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 = ®s->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 (nla_get_u8(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"); 128