expr: add inner support

This patch adds support for the inner expression which allows you to
match on the inner tunnel headers, eg. VxLAN.

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

2 files changed, 216 insertions, 1 deletions

diff --git a/src/expr/inner.c b/src/expr/inner.c
new file mode 100644
index 0000000..7daae4f
--- /dev/null
+++ b/src/expr/inner.c
@@ -0,0 +1,214 @@
+/*
+ * (C) 2012-2022 by Pablo Neira Ayuso <pablo@netfilter.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published
+ * by the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#include "internal.h"
+
+#include <stdio.h>
+#include <stdint.h>
+#include <string.h>
+#include <limits.h>
+#include <arpa/inet.h>
+#include <errno.h>
+#include <libmnl/libmnl.h>
+
+#include <linux/netfilter/nf_tables.h>
+
+#include <libnftnl/expr.h>
+#include <libnftnl/rule.h>
+
+struct nftnl_expr_inner {
+	uint32_t	type;
+	uint32_t	flags;
+	uint32_t	hdrsize;
+	struct nftnl_expr *expr;
+};
+
+static void nftnl_expr_inner_free(const struct nftnl_expr *e)
+{
+	struct nftnl_expr_inner *inner = nftnl_expr_data(e);
+
+	if (inner->expr)
+		nftnl_expr_free(inner->expr);
+}
+
+static int
+nftnl_expr_inner_set(struct nftnl_expr *e, uint16_t type,
+		     const void *data, uint32_t data_len)
+{
+	struct nftnl_expr_inner *inner = nftnl_expr_data(e);
+
+	switch(type) {
+	case NFTNL_EXPR_INNER_TYPE:
+		memcpy(&inner->type, data, sizeof(inner->type));
+		break;
+	case NFTNL_EXPR_INNER_FLAGS:
+		memcpy(&inner->flags, data, sizeof(inner->flags));
+		break;
+	case NFTNL_EXPR_INNER_HDRSIZE:
+		memcpy(&inner->hdrsize, data, sizeof(inner->hdrsize));
+		break;
+	case NFTNL_EXPR_INNER_EXPR:
+		if (inner->expr)
+			nftnl_expr_free(inner->expr);
+
+		inner->expr = (void *)data;
+		break;
+	default:
+		return -1;
+	}
+	return 0;
+}
+
+static const void *
+nftnl_expr_inner_get(const struct nftnl_expr *e, uint16_t type,
+		     uint32_t *data_len)
+{
+	struct nftnl_expr_inner *inner = nftnl_expr_data(e);
+
+	switch(type) {
+	case NFTNL_EXPR_INNER_FLAGS:
+		*data_len = sizeof(inner->flags);
+		return &inner->flags;
+	case NFTNL_EXPR_INNER_TYPE:
+		*data_len = sizeof(inner->type);
+		return &inner->type;
+	case NFTNL_EXPR_INNER_HDRSIZE:
+		*data_len = sizeof(inner->hdrsize);
+		return &inner->hdrsize;
+	case NFTNL_EXPR_INNER_EXPR:
+		return inner->expr;
+	}
+	return NULL;
+}
+
+static void
+nftnl_expr_inner_build(struct nlmsghdr *nlh, const struct nftnl_expr *e)
+{
+	struct nftnl_expr_inner *inner = nftnl_expr_data(e);
+	struct nlattr *nest;
+
+	mnl_attr_put_u32(nlh, NFTA_INNER_NUM, htonl(0));
+	if (e->flags & (1 << NFTNL_EXPR_INNER_TYPE))
+		mnl_attr_put_u32(nlh, NFTA_INNER_TYPE, htonl(inner->type));
+	if (e->flags & (1 << NFTNL_EXPR_INNER_FLAGS))
+		mnl_attr_put_u32(nlh, NFTA_INNER_FLAGS, htonl(inner->flags));
+	if (e->flags & (1 << NFTNL_EXPR_INNER_HDRSIZE))
+		mnl_attr_put_u32(nlh, NFTA_INNER_HDRSIZE, htonl(inner->hdrsize));
+	if (e->flags & (1 << NFTNL_EXPR_INNER_EXPR)) {
+		nest = mnl_attr_nest_start(nlh, NFTA_INNER_EXPR);
+		nftnl_expr_build_payload(nlh, inner->expr);
+		mnl_attr_nest_end(nlh, nest);
+	}
+}
+
+static int nftnl_inner_parse_cb(const struct nlattr *attr, void *data)
+{
+	const struct nlattr **tb = data;
+	int type = mnl_attr_get_type(attr);
+
+	if (mnl_attr_type_valid(attr, NFTA_INNER_MAX) < 0)
+		return MNL_CB_OK;
+
+	switch(type) {
+	case NFTA_INNER_NUM:
+	case NFTA_INNER_TYPE:
+	case NFTA_INNER_HDRSIZE:
+	case NFTA_INNER_FLAGS:
+		if (mnl_attr_validate(attr, MNL_TYPE_U32) < 0)
+			abi_breakage();
+		break;
+	case NFTA_INNER_EXPR:
+		if (mnl_attr_validate(attr, MNL_TYPE_NESTED) < 0)
+			abi_breakage();
+		break;
+	}
+
+	tb[type] = attr;
+
+	return MNL_CB_OK;
+}
+
+static int
+nftnl_expr_inner_parse(struct nftnl_expr *e, struct nlattr *attr)
+{
+	struct nftnl_expr_inner *inner = nftnl_expr_data(e);
+	struct nlattr *tb[NFTA_INNER_MAX + 1] = {};
+	struct nftnl_expr *expr;
+	int err;
+
+	err = mnl_attr_parse_nested(attr, nftnl_inner_parse_cb, tb);
+	if (err < 0)
+		return err;
+
+	if (tb[NFTA_INNER_HDRSIZE]) {
+		inner->hdrsize =
+			ntohl(mnl_attr_get_u32(tb[NFTA_INNER_HDRSIZE]));
+		e->flags |= (1 << NFTNL_EXPR_INNER_HDRSIZE);
+	}
+	if (tb[NFTA_INNER_FLAGS]) {
+		inner->flags =
+			ntohl(mnl_attr_get_u32(tb[NFTA_INNER_FLAGS]));
+		e->flags |= (1 << NFTNL_EXPR_INNER_FLAGS);
+	}
+	if (tb[NFTA_INNER_TYPE]) {
+		inner->type =
+			ntohl(mnl_attr_get_u32(tb[NFTA_INNER_TYPE]));
+		e->flags |= (1 << NFTNL_EXPR_INNER_TYPE);
+	}
+	if (tb[NFTA_INNER_EXPR]) {
+		expr = nftnl_expr_parse(tb[NFTA_INNER_EXPR]);
+		if (!expr)
+			return -1;
+
+		if (inner->expr)
+			nftnl_expr_free(inner->expr);
+
+		inner->expr = expr;
+		e->flags |= (1 << NFTNL_EXPR_INNER_EXPR);
+	}
+
+	return 0;
+}
+
+static int
+nftnl_expr_inner_snprintf(char *buf, size_t remain, uint32_t flags,
+			  const struct nftnl_expr *e)
+{
+	struct nftnl_expr_inner *inner = nftnl_expr_data(e);
+	uint32_t offset = 0;
+	int ret;
+
+	ret = snprintf(buf, remain, "type %u hdrsize %u flags %x [",
+		       inner->type, inner->hdrsize, inner->flags);
+	SNPRINTF_BUFFER_SIZE(ret, remain, offset);
+
+	ret = snprintf(buf + offset, remain, " %s ", inner->expr->ops->name);
+	SNPRINTF_BUFFER_SIZE(ret, remain, offset);
+
+	ret = nftnl_expr_snprintf(buf + offset, remain, inner->expr,
+				  NFTNL_OUTPUT_DEFAULT, 0);
+	SNPRINTF_BUFFER_SIZE(ret, remain, offset);
+
+	ret = snprintf(buf + offset, remain, "] ");
+	SNPRINTF_BUFFER_SIZE(ret, remain, offset);
+
+	return offset;
+}
+
+struct expr_ops expr_ops_inner = {
+	.name		= "inner",
+	.alloc_len	= sizeof(struct nftnl_expr_inner),
+	.max_attr	= NFTA_INNER_MAX,
+	.free		= nftnl_expr_inner_free,
+	.set		= nftnl_expr_inner_set,
+	.get		= nftnl_expr_inner_get,
+	.parse		= nftnl_expr_inner_parse,
+	.build		= nftnl_expr_inner_build,
+	.output		= nftnl_expr_inner_snprintf,
+};
diff --git a/src/expr/payload.c b/src/expr/payload.c
index 88fff5f..c633e33 100644
--- a/src/expr/payload.c
+++ b/src/expr/payload.c
@@ -203,11 +203,12 @@ nftnl_expr_payload_parse(struct nftnl_expr *e, struct nlattr *attr)
 	return 0;
 }
 
-static const char *base2str_array[NFT_PAYLOAD_INNER_HEADER + 1] = {
+static const char *base2str_array[NFT_PAYLOAD_TUN_HEADER + 1] = {
 	[NFT_PAYLOAD_LL_HEADER]		= "link",
 	[NFT_PAYLOAD_NETWORK_HEADER] 	= "network",
 	[NFT_PAYLOAD_TRANSPORT_HEADER]	= "transport",
 	[NFT_PAYLOAD_INNER_HEADER]	= "inner",
+	[NFT_PAYLOAD_TUN_HEADER]	= "tunnel",
 };
 
 static const char *base2str(enum nft_payload_bases base)