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 <linux/kernel.h> 12 #include <linux/init.h> 13 #include <linux/module.h> 14 #include <linux/netlink.h> 15 #include <linux/netfilter.h> 16 #include <linux/netfilter/nf_tables.h> 17 #include <net/netfilter/nf_tables.h> 18 #include <net/tcp.h> 19 20 struct nft_exthdr { 21 u8 type; 22 u8 offset; 23 u8 len; 24 u8 op; 25 enum nft_registers dreg:8; 26 u8 flags; 27 }; 28 29 static unsigned int optlen(const u8 *opt, unsigned int offset) 30 { 31 /* Beware zero-length options: make finite progress */ 32 if (opt[offset] <= TCPOPT_NOP || opt[offset + 1] == 0) 33 return 1; 34 else 35 return opt[offset + 1]; 36 } 37 38 static void nft_exthdr_ipv6_eval(const struct nft_expr *expr, 39 struct nft_regs *regs, 40 const struct nft_pktinfo *pkt) 41 { 42 struct nft_exthdr *priv = nft_expr_priv(expr); 43 u32 *dest = ®s->data[priv->dreg]; 44 unsigned int offset = 0; 45 int err; 46 47 err = ipv6_find_hdr(pkt->skb, &offset, priv->type, NULL, NULL); 48 if (priv->flags & NFT_EXTHDR_F_PRESENT) { 49 *dest = (err >= 0); 50 return; 51 } else if (err < 0) { 52 goto err; 53 } 54 offset += priv->offset; 55 56 dest[priv->len / NFT_REG32_SIZE] = 0; 57 if (skb_copy_bits(pkt->skb, offset, dest, priv->len) < 0) 58 goto err; 59 return; 60 err: 61 regs->verdict.code = NFT_BREAK; 62 } 63 64 static void nft_exthdr_tcp_eval(const struct nft_expr *expr, 65 struct nft_regs *regs, 66 const struct nft_pktinfo *pkt) 67 { 68 u8 buff[sizeof(struct tcphdr) + MAX_TCP_OPTION_SPACE]; 69 struct nft_exthdr *priv = nft_expr_priv(expr); 70 unsigned int i, optl, tcphdr_len, offset; 71 u32 *dest = ®s->data[priv->dreg]; 72 struct tcphdr *tcph; 73 u8 *opt; 74 75 if (!pkt->tprot_set || pkt->tprot != IPPROTO_TCP) 76 goto err; 77 78 tcph = skb_header_pointer(pkt->skb, pkt->xt.thoff, sizeof(*tcph), buff); 79 if (!tcph) 80 goto err; 81 82 tcphdr_len = __tcp_hdrlen(tcph); 83 if (tcphdr_len < sizeof(*tcph)) 84 goto err; 85 86 tcph = skb_header_pointer(pkt->skb, pkt->xt.thoff, tcphdr_len, buff); 87 if (!tcph) 88 goto err; 89 90 opt = (u8 *)tcph; 91 for (i = sizeof(*tcph); i < tcphdr_len - 1; i += optl) { 92 optl = optlen(opt, i); 93 94 if (priv->type != opt[i]) 95 continue; 96 97 if (i + optl > tcphdr_len || priv->len + priv->offset > optl) 98 goto err; 99 100 offset = i + priv->offset; 101 dest[priv->len / NFT_REG32_SIZE] = 0; 102 memcpy(dest, opt + offset, priv->len); 103 104 return; 105 } 106 107 err: 108 regs->verdict.code = NFT_BREAK; 109 } 110 111 static const struct nla_policy nft_exthdr_policy[NFTA_EXTHDR_MAX + 1] = { 112 [NFTA_EXTHDR_DREG] = { .type = NLA_U32 }, 113 [NFTA_EXTHDR_TYPE] = { .type = NLA_U8 }, 114 [NFTA_EXTHDR_OFFSET] = { .type = NLA_U32 }, 115 [NFTA_EXTHDR_LEN] = { .type = NLA_U32 }, 116 [NFTA_EXTHDR_FLAGS] = { .type = NLA_U32 }, 117 }; 118 119 static int nft_exthdr_init(const struct nft_ctx *ctx, 120 const struct nft_expr *expr, 121 const struct nlattr * const tb[]) 122 { 123 struct nft_exthdr *priv = nft_expr_priv(expr); 124 u32 offset, len, flags = 0, op = NFT_EXTHDR_OP_IPV6; 125 int err; 126 127 if (!tb[NFTA_EXTHDR_DREG] || 128 !tb[NFTA_EXTHDR_TYPE] || 129 !tb[NFTA_EXTHDR_OFFSET] || 130 !tb[NFTA_EXTHDR_LEN]) 131 return -EINVAL; 132 133 err = nft_parse_u32_check(tb[NFTA_EXTHDR_OFFSET], U8_MAX, &offset); 134 if (err < 0) 135 return err; 136 137 err = nft_parse_u32_check(tb[NFTA_EXTHDR_LEN], U8_MAX, &len); 138 if (err < 0) 139 return err; 140 141 if (tb[NFTA_EXTHDR_FLAGS]) { 142 err = nft_parse_u32_check(tb[NFTA_EXTHDR_FLAGS], U8_MAX, &flags); 143 if (err < 0) 144 return err; 145 146 if (flags & ~NFT_EXTHDR_F_PRESENT) 147 return -EINVAL; 148 } 149 150 if (tb[NFTA_EXTHDR_OP]) { 151 err = nft_parse_u32_check(tb[NFTA_EXTHDR_OP], U8_MAX, &op); 152 if (err < 0) 153 return err; 154 } 155 156 priv->type = nla_get_u8(tb[NFTA_EXTHDR_TYPE]); 157 priv->offset = offset; 158 priv->len = len; 159 priv->dreg = nft_parse_register(tb[NFTA_EXTHDR_DREG]); 160 priv->flags = flags; 161 priv->op = op; 162 163 return nft_validate_register_store(ctx, priv->dreg, NULL, 164 NFT_DATA_VALUE, priv->len); 165 } 166 167 static int nft_exthdr_dump(struct sk_buff *skb, const struct nft_expr *expr) 168 { 169 const struct nft_exthdr *priv = nft_expr_priv(expr); 170 171 if (nft_dump_register(skb, NFTA_EXTHDR_DREG, priv->dreg)) 172 goto nla_put_failure; 173 if (nla_put_u8(skb, NFTA_EXTHDR_TYPE, priv->type)) 174 goto nla_put_failure; 175 if (nla_put_be32(skb, NFTA_EXTHDR_OFFSET, htonl(priv->offset))) 176 goto nla_put_failure; 177 if (nla_put_be32(skb, NFTA_EXTHDR_LEN, htonl(priv->len))) 178 goto nla_put_failure; 179 if (nla_put_be32(skb, NFTA_EXTHDR_FLAGS, htonl(priv->flags))) 180 goto nla_put_failure; 181 if (nla_put_be32(skb, NFTA_EXTHDR_OP, htonl(priv->op))) 182 goto nla_put_failure; 183 return 0; 184 185 nla_put_failure: 186 return -1; 187 } 188 189 static struct nft_expr_type nft_exthdr_type; 190 static const struct nft_expr_ops nft_exthdr_ipv6_ops = { 191 .type = &nft_exthdr_type, 192 .size = NFT_EXPR_SIZE(sizeof(struct nft_exthdr)), 193 .eval = nft_exthdr_ipv6_eval, 194 .init = nft_exthdr_init, 195 .dump = nft_exthdr_dump, 196 }; 197 198 static const struct nft_expr_ops nft_exthdr_tcp_ops = { 199 .type = &nft_exthdr_type, 200 .size = NFT_EXPR_SIZE(sizeof(struct nft_exthdr)), 201 .eval = nft_exthdr_tcp_eval, 202 .init = nft_exthdr_init, 203 .dump = nft_exthdr_dump, 204 }; 205 206 static const struct nft_expr_ops * 207 nft_exthdr_select_ops(const struct nft_ctx *ctx, 208 const struct nlattr * const tb[]) 209 { 210 u32 op; 211 212 if (!tb[NFTA_EXTHDR_OP]) 213 return &nft_exthdr_ipv6_ops; 214 215 op = ntohl(nla_get_u32(tb[NFTA_EXTHDR_OP])); 216 switch (op) { 217 case NFT_EXTHDR_OP_TCPOPT: 218 return &nft_exthdr_tcp_ops; 219 case NFT_EXTHDR_OP_IPV6: 220 return &nft_exthdr_ipv6_ops; 221 } 222 223 return ERR_PTR(-EOPNOTSUPP); 224 } 225 226 static struct nft_expr_type nft_exthdr_type __read_mostly = { 227 .name = "exthdr", 228 .select_ops = &nft_exthdr_select_ops, 229 .policy = nft_exthdr_policy, 230 .maxattr = NFTA_EXTHDR_MAX, 231 .owner = THIS_MODULE, 232 }; 233 234 static int __init nft_exthdr_module_init(void) 235 { 236 return nft_register_expr(&nft_exthdr_type); 237 } 238 239 static void __exit nft_exthdr_module_exit(void) 240 { 241 nft_unregister_expr(&nft_exthdr_type); 242 } 243 244 module_init(nft_exthdr_module_init); 245 module_exit(nft_exthdr_module_exit); 246 247 MODULE_LICENSE("GPL"); 248 MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>"); 249 MODULE_ALIAS_NFT_EXPR("exthdr"); 250