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      1 /*	$NetBSD: npf_ext_rndblock.c,v 1.4 2014/05/19 18:45:51 jakllsch Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2012 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  * 1. Redistributions of source code must retain the above copyright
     11  *    notice, this list of conditions and the following disclaimer.
     12  * 2. Redistributions in binary form must reproduce the above copyright
     13  *    notice, this list of conditions and the following disclaimer in the
     14  *    documentation and/or other materials provided with the distribution.
     15  *
     16  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     17  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     18  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     19  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     20  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     21  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     22  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     23  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     24  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     25  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     26  * POSSIBILITY OF SUCH DAMAGE.
     27  */
     28 
     29 /*
     30  * NPF random blocking extension - kernel module.
     31  * This is also a demo extension.
     32  */
     33 
     34 #include <sys/cdefs.h>
     35 __KERNEL_RCSID(0, "$NetBSD: npf_ext_rndblock.c,v 1.4 2014/05/19 18:45:51 jakllsch Exp $");
     36 
     37 #include <sys/types.h>
     38 #include <sys/cprng.h>
     39 #include <sys/atomic.h>
     40 #include <sys/module.h>
     41 #include <sys/kmem.h>
     42 
     43 #include "npf.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, prop_dictionary_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 	prop_dictionary_get_uint32(params, "mod", &meta->mod);
     80 	prop_dictionary_get_uint32(params, "percentage", &meta->percentage);
     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, int *decision)
    101 {
    102 	npf_ext_rndblock_t *rndblock = meta;
    103 	unsigned long c;
    104 
    105 	/* Skip, if already blocking. */
    106 	if (*decision == NPF_DECISION_BLOCK) {
    107 		return true;
    108 	}
    109 
    110 	/*
    111 	 * Sample demo:
    112 	 *
    113 	 * Drop the packets according to the given module or percentage.
    114 	 *
    115 	 * Rule procedures may be executed concurrently in an SMP system.
    116 	 * Use atomic operation to increment the counter.
    117 	 */
    118 	c = atomic_inc_ulong_nv(&rndblock->counter);
    119 
    120 	if (rndblock->mod) {
    121 		if ((c % rndblock->mod) == 0) {
    122 			*decision = NPF_DECISION_BLOCK;
    123 		}
    124 	}
    125 
    126 	if (rndblock->percentage) {
    127 		uint32_t w = cprng_fast32() % PERCENTAGE_BASE;
    128 		if (w <= rndblock->percentage) {
    129 			*decision = NPF_DECISION_BLOCK;
    130 		}
    131 	}
    132 
    133 	return true;
    134 }
    135 
    136 /*
    137  * Module interface.
    138  */
    139 static int
    140 npf_ext_rndblock_modcmd(modcmd_t cmd, void *arg)
    141 {
    142 	static const npf_ext_ops_t npf_rndblock_ops = {
    143 		.version	= NPFEXT_RNDBLOCK_VER,
    144 		.ctx		= NULL,
    145 		.ctor		= npf_ext_rndblock_ctor,
    146 		.dtor		= npf_ext_rndblock_dtor,
    147 		.proc		= npf_ext_rndblock
    148 	};
    149 
    150 	switch (cmd) {
    151 	case MODULE_CMD_INIT:
    152 		/*
    153 		 * Initialise the NPF extension module.  Register the
    154 		 * "rndblock" extensions calls (constructor, destructor,
    155 		 * the processing * routine, etc).
    156 		 */
    157 		npf_ext_rndblock_id = npf_ext_register("rndblock",
    158 		    &npf_rndblock_ops);
    159 		return npf_ext_rndblock_id ? 0 : EEXIST;
    160 
    161 	case MODULE_CMD_FINI:
    162 		/*
    163 		 * Unregister our rndblock extension.  NPF may return an
    164 		 * if there are references and it cannot drain them.
    165 		 */
    166 		return npf_ext_unregister(npf_ext_rndblock_id);
    167 
    168 	case MODULE_CMD_AUTOUNLOAD:
    169 		/* Allow auto-unload only if NPF permits it. */
    170 		return npf_autounload_p() ? 0 : EBUSY;
    171 
    172 	default:
    173 		return ENOTTY;
    174 	}
    175 	return 0;
    176 }
    177