net/netfilter/nft_hash.c

   1 /*
   2  * Copyright (c) 2016 Laura Garcia <nevola@gmail.com>
   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  */
   9
  10 #include <linux/kernel.h>
  11 #include <linux/init.h>
  12 #include <linux/module.h>
  13 #include <linux/netlink.h>
  14 #include <linux/netfilter.h>
  15 #include <linux/netfilter/nf_tables.h>
  16 #include <net/netfilter/nf_tables.h>
  17 #include <net/netfilter/nf_tables_core.h>
  18 #include <linux/jhash.h>
  19
  20 struct nft_jhash {
  21         enum nft_registers      sreg:8;
  22         enum nft_registers      dreg:8;
  23         u8                      len;
  24         u32                     modulus;
  25         u32                     seed;
  26         u32                     offset;
  27 };
  28
  29 static void nft_jhash_eval(const struct nft_expr *expr,
  30                            struct nft_regs *regs,
  31                            const struct nft_pktinfo *pkt)
  32 {
  33         struct nft_jhash *priv = nft_expr_priv(expr);
  34         const void *data = &regs->data[priv->sreg];
  35         u32 h;
  36
  37         h = reciprocal_scale(jhash(data, priv->len, priv->seed), priv->modulus);
  38         regs->data[priv->dreg] = h + priv->offset;
  39 }
  40
  41 struct nft_symhash {
  42         enum nft_registers      dreg:8;
  43         u32                     modulus;
  44         u32                     offset;
  45 };
  46
  47 static void nft_symhash_eval(const struct nft_expr *expr,
  48                              struct nft_regs *regs,
  49                              const struct nft_pktinfo *pkt)
  50 {
  51         struct nft_symhash *priv = nft_expr_priv(expr);
  52         struct sk_buff *skb = pkt->skb;
  53         u32 h;
  54
  55         h = reciprocal_scale(__skb_get_hash_symmetric(skb), priv->modulus);
  56
  57         regs->data[priv->dreg] = h + priv->offset;
  58 }
  59
  60 static const struct nla_policy nft_hash_policy[NFTA_HASH_MAX + 1] = {
  61         [NFTA_HASH_SREG]        = { .type = NLA_U32 },
  62         [NFTA_HASH_DREG]        = { .type = NLA_U32 },
  63         [NFTA_HASH_LEN]         = { .type = NLA_U32 },
  64         [NFTA_HASH_MODULUS]     = { .type = NLA_U32 },
  65         [NFTA_HASH_SEED]        = { .type = NLA_U32 },
  66         [NFTA_HASH_OFFSET]      = { .type = NLA_U32 },
  67         [NFTA_HASH_TYPE]        = { .type = NLA_U32 },
  68 };
  69
  70 static int nft_jhash_init(const struct nft_ctx *ctx,
  71                           const struct nft_expr *expr,
  72                           const struct nlattr * const tb[])
  73 {
  74         struct nft_jhash *priv = nft_expr_priv(expr);
  75         u32 len;
  76         int err;
  77
  78         if (!tb[NFTA_HASH_SREG] ||
  79             !tb[NFTA_HASH_DREG] ||
  80             !tb[NFTA_HASH_LEN]  ||
  81             !tb[NFTA_HASH_MODULUS])
  82                 return -EINVAL;
  83
  84         if (tb[NFTA_HASH_OFFSET])
  85                 priv->offset = ntohl(nla_get_be32(tb[NFTA_HASH_OFFSET]));
  86
  87         priv->sreg = nft_parse_register(tb[NFTA_HASH_SREG]);
  88         priv->dreg = nft_parse_register(tb[NFTA_HASH_DREG]);
  89
  90         err = nft_parse_u32_check(tb[NFTA_HASH_LEN], U8_MAX, &len);
  91         if (err < 0)
  92                 return err;
  93         if (len == 0)
  94                 return -ERANGE;
  95
  96         priv->len = len;
  97
  98         priv->modulus = ntohl(nla_get_be32(tb[NFTA_HASH_MODULUS]));
  99         if (priv->modulus <= 1)
 100                 return -ERANGE;
 101
 102         if (priv->offset + priv->modulus - 1 < priv->offset)
 103                 return -EOVERFLOW;
 104
 105         if (tb[NFTA_HASH_SEED])
 106                 priv->seed = ntohl(nla_get_be32(tb[NFTA_HASH_SEED]));
 107         else
 108                 get_random_bytes(&priv->seed, sizeof(priv->seed));
 109
 110         return nft_validate_register_load(priv->sreg, len) &&
 111                nft_validate_register_store(ctx, priv->dreg, NULL,
 112                                            NFT_DATA_VALUE, sizeof(u32));
 113 }
 114
 115 static int nft_symhash_init(const struct nft_ctx *ctx,
 116                             const struct nft_expr *expr,
 117                             const struct nlattr * const tb[])
 118 {
 119         struct nft_symhash *priv = nft_expr_priv(expr);
 120
 121         if (!tb[NFTA_HASH_DREG]    ||
 122             !tb[NFTA_HASH_MODULUS])
 123                 return -EINVAL;
 124
 125         if (tb[NFTA_HASH_OFFSET])
 126                 priv->offset = ntohl(nla_get_be32(tb[NFTA_HASH_OFFSET]));
 127
 128         priv->dreg = nft_parse_register(tb[NFTA_HASH_DREG]);
 129
 130         priv->modulus = ntohl(nla_get_be32(tb[NFTA_HASH_MODULUS]));
 131         if (priv->modulus <= 1)
 132                 return -ERANGE;
 133
 134         if (priv->offset + priv->modulus - 1 < priv->offset)
 135                 return -EOVERFLOW;
 136
 137         return nft_validate_register_store(ctx, priv->dreg, NULL,
 138                                            NFT_DATA_VALUE, sizeof(u32));
 139 }
 140
 141 static int nft_jhash_dump(struct sk_buff *skb,
 142                           const struct nft_expr *expr)
 143 {
 144         const struct nft_jhash *priv = nft_expr_priv(expr);
 145
 146         if (nft_dump_register(skb, NFTA_HASH_SREG, priv->sreg))
 147                 goto nla_put_failure;
 148         if (nft_dump_register(skb, NFTA_HASH_DREG, priv->dreg))
 149                 goto nla_put_failure;
 150         if (nla_put_be32(skb, NFTA_HASH_LEN, htonl(priv->len)))
 151                 goto nla_put_failure;
 152         if (nla_put_be32(skb, NFTA_HASH_MODULUS, htonl(priv->modulus)))
 153                 goto nla_put_failure;
 154         if (nla_put_be32(skb, NFTA_HASH_SEED, htonl(priv->seed)))
 155                 goto nla_put_failure;
 156         if (priv->offset != 0)
 157                 if (nla_put_be32(skb, NFTA_HASH_OFFSET, htonl(priv->offset)))
 158                         goto nla_put_failure;
 159         if (nla_put_be32(skb, NFTA_HASH_TYPE, htonl(NFT_HASH_JENKINS)))
 160                 goto nla_put_failure;
 161         return 0;
 162
 163 nla_put_failure:
 164         return -1;
 165 }
 166
 167 static int nft_symhash_dump(struct sk_buff *skb,
 168                             const struct nft_expr *expr)
 169 {
 170         const struct nft_symhash *priv = nft_expr_priv(expr);
 171
 172         if (nft_dump_register(skb, NFTA_HASH_DREG, priv->dreg))
 173                 goto nla_put_failure;
 174         if (nla_put_be32(skb, NFTA_HASH_MODULUS, htonl(priv->modulus)))
 175                 goto nla_put_failure;
 176         if (priv->offset != 0)
 177                 if (nla_put_be32(skb, NFTA_HASH_OFFSET, htonl(priv->offset)))
 178                         goto nla_put_failure;
 179         if (nla_put_be32(skb, NFTA_HASH_TYPE, htonl(NFT_HASH_SYM)))
 180                 goto nla_put_failure;
 181         return 0;
 182
 183 nla_put_failure:
 184         return -1;
 185 }
 186
 187 static struct nft_expr_type nft_hash_type;
 188 static const struct nft_expr_ops nft_jhash_ops = {
 189         .type           = &nft_hash_type,
 190         .size           = NFT_EXPR_SIZE(sizeof(struct nft_jhash)),
 191         .eval           = nft_jhash_eval,
 192         .init           = nft_jhash_init,
 193         .dump           = nft_jhash_dump,
 194 };
 195
 196 static const struct nft_expr_ops nft_symhash_ops = {
 197         .type           = &nft_hash_type,
 198         .size           = NFT_EXPR_SIZE(sizeof(struct nft_symhash)),
 199         .eval           = nft_symhash_eval,
 200         .init           = nft_symhash_init,
 201         .dump           = nft_symhash_dump,
 202 };
 203
 204 static const struct nft_expr_ops *
 205 nft_hash_select_ops(const struct nft_ctx *ctx,
 206                     const struct nlattr * const tb[])
 207 {
 208         u32 type;
 209
 210         if (!tb[NFTA_HASH_TYPE])
 211                 return &nft_jhash_ops;
 212
 213         type = ntohl(nla_get_be32(tb[NFTA_HASH_TYPE]));
 214         switch (type) {
 215         case NFT_HASH_SYM:
 216                 return &nft_symhash_ops;
 217         case NFT_HASH_JENKINS:
 218                 return &nft_jhash_ops;
 219         default:
 220                 break;
 221         }
 222         return ERR_PTR(-EOPNOTSUPP);
 223 }
 224
 225 static struct nft_expr_type nft_hash_type __read_mostly = {
 226         .name           = "hash",
 227         .select_ops     = &nft_hash_select_ops,
 228         .policy         = nft_hash_policy,
 229         .maxattr        = NFTA_HASH_MAX,
 230         .owner          = THIS_MODULE,
 231 };
 232
 233 static int __init nft_hash_module_init(void)
 234 {
 235         return nft_register_expr(&nft_hash_type);
 236 }
 237
 238 static void __exit nft_hash_module_exit(void)
 239 {
 240         nft_unregister_expr(&nft_hash_type);
 241 }
 242
 243 module_init(nft_hash_module_init);
 244 module_exit(nft_hash_module_exit);
 245
 246 MODULE_LICENSE("GPL");
 247 MODULE_AUTHOR("Laura Garcia <nevola@gmail.com>");
 248 MODULE_ALIAS_NFT_EXPR("hash");