1// SPDX-License-Identifier: GPL-2.0-only
  2#include <net/ip.h>
  3#include <net/tcp.h>
  4
  5#include <net/netfilter/nf_tables.h>
  6#include <linux/netfilter/nfnetlink_osf.h>
  7
  8struct nft_osf {
  9	enum nft_registers	dreg:8;
 10	u8			ttl;
 11	u32			flags;
 12};
 13
 14static const struct nla_policy nft_osf_policy[NFTA_OSF_MAX + 1] = {
 15	[NFTA_OSF_DREG]		= { .type = NLA_U32 },
 16	[NFTA_OSF_TTL]		= { .type = NLA_U8 },
 17	[NFTA_OSF_FLAGS]	= { .type = NLA_U32 },
 18};
 19
 20static void nft_osf_eval(const struct nft_expr *expr, struct nft_regs *regs,
 21			 const struct nft_pktinfo *pkt)
 22{
 23	struct nft_osf *priv = nft_expr_priv(expr);
 24	u32 *dest = &regs->data[priv->dreg];
 25	struct sk_buff *skb = pkt->skb;
 26	char os_match[NFT_OSF_MAXGENRELEN + 1];
 27	const struct tcphdr *tcp;
 28	struct nf_osf_data data;
 29	struct tcphdr _tcph;
 30
 31	tcp = skb_header_pointer(skb, ip_hdrlen(skb),
 32				 sizeof(struct tcphdr), &_tcph);
 33	if (!tcp) {
 34		regs->verdict.code = NFT_BREAK;
 35		return;
 36	}
 37	if (!tcp->syn) {
 38		regs->verdict.code = NFT_BREAK;
 39		return;
 40	}
 41
 42	if (!nf_osf_find(skb, nf_osf_fingers, priv->ttl, &data)) {
 43		strncpy((char *)dest, "unknown", NFT_OSF_MAXGENRELEN);
 44	} else {
 45		if (priv->flags & NFT_OSF_F_VERSION)
 46			snprintf(os_match, NFT_OSF_MAXGENRELEN, "%s:%s",
 47				 data.genre, data.version);
 48		else
 49			strlcpy(os_match, data.genre, NFT_OSF_MAXGENRELEN);
 50
 51		strncpy((char *)dest, os_match, NFT_OSF_MAXGENRELEN);
 52	}
 53}
 54
 55static int nft_osf_init(const struct nft_ctx *ctx,
 56			const struct nft_expr *expr,
 57			const struct nlattr * const tb[])
 58{
 59	struct nft_osf *priv = nft_expr_priv(expr);
 60	u32 flags;
 61	int err;
 62	u8 ttl;
 63
 64	if (tb[NFTA_OSF_TTL]) {
 65		ttl = nla_get_u8(tb[NFTA_OSF_TTL]);
 66		if (ttl > 2)
 67			return -EINVAL;
 68		priv->ttl = ttl;
 69	}
 70
 71	if (tb[NFTA_OSF_FLAGS]) {
 72		flags = ntohl(nla_get_be32(tb[NFTA_OSF_FLAGS]));
 73		if (flags != NFT_OSF_F_VERSION)
 74			return -EINVAL;
 75		priv->flags = flags;
 76	}
 77
 78	priv->dreg = nft_parse_register(tb[NFTA_OSF_DREG]);
 79	err = nft_validate_register_store(ctx, priv->dreg, NULL,
 80					  NFT_DATA_VALUE, NFT_OSF_MAXGENRELEN);
 81	if (err < 0)
 82		return err;
 83
 84	return 0;
 85}
 86
 87static int nft_osf_dump(struct sk_buff *skb, const struct nft_expr *expr)
 88{
 89	const struct nft_osf *priv = nft_expr_priv(expr);
 90
 91	if (nla_put_u8(skb, NFTA_OSF_TTL, priv->ttl))
 92		goto nla_put_failure;
 93
 94	if (nla_put_be32(skb, NFTA_OSF_FLAGS, ntohl(priv->flags)))
 95		goto nla_put_failure;
 96
 97	if (nft_dump_register(skb, NFTA_OSF_DREG, priv->dreg))
 98		goto nla_put_failure;
 99
100	return 0;
101
102nla_put_failure:
103	return -1;
104}
105
106static int nft_osf_validate(const struct nft_ctx *ctx,
107			    const struct nft_expr *expr,
108			    const struct nft_data **data)
109{
110	return nft_chain_validate_hooks(ctx->chain, (1 << NF_INET_LOCAL_IN) |
111						    (1 << NF_INET_PRE_ROUTING) |
112						    (1 << NF_INET_FORWARD));
113}
114
115static struct nft_expr_type nft_osf_type;
116static const struct nft_expr_ops nft_osf_op = {
117	.eval		= nft_osf_eval,
118	.size		= NFT_EXPR_SIZE(sizeof(struct nft_osf)),
119	.init		= nft_osf_init,
120	.dump		= nft_osf_dump,
121	.type		= &nft_osf_type,
122	.validate	= nft_osf_validate,
123};
124
125static struct nft_expr_type nft_osf_type __read_mostly = {
126	.ops		= &nft_osf_op,
127	.name		= "osf",
128	.owner		= THIS_MODULE,
129	.policy		= nft_osf_policy,
130	.maxattr	= NFTA_OSF_MAX,
131};
132
133static int __init nft_osf_module_init(void)
134{
135	return nft_register_expr(&nft_osf_type);
136}
137
138static void __exit nft_osf_module_exit(void)
139{
140	return nft_unregister_expr(&nft_osf_type);
141}
142
143module_init(nft_osf_module_init);
144module_exit(nft_osf_module_exit);
145
146MODULE_LICENSE("GPL");
147MODULE_AUTHOR("Fernando Fernandez <ffmancera@riseup.net>");
148MODULE_ALIAS_NFT_EXPR("osf");