t *npf = npf_getkernctx();
    175 
    176 	switch (cmd) {
    177 	case MODULE_CMD_INIT:
    178 		return npf_ext_rndblock_init(npf);
    179 	case MODULE_CMD_FINI:
    180 		return npf_ext_rndblock_fini(npf);
    181 	case MODULE_CMD_AUTOUNLOAD:
    182 		/* Allow auto-unload only if NPF permits it. */
    183 		return npf_autounload_p() ? 0 : EBUSY;
    184 	default:
    185 		return ENOTTY;
    186 	}
    187 	return 0;
    188 }
    189 #endif
    190