net/netfilter/nft_payload.c

   1 /*
   2  * Copyright (c) 2008-2009 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_core.h>
  18 #include <net/netfilter/nf_tables.h>
  19
  20 static void nft_payload_eval(const struct nft_expr *expr,
  21                              struct nft_regs *regs,
  22                              const struct nft_pktinfo *pkt)
  23 {
  24         const struct nft_payload *priv = nft_expr_priv(expr);
  25         const struct sk_buff *skb = pkt->skb;
  26         u32 *dest = &regs->data[priv->dreg];
  27         int offset;
  28
  29         switch (priv->base) {
  30         case NFT_PAYLOAD_LL_HEADER:
  31                 if (!skb_mac_header_was_set(skb))
  32                         goto err;
  33                 offset = skb_mac_header(skb) - skb->data;
  34                 break;
  35         case NFT_PAYLOAD_NETWORK_HEADER:
  36                 offset = skb_network_offset(skb);
  37                 break;
  38         case NFT_PAYLOAD_TRANSPORT_HEADER:
  39                 offset = pkt->xt.thoff;
  40                 break;
  41         default:
  42                 BUG();
  43         }
  44         offset += priv->offset;
  45
  46         dest[priv->len / NFT_REG32_SIZE] = 0;
  47         if (skb_copy_bits(skb, offset, dest, priv->len) < 0)
  48                 goto err;
  49         return;
  50 err:
  51         regs->verdict.code = NFT_BREAK;
  52 }
  53
  54 static const struct nla_policy nft_payload_policy[NFTA_PAYLOAD_MAX + 1] = {
  55         [NFTA_PAYLOAD_DREG]     = { .type = NLA_U32 },
  56         [NFTA_PAYLOAD_BASE]     = { .type = NLA_U32 },
  57         [NFTA_PAYLOAD_OFFSET]   = { .type = NLA_U32 },
  58         [NFTA_PAYLOAD_LEN]      = { .type = NLA_U32 },
  59 };
  60
  61 static int nft_payload_init(const struct nft_ctx *ctx,
  62                             const struct nft_expr *expr,
  63                             const struct nlattr * const tb[])
  64 {
  65         struct nft_payload *priv = nft_expr_priv(expr);
  66
  67         priv->base   = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_BASE]));
  68         priv->offset = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_OFFSET]));
  69         priv->len    = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_LEN]));
  70         priv->dreg   = nft_parse_register(tb[NFTA_PAYLOAD_DREG]);
  71
  72         return nft_validate_register_store(ctx, priv->dreg, NULL,
  73                                            NFT_DATA_VALUE, priv->len);
  74 }
  75
  76 static int nft_payload_dump(struct sk_buff *skb, const struct nft_expr *expr)
  77 {
  78         const struct nft_payload *priv = nft_expr_priv(expr);
  79
  80         if (nft_dump_register(skb, NFTA_PAYLOAD_DREG, priv->dreg) ||
  81             nla_put_be32(skb, NFTA_PAYLOAD_BASE, htonl(priv->base)) ||
  82             nla_put_be32(skb, NFTA_PAYLOAD_OFFSET, htonl(priv->offset)) ||
  83             nla_put_be32(skb, NFTA_PAYLOAD_LEN, htonl(priv->len)))
  84                 goto nla_put_failure;
  85         return 0;
  86
  87 nla_put_failure:
  88         return -1;
  89 }
  90
  91 static struct nft_expr_type nft_payload_type;
  92 static const struct nft_expr_ops nft_payload_ops = {
  93         .type           = &nft_payload_type,
  94         .size           = NFT_EXPR_SIZE(sizeof(struct nft_payload)),
  95         .eval           = nft_payload_eval,
  96         .init           = nft_payload_init,
  97         .dump           = nft_payload_dump,
  98 };
  99
 100 const struct nft_expr_ops nft_payload_fast_ops = {
 101         .type           = &nft_payload_type,
 102         .size           = NFT_EXPR_SIZE(sizeof(struct nft_payload)),
 103         .eval           = nft_payload_eval,
 104         .init           = nft_payload_init,
 105         .dump           = nft_payload_dump,
 106 };
 107
 108 static const struct nft_expr_ops *
 109 nft_payload_select_ops(const struct nft_ctx *ctx,
 110                        const struct nlattr * const tb[])
 111 {
 112         enum nft_payload_bases base;
 113         unsigned int offset, len;
 114
 115         if (tb[NFTA_PAYLOAD_DREG] == NULL ||
 116             tb[NFTA_PAYLOAD_BASE] == NULL ||
 117             tb[NFTA_PAYLOAD_OFFSET] == NULL ||
 118             tb[NFTA_PAYLOAD_LEN] == NULL)
 119                 return ERR_PTR(-EINVAL);
 120
 121         base = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_BASE]));
 122         switch (base) {
 123         case NFT_PAYLOAD_LL_HEADER:
 124         case NFT_PAYLOAD_NETWORK_HEADER:
 125         case NFT_PAYLOAD_TRANSPORT_HEADER:
 126                 break;
 127         default:
 128                 return ERR_PTR(-EOPNOTSUPP);
 129         }
 130
 131         offset = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_OFFSET]));
 132         len    = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_LEN]));
 133
 134         if (len <= 4 && is_power_of_2(len) && IS_ALIGNED(offset, len) &&
 135             base != NFT_PAYLOAD_LL_HEADER)
 136                 return &nft_payload_fast_ops;
 137         else
 138                 return &nft_payload_ops;
 139 }
 140
 141 static struct nft_expr_type nft_payload_type __read_mostly = {
 142         .name           = "payload",
 143         .select_ops     = nft_payload_select_ops,
 144         .policy         = nft_payload_policy,
 145         .maxattr        = NFTA_PAYLOAD_MAX,
 146         .owner          = THIS_MODULE,
 147 };
 148
 149 int __init nft_payload_module_init(void)
 150 {
 151         return nft_register_expr(&nft_payload_type);
 152 }
 153
 154 void nft_payload_module_exit(void)
 155 {
 156         nft_unregister_expr(&nft_payload_type);
 157 }