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 1.8 2018/09/29 14:41:36 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 /* 138 * Module interface. 139 */ 140 static int 141 npf_ext_rndblock_modcmd(modcmd_t cmd, void *arg) 142 { 143 static const npf_ext_ops_t npf_rndblock_ops = { 144 .version = NPFEXT_RNDBLOCK_VER, 145 .ctx = NULL, 146 .ctor = npf_ext_rndblock_ctor, 147 .dtor = npf_ext_rndblock_dtor, 148 .proc = npf_ext_rndblock 149 }; 150 npf_t *npf = npf_getkernctx(); 151 152 switch (cmd) { 153 case MODULE_CMD_INIT: 154 /* 155 * Initialise the NPF extension module. Register the 156 * "rndblock" extensions calls (constructor, destructor, 157 * the processing * routine, etc). 158 */ 159 npf_ext_rndblock_id = npf_ext_register(npf, "rndblock", 160 &npf_rndblock_ops); 161 return npf_ext_rndblock_id ? 0 : EEXIST; 162 163 case MODULE_CMD_FINI: 164 /* 165 * Unregister our rndblock extension. NPF may return an 166 * if there are references and it cannot drain them. 167 */ 168 return npf_ext_unregister(npf, npf_ext_rndblock_id); 169 170 case MODULE_CMD_AUTOUNLOAD: 171 /* Allow auto-unload only if NPF permits it. */ 172 return npf_autounload_p() ? 0 : EBUSY; 173 174 default: 175 return ENOTTY; 176 } 177 return 0; 178 } 179