diff mbox series

[libnftnl,v5] expr: add support to math expression

Message ID 20260925135108.4561-1-fmancera@suse.de
State New
Headers show
Series [libnftnl,v5] expr: add support to math expression | expand

Commit Message

Fernando Fernandez Mancera Sept. 25, 2026, 1:51 p.m. UTC 
Signed-off-by: Fernando Fernandez Mancera <fmancera@suse.de>
---
v2: adjusted the new fields and fixed the duplicated "math" on print
v3: removed NFTNL_EXPR_MATH_LEN and simplified printing
v4: adjusted byteordering, both bitmask and op are u32
v5: rebased in top of new changes and adjusted types to be32
---
 include/libnftnl/expr.h             |   8 ++
 include/linux/netfilter/nf_tables.h |  25 ++++
 src/Makefile.am                     |   1 +
 src/expr/math.c                     | 178 ++++++++++++++++++++++++++++
 src/expr_ops.c                      |   2 +
 5 files changed, 214 insertions(+)
 create mode 100644 src/expr/math.c
diff mbox series

Patch

diff --git a/include/libnftnl/expr.h b/include/libnftnl/expr.h
index 41e9f30..e21752f 100644
--- a/include/libnftnl/expr.h
+++ b/include/libnftnl/expr.h
@@ -364,6 +364,14 @@  enum {
 	__NFTNL_EXPR_INNER_MAX
 };
 
+enum {
+	NFTNL_EXPR_MATH_SREG	= NFTNL_EXPR_BASE,
+	NFTNL_EXPR_MATH_DREG,
+	NFTNL_EXPR_MATH_OP,
+	NFTNL_EXPR_MATH_BITMASK,
+	__NFTNL_EXPR_MATH_MAX
+};
+
 #ifdef __cplusplus
 } /* extern "C" */
 #endif
diff --git a/include/linux/netfilter/nf_tables.h b/include/linux/netfilter/nf_tables.h
index 7c0c915..ee8df9a 100644
--- a/include/linux/netfilter/nf_tables.h
+++ b/include/linux/netfilter/nf_tables.h
@@ -2015,4 +2015,29 @@  enum nft_tunnel_attributes {
 };
 #define NFTA_TUNNEL_MAX	(__NFTA_TUNNEL_MAX - 1)
 
+/**
+ * enum nft_math_attributes - nftables math expression netlink attributes
+ *
+ * @NFTA_MATH_SREG: source register (NLA_U32: nft_registers)
+ * @NFTA_MATH_DREG: destination register (NLA_U32: nft_registers)
+ * @NFTA_MATH_OP: operation to be performed (NLA_U32)
+ * @NFTA_MATH_BITMASK: bitmask to be applied on the operation (NLA_U32)
+ */
+enum nft_math_attributes {
+	NFTA_MATH_UNSPEC,
+	NFTA_MATH_SREG,
+	NFTA_MATH_DREG,
+	NFTA_MATH_OP,
+	NFTA_MATH_BITMASK,
+	__NFTA_MATH_MAX,
+};
+#define NFTA_MATH_MAX (__NFTA_MATH_MAX - 1)
+
+enum nft_math_op {
+	NFT_MATH_OP_INC,
+	NFT_MATH_OP_DEC,
+	__NFT_MATH_OP_MAX,
+};
+#define NFT_MATH_OP_MAX (__NFT_MATH_OP_MAX - 1)
+
 #endif /* _LINUX_NF_TABLES_H */
diff --git a/src/Makefile.am b/src/Makefile.am
index 14c6dd5..5ac2564 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -62,6 +62,7 @@  libnftnl_la_SOURCES = utils.c		\
 		      expr/synproxy.c	\
 		      expr/osf.c	\
 		      expr/xfrm.c	\
+		      expr/math.c	\
 		      obj/counter.c	\
 		      obj/ct_helper.c	\
 		      obj/quota.c	\
diff --git a/src/expr/math.c b/src/expr/math.c
new file mode 100644
index 0000000..e351b96
--- /dev/null
+++ b/src/expr/math.c
@@ -0,0 +1,178 @@ 
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+/*
+ * (C) 2025 by Fernando Fernandez Mancera <fmancera@suse.de>
+ */
+
+#include <arpa/inet.h>
+#include <linux/netfilter/nf_tables.h>
+
+#include "internal.h"
+#include <libmnl/libmnl.h>
+#include <libnftnl/expr.h>
+#include <libnftnl/rule.h>
+
+struct nftnl_expr_math {
+	enum nft_registers sreg;
+	enum nft_registers dreg;
+	enum nft_math_op   op;
+	uint32_t	   bitmask;
+};
+
+static int nftnl_expr_math_set(struct nftnl_expr *e, uint16_t type,
+			       const void *data, uint32_t data_len,
+			       uint32_t byteorder)
+{
+	struct nftnl_expr_math *math = nftnl_expr_data(e);
+
+	switch(type) {
+	case NFTNL_EXPR_MATH_SREG:
+		memcpy(&math->sreg, data, data_len);
+		break;
+	case NFTNL_EXPR_MATH_DREG:
+		memcpy(&math->dreg, data, data_len);
+		break;
+	case NFTNL_EXPR_MATH_OP:
+		memcpy(&math->op, data, data_len);
+		break;
+	case NFTNL_EXPR_MATH_BITMASK:
+		memcpy(&math->bitmask, data, data_len);
+		break;
+	}
+	return 0;
+}
+
+static const void *
+nftnl_expr_math_get(const struct nftnl_expr *e, uint16_t type,
+		    uint32_t *data_len)
+{
+	struct nftnl_expr_math *math = nftnl_expr_data(e);
+
+	switch(type) {
+	case NFTNL_EXPR_MATH_SREG:
+		*data_len = sizeof(math->sreg);
+		return &math->sreg;
+	case NFTNL_EXPR_MATH_DREG:
+		*data_len = sizeof(math->dreg);
+		return &math->dreg;
+	case NFTNL_EXPR_MATH_OP:
+		*data_len = sizeof(math->op);
+		return &math->op;
+	case NFTNL_EXPR_MATH_BITMASK:
+		*data_len = sizeof(math->bitmask);
+		return &math->bitmask;
+	}
+	return NULL;
+}
+
+static void
+nftnl_expr_math_build(struct nlmsghdr *nlh, const struct nftnl_expr *e)
+{
+	struct nftnl_expr_math *math = nftnl_expr_data(e);
+
+	if ((e->flags & (1 << NFTNL_EXPR_MATH_SREG)) &&
+	    (e->flags & (1 << NFTNL_EXPR_MATH_DREG)) &&
+	    (e->flags & (1 << NFTNL_EXPR_MATH_BITMASK)) &&
+	    (e->flags & (1 << NFTNL_EXPR_MATH_OP))) {
+		mnl_attr_put_u32(nlh, NFTA_MATH_BITMASK, htonl(math->bitmask));
+		mnl_attr_put_u32(nlh, NFTA_MATH_SREG, htonl(math->sreg));
+		mnl_attr_put_u32(nlh, NFTA_MATH_DREG, htonl(math->dreg));
+		mnl_attr_put_u32(nlh, NFTA_MATH_OP, htonl(math->op));
+	}
+
+}
+
+static int nftnl_expr_math_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_MATH_MAX) < 0)
+		return MNL_CB_OK;
+
+	switch(type) {
+	case NFTA_MATH_SREG:
+	case NFTA_MATH_DREG:
+	case NFTA_MATH_BITMASK:
+	case NFTA_MATH_OP:
+		if (mnl_attr_validate(attr, MNL_TYPE_U32) < 0)
+			abi_breakage();
+		break;
+	}
+
+	tb[type] = attr;
+	return MNL_CB_OK;
+}
+
+static int
+nftnl_expr_math_parse(struct nftnl_expr *e, struct nlattr *attr)
+{
+	struct nftnl_expr_math *math = nftnl_expr_data(e);
+	struct nlattr *tb[NFTA_MATH_MAX + 1] = {};
+
+	if (mnl_attr_parse_nested(attr, nftnl_expr_math_cb, tb) < 0)
+		return -1;
+
+	if (tb[NFTA_MATH_SREG]) {
+		math->sreg = ntohl(mnl_attr_get_u32(tb[NFTA_MATH_SREG]));
+		e->flags |= (1 << NFTNL_EXPR_MATH_SREG);
+	}
+
+	if (tb[NFTA_MATH_DREG]) {
+		math->dreg = ntohl(mnl_attr_get_u32(tb[NFTA_MATH_DREG]));
+		e->flags |= (1 << NFTNL_EXPR_MATH_DREG);
+	}
+
+	if (tb[NFTA_MATH_OP]) {
+		math->op = ntohl(mnl_attr_get_u32(tb[NFTA_MATH_OP]));
+		e->flags |= (1 << NFTNL_EXPR_MATH_OP);
+	}
+
+	if (tb[NFTA_MATH_BITMASK]) {
+		math->bitmask = ntohl(mnl_attr_get_u32(tb[NFTA_MATH_BITMASK]));
+		e->flags |= (1 << NFTNL_EXPR_MATH_BITMASK);
+	}
+
+	return 0;
+}
+
+static char op2char(enum nft_math_op op)
+{
+	switch (op) {
+	case NFT_MATH_OP_INC:
+		return '+';
+	case NFT_MATH_OP_DEC:
+		return '-';
+	default:
+		return '?';
+	}
+}
+
+static int
+nftnl_expr_math_snprintf(char *buf, size_t len,
+			 uint32_t flags, const struct nftnl_expr *e)
+{
+	struct nftnl_expr_math *math = nftnl_expr_data(e);
+
+	return snprintf(buf, len, "mask 0x%.8x reg %u %c 1 => %u",
+			math->bitmask, math->sreg, op2char(math->op),
+			math->dreg);
+}
+
+static struct attr_policy math_attr_policy[__NFTNL_EXPR_MATH_MAX] = {
+	[NFTNL_EXPR_MATH_SREG]		= { .maxlen = sizeof(uint32_t) },
+	[NFTNL_EXPR_MATH_DREG]		= { .maxlen = sizeof(uint32_t) },
+	[NFTNL_EXPR_MATH_BITMASK]	= { .maxlen = sizeof(uint32_t) },
+	[NFTNL_EXPR_MATH_OP]		= { .maxlen = sizeof(uint32_t) },
+};
+
+struct expr_ops expr_ops_math = {
+	.name		= "math",
+	.alloc_len	= sizeof(struct nftnl_expr_math),
+	.nftnl_max_attr	= __NFTNL_EXPR_MATH_MAX - 1,
+	.attr_policy	= math_attr_policy,
+	.set		= nftnl_expr_math_set,
+	.get		= nftnl_expr_math_get,
+	.parse		= nftnl_expr_math_parse,
+	.build		= nftnl_expr_math_build,
+	.output		= nftnl_expr_math_snprintf,
+};
diff --git a/src/expr_ops.c b/src/expr_ops.c
index b85f472..b654fa0 100644
--- a/src/expr_ops.c
+++ b/src/expr_ops.c
@@ -43,6 +43,7 @@  extern struct expr_ops expr_ops_synproxy;
 extern struct expr_ops expr_ops_tunnel;
 extern struct expr_ops expr_ops_osf;
 extern struct expr_ops expr_ops_xfrm;
+extern struct expr_ops expr_ops_math;
 
 static struct expr_ops expr_ops_notrack = {
 	.name	= "notrack",
@@ -89,6 +90,7 @@  static struct expr_ops *expr_ops[] = {
 	&expr_ops_tunnel,
 	&expr_ops_osf,
 	&expr_ops_xfrm,
+	&expr_ops_math,
 	NULL,
 };