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Linux/net/netfilter/nft_hash.c

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  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         bool                    autogen_seed:1;
 25         u32                     modulus;
 26         u32                     seed;
 27         u32                     offset;
 28 };
 29 
 30 static void nft_jhash_eval(const struct nft_expr *expr,
 31                            struct nft_regs *regs,
 32                            const struct nft_pktinfo *pkt)
 33 {
 34         struct nft_jhash *priv = nft_expr_priv(expr);
 35         const void *data = &regs->data[priv->sreg];
 36         u32 h;
 37 
 38         h = reciprocal_scale(jhash(data, priv->len, priv->seed), priv->modulus);
 39         regs->data[priv->dreg] = h + priv->offset;
 40 }
 41 
 42 struct nft_symhash {
 43         enum nft_registers      dreg:8;
 44         u32                     modulus;
 45         u32                     offset;
 46 };
 47 
 48 static void nft_symhash_eval(const struct nft_expr *expr,
 49                              struct nft_regs *regs,
 50                              const struct nft_pktinfo *pkt)
 51 {
 52         struct nft_symhash *priv = nft_expr_priv(expr);
 53         struct sk_buff *skb = pkt->skb;
 54         u32 h;
 55 
 56         h = reciprocal_scale(__skb_get_hash_symmetric(skb), priv->modulus);
 57 
 58         regs->data[priv->dreg] = h + priv->offset;
 59 }
 60 
 61 static const struct nla_policy nft_hash_policy[NFTA_HASH_MAX + 1] = {
 62         [NFTA_HASH_SREG]        = { .type = NLA_U32 },
 63         [NFTA_HASH_DREG]        = { .type = NLA_U32 },
 64         [NFTA_HASH_LEN]         = { .type = NLA_U32 },
 65         [NFTA_HASH_MODULUS]     = { .type = NLA_U32 },
 66         [NFTA_HASH_SEED]        = { .type = NLA_U32 },
 67         [NFTA_HASH_OFFSET]      = { .type = NLA_U32 },
 68         [NFTA_HASH_TYPE]        = { .type = NLA_U32 },
 69 };
 70 
 71 static int nft_jhash_init(const struct nft_ctx *ctx,
 72                           const struct nft_expr *expr,
 73                           const struct nlattr * const tb[])
 74 {
 75         struct nft_jhash *priv = nft_expr_priv(expr);
 76         u32 len;
 77         int err;
 78 
 79         if (!tb[NFTA_HASH_SREG] ||
 80             !tb[NFTA_HASH_DREG] ||
 81             !tb[NFTA_HASH_LEN]  ||
 82             !tb[NFTA_HASH_MODULUS])
 83                 return -EINVAL;
 84 
 85         if (tb[NFTA_HASH_OFFSET])
 86                 priv->offset = ntohl(nla_get_be32(tb[NFTA_HASH_OFFSET]));
 87 
 88         priv->sreg = nft_parse_register(tb[NFTA_HASH_SREG]);
 89         priv->dreg = nft_parse_register(tb[NFTA_HASH_DREG]);
 90 
 91         err = nft_parse_u32_check(tb[NFTA_HASH_LEN], U8_MAX, &len);
 92         if (err < 0)
 93                 return err;
 94         if (len == 0)
 95                 return -ERANGE;
 96 
 97         priv->len = len;
 98 
 99         priv->modulus = ntohl(nla_get_be32(tb[NFTA_HASH_MODULUS]));
100         if (priv->modulus <= 1)
101                 return -ERANGE;
102 
103         if (priv->offset + priv->modulus - 1 < priv->offset)
104                 return -EOVERFLOW;
105 
106         if (tb[NFTA_HASH_SEED]) {
107                 priv->seed = ntohl(nla_get_be32(tb[NFTA_HASH_SEED]));
108         } else {
109                 priv->autogen_seed = true;
110                 get_random_bytes(&priv->seed, sizeof(priv->seed));
111         }
112 
113         return nft_validate_register_load(priv->sreg, len) &&
114                nft_validate_register_store(ctx, priv->dreg, NULL,
115                                            NFT_DATA_VALUE, sizeof(u32));
116 }
117 
118 static int nft_symhash_init(const struct nft_ctx *ctx,
119                             const struct nft_expr *expr,
120                             const struct nlattr * const tb[])
121 {
122         struct nft_symhash *priv = nft_expr_priv(expr);
123 
124         if (!tb[NFTA_HASH_DREG]    ||
125             !tb[NFTA_HASH_MODULUS])
126                 return -EINVAL;
127 
128         if (tb[NFTA_HASH_OFFSET])
129                 priv->offset = ntohl(nla_get_be32(tb[NFTA_HASH_OFFSET]));
130 
131         priv->dreg = nft_parse_register(tb[NFTA_HASH_DREG]);
132 
133         priv->modulus = ntohl(nla_get_be32(tb[NFTA_HASH_MODULUS]));
134         if (priv->modulus <= 1)
135                 return -ERANGE;
136 
137         if (priv->offset + priv->modulus - 1 < priv->offset)
138                 return -EOVERFLOW;
139 
140         return nft_validate_register_store(ctx, priv->dreg, NULL,
141                                            NFT_DATA_VALUE, sizeof(u32));
142 }
143 
144 static int nft_jhash_dump(struct sk_buff *skb,
145                           const struct nft_expr *expr)
146 {
147         const struct nft_jhash *priv = nft_expr_priv(expr);
148 
149         if (nft_dump_register(skb, NFTA_HASH_SREG, priv->sreg))
150                 goto nla_put_failure;
151         if (nft_dump_register(skb, NFTA_HASH_DREG, priv->dreg))
152                 goto nla_put_failure;
153         if (nla_put_be32(skb, NFTA_HASH_LEN, htonl(priv->len)))
154                 goto nla_put_failure;
155         if (nla_put_be32(skb, NFTA_HASH_MODULUS, htonl(priv->modulus)))
156                 goto nla_put_failure;
157         if (!priv->autogen_seed &&
158             nla_put_be32(skb, NFTA_HASH_SEED, htonl(priv->seed)))
159                 goto nla_put_failure;
160         if (priv->offset != 0)
161                 if (nla_put_be32(skb, NFTA_HASH_OFFSET, htonl(priv->offset)))
162                         goto nla_put_failure;
163         if (nla_put_be32(skb, NFTA_HASH_TYPE, htonl(NFT_HASH_JENKINS)))
164                 goto nla_put_failure;
165         return 0;
166 
167 nla_put_failure:
168         return -1;
169 }
170 
171 static int nft_symhash_dump(struct sk_buff *skb,
172                             const struct nft_expr *expr)
173 {
174         const struct nft_symhash *priv = nft_expr_priv(expr);
175 
176         if (nft_dump_register(skb, NFTA_HASH_DREG, priv->dreg))
177                 goto nla_put_failure;
178         if (nla_put_be32(skb, NFTA_HASH_MODULUS, htonl(priv->modulus)))
179                 goto nla_put_failure;
180         if (priv->offset != 0)
181                 if (nla_put_be32(skb, NFTA_HASH_OFFSET, htonl(priv->offset)))
182                         goto nla_put_failure;
183         if (nla_put_be32(skb, NFTA_HASH_TYPE, htonl(NFT_HASH_SYM)))
184                 goto nla_put_failure;
185         return 0;
186 
187 nla_put_failure:
188         return -1;
189 }
190 
191 static struct nft_expr_type nft_hash_type;
192 static const struct nft_expr_ops nft_jhash_ops = {
193         .type           = &nft_hash_type,
194         .size           = NFT_EXPR_SIZE(sizeof(struct nft_jhash)),
195         .eval           = nft_jhash_eval,
196         .init           = nft_jhash_init,
197         .dump           = nft_jhash_dump,
198 };
199 
200 static const struct nft_expr_ops nft_symhash_ops = {
201         .type           = &nft_hash_type,
202         .size           = NFT_EXPR_SIZE(sizeof(struct nft_symhash)),
203         .eval           = nft_symhash_eval,
204         .init           = nft_symhash_init,
205         .dump           = nft_symhash_dump,
206 };
207 
208 static const struct nft_expr_ops *
209 nft_hash_select_ops(const struct nft_ctx *ctx,
210                     const struct nlattr * const tb[])
211 {
212         u32 type;
213 
214         if (!tb[NFTA_HASH_TYPE])
215                 return &nft_jhash_ops;
216 
217         type = ntohl(nla_get_be32(tb[NFTA_HASH_TYPE]));
218         switch (type) {
219         case NFT_HASH_SYM:
220                 return &nft_symhash_ops;
221         case NFT_HASH_JENKINS:
222                 return &nft_jhash_ops;
223         default:
224                 break;
225         }
226         return ERR_PTR(-EOPNOTSUPP);
227 }
228 
229 static struct nft_expr_type nft_hash_type __read_mostly = {
230         .name           = "hash",
231         .select_ops     = nft_hash_select_ops,
232         .policy         = nft_hash_policy,
233         .maxattr        = NFTA_HASH_MAX,
234         .owner          = THIS_MODULE,
235 };
236 
237 static int __init nft_hash_module_init(void)
238 {
239         return nft_register_expr(&nft_hash_type);
240 }
241 
242 static void __exit nft_hash_module_exit(void)
243 {
244         nft_unregister_expr(&nft_hash_type);
245 }
246 
247 module_init(nft_hash_module_init);
248 module_exit(nft_hash_module_exit);
249 
250 MODULE_LICENSE("GPL");
251 MODULE_AUTHOR("Laura Garcia <nevola@gmail.com>");
252 MODULE_ALIAS_NFT_EXPR("hash");
253 

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