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_hash { 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_hash_eval(const struct nft_expr *expr, 30 struct nft_regs *regs, 31 const struct nft_pktinfo *pkt) 32 { 33 struct nft_hash *priv = nft_expr_priv(expr); 34 const void *data = ®s->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 static const struct nla_policy nft_hash_policy[NFTA_HASH_MAX + 1] = { 42 [NFTA_HASH_SREG] = { .type = NLA_U32 }, 43 [NFTA_HASH_DREG] = { .type = NLA_U32 }, 44 [NFTA_HASH_LEN] = { .type = NLA_U32 }, 45 [NFTA_HASH_MODULUS] = { .type = NLA_U32 }, 46 [NFTA_HASH_SEED] = { .type = NLA_U32 }, 47 [NFTA_HASH_OFFSET] = { .type = NLA_U32 }, 48 }; 49 50 static int nft_hash_init(const struct nft_ctx *ctx, 51 const struct nft_expr *expr, 52 const struct nlattr * const tb[]) 53 { 54 struct nft_hash *priv = nft_expr_priv(expr); 55 u32 len; 56 57 if (!tb[NFTA_HASH_SREG] || 58 !tb[NFTA_HASH_DREG] || 59 !tb[NFTA_HASH_LEN] || 60 !tb[NFTA_HASH_SEED] || 61 !tb[NFTA_HASH_MODULUS]) 62 return -EINVAL; 63 64 if (tb[NFTA_HASH_OFFSET]) 65 priv->offset = ntohl(nla_get_be32(tb[NFTA_HASH_OFFSET])); 66 67 priv->sreg = nft_parse_register(tb[NFTA_HASH_SREG]); 68 priv->dreg = nft_parse_register(tb[NFTA_HASH_DREG]); 69 70 len = ntohl(nla_get_be32(tb[NFTA_HASH_LEN])); 71 if (len == 0 || len > U8_MAX) 72 return -ERANGE; 73 74 priv->len = len; 75 76 priv->modulus = ntohl(nla_get_be32(tb[NFTA_HASH_MODULUS])); 77 if (priv->modulus <= 1) 78 return -ERANGE; 79 80 if (priv->offset + priv->modulus - 1 < priv->offset) 81 return -EOVERFLOW; 82 83 priv->seed = ntohl(nla_get_be32(tb[NFTA_HASH_SEED])); 84 85 return nft_validate_register_load(priv->sreg, len) && 86 nft_validate_register_store(ctx, priv->dreg, NULL, 87 NFT_DATA_VALUE, sizeof(u32)); 88 } 89 90 static int nft_hash_dump(struct sk_buff *skb, 91 const struct nft_expr *expr) 92 { 93 const struct nft_hash *priv = nft_expr_priv(expr); 94 95 if (nft_dump_register(skb, NFTA_HASH_SREG, priv->sreg)) 96 goto nla_put_failure; 97 if (nft_dump_register(skb, NFTA_HASH_DREG, priv->dreg)) 98 goto nla_put_failure; 99 if (nla_put_be32(skb, NFTA_HASH_LEN, htonl(priv->len))) 100 goto nla_put_failure; 101 if (nla_put_be32(skb, NFTA_HASH_MODULUS, htonl(priv->modulus))) 102 goto nla_put_failure; 103 if (nla_put_be32(skb, NFTA_HASH_SEED, htonl(priv->seed))) 104 goto nla_put_failure; 105 if (priv->offset != 0) 106 if (nla_put_be32(skb, NFTA_HASH_OFFSET, htonl(priv->offset))) 107 goto nla_put_failure; 108 return 0; 109 110 nla_put_failure: 111 return -1; 112 } 113 114 static struct nft_expr_type nft_hash_type; 115 static const struct nft_expr_ops nft_hash_ops = { 116 .type = &nft_hash_type, 117 .size = NFT_EXPR_SIZE(sizeof(struct nft_hash)), 118 .eval = nft_hash_eval, 119 .init = nft_hash_init, 120 .dump = nft_hash_dump, 121 }; 122 123 static struct nft_expr_type nft_hash_type __read_mostly = { 124 .name = "hash", 125 .ops = &nft_hash_ops, 126 .policy = nft_hash_policy, 127 .maxattr = NFTA_HASH_MAX, 128 .owner = THIS_MODULE, 129 }; 130 131 static int __init nft_hash_module_init(void) 132 { 133 return nft_register_expr(&nft_hash_type); 134 } 135 136 static void __exit nft_hash_module_exit(void) 137 { 138 nft_unregister_expr(&nft_hash_type); 139 } 140 141 module_init(nft_hash_module_init); 142 module_exit(nft_hash_module_exit); 143 144 MODULE_LICENSE("GPL"); 145 MODULE_AUTHOR("Laura Garcia <nevola@gmail.com>"); 146 MODULE_ALIAS_NFT_EXPR("hash"); 147