1 /*- 2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD 3 * 4 * Copyright (c) 2005 Paolo Pisati <piso@FreeBSD.org> 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 AUTHOR AND CONTRIBUTORS ``AS IS'' AND 17 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 18 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 19 * ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 20 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 21 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 22 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 23 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 24 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 25 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 */ 28 29 #include <sys/cdefs.h> 30 __FBSDID("$FreeBSD$"); 31 32 /* 33 * Alias_dummy is just an empty skeleton used to demostrate how to write 34 * a module for libalias, that will run unalterated in userland or in 35 * kernel land. 36 */ 37 38 #ifdef _KERNEL 39 #include <sys/param.h> 40 #include <sys/kernel.h> 41 #include <sys/module.h> 42 #else 43 #include <errno.h> 44 #include <sys/types.h> 45 #include <stdio.h> 46 #endif 47 48 #include <netinet/in_systm.h> 49 #include <netinet/in.h> 50 #include <netinet/ip.h> 51 #include <netinet/udp.h> 52 53 #ifdef _KERNEL 54 #include <netinet/libalias/alias_local.h> 55 #include <netinet/libalias/alias_mod.h> 56 #else 57 #include "alias_local.h" 58 #include "alias_mod.h" 59 #endif 60 61 static void 62 AliasHandleDummy(struct libalias *la, struct ip *ip, struct alias_data *ah); 63 64 static int 65 fingerprint(struct libalias *la, struct alias_data *ah) 66 { 67 /* 68 * Check here all the data that will be used later, if any field 69 * is empy/NULL, return a -1 value. 70 */ 71 if (ah->dport == NULL || ah->sport == NULL || ah->lnk == NULL || 72 ah->maxpktsize == 0) 73 return (-1); 74 /* 75 * Fingerprint the incoming packet, if it matches any conditions 76 * return an OK value. 77 */ 78 if (ntohs(*ah->dport) == 123 || ntohs(*ah->sport) == 456) 79 return (0); /* I know how to handle it. */ 80 return (-1); /* I don't recognize this packet. */ 81 } 82 83 /* 84 * Wrap in this general purpose function, the real function used to alias the 85 * packets. 86 */ 87 88 static int 89 protohandler(struct libalias *la, struct ip *pip, struct alias_data *ah) 90 { 91 AliasHandleDummy(la, pip, ah); 92 return (0); 93 } 94 95 /* 96 * NOTA BENE: the next variable MUST NOT be renamed in any case if you want 97 * your module to work in userland, cause it's used to find and use all 98 * the protocol handlers present in every module. 99 * So WATCH OUT, your module needs this variables and it needs it with 100 * ITS EXACT NAME: handlers. 101 */ 102 103 struct proto_handler handlers [] = { 104 { 105 .pri = 666, 106 .dir = IN|OUT, 107 .proto = UDP|TCP, 108 .fingerprint = &fingerprint, 109 .protohandler = &protohandler 110 }, 111 { EOH } 112 }; 113 114 static int 115 mod_handler(module_t mod, int type, void *data) 116 { 117 int error; 118 119 switch (type) { 120 case MOD_LOAD: 121 error = 0; 122 LibAliasAttachHandlers(handlers); 123 break; 124 case MOD_UNLOAD: 125 error = 0; 126 LibAliasDetachHandlers(handlers); 127 break; 128 default: 129 error = EINVAL; 130 } 131 return (error); 132 } 133 134 #ifdef _KERNEL 135 static 136 #endif 137 moduledata_t alias_mod = { 138 "alias_dummy", mod_handler, NULL 139 }; 140 141 #ifdef _KERNEL 142 DECLARE_MODULE(alias_dummy, alias_mod, SI_SUB_DRIVERS, SI_ORDER_SECOND); 143 MODULE_VERSION(alias_dummy, 1); 144 MODULE_DEPEND(alias_dummy, libalias, 1, 1, 1); 145 #endif 146 147 static void 148 AliasHandleDummy(struct libalias *la, struct ip *ip, struct alias_data *ah) 149 { 150 ; /* Dummy. */ 151 } 152