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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 | /* Kernel module to match Hop-by-Hop and Destination parameters. */ #include <linux/module.h> #include <linux/skbuff.h> #include <linux/ipv6.h> #include <linux/types.h> #include <net/checksum.h> #include <net/ipv6.h> #include <asm/byteorder.h> #include <linux/netfilter_ipv6/ip6_tables.h> #include <linux/netfilter_ipv6/ip6t_opts.h> #define LOW(n) (n & 0x00FF) #define HOPBYHOP 0 EXPORT_NO_SYMBOLS; MODULE_LICENSE("GPL"); #if HOPBYHOP MODULE_DESCRIPTION("IPv6 HbH match"); #else MODULE_DESCRIPTION("IPv6 DST match"); #endif MODULE_AUTHOR("Andras Kis-Szabo <kisza@sch.bme.hu>"); #if 0 #define DEBUGP printk #else #define DEBUGP(format, args...) #endif /* * (Type & 0xC0) >> 6 * 0 -> ignorable * 1 -> must drop the packet * 2 -> send ICMP PARM PROB regardless and drop packet * 3 -> Send ICMP if not a multicast address and drop packet * (Type & 0x20) >> 5 * 0 -> invariant * 1 -> can change the routing * (Type & 0x1F) Type * 0 -> PAD0 (only 1 byte!) * 1 -> PAD1 LENGTH info (total length = length + 2) * C0 | 2 -> JUMBO 4 x x x x ( xxxx > 64k ) * 5 -> RTALERT 2 x x */ static int match(const struct sk_buff *skb, const struct net_device *in, const struct net_device *out, const void *matchinfo, int offset, const void *protohdr, u_int16_t datalen, int *hotdrop) { struct ipv6_opt_hdr *optsh = NULL; const struct ip6t_opts *optinfo = matchinfo; unsigned int temp; unsigned int len; u8 nexthdr; unsigned int ptr; unsigned int hdrlen = 0; unsigned int ret = 0; u_int16_t *optdesc = NULL; /* type of the 1st exthdr */ nexthdr = skb->nh.ipv6h->nexthdr; /* pointer to the 1st exthdr */ ptr = sizeof(struct ipv6hdr); /* available length */ len = skb->len - ptr; temp = 0; while (ip6t_ext_hdr(nexthdr)) { struct ipv6_opt_hdr *hdr; DEBUGP("ipv6_opts header iteration \n"); /* Is there enough space for the next ext header? */ if (len < (int)sizeof(struct ipv6_opt_hdr)) return 0; /* No more exthdr -> evaluate */ if (nexthdr == NEXTHDR_NONE) { break; } /* ESP -> evaluate */ if (nexthdr == NEXTHDR_ESP) { break; } hdr=(void *)(skb->data)+ptr; /* Calculate the header length */ if (nexthdr == NEXTHDR_FRAGMENT) { hdrlen = 8; } else if (nexthdr == NEXTHDR_AUTH) hdrlen = (hdr->hdrlen+2)<<2; else hdrlen = ipv6_optlen(hdr); /* OPTS -> evaluate */ #if HOPBYHOP if (nexthdr == NEXTHDR_HOP) { temp |= MASK_HOPOPTS; #else if (nexthdr == NEXTHDR_DEST) { temp |= MASK_DSTOPTS; #endif break; } /* set the flag */ switch (nexthdr){ case NEXTHDR_HOP: case NEXTHDR_ROUTING: case NEXTHDR_FRAGMENT: case NEXTHDR_AUTH: case NEXTHDR_DEST: break; default: DEBUGP("ipv6_opts match: unknown nextheader %u\n",nexthdr); return 0; break; } nexthdr = hdr->nexthdr; len -= hdrlen; ptr += hdrlen; if ( ptr > skb->len ) { DEBUGP("ipv6_opts: new pointer is too large! \n"); break; } } /* OPTIONS header not found */ #if HOPBYHOP if ( temp != MASK_HOPOPTS ) return 0; #else if ( temp != MASK_DSTOPTS ) return 0; #endif if (len < (int)sizeof(struct ipv6_opt_hdr)){ *hotdrop = 1; return 0; } if (len < hdrlen){ /* Packet smaller than it's length field */ return 0; } optsh=(void *)(skb->data)+ptr; DEBUGP("IPv6 OPTS LEN %u %u ", hdrlen, optsh->hdrlen); DEBUGP("len %02X %04X %02X ", optinfo->hdrlen, hdrlen, (!(optinfo->flags & IP6T_OPTS_LEN) || ((optinfo->hdrlen == hdrlen) ^ !!(optinfo->invflags & IP6T_OPTS_INV_LEN)))); ret = (optsh != NULL) && (!(optinfo->flags & IP6T_OPTS_LEN) || ((optinfo->hdrlen == hdrlen) ^ !!(optinfo->invflags & IP6T_OPTS_INV_LEN))); temp = len = 0; ptr += 2; hdrlen -= 2; if ( !(optinfo->flags & IP6T_OPTS_OPTS) ){ return ret; } else if (optinfo->flags & IP6T_OPTS_NSTRICT) { DEBUGP("Not strict - not implemented"); } else { DEBUGP("Strict "); DEBUGP("#%d ",optinfo->optsnr); for(temp=0; temp<optinfo->optsnr; temp++){ optdesc = (void *)(skb->data)+ptr; /* Type check */ if ( (unsigned char)*optdesc != (optinfo->opts[temp] & 0xFF00)>>8 ){ DEBUGP("Tbad %02X %02X\n", (unsigned char)*optdesc, (optinfo->opts[temp] & 0xFF00)>>8); return 0; } else { DEBUGP("Tok "); } /* Length check */ if (((optinfo->opts[temp] & 0x00FF) != 0xFF) && (unsigned char)*optdesc != 0){ if ( ntohs((u16)*optdesc) != optinfo->opts[temp] ){ DEBUGP("Lbad %02X %04X %04X\n", (unsigned char)*optdesc, ntohs((u16)*optdesc), optinfo->opts[temp]); return 0; } else { DEBUGP("Lok "); } } /* Step to the next */ if ((unsigned char)*optdesc == 0){ DEBUGP("PAD0 \n"); ptr++; hdrlen--; } else { ptr += LOW(ntohs(*optdesc)); hdrlen -= LOW(ntohs(*optdesc)); DEBUGP("len%04X \n", LOW(ntohs(*optdesc))); } if (ptr > skb->len || ( !hdrlen && (temp != optinfo->optsnr - 1))) { DEBUGP("new pointer is too large! \n"); break; } } if (temp == optinfo->optsnr) return ret; else return 0; } return 0; } /* Called when user tries to insert an entry of this type. */ static int checkentry(const char *tablename, const struct ip6t_ip6 *ip, void *matchinfo, unsigned int matchinfosize, unsigned int hook_mask) { const struct ip6t_opts *optsinfo = matchinfo; if (matchinfosize != IP6T_ALIGN(sizeof(struct ip6t_opts))) { DEBUGP("ip6t_opts: matchsize %u != %u\n", matchinfosize, IP6T_ALIGN(sizeof(struct ip6t_opts))); return 0; } if (optsinfo->invflags & ~IP6T_OPTS_INV_MASK) { DEBUGP("ip6t_opts: unknown flags %X\n", optsinfo->invflags); return 0; } return 1; } static struct ip6t_match opts_match #if HOPBYHOP = { { NULL, NULL }, "hbh", &match, &checkentry, NULL, THIS_MODULE }; #else = { { NULL, NULL }, "dst", &match, &checkentry, NULL, THIS_MODULE }; #endif static int __init init(void) { return ip6t_register_match(&opts_match); } static void __exit cleanup(void) { ip6t_unregister_match(&opts_match); } module_init(init); module_exit(cleanup); |