netfilter: nft_osf: Add version option support

Add version option support to the nftables "osf" expression.
Signed-off-by: Fernando Fernandez Mancera <ffmancera@riseup.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/linux/netfilter/nfnetlink_osf.h

@@ -21,13 +21,18 @@ struct nf_osf_finger {
 	struct nf_osf_user_finger	finger;
 };
 
+struct nf_osf_data {
+	const char *genre;
+	const char *version;
+};
+
 bool nf_osf_match(const struct sk_buff *skb, u_int8_t family,
 		  int hooknum, struct net_device *in, struct net_device *out,
 		  const struct nf_osf_info *info, struct net *net,
 		  const struct list_head *nf_osf_fingers);
 
-const char *nf_osf_find(const struct sk_buff *skb,
+bool nf_osf_find(const struct sk_buff *skb,
 		 const struct list_head *nf_osf_fingers,
-			const int ttl_check);
+		 const int ttl_check, struct nf_osf_data *data);
 
 #endif /* _NFOSF_H */

include/uapi/linux/netfilter/nf_tables.h

@@ -1522,15 +1522,21 @@ enum nft_flowtable_hook_attributes {
  *
  * @NFTA_OSF_DREG: destination register (NLA_U32: nft_registers)
  * @NFTA_OSF_TTL: Value of the TTL osf option (NLA_U8)
+ * @NFTA_OSF_FLAGS: flags (NLA_U32)
  */
 enum nft_osf_attributes {
 	NFTA_OSF_UNSPEC,
 	NFTA_OSF_DREG,
 	NFTA_OSF_TTL,
+	NFTA_OSF_FLAGS,
 	__NFTA_OSF_MAX,
 };
 #define NFTA_OSF_MAX (__NFTA_OSF_MAX - 1)
 
+enum nft_osf_flags {
+	NFT_OSF_F_VERSION = (1 << 0),
+};
+
 /**
  * enum nft_device_attributes - nf_tables device netlink attributes
  *

net/netfilter/nfnetlink_osf.c

@@ -255,9 +255,9 @@ nf_osf_match(const struct sk_buff *skb, u_int8_t family,
 }
 EXPORT_SYMBOL_GPL(nf_osf_match);
 
-const char *nf_osf_find(const struct sk_buff *skb,
+bool nf_osf_find(const struct sk_buff *skb,
 		 const struct list_head *nf_osf_fingers,
-			const int ttl_check)
+		 const int ttl_check, struct nf_osf_data *data)
 {
 	const struct iphdr *ip = ip_hdr(skb);
 	const struct nf_osf_user_finger *f;
@@ -265,24 +265,24 @@ const char *nf_osf_find(const struct sk_buff *skb,
 	const struct nf_osf_finger *kf;
 	struct nf_osf_hdr_ctx ctx;
 	const struct tcphdr *tcp;
-	const char *genre = NULL;
 
 	memset(&ctx, 0, sizeof(ctx));
 
 	tcp = nf_osf_hdr_ctx_init(&ctx, skb, ip, opts);
 	if (!tcp)
-		return NULL;
+		return false;
 
 	list_for_each_entry_rcu(kf, &nf_osf_fingers[ctx.df], finger_entry) {
 		f = &kf->finger;
 		if (!nf_osf_match_one(skb, f, ttl_check, &ctx))
 			continue;
 
-		genre = f->genre;
+		data->genre = f->genre;
+		data->version = f->version;
 		break;
 	}
 
-	return genre;
+	return true;
 }
 EXPORT_SYMBOL_GPL(nf_osf_find);
 

net/netfilter/nft_osf.c

@@ -7,11 +7,13 @@
 struct nft_osf {
 	enum nft_registers	dreg:8;
 	u8			ttl;
+	u32			flags;
 };
 
 static const struct nla_policy nft_osf_policy[NFTA_OSF_MAX + 1] = {
 	[NFTA_OSF_DREG]		= { .type = NLA_U32 },
 	[NFTA_OSF_TTL]		= { .type = NLA_U8 },
+	[NFTA_OSF_FLAGS]	= { .type = NLA_U32 },
 };
 
 static void nft_osf_eval(const struct nft_expr *expr, struct nft_regs *regs,
@@ -20,9 +22,10 @@ static void nft_osf_eval(const struct nft_expr *expr, struct nft_regs *regs,
 	struct nft_osf *priv = nft_expr_priv(expr);
 	u32 *dest = &regs->data[priv->dreg];
 	struct sk_buff *skb = pkt->skb;
+	char os_match[NFT_OSF_MAXGENRELEN + 1];
 	const struct tcphdr *tcp;
+	struct nf_osf_data data;
 	struct tcphdr _tcph;
-	const char *os_name;
 
 	tcp = skb_header_pointer(skb, ip_hdrlen(skb),
 				 sizeof(struct tcphdr), &_tcph);
@@ -35,11 +38,17 @@ static void nft_osf_eval(const struct nft_expr *expr, struct nft_regs *regs,
 		return;
 	}
 
-	os_name = nf_osf_find(skb, nf_osf_fingers, priv->ttl);
-	if (!os_name)
+	if (!nf_osf_find(skb, nf_osf_fingers, priv->ttl, &data)) {
 		strncpy((char *)dest, "unknown", NFT_OSF_MAXGENRELEN);
+	} else {
+		if (priv->flags & NFT_OSF_F_VERSION)
+			snprintf(os_match, NFT_OSF_MAXGENRELEN, "%s:%s",
+				 data.genre, data.version);
 		else
-		strncpy((char *)dest, os_name, NFT_OSF_MAXGENRELEN);
+			strlcpy(os_match, data.genre, NFT_OSF_MAXGENRELEN);
+
+		strncpy((char *)dest, os_match, NFT_OSF_MAXGENRELEN);
+	}
 }
 
 static int nft_osf_init(const struct nft_ctx *ctx,
@@ -47,6 +56,7 @@ static int nft_osf_init(const struct nft_ctx *ctx,
 			const struct nlattr * const tb[])
 {
 	struct nft_osf *priv = nft_expr_priv(expr);
+	u32 flags;
 	int err;
 	u8 ttl;
 
@@ -57,6 +67,13 @@ static int nft_osf_init(const struct nft_ctx *ctx,
 		priv->ttl = ttl;
 	}
 
+	if (tb[NFTA_OSF_FLAGS]) {
+		flags = ntohl(nla_get_be32(tb[NFTA_OSF_FLAGS]));
+		if (flags != NFT_OSF_F_VERSION)
+			return -EINVAL;
+		priv->flags = flags;
+	}
+
 	priv->dreg = nft_parse_register(tb[NFTA_OSF_DREG]);
 	err = nft_validate_register_store(ctx, priv->dreg, NULL,
 					  NFT_DATA_VALUE, NFT_OSF_MAXGENRELEN);
@@ -73,6 +90,9 @@ static int nft_osf_dump(struct sk_buff *skb, const struct nft_expr *expr)
 	if (nla_put_u8(skb, NFTA_OSF_TTL, priv->ttl))
 		goto nla_put_failure;
 
+	if (nla_put_be32(skb, NFTA_OSF_FLAGS, ntohl(priv->flags)))
+		goto nla_put_failure;
+
 	if (nft_dump_register(skb, NFTA_OSF_DREG, priv->dreg))
 		goto nla_put_failure;