net/netfilter/nft_osf.c

   1 #include <net/ip.h>
   2 #include <net/tcp.h>
   3
   4 #include <net/netfilter/nf_tables.h>
   5 #include <linux/netfilter/nfnetlink_osf.h>
   6
   7 struct nft_osf {
   8         enum nft_registers      dreg:8;
   9         u8                      ttl;
  10 };
  11
  12 static const struct nla_policy nft_osf_policy[NFTA_OSF_MAX + 1] = {
  13         [NFTA_OSF_DREG]         = { .type = NLA_U32 },
  14         [NFTA_OSF_TTL]          = { .type = NLA_U8 },
  15 };
  16
  17 static void nft_osf_eval(const struct nft_expr *expr, struct nft_regs *regs,
  18                          const struct nft_pktinfo *pkt)
  19 {
  20         struct nft_osf *priv = nft_expr_priv(expr);
  21         u32 *dest = &regs->data[priv->dreg];
  22         struct sk_buff *skb = pkt->skb;
  23         const struct tcphdr *tcp;
  24         struct tcphdr _tcph;
  25         const char *os_name;
  26
  27         tcp = skb_header_pointer(skb, ip_hdrlen(skb),
  28                                  sizeof(struct tcphdr), &_tcph);
  29         if (!tcp) {
  30                 regs->verdict.code = NFT_BREAK;
  31                 return;
  32         }
  33         if (!tcp->syn) {
  34                 regs->verdict.code = NFT_BREAK;
  35                 return;
  36         }
  37
  38         os_name = nf_osf_find(skb, nf_osf_fingers, priv->ttl);
  39         if (!os_name)
  40                 strncpy((char *)dest, "unknown", NFT_OSF_MAXGENRELEN);
  41         else
  42                 strncpy((char *)dest, os_name, NFT_OSF_MAXGENRELEN);
  43 }
  44
  45 static int nft_osf_init(const struct nft_ctx *ctx,
  46                         const struct nft_expr *expr,
  47                         const struct nlattr * const tb[])
  48 {
  49         struct nft_osf *priv = nft_expr_priv(expr);
  50         int err;
  51         u8 ttl;
  52
  53         if (tb[NFTA_OSF_TTL]) {
  54                 ttl = nla_get_u8(tb[NFTA_OSF_TTL]);
  55                 if (ttl > 2)
  56                         return -EINVAL;
  57                 priv->ttl = ttl;
  58         }
  59
  60         priv->dreg = nft_parse_register(tb[NFTA_OSF_DREG]);
  61         err = nft_validate_register_store(ctx, priv->dreg, NULL,
  62                                           NFT_DATA_VALUE, NFT_OSF_MAXGENRELEN);
  63         if (err < 0)
  64                 return err;
  65
  66         return 0;
  67 }
  68
  69 static int nft_osf_dump(struct sk_buff *skb, const struct nft_expr *expr)
  70 {
  71         const struct nft_osf *priv = nft_expr_priv(expr);
  72
  73         if (nla_put_u8(skb, NFTA_OSF_TTL, priv->ttl))
  74                 goto nla_put_failure;
  75
  76         if (nft_dump_register(skb, NFTA_OSF_DREG, priv->dreg))
  77                 goto nla_put_failure;
  78
  79         return 0;
  80
  81 nla_put_failure:
  82         return -1;
  83 }
  84
  85 static int nft_osf_validate(const struct nft_ctx *ctx,
  86                             const struct nft_expr *expr,
  87                             const struct nft_data **data)
  88 {
  89         return nft_chain_validate_hooks(ctx->chain, (1 << NF_INET_LOCAL_IN) |
  90                                                     (1 << NF_INET_PRE_ROUTING) |
  91                                                     (1 << NF_INET_FORWARD));
  92 }
  93
  94 static struct nft_expr_type nft_osf_type;
  95 static const struct nft_expr_ops nft_osf_op = {
  96         .eval           = nft_osf_eval,
  97         .size           = NFT_EXPR_SIZE(sizeof(struct nft_osf)),
  98         .init           = nft_osf_init,
  99         .dump           = nft_osf_dump,
 100         .type           = &nft_osf_type,
 101         .validate       = nft_osf_validate,
 102 };
 103
 104 static struct nft_expr_type nft_osf_type __read_mostly = {
 105         .ops            = &nft_osf_op,
 106         .name           = "osf",
 107         .owner          = THIS_MODULE,
 108         .policy         = nft_osf_policy,
 109         .maxattr        = NFTA_OSF_MAX,
 110 };
 111
 112 static int __init nft_osf_module_init(void)
 113 {
 114         return nft_register_expr(&nft_osf_type);
 115 }
 116
 117 static void __exit nft_osf_module_exit(void)
 118 {
 119         return nft_unregister_expr(&nft_osf_type);
 120 }
 121
 122 module_init(nft_osf_module_init);
 123 module_exit(nft_osf_module_exit);
 124
 125 MODULE_LICENSE("GPL");
 126 MODULE_AUTHOR("Fernando Fernandez <ffmancera@riseup.net>");
 127 MODULE_ALIAS_NFT_EXPR("osf");