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_data data[NFT_REG_MAX + 1],
  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         struct nft_data *dest = &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         if (skb_copy_bits(skb, offset, dest->data, priv->len) < 0)
  47                 goto err;
  48         return;
  49 err:
  50         data[NFT_REG_VERDICT].verdict = NFT_BREAK;
  51 }
  52
  53 static const struct nla_policy nft_payload_policy[NFTA_PAYLOAD_MAX + 1] = {
  54         [NFTA_PAYLOAD_DREG]     = { .type = NLA_U32 },
  55         [NFTA_PAYLOAD_BASE]     = { .type = NLA_U32 },
  56         [NFTA_PAYLOAD_OFFSET]   = { .type = NLA_U32 },
  57         [NFTA_PAYLOAD_LEN]      = { .type = NLA_U32 },
  58 };
  59
  60 static int nft_payload_init(const struct nft_ctx *ctx,
  61                             const struct nft_expr *expr,
  62                             const struct nlattr * const tb[])
  63 {
  64         struct nft_payload *priv = nft_expr_priv(expr);
  65         int err;
  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
  71         priv->dreg = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_DREG]));
  72         err = nft_validate_output_register(priv->dreg);
  73         if (err < 0)
  74                 return err;
  75         return nft_validate_data_load(ctx, priv->dreg, NULL,
  76                                       NFT_DATA_VALUE, priv->len);
  77 }
  78
  79 static int nft_payload_dump(struct sk_buff *skb, const struct nft_expr *expr)
  80 {
  81         const struct nft_payload *priv = nft_expr_priv(expr);
  82
  83         if (nla_put_be32(skb, NFTA_PAYLOAD_DREG, htonl(priv->dreg)) ||
  84             nla_put_be32(skb, NFTA_PAYLOAD_BASE, htonl(priv->base)) ||
  85             nla_put_be32(skb, NFTA_PAYLOAD_OFFSET, htonl(priv->offset)) ||
  86             nla_put_be32(skb, NFTA_PAYLOAD_LEN, htonl(priv->len)))
  87                 goto nla_put_failure;
  88         return 0;
  89
  90 nla_put_failure:
  91         return -1;
  92 }
  93
  94 static struct nft_expr_type nft_payload_type;
  95 static const struct nft_expr_ops nft_payload_ops = {
  96         .type           = &nft_payload_type,
  97         .size           = NFT_EXPR_SIZE(sizeof(struct nft_payload)),
  98         .eval           = nft_payload_eval,
  99         .init           = nft_payload_init,
 100         .dump           = nft_payload_dump,
 101 };
 102
 103 const struct nft_expr_ops nft_payload_fast_ops = {
 104         .type           = &nft_payload_type,
 105         .size           = NFT_EXPR_SIZE(sizeof(struct nft_payload)),
 106         .eval           = nft_payload_eval,
 107         .init           = nft_payload_init,
 108         .dump           = nft_payload_dump,
 109 };
 110
 111 static const struct nft_expr_ops *
 112 nft_payload_select_ops(const struct nft_ctx *ctx,
 113                        const struct nlattr * const tb[])
 114 {
 115         enum nft_payload_bases base;
 116         unsigned int offset, len;
 117
 118         if (tb[NFTA_PAYLOAD_DREG] == NULL ||
 119             tb[NFTA_PAYLOAD_BASE] == NULL ||
 120             tb[NFTA_PAYLOAD_OFFSET] == NULL ||
 121             tb[NFTA_PAYLOAD_LEN] == NULL)
 122                 return ERR_PTR(-EINVAL);
 123
 124         base = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_BASE]));
 125         switch (base) {
 126         case NFT_PAYLOAD_LL_HEADER:
 127         case NFT_PAYLOAD_NETWORK_HEADER:
 128         case NFT_PAYLOAD_TRANSPORT_HEADER:
 129                 break;
 130         default:
 131                 return ERR_PTR(-EOPNOTSUPP);
 132         }
 133
 134         offset = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_OFFSET]));
 135         len    = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_LEN]));
 136
 137         if (len <= 4 && is_power_of_2(len) && IS_ALIGNED(offset, len) &&
 138             base != NFT_PAYLOAD_LL_HEADER)
 139                 return &nft_payload_fast_ops;
 140         else
 141                 return &nft_payload_ops;
 142 }
 143
 144 static struct nft_expr_type nft_payload_type __read_mostly = {
 145         .name           = "payload",
 146         .select_ops     = nft_payload_select_ops,
 147         .policy         = nft_payload_policy,
 148         .maxattr        = NFTA_PAYLOAD_MAX,
 149         .owner          = THIS_MODULE,
 150 };
 151
 152 int __init nft_payload_module_init(void)
 153 {
 154         return nft_register_expr(&nft_payload_type);
 155 }
 156
 157 void nft_payload_module_exit(void)
 158 {
 159         nft_unregister_expr(&nft_payload_type);
 160 }