1 /* 2 * Copyright (c) 2008 Patrick McHardy <kaber@trash.net> 3 * 4 * This program is free software; you can redistribute it and/or modify 5 * it under the terms of the GNU General Public License version 2 as 6 * published by the Free Software Foundation. 7 * 8 * Development of this code funded by Astaro AG (http://www.astaro.com/) 9 */ 10 11 #include <asm/unaligned.h> 12 #include <linux/kernel.h> 13 #include <linux/init.h> 14 #include <linux/module.h> 15 #include <linux/netlink.h> 16 #include <linux/netfilter.h> 17 #include <linux/netfilter/nf_tables.h> 18 #include <net/netfilter/nf_tables.h> 19 #include <net/tcp.h> 20 21 struct nft_exthdr { 22 u8 type; 23 u8 offset; 24 u8 len; 25 u8 op; 26 enum nft_registers dreg:8; 27 enum nft_registers sreg:8; 28 u8 flags; 29 }; 30 31 static unsigned int optlen(const u8 *opt, unsigned int offset) 32 { 33 /* Beware zero-length options: make finite progress */ 34 if (opt[offset] <= TCPOPT_NOP || opt[offset + 1] == 0) 35 return 1; 36 else 37 return opt[offset + 1]; 38 } 39 40 static void nft_exthdr_ipv6_eval(const struct nft_expr *expr, 41 struct nft_regs *regs, 42 const struct nft_pktinfo *pkt) 43 { 44 struct nft_exthdr *priv = nft_expr_priv(expr); 45 u32 *dest = ®s->data[priv->dreg]; 46 unsigned int offset = 0; 47 int err; 48 49 err = ipv6_find_hdr(pkt->skb, &offset, priv->type, NULL, NULL); 50 if (priv->flags & NFT_EXTHDR_F_PRESENT) { 51 *dest = (err >= 0); 52 return; 53 } else if (err < 0) { 54 goto err; 55 } 56 offset += priv->offset; 57 58 dest[priv->len / NFT_REG32_SIZE] = 0; 59 if (skb_copy_bits(pkt->skb, offset, dest, priv->len) < 0) 60 goto err; 61 return; 62 err: 63 regs->verdict.code = NFT_BREAK; 64 } 65 66 static void * 67 nft_tcp_header_pointer(const struct nft_pktinfo *pkt, 68 unsigned int len, void *buffer, unsigned int *tcphdr_len) 69 { 70 struct tcphdr *tcph; 71 72 if (!pkt->tprot_set || pkt->tprot != IPPROTO_TCP) 73 return NULL; 74 75 tcph = skb_header_pointer(pkt->skb, pkt->xt.thoff, sizeof(*tcph), buffer); 76 if (!tcph) 77 return NULL; 78 79 *tcphdr_len = __tcp_hdrlen(tcph); 80 if (*tcphdr_len < sizeof(*tcph) || *tcphdr_len > len) 81 return NULL; 82 83 return skb_header_pointer(pkt->skb, pkt->xt.thoff, *tcphdr_len, buffer); 84 } 85 86 static void nft_exthdr_tcp_eval(const struct nft_expr *expr, 87 struct nft_regs *regs, 88 const struct nft_pktinfo *pkt) 89 { 90 u8 buff[sizeof(struct tcphdr) + MAX_TCP_OPTION_SPACE]; 91 struct nft_exthdr *priv = nft_expr_priv(expr); 92 unsigned int i, optl, tcphdr_len, offset; 93 u32 *dest = ®s->data[priv->dreg]; 94 struct tcphdr *tcph; 95 u8 *opt; 96 97 tcph = nft_tcp_header_pointer(pkt, sizeof(buff), buff, &tcphdr_len); 98 if (!tcph) 99 goto err; 100 101 opt = (u8 *)tcph; 102 for (i = sizeof(*tcph); i < tcphdr_len - 1; i += optl) { 103 optl = optlen(opt, i); 104 105 if (priv->type != opt[i]) 106 continue; 107 108 if (i + optl > tcphdr_len || priv->len + priv->offset > optl) 109 goto err; 110 111 offset = i + priv->offset; 112 if (priv->flags & NFT_EXTHDR_F_PRESENT) { 113 *dest = 1; 114 } else { 115 dest[priv->len / NFT_REG32_SIZE] = 0; 116 memcpy(dest, opt + offset, priv->len); 117 } 118 119 return; 120 } 121 122 err: 123 if (priv->flags & NFT_EXTHDR_F_PRESENT) 124 *dest = 0; 125 else 126 regs->verdict.code = NFT_BREAK; 127 } 128 129 static void nft_exthdr_tcp_set_eval(const struct nft_expr *expr, 130 struct nft_regs *regs, 131 const struct nft_pktinfo *pkt) 132 { 133 u8 buff[sizeof(struct tcphdr) + MAX_TCP_OPTION_SPACE]; 134 struct nft_exthdr *priv = nft_expr_priv(expr); 135 unsigned int i, optl, tcphdr_len, offset; 136 struct tcphdr *tcph; 137 u8 *opt; 138 u32 src; 139 140 tcph = nft_tcp_header_pointer(pkt, sizeof(buff), buff, &tcphdr_len); 141 if (!tcph) 142 return; 143 144 opt = (u8 *)tcph; 145 for (i = sizeof(*tcph); i < tcphdr_len - 1; i += optl) { 146 union { 147 u8 octet; 148 __be16 v16; 149 __be32 v32; 150 } old, new; 151 152 optl = optlen(opt, i); 153 154 if (priv->type != opt[i]) 155 continue; 156 157 if (i + optl > tcphdr_len || priv->len + priv->offset > optl) 158 return; 159 160 if (!skb_make_writable(pkt->skb, pkt->xt.thoff + i + priv->len)) 161 return; 162 163 tcph = nft_tcp_header_pointer(pkt, sizeof(buff), buff, 164 &tcphdr_len); 165 if (!tcph) 166 return; 167 168 src = regs->data[priv->sreg]; 169 offset = i + priv->offset; 170 171 switch (priv->len) { 172 case 2: 173 old.v16 = get_unaligned((u16 *)(opt + offset)); 174 new.v16 = src; 175 176 switch (priv->type) { 177 case TCPOPT_MSS: 178 /* increase can cause connection to stall */ 179 if (ntohs(old.v16) <= ntohs(new.v16)) 180 return; 181 break; 182 } 183 184 if (old.v16 == new.v16) 185 return; 186 187 put_unaligned(new.v16, (u16*)(opt + offset)); 188 inet_proto_csum_replace2(&tcph->check, pkt->skb, 189 old.v16, new.v16, false); 190 break; 191 case 4: 192 new.v32 = src; 193 old.v32 = get_unaligned((u32 *)(opt + offset)); 194 195 if (old.v32 == new.v32) 196 return; 197 198 put_unaligned(new.v32, (u32*)(opt + offset)); 199 inet_proto_csum_replace4(&tcph->check, pkt->skb, 200 old.v32, new.v32, false); 201 break; 202 default: 203 WARN_ON_ONCE(1); 204 break; 205 } 206 207 return; 208 } 209 } 210 211 static const struct nla_policy nft_exthdr_policy[NFTA_EXTHDR_MAX + 1] = { 212 [NFTA_EXTHDR_DREG] = { .type = NLA_U32 }, 213 [NFTA_EXTHDR_TYPE] = { .type = NLA_U8 }, 214 [NFTA_EXTHDR_OFFSET] = { .type = NLA_U32 }, 215 [NFTA_EXTHDR_LEN] = { .type = NLA_U32 }, 216 [NFTA_EXTHDR_FLAGS] = { .type = NLA_U32 }, 217 [NFTA_EXTHDR_OP] = { .type = NLA_U32 }, 218 [NFTA_EXTHDR_SREG] = { .type = NLA_U32 }, 219 }; 220 221 static int nft_exthdr_init(const struct nft_ctx *ctx, 222 const struct nft_expr *expr, 223 const struct nlattr * const tb[]) 224 { 225 struct nft_exthdr *priv = nft_expr_priv(expr); 226 u32 offset, len, flags = 0, op = NFT_EXTHDR_OP_IPV6; 227 int err; 228 229 if (!tb[NFTA_EXTHDR_DREG] || 230 !tb[NFTA_EXTHDR_TYPE] || 231 !tb[NFTA_EXTHDR_OFFSET] || 232 !tb[NFTA_EXTHDR_LEN]) 233 return -EINVAL; 234 235 err = nft_parse_u32_check(tb[NFTA_EXTHDR_OFFSET], U8_MAX, &offset); 236 if (err < 0) 237 return err; 238 239 err = nft_parse_u32_check(tb[NFTA_EXTHDR_LEN], U8_MAX, &len); 240 if (err < 0) 241 return err; 242 243 if (tb[NFTA_EXTHDR_FLAGS]) { 244 err = nft_parse_u32_check(tb[NFTA_EXTHDR_FLAGS], U8_MAX, &flags); 245 if (err < 0) 246 return err; 247 248 if (flags & ~NFT_EXTHDR_F_PRESENT) 249 return -EINVAL; 250 } 251 252 if (tb[NFTA_EXTHDR_OP]) { 253 err = nft_parse_u32_check(tb[NFTA_EXTHDR_OP], U8_MAX, &op); 254 if (err < 0) 255 return err; 256 } 257 258 priv->type = nla_get_u8(tb[NFTA_EXTHDR_TYPE]); 259 priv->offset = offset; 260 priv->len = len; 261 priv->dreg = nft_parse_register(tb[NFTA_EXTHDR_DREG]); 262 priv->flags = flags; 263 priv->op = op; 264 265 return nft_validate_register_store(ctx, priv->dreg, NULL, 266 NFT_DATA_VALUE, priv->len); 267 } 268 269 static int nft_exthdr_tcp_set_init(const struct nft_ctx *ctx, 270 const struct nft_expr *expr, 271 const struct nlattr * const tb[]) 272 { 273 struct nft_exthdr *priv = nft_expr_priv(expr); 274 u32 offset, len, flags = 0, op = NFT_EXTHDR_OP_IPV6; 275 int err; 276 277 if (!tb[NFTA_EXTHDR_SREG] || 278 !tb[NFTA_EXTHDR_TYPE] || 279 !tb[NFTA_EXTHDR_OFFSET] || 280 !tb[NFTA_EXTHDR_LEN]) 281 return -EINVAL; 282 283 if (tb[NFTA_EXTHDR_DREG] || tb[NFTA_EXTHDR_FLAGS]) 284 return -EINVAL; 285 286 err = nft_parse_u32_check(tb[NFTA_EXTHDR_OFFSET], U8_MAX, &offset); 287 if (err < 0) 288 return err; 289 290 err = nft_parse_u32_check(tb[NFTA_EXTHDR_LEN], U8_MAX, &len); 291 if (err < 0) 292 return err; 293 294 if (offset < 2) 295 return -EOPNOTSUPP; 296 297 switch (len) { 298 case 2: break; 299 case 4: break; 300 default: 301 return -EOPNOTSUPP; 302 } 303 304 err = nft_parse_u32_check(tb[NFTA_EXTHDR_OP], U8_MAX, &op); 305 if (err < 0) 306 return err; 307 308 priv->type = nla_get_u8(tb[NFTA_EXTHDR_TYPE]); 309 priv->offset = offset; 310 priv->len = len; 311 priv->sreg = nft_parse_register(tb[NFTA_EXTHDR_SREG]); 312 priv->flags = flags; 313 priv->op = op; 314 315 return nft_validate_register_load(priv->sreg, priv->len); 316 } 317 318 static int nft_exthdr_dump_common(struct sk_buff *skb, const struct nft_exthdr *priv) 319 { 320 if (nla_put_u8(skb, NFTA_EXTHDR_TYPE, priv->type)) 321 goto nla_put_failure; 322 if (nla_put_be32(skb, NFTA_EXTHDR_OFFSET, htonl(priv->offset))) 323 goto nla_put_failure; 324 if (nla_put_be32(skb, NFTA_EXTHDR_LEN, htonl(priv->len))) 325 goto nla_put_failure; 326 if (nla_put_be32(skb, NFTA_EXTHDR_FLAGS, htonl(priv->flags))) 327 goto nla_put_failure; 328 if (nla_put_be32(skb, NFTA_EXTHDR_OP, htonl(priv->op))) 329 goto nla_put_failure; 330 return 0; 331 332 nla_put_failure: 333 return -1; 334 } 335 336 static int nft_exthdr_dump(struct sk_buff *skb, const struct nft_expr *expr) 337 { 338 const struct nft_exthdr *priv = nft_expr_priv(expr); 339 340 if (nft_dump_register(skb, NFTA_EXTHDR_DREG, priv->dreg)) 341 return -1; 342 343 return nft_exthdr_dump_common(skb, priv); 344 } 345 346 static int nft_exthdr_dump_set(struct sk_buff *skb, const struct nft_expr *expr) 347 { 348 const struct nft_exthdr *priv = nft_expr_priv(expr); 349 350 if (nft_dump_register(skb, NFTA_EXTHDR_SREG, priv->sreg)) 351 return -1; 352 353 return nft_exthdr_dump_common(skb, priv); 354 } 355 356 static struct nft_expr_type nft_exthdr_type; 357 static const struct nft_expr_ops nft_exthdr_ipv6_ops = { 358 .type = &nft_exthdr_type, 359 .size = NFT_EXPR_SIZE(sizeof(struct nft_exthdr)), 360 .eval = nft_exthdr_ipv6_eval, 361 .init = nft_exthdr_init, 362 .dump = nft_exthdr_dump, 363 }; 364 365 static const struct nft_expr_ops nft_exthdr_tcp_ops = { 366 .type = &nft_exthdr_type, 367 .size = NFT_EXPR_SIZE(sizeof(struct nft_exthdr)), 368 .eval = nft_exthdr_tcp_eval, 369 .init = nft_exthdr_init, 370 .dump = nft_exthdr_dump, 371 }; 372 373 static const struct nft_expr_ops nft_exthdr_tcp_set_ops = { 374 .type = &nft_exthdr_type, 375 .size = NFT_EXPR_SIZE(sizeof(struct nft_exthdr)), 376 .eval = nft_exthdr_tcp_set_eval, 377 .init = nft_exthdr_tcp_set_init, 378 .dump = nft_exthdr_dump_set, 379 }; 380 381 static const struct nft_expr_ops * 382 nft_exthdr_select_ops(const struct nft_ctx *ctx, 383 const struct nlattr * const tb[]) 384 { 385 u32 op; 386 387 if (!tb[NFTA_EXTHDR_OP]) 388 return &nft_exthdr_ipv6_ops; 389 390 if (tb[NFTA_EXTHDR_SREG] && tb[NFTA_EXTHDR_DREG]) 391 return ERR_PTR(-EOPNOTSUPP); 392 393 op = ntohl(nla_get_be32(tb[NFTA_EXTHDR_OP])); 394 switch (op) { 395 case NFT_EXTHDR_OP_TCPOPT: 396 if (tb[NFTA_EXTHDR_SREG]) 397 return &nft_exthdr_tcp_set_ops; 398 if (tb[NFTA_EXTHDR_DREG]) 399 return &nft_exthdr_tcp_ops; 400 break; 401 case NFT_EXTHDR_OP_IPV6: 402 if (tb[NFTA_EXTHDR_DREG]) 403 return &nft_exthdr_ipv6_ops; 404 break; 405 } 406 407 return ERR_PTR(-EOPNOTSUPP); 408 } 409 410 static struct nft_expr_type nft_exthdr_type __read_mostly = { 411 .name = "exthdr", 412 .select_ops = nft_exthdr_select_ops, 413 .policy = nft_exthdr_policy, 414 .maxattr = NFTA_EXTHDR_MAX, 415 .owner = THIS_MODULE, 416 }; 417 418 static int __init nft_exthdr_module_init(void) 419 { 420 return nft_register_expr(&nft_exthdr_type); 421 } 422 423 static void __exit nft_exthdr_module_exit(void) 424 { 425 nft_unregister_expr(&nft_exthdr_type); 426 } 427 428 module_init(nft_exthdr_module_init); 429 module_exit(nft_exthdr_module_exit); 430 431 MODULE_LICENSE("GPL"); 432 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>"); 433 MODULE_ALIAS_NFT_EXPR("exthdr"); 434