netdev - [PATCH RFC 2/3] netfilter: add ast to target transformation

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Message-Id: <20180219163706.5388-3-pablo@netfilter.org>
Date:   Mon, 19 Feb 2018 17:37:05 +0100
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     netfilter-devel@...r.kernel.org
Cc:     davem@...emloft.net, netdev@...r.kernel.org, laforge@...filter.org,
        fw@...len.de, daniel@...earbox.net, alexei.starovoitov@...il.com
Subject: [PATCH RFC 2/3] netfilter: add ast to target transformation

This patch adds the generic infrastructure is used to describe the
transformation from abstract syntax tree to target internal
representation.

The target has to define the transformation callbacks:

struct nft_ast_xfrm_desc {
       const struct nft_ast_proto_desc *proto_desc;
       const struct nft_ast_meta_desc  *meta_desc;
};

The protocol and meta description structure provide the callback to
transform internal representation to the corresponding target.

struct nft_ast_{proto,meta}_desc {
       int (*xfrm)(const struct nft_ast_expr *dlexpr,
                   struct nft_ast_xfrm_state *state, void *data);
};

Signed-off-by: Pablo Neira Ayuso <pablo@...filter.org>
---
 include/net/netfilter/nf_tables_jit.h | 39 +++++++++++++++++++
 net/netfilter/nf_tables_jit.c         | 71 +++++++++++++++++++++++++++++++++++
 2 files changed, 110 insertions(+)

diff --git a/include/net/netfilter/nf_tables_jit.h b/include/net/netfilter/nf_tables_jit.h
index 124d3da91b0d..dff3af7ad420 100644
--- a/include/net/netfilter/nf_tables_jit.h
+++ b/include/net/netfilter/nf_tables_jit.h
@@ -81,4 +81,43 @@ void nft_ast_stmt_list_print(struct list_head *stmt_list);
 
 int nft_delinearize(struct list_head *ast_stmt_list, struct nft_rule *rule);
 
+/*
+ * Tree of transformation callback definitions.
+ */
+struct nft_ast_xfrm_state;
+
+/**
+ *	struct nft_ast_proto_desc - nf_tables protocol transformation description
+ *
+ *	@xfrm: transformation callback
+ */
+struct nft_ast_proto_desc {
+	int (*xfrm)(const struct nft_ast_expr *dlexpr,
+		    struct nft_ast_xfrm_state *state, void *data);
+};
+
+/**
+ *	struct nft_ast_meta_desc - nf_tables meta transformation description
+ *
+ *	@xfrm: transformation callback
+ */
+struct nft_ast_meta_desc {
+	int (*xfrm)(const struct nft_ast_expr *dlexpr,
+		    struct nft_ast_xfrm_state *state, void *data);
+};
+
+/**
+ *	struct nft_ast_xfrm_desc - nf_tables generic transformation description
+ *
+ *	@key: meta key
+ *	@xfrm: transformation callback
+ */
+struct nft_ast_xfrm_desc {
+	const struct nft_ast_proto_desc	*proto_desc;
+	const struct nft_ast_meta_desc	*meta_desc;
+};
+
+int nft_ast_xfrm(const struct list_head *ast_stmt_list,
+		 const struct nft_ast_xfrm_desc *base_desc, void *data);
+
 #endif
diff --git a/net/netfilter/nf_tables_jit.c b/net/netfilter/nf_tables_jit.c
index e971b94bbc69..63673ea42be8 100644
--- a/net/netfilter/nf_tables_jit.c
+++ b/net/netfilter/nf_tables_jit.c
@@ -134,3 +134,74 @@ void nft_ast_stmt_list_print(struct list_head *stmt_list)
 	}
 }
 EXPORT_SYMBOL_GPL(nft_ast_stmt_list_print);
+
+struct nft_ast_xfrm_state {
+	const struct nft_ast_xfrm_desc *xfrm_desc;
+	void *data;
+};
+
+static int nft_ast_xfrm_relational(const struct nft_ast_expr *dlexpr,
+				   struct nft_ast_xfrm_state *state)
+{
+	const struct nft_ast_expr *left = dlexpr->relational.left;
+	const struct nft_ast_expr *right = dlexpr->relational.right;
+	const struct nft_ast_xfrm_desc *xfrm_desc = state->xfrm_desc;
+	int err;
+
+	if (right->type != NFT_AST_EXPR_VALUE)
+		return -EOPNOTSUPP;
+
+	switch (left->type) {
+	case NFT_AST_EXPR_META:
+		err = xfrm_desc->meta_desc->xfrm(dlexpr, state, state->data);
+		break;
+	case NFT_AST_EXPR_PAYLOAD:
+		err = xfrm_desc->proto_desc->xfrm(dlexpr, state, state->data);
+		break;
+	default:
+		return -EOPNOTSUPP;
+	}
+
+	return err;
+}
+
+static int nft_ast_xfrm_expr(const struct nft_ast_expr *dlexpr,
+			     struct nft_ast_xfrm_state *state)
+{
+	int err;
+
+	switch (dlexpr->type) {
+	case NFT_AST_EXPR_RELATIONAL:
+		err = nft_ast_xfrm_relational(dlexpr, state);
+		break;
+	default:
+		return -EOPNOTSUPP;
+	}
+
+	return err;
+}
+
+int nft_ast_xfrm(const struct list_head *ast_stmt_list,
+		 const struct nft_ast_xfrm_desc *xfrm_desc, void *data)
+{
+	struct nft_ast_xfrm_state state = {
+		.xfrm_desc	= xfrm_desc,
+		.data		= data,
+	};
+	struct nft_ast_stmt *stmt;
+	int err = 0;
+
+	list_for_each_entry(stmt, ast_stmt_list, list) {
+		switch (stmt->type) {
+		case NFT_AST_STMT_EXPR:
+			err = nft_ast_xfrm_expr(stmt->expr, &state);
+			if (err < 0)
+				return err;
+			break;
+		default:
+			return -EOPNOTSUPP;
+		}
+	}
+	return err;
+}
+EXPORT_SYMBOL_GPL(nft_ast_xfrm);
-- 
2.11.0