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].data[0];
  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, priv->len) < 0)
  47                 goto err;
  48         return;
  49 err:
  50         regs->verdict.code = 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
  66         priv->base   = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_BASE]));
  67         priv->offset = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_OFFSET]));
  68         priv->len    = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_LEN]));
  69         priv->dreg   = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_DREG]));
  70
  71         return nft_validate_register_store(ctx, priv->dreg, NULL,
  72                                            NFT_DATA_VALUE, priv->len);
  73 }
  74
  75 static int nft_payload_dump(struct sk_buff *skb, const struct nft_expr *expr)
  76 {
  77         const struct nft_payload *priv = nft_expr_priv(expr);
  78
  79         if (nla_put_be32(skb, NFTA_PAYLOAD_DREG, htonl(priv->dreg)) ||
  80             nla_put_be32(skb, NFTA_PAYLOAD_BASE, htonl(priv->base)) ||
  81             nla_put_be32(skb, NFTA_PAYLOAD_OFFSET, htonl(priv->offset)) ||
  82             nla_put_be32(skb, NFTA_PAYLOAD_LEN, htonl(priv->len)))
  83                 goto nla_put_failure;
  84         return 0;
  85
  86 nla_put_failure:
  87         return -1;
  88 }
  89
  90 static struct nft_expr_type nft_payload_type;
  91 static const struct nft_expr_ops nft_payload_ops = {
  92         .type           = &nft_payload_type,
  93         .size           = NFT_EXPR_SIZE(sizeof(struct nft_payload)),
  94         .eval           = nft_payload_eval,
  95         .init           = nft_payload_init,
  96         .dump           = nft_payload_dump,
  97 };
  98
  99 const struct nft_expr_ops nft_payload_fast_ops = {
 100         .type           = &nft_payload_type,
 101         .size           = NFT_EXPR_SIZE(sizeof(struct nft_payload)),
 102         .eval           = nft_payload_eval,
 103         .init           = nft_payload_init,
 104         .dump           = nft_payload_dump,
 105 };
 106
 107 static const struct nft_expr_ops *
 108 nft_payload_select_ops(const struct nft_ctx *ctx,
 109                        const struct nlattr * const tb[])
 110 {
 111         enum nft_payload_bases base;
 112         unsigned int offset, len;
 113
 114         if (tb[NFTA_PAYLOAD_DREG] == NULL ||
 115             tb[NFTA_PAYLOAD_BASE] == NULL ||
 116             tb[NFTA_PAYLOAD_OFFSET] == NULL ||
 117             tb[NFTA_PAYLOAD_LEN] == NULL)
 118                 return ERR_PTR(-EINVAL);
 119
 120         base = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_BASE]));
 121         switch (base) {
 122         case NFT_PAYLOAD_LL_HEADER:
 123         case NFT_PAYLOAD_NETWORK_HEADER:
 124         case NFT_PAYLOAD_TRANSPORT_HEADER:
 125                 break;
 126         default:
 127                 return ERR_PTR(-EOPNOTSUPP);
 128         }
 129
 130         offset = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_OFFSET]));
 131         len    = ntohl(nla_get_be32(tb[NFTA_PAYLOAD_LEN]));
 132
 133         if (len <= 4 && is_power_of_2(len) && IS_ALIGNED(offset, len) &&
 134             base != NFT_PAYLOAD_LL_HEADER)
 135                 return &nft_payload_fast_ops;
 136         else
 137                 return &nft_payload_ops;
 138 }
 139
 140 static struct nft_expr_type nft_payload_type __read_mostly = {
 141         .name           = "payload",
 142         .select_ops     = nft_payload_select_ops,
 143         .policy         = nft_payload_policy,
 144         .maxattr        = NFTA_PAYLOAD_MAX,
 145         .owner          = THIS_MODULE,
 146 };
 147
 148 int __init nft_payload_module_init(void)
 149 {
 150         return nft_register_expr(&nft_payload_type);
 151 }
 152
 153 void nft_payload_module_exit(void)
 154 {
 155         nft_unregister_expr(&nft_payload_type);
 156 }