libnftnl: constify object arguments to various functions

flow table support needs constant object arguments to printing functions
to avoid ugly casts. While at it, also constify object arguments to message
construction, destructor and a few helper functions.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

23 files changed, 119 insertions, 105 deletions

diff --git a/src/expr/bitwise.c b/src/expr/bitwise.c
index a18aad5..2fd4b74 100644
--- a/src/expr/bitwise.c
+++ b/src/expr/bitwise.c
@@ -112,7 +112,7 @@ static int nftnl_expr_bitwise_cb(const struct nlattr *attr, void *data)
 }
 
 static void
-nftnl_expr_bitwise_build(struct nlmsghdr *nlh, struct nftnl_expr *e)
+nftnl_expr_bitwise_build(struct nlmsghdr *nlh, const struct nftnl_expr *e)
 {
 	struct nftnl_expr_bitwise *bitwise = nftnl_expr_data(e);
 
@@ -251,7 +251,7 @@ nftnl_expr_bitwise_xml_parse(struct nftnl_expr *e, mxml_node_t *tree,
 }
 
 static int nftnl_expr_bitwise_export(char *buf, size_t size,
-					struct nftnl_expr *e, int type)
+				     const struct nftnl_expr *e, int type)
 {
 	struct nftnl_expr_bitwise *bitwise = nftnl_expr_data(e);
 	NFTNL_BUF_INIT(b, buf, size);
@@ -271,7 +271,7 @@ static int nftnl_expr_bitwise_export(char *buf, size_t size,
 }
 
 static int nftnl_expr_bitwise_snprintf_default(char *buf, size_t size,
-						  struct nftnl_expr *e)
+					       const struct nftnl_expr *e)
 {
 	struct nftnl_expr_bitwise *bitwise = nftnl_expr_data(e);
 	int len = size, offset = 0, ret;
@@ -296,7 +296,7 @@ static int nftnl_expr_bitwise_snprintf_default(char *buf, size_t size,
 
 static int
 nftnl_expr_bitwise_snprintf(char *buf, size_t size, uint32_t type,
-			       uint32_t flags, struct nftnl_expr *e)
+			    uint32_t flags, const struct nftnl_expr *e)
 {
 	switch (type) {
 	case NFTNL_OUTPUT_DEFAULT:
diff --git a/src/expr/byteorder.c b/src/expr/byteorder.c
index f16bbf7..ca697cf 100644
--- a/src/expr/byteorder.c
+++ b/src/expr/byteorder.c
@@ -107,7 +107,7 @@ static int nftnl_expr_byteorder_cb(const struct nlattr *attr, void *data)
 }
 
 static void
-nftnl_expr_byteorder_build(struct nlmsghdr *nlh, struct nftnl_expr *e)
+nftnl_expr_byteorder_build(struct nlmsghdr *nlh, const struct nftnl_expr *e)
 {
 	struct nftnl_expr_byteorder *byteorder = nftnl_expr_data(e);
 
@@ -277,7 +277,7 @@ nftnl_expr_byteorder_xml_parse(struct nftnl_expr *e, mxml_node_t *tree,
 }
 
 static int nftnl_expr_byteorder_export(char *buf, size_t size,
-					  struct nftnl_expr *e, int type)
+				       const struct nftnl_expr *e, int type)
 {
 	struct nftnl_expr_byteorder *byteorder = nftnl_expr_data(e);
 	NFTNL_BUF_INIT(b, buf, size);
@@ -297,7 +297,7 @@ static int nftnl_expr_byteorder_export(char *buf, size_t size,
 }
 
 static int nftnl_expr_byteorder_snprintf_default(char *buf, size_t size,
-						    struct nftnl_expr *e)
+						 const struct nftnl_expr *e)
 {
 	struct nftnl_expr_byteorder *byteorder = nftnl_expr_data(e);
 	int len = size, offset = 0, ret;
@@ -312,7 +312,7 @@ static int nftnl_expr_byteorder_snprintf_default(char *buf, size_t size,
 
 static int
 nftnl_expr_byteorder_snprintf(char *buf, size_t size, uint32_t type,
-				 uint32_t flags, struct nftnl_expr *e)
+			      uint32_t flags, const struct nftnl_expr *e)
 {
 	switch (type) {
 	case NFTNL_OUTPUT_DEFAULT:
diff --git a/src/expr/cmp.c b/src/expr/cmp.c
index 4125689..f3dd62c 100644
--- a/src/expr/cmp.c
+++ b/src/expr/cmp.c
@@ -96,7 +96,7 @@ static int nftnl_expr_cmp_cb(const struct nlattr *attr, void *data)
 }
 
 static void
-nftnl_expr_cmp_build(struct nlmsghdr *nlh, struct nftnl_expr *e)
+nftnl_expr_cmp_build(struct nlmsghdr *nlh, const struct nftnl_expr *e)
 {
 	struct nftnl_expr_cmp *cmp = nftnl_expr_data(e);
 
@@ -245,7 +245,7 @@ static int nftnl_expr_cmp_xml_parse(struct nftnl_expr *e, mxml_node_t *tree,
 }
 
 static int nftnl_expr_cmp_export(char *buf, size_t size,
-				    struct nftnl_expr *e, int type)
+				 const struct nftnl_expr *e, int type)
 {
 	struct nftnl_expr_cmp *cmp = nftnl_expr_data(e);
 	NFTNL_BUF_INIT(b, buf, size);
@@ -261,7 +261,7 @@ static int nftnl_expr_cmp_export(char *buf, size_t size,
 }
 
 static int nftnl_expr_cmp_snprintf_default(char *buf, size_t size,
-					      struct nftnl_expr *e)
+					   const struct nftnl_expr *e)
 {
 	struct nftnl_expr_cmp *cmp = nftnl_expr_data(e);
 	int len = size, offset = 0, ret;
@@ -279,7 +279,7 @@ static int nftnl_expr_cmp_snprintf_default(char *buf, size_t size,
 
 static int
 nftnl_expr_cmp_snprintf(char *buf, size_t size, uint32_t type,
-			   uint32_t flags, struct nftnl_expr *e)
+			uint32_t flags, const struct nftnl_expr *e)
 {
 	switch (type) {
 	case NFTNL_OUTPUT_DEFAULT:
diff --git a/src/expr/counter.c b/src/expr/counter.c
index 4b5fb3f..1f818c4 100644
--- a/src/expr/counter.c
+++ b/src/expr/counter.c
@@ -84,7 +84,7 @@ static int nftnl_expr_counter_cb(const struct nlattr *attr, void *data)
 }
 
 static void
-nftnl_expr_counter_build(struct nlmsghdr *nlh, struct nftnl_expr *e)
+nftnl_expr_counter_build(struct nlmsghdr *nlh, const struct nftnl_expr *e)
 {
 	struct nftnl_expr_counter *ctr = nftnl_expr_data(e);
 
@@ -160,7 +160,7 @@ nftnl_expr_counter_xml_parse(struct nftnl_expr *e, mxml_node_t *tree,
 }
 
 static int nftnl_expr_counter_export(char *buf, size_t size,
-					struct nftnl_expr *e, int type)
+				     const struct nftnl_expr *e, int type)
 {
 	struct nftnl_expr_counter *ctr = nftnl_expr_data(e);
 	NFTNL_BUF_INIT(b, buf, size);
@@ -174,7 +174,7 @@ static int nftnl_expr_counter_export(char *buf, size_t size,
 }
 
 static int nftnl_expr_counter_snprintf_default(char *buf, size_t len,
-						  struct nftnl_expr *e)
+					       const struct nftnl_expr *e)
 {
 	struct nftnl_expr_counter *ctr = nftnl_expr_data(e);
 
@@ -183,8 +183,8 @@ static int nftnl_expr_counter_snprintf_default(char *buf, size_t len,
 }
 
 static int nftnl_expr_counter_snprintf(char *buf, size_t len, uint32_t type,
-					  uint32_t flags,
-					  struct nftnl_expr *e)
+				       uint32_t flags,
+				       const struct nftnl_expr *e)
 {
 	switch (type) {
 	case NFTNL_OUTPUT_DEFAULT:
diff --git a/src/expr/ct.c b/src/expr/ct.c
index a38f40c..d69d56b 100644
--- a/src/expr/ct.c
+++ b/src/expr/ct.c
@@ -109,7 +109,7 @@ static int nftnl_expr_ct_cb(const struct nlattr *attr, void *data)
 }
 
 static void
-nftnl_expr_ct_build(struct nlmsghdr *nlh, struct nftnl_expr *e)
+nftnl_expr_ct_build(struct nlmsghdr *nlh, const struct nftnl_expr *e)
 {
 	struct nftnl_expr_ct *ct = nftnl_expr_data(e);
 
@@ -311,7 +311,8 @@ err:
 }
 
 static int
-nftnl_expr_ct_export(char *buf, size_t size, struct nftnl_expr *e, int type)
+nftnl_expr_ct_export(char *buf, size_t size, const struct nftnl_expr *e,
+		     int type)
 {
 	struct nftnl_expr_ct *ct = nftnl_expr_data(e);
 	NFTNL_BUF_INIT(b, buf, size);
@@ -329,7 +330,8 @@ nftnl_expr_ct_export(char *buf, size_t size, struct nftnl_expr *e, int type)
 }
 
 static int
-nftnl_expr_ct_snprintf_default(char *buf, size_t size, struct nftnl_expr *e)
+nftnl_expr_ct_snprintf_default(char *buf, size_t size,
+			       const struct nftnl_expr *e)
 {
 	int ret, len = size, offset = 0;
 	struct nftnl_expr_ct *ct = nftnl_expr_data(e);
@@ -357,7 +359,7 @@ nftnl_expr_ct_snprintf_default(char *buf, size_t size, struct nftnl_expr *e)
 
 static int
 nftnl_expr_ct_snprintf(char *buf, size_t len, uint32_t type,
-			    uint32_t flags, struct nftnl_expr *e)
+		       uint32_t flags, const struct nftnl_expr *e)
 {
 	switch (type) {
 	case NFTNL_OUTPUT_DEFAULT:
diff --git a/src/expr/data_reg.c b/src/expr/data_reg.c
index b85d2ef..2a23285 100644
--- a/src/expr/data_reg.c
+++ b/src/expr/data_reg.c
@@ -186,8 +186,8 @@ err:
 
 static int
 nftnl_data_reg_value_snprintf_json(char *buf, size_t size,
-					   union nftnl_data_reg *reg,
-					   uint32_t flags)
+				   const union nftnl_data_reg *reg,
+				   uint32_t flags)
 {
 	int len = size, offset = 0, ret, i, j;
 	uint32_t utemp;
@@ -223,7 +223,8 @@ nftnl_data_reg_value_snprintf_json(char *buf, size_t size,
 
 static
 int nftnl_data_reg_value_snprintf_xml(char *buf, size_t size,
-				    union nftnl_data_reg *reg, uint32_t flags)
+				      const union nftnl_data_reg *reg,
+				      uint32_t flags)
 {
 	int len = size, offset = 0, ret, i, j;
 	uint32_t be;
@@ -259,7 +260,8 @@ int nftnl_data_reg_value_snprintf_xml(char *buf, size_t size,
 
 static int
 nftnl_data_reg_value_snprintf_default(char *buf, size_t size,
-				    union nftnl_data_reg *reg, uint32_t flags)
+				      const union nftnl_data_reg *reg,
+				      uint32_t flags)
 {
 	int len = size, offset = 0, ret, i;
 
@@ -273,7 +275,8 @@ nftnl_data_reg_value_snprintf_default(char *buf, size_t size,
 
 static int
 nftnl_data_reg_verdict_snprintf_def(char *buf, size_t size,
-				  union nftnl_data_reg *reg, uint32_t flags)
+				    const union nftnl_data_reg *reg,
+				    uint32_t flags)
 {
 	int len = size, offset = 0, ret = 0;
 
@@ -290,7 +293,8 @@ nftnl_data_reg_verdict_snprintf_def(char *buf, size_t size,
 
 static int
 nftnl_data_reg_verdict_snprintf_xml(char *buf, size_t size,
-				  union nftnl_data_reg *reg, uint32_t flags)
+				    const union nftnl_data_reg *reg,
+				    uint32_t flags)
 {
 	int len = size, offset = 0, ret = 0;
 
@@ -312,7 +316,8 @@ nftnl_data_reg_verdict_snprintf_xml(char *buf, size_t size,
 
 static int
 nftnl_data_reg_verdict_snprintf_json(char *buf, size_t size,
-				   union nftnl_data_reg *reg, uint32_t flags)
+				     const union nftnl_data_reg *reg,
+				     uint32_t flags)
 {
 	int len = size, offset = 0, ret = 0;
 
@@ -332,8 +337,10 @@ nftnl_data_reg_verdict_snprintf_json(char *buf, size_t size,
 	return offset;
 }
 
-int nftnl_data_reg_snprintf(char *buf, size_t size, union nftnl_data_reg *reg,
-			  uint32_t output_format, uint32_t flags, int reg_type)
+int nftnl_data_reg_snprintf(char *buf, size_t size,
+			    const union nftnl_data_reg *reg,
+			    uint32_t output_format, uint32_t flags,
+			    int reg_type)
 {
 	switch(reg_type) {
 	case DATA_VALUE:
@@ -499,7 +506,7 @@ int nftnl_parse_data(union nftnl_data_reg *data, struct nlattr *attr, int *type)
 	return ret;
 }
 
-void nftnl_free_verdict(union nftnl_data_reg *data)
+void nftnl_free_verdict(const union nftnl_data_reg *data)
 {
 	switch(data->verdict) {
 	case NFT_JUMP:
diff --git a/src/expr/dup.c b/src/expr/dup.c
index 046751e..694db32 100644
--- a/src/expr/dup.c
+++ b/src/expr/dup.c
@@ -80,7 +80,8 @@ static int nftnl_expr_dup_cb(const struct nlattr *attr, void *data)
 	return MNL_CB_OK;
 }
 
-static void nftnl_expr_dup_build(struct nlmsghdr *nlh, struct nftnl_expr *e)
+static void nftnl_expr_dup_build(struct nlmsghdr *nlh,
+				 const struct nftnl_expr *e)
 {
 	struct nftnl_expr_dup *dup = nftnl_expr_data(e);
 
@@ -152,8 +153,8 @@ static int nftnl_expr_dup_xml_parse(struct nftnl_expr *e, mxml_node_t *tree,
 #endif
 }
 
-static int nftnl_expr_dup_export(char *buf, size_t size, struct nftnl_expr *e,
-				 int type)
+static int nftnl_expr_dup_export(char *buf, size_t size,
+				 const struct nftnl_expr *e, int type)
 {
 	struct nftnl_expr_dup *dup = nftnl_expr_data(e);
 	NFTNL_BUF_INIT(b, buf, size);
@@ -167,7 +168,8 @@ static int nftnl_expr_dup_export(char *buf, size_t size, struct nftnl_expr *e,
 }
 
 static int nftnl_expr_dup_snprintf_default(char *buf, size_t len,
-					   struct nftnl_expr *e, uint32_t flags)
+					   const struct nftnl_expr *e,
+					   uint32_t flags)
 {
 	int size = len, offset = 0, ret;
 	struct nftnl_expr_dup *dup = nftnl_expr_data(e);
@@ -186,7 +188,7 @@ static int nftnl_expr_dup_snprintf_default(char *buf, size_t len,
 }
 
 static int nftnl_expr_dup_snprintf(char *buf, size_t len, uint32_t type,
-				   uint32_t flags, struct nftnl_expr *e)
+				   uint32_t flags, const struct nftnl_expr *e)
 {
 	switch (type) {
 	case NFTNL_OUTPUT_DEFAULT:
diff --git a/src/expr/dynset.c b/src/expr/dynset.c
index e82b10b..c8d97a5 100644
--- a/src/expr/dynset.c
+++ b/src/expr/dynset.c
@@ -130,7 +130,7 @@ static int nftnl_expr_dynset_cb(const struct nlattr *attr, void *data)
 }
 
 static void
-nftnl_expr_dynset_build(struct nlmsghdr *nlh, struct nftnl_expr *e)
+nftnl_expr_dynset_build(struct nlmsghdr *nlh, const struct nftnl_expr *e)
 {
 	struct nftnl_expr_dynset *dynset = nftnl_expr_data(e);
 	struct nlattr *nest;
@@ -274,7 +274,7 @@ nftnl_expr_dynset_xml_parse(struct nftnl_expr *e, mxml_node_t *tree,
 
 static int
 nftnl_expr_dynset_export(char *buf, size_t size,
-			    struct nftnl_expr *e, int type)
+			 const struct nftnl_expr *e, int type)
 {
 	struct nftnl_expr_dynset *dynset = nftnl_expr_data(e);
 	NFTNL_BUF_INIT(b, buf, size);
@@ -303,7 +303,7 @@ static const char *op2str(enum nft_dynset_ops op)
 
 static int
 nftnl_expr_dynset_snprintf_default(char *buf, size_t size,
-				      struct nftnl_expr *e)
+				   const struct nftnl_expr *e)
 {
 	struct nftnl_expr_dynset *dynset = nftnl_expr_data(e);
 	struct nftnl_expr *expr;
@@ -342,7 +342,7 @@ nftnl_expr_dynset_snprintf_default(char *buf, size_t size,
 
 static int
 nftnl_expr_dynset_snprintf(char *buf, size_t size, uint32_t type,
-			      uint32_t flags, struct nftnl_expr *e)
+			   uint32_t flags, const struct nftnl_expr *e)
 {
 
 	switch (type) {
@@ -357,7 +357,7 @@ nftnl_expr_dynset_snprintf(char *buf, size_t size, uint32_t type,
 	return -1;
 }
 
-static void nftnl_expr_dynset_free(struct nftnl_expr *e)
+static void nftnl_expr_dynset_free(const struct nftnl_expr *e)
 {
 	struct nftnl_expr_dynset *dynset = nftnl_expr_data(e);
 
diff --git a/src/expr/exthdr.c b/src/expr/exthdr.c
index 2e9b0b0..6489a48 100644
--- a/src/expr/exthdr.c
+++ b/src/expr/exthdr.c
@@ -109,7 +109,7 @@ static int nftnl_expr_exthdr_cb(const struct nlattr *attr, void *data)
 }
 
 static void
-nftnl_expr_exthdr_build(struct nlmsghdr *nlh, struct nftnl_expr *e)
+nftnl_expr_exthdr_build(struct nlmsghdr *nlh, const struct nftnl_expr *e)
 {
 	struct nftnl_expr_exthdr *exthdr = nftnl_expr_data(e);
 
@@ -261,7 +261,7 @@ nftnl_expr_exthdr_xml_parse(struct nftnl_expr *e, mxml_node_t *tree,
 }
 
 static int nftnl_expr_exthdr_export(char *buf, size_t len,
-				       struct nftnl_expr *e, int type)
+				    const struct nftnl_expr *e, int type)
 {
 	struct nftnl_expr_exthdr *exthdr = nftnl_expr_data(e);
 	NFTNL_BUF_INIT(b, buf, len);
@@ -279,7 +279,7 @@ static int nftnl_expr_exthdr_export(char *buf, size_t len,
 }
 
 static int nftnl_expr_exthdr_snprintf_default(char *buf, size_t len,
-						 struct nftnl_expr *e)
+					      const struct nftnl_expr *e)
 {
 	struct nftnl_expr_exthdr *exthdr = nftnl_expr_data(e);
 
@@ -290,7 +290,7 @@ static int nftnl_expr_exthdr_snprintf_default(char *buf, size_t len,
 
 static int
 nftnl_expr_exthdr_snprintf(char *buf, size_t len, uint32_t type,
-			       uint32_t flags, struct nftnl_expr *e)
+			   uint32_t flags, const struct nftnl_expr *e)
 {
 	switch (type) {
 	case NFTNL_OUTPUT_DEFAULT:
diff --git a/src/expr/fwd.c b/src/expr/fwd.c
index 1131c10..8fa6d66 100644
--- a/src/expr/fwd.c
+++ b/src/expr/fwd.c
@@ -72,7 +72,8 @@ static int nftnl_expr_fwd_cb(const struct nlattr *attr, void *data)
 	return MNL_CB_OK;
 }
 
-static void nftnl_expr_fwd_build(struct nlmsghdr *nlh, struct nftnl_expr *e)
+static void nftnl_expr_fwd_build(struct nlmsghdr *nlh,
+				 const struct nftnl_expr *e)
 {
 	struct nftnl_expr_fwd *fwd = nftnl_expr_data(e);
 
@@ -132,8 +133,8 @@ static int nftnl_expr_fwd_xml_parse(struct nftnl_expr *e, mxml_node_t *tree,
 #endif
 }
 
-static int nftnl_expr_fwd_export(char *buf, size_t size, struct nftnl_expr *e,
-				 int type)
+static int nftnl_expr_fwd_export(char *buf, size_t size,
+				 const struct nftnl_expr *e, int type)
 {
 	struct nftnl_expr_fwd *fwd = nftnl_expr_data(e);
 	NFTNL_BUF_INIT(b, buf, size);
@@ -145,7 +146,8 @@ static int nftnl_expr_fwd_export(char *buf, size_t size, struct nftnl_expr *e,
 }
 
 static int nftnl_expr_fwd_snprintf_default(char *buf, size_t len,
-					   struct nftnl_expr *e, uint32_t flags)
+					   const struct nftnl_expr *e,
+					   uint32_t flags)
 {
 	int size = len, offset = 0, ret;
 	struct nftnl_expr_fwd *fwd = nftnl_expr_data(e);
@@ -159,7 +161,7 @@ static int nftnl_expr_fwd_snprintf_default(char *buf, size_t len,
 }
 
 static int nftnl_expr_fwd_snprintf(char *buf, size_t len, uint32_t type,
-				   uint32_t flags, struct nftnl_expr *e)
+				   uint32_t flags, const struct nftnl_expr *e)
 {
 	switch (type) {
 	case NFTNL_OUTPUT_DEFAULT:
diff --git a/src/expr/immediate.c b/src/expr/immediate.c
index c2fb9ad..eb2ca0f 100644
--- a/src/expr/immediate.c
+++ b/src/expr/immediate.c
@@ -101,7 +101,7 @@ static int nftnl_expr_immediate_cb(const struct nlattr *attr, void *data)
 }
 
 static void
-nftnl_expr_immediate_build(struct nlmsghdr *nlh, struct nftnl_expr *e)
+nftnl_expr_immediate_build(struct nlmsghdr *nlh, const struct nftnl_expr *e)
 {
 	struct nftnl_expr_immediate *imm = nftnl_expr_data(e);
 
@@ -246,8 +246,8 @@ nftnl_expr_immediate_xml_parse(struct nftnl_expr *e, mxml_node_t *tree,
 }
 
 static int
-nftnl_expr_immediate_export(char *buf, size_t size, struct nftnl_expr *e,
-			       int type)
+nftnl_expr_immediate_export(char *buf, size_t size, const struct nftnl_expr *e,
+			    int type)
 {
 	struct nftnl_expr_immediate *imm = nftnl_expr_data(e);
 	NFTNL_BUF_INIT(b, buf, size);
@@ -266,7 +266,8 @@ nftnl_expr_immediate_export(char *buf, size_t size, struct nftnl_expr *e,
 
 static int
 nftnl_expr_immediate_snprintf_default(char *buf, size_t len,
-				struct nftnl_expr *e, uint32_t flags)
+				      const struct nftnl_expr *e,
+				      uint32_t flags)
 {
 	int size = len, offset = 0, ret;
 	struct nftnl_expr_immediate *imm = nftnl_expr_data(e);
@@ -295,7 +296,7 @@ nftnl_expr_immediate_snprintf_default(char *buf, size_t len,
 
 static int
 nftnl_expr_immediate_snprintf(char *buf, size_t len, uint32_t type,
-				 uint32_t flags, struct nftnl_expr *e)
+			      uint32_t flags, const struct nftnl_expr *e)
 {
 	switch(type) {
 	case NFTNL_OUTPUT_DEFAULT:
@@ -309,7 +310,7 @@ nftnl_expr_immediate_snprintf(char *buf, size_t len, uint32_t type,
 	return -1;
 }
 
-static void nftnl_expr_immediate_free(struct nftnl_expr *e)
+static void nftnl_expr_immediate_free(const struct nftnl_expr *e)
 {
 	struct nftnl_expr_immediate *imm = nftnl_expr_data(e);
 
diff --git a/src/expr/limit.c b/src/expr/limit.c
index 2c21eb5..4bd096e 100644
--- a/src/expr/limit.c
+++ b/src/expr/limit.c
@@ -111,7 +111,7 @@ static int nftnl_expr_limit_cb(const struct nlattr *attr, void *data)
 }
 
 static void
-nftnl_expr_limit_build(struct nlmsghdr *nlh, struct nftnl_expr *e)
+nftnl_expr_limit_build(struct nlmsghdr *nlh, const struct nftnl_expr *e)
 {
 	struct nftnl_expr_limit *limit = nftnl_expr_data(e);
 
@@ -231,7 +231,7 @@ static const char *get_unit(uint64_t u)
 }
 
 static int nftnl_expr_limit_export(char *buf, size_t size,
-				      struct nftnl_expr *e, int type)
+				   const struct nftnl_expr *e, int type)
 {
 	struct nftnl_expr_limit *limit = nftnl_expr_data(e);
 	NFTNL_BUF_INIT(b, buf, size);
@@ -263,7 +263,7 @@ static const char *limit_to_type(enum nft_limit_type type)
 }
 
 static int nftnl_expr_limit_snprintf_default(char *buf, size_t len,
-						struct nftnl_expr *e)
+					     const struct nftnl_expr *e)
 {
 	struct nftnl_expr_limit *limit = nftnl_expr_data(e);
 
@@ -274,7 +274,7 @@ static int nftnl_expr_limit_snprintf_default(char *buf, size_t len,
 
 static int
 nftnl_expr_limit_snprintf(char *buf, size_t len, uint32_t type,
-			    uint32_t flags, struct nftnl_expr *e)
+			  uint32_t flags, const struct nftnl_expr *e)
 {
 	switch(type) {
 	case NFTNL_OUTPUT_DEFAULT:
diff --git a/src/expr/log.c b/src/expr/log.c
index f615d8e..c3dc0a6 100644
--- a/src/expr/log.c
+++ b/src/expr/log.c
@@ -123,7 +123,7 @@ static int nftnl_expr_log_cb(const struct nlattr *attr, void *data)
 }
 
 static void
-nftnl_expr_log_build(struct nlmsghdr *nlh, struct nftnl_expr *e)
+nftnl_expr_log_build(struct nlmsghdr *nlh, const struct nftnl_expr *e)
 {
 	struct nftnl_expr_log *log = nftnl_expr_data(e);
 
@@ -265,7 +265,7 @@ static int nftnl_expr_log_xml_parse(struct nftnl_expr *e,
 }
 
 static int nftnl_expr_log_snprintf_default(char *buf, size_t size,
-					      struct nftnl_expr *e)
+					   const struct nftnl_expr *e)
 {
 	struct nftnl_expr_log *log = nftnl_expr_data(e);
 	int ret, offset = 0, len = size;
@@ -288,7 +288,7 @@ static int nftnl_expr_log_snprintf_default(char *buf, size_t size,
 }
 
 static int nftnl_expr_log_export(char *buf, size_t size,
-				    struct nftnl_expr *e, int type)
+				 const struct nftnl_expr *e, int type)
 {
 	struct nftnl_expr_log *log = nftnl_expr_data(e);
 	NFTNL_BUF_INIT(b, buf, size);
@@ -311,7 +311,7 @@ static int nftnl_expr_log_export(char *buf, size_t size,
 
 static int
 nftnl_expr_log_snprintf(char *buf, size_t len, uint32_t type,
-			    uint32_t flags, struct nftnl_expr *e)
+			uint32_t flags, const struct nftnl_expr *e)
 {
 	switch(type) {
 	case NFTNL_OUTPUT_DEFAULT:
@@ -325,7 +325,7 @@ nftnl_expr_log_snprintf(char *buf, size_t len, uint32_t type,
 	return -1;
 }
 
-static void nftnl_expr_log_free(struct nftnl_expr *e)
+static void nftnl_expr_log_free(const struct nftnl_expr *e)
 {
 	struct nftnl_expr_log *log = nftnl_expr_data(e);
 
diff --git a/src/expr/lookup.c b/src/expr/lookup.c
index b26d9e5..ed32ba6 100644
--- a/src/expr/lookup.c
+++ b/src/expr/lookup.c
@@ -100,7 +100,7 @@ static int nftnl_expr_lookup_cb(const struct nlattr *attr, void *data)
 }
 
 static void
-nftnl_expr_lookup_build(struct nlmsghdr *nlh, struct nftnl_expr *e)
+nftnl_expr_lookup_build(struct nlmsghdr *nlh, const struct nftnl_expr *e)
 {
 	struct nftnl_expr_lookup *lookup = nftnl_expr_data(e);
 
@@ -203,7 +203,7 @@ nftnl_expr_lookup_xml_parse(struct nftnl_expr *e, mxml_node_t *tree,
 
 static int
 nftnl_expr_lookup_export(char *buf, size_t size,
-			    struct nftnl_expr *e, int type)
+			 const struct nftnl_expr *e, int type)
 {
 	struct nftnl_expr_lookup *l = nftnl_expr_data(e);
 	NFTNL_BUF_INIT(b, buf, size);
@@ -220,7 +220,7 @@ nftnl_expr_lookup_export(char *buf, size_t size,
 
 static int
 nftnl_expr_lookup_snprintf_default(char *buf, size_t size,
-				      struct nftnl_expr *e)
+				   const struct nftnl_expr *e)
 {
 	int len = size, offset = 0, ret;
 	struct nftnl_expr_lookup *l = nftnl_expr_data(e);
@@ -239,7 +239,7 @@ nftnl_expr_lookup_snprintf_default(char *buf, size_t size,
 
 static int
 nftnl_expr_lookup_snprintf(char *buf, size_t size, uint32_t type,
-			       uint32_t flags, struct nftnl_expr *e)
+			   uint32_t flags, const struct nftnl_expr *e)
 {
 
 	switch(type) {
@@ -254,7 +254,7 @@ nftnl_expr_lookup_snprintf(char *buf, size_t size, uint32_t type,
 	return -1;
 }
 
-static void nftnl_expr_lookup_free(struct nftnl_expr *e)
+static void nftnl_expr_lookup_free(const struct nftnl_expr *e)
 {
 	struct nftnl_expr_lookup *lookup = nftnl_expr_data(e);
 
diff --git a/src/expr/masq.c b/src/expr/masq.c
index ff72e2d..7296590 100644
--- a/src/expr/masq.c
+++ b/src/expr/masq.c
@@ -90,7 +90,7 @@ static int nftnl_expr_masq_cb(const struct nlattr *attr, void *data)
 }
 
 static void
-nftnl_expr_masq_build(struct nlmsghdr *nlh, struct nftnl_expr *e)
+nftnl_expr_masq_build(struct nlmsghdr *nlh, const struct nftnl_expr *e)
 {
 	struct nftnl_expr_masq *masq = nftnl_expr_data(e);
 
@@ -182,7 +182,7 @@ nftnl_expr_masq_xml_parse(struct nftnl_expr *e, mxml_node_t *tree,
 #endif
 }
 static int nftnl_expr_masq_export(char *buf, size_t size,
-				     struct nftnl_expr *e, int type)
+				  const struct nftnl_expr *e, int type)
 {
 	struct nftnl_expr_masq *masq = nftnl_expr_data(e);
 	NFTNL_BUF_INIT(b, buf, size);
@@ -198,7 +198,7 @@ static int nftnl_expr_masq_export(char *buf, size_t size,
 }
 
 static int nftnl_expr_masq_snprintf_default(char *buf, size_t len,
-					       struct nftnl_expr *e)
+					    const struct nftnl_expr *e)
 {
 	struct nftnl_expr_masq *masq = nftnl_expr_data(e);
 
@@ -214,7 +214,7 @@ static int nftnl_expr_masq_snprintf_default(char *buf, size_t len,
 }
 
 static int nftnl_expr_masq_snprintf(char *buf, size_t len, uint32_t type,
-				       uint32_t flags, struct nftnl_expr *e)
+				    uint32_t flags, const struct nftnl_expr *e)
 {
 	switch (type) {
 	case NFTNL_OUTPUT_DEFAULT:
diff --git a/src/expr/match.c b/src/expr/match.c
index ddecb43..2929b43 100644
--- a/src/expr/match.c
+++ b/src/expr/match.c
@@ -109,7 +109,7 @@ static int nftnl_expr_match_cb(const struct nlattr *attr, void *data)
 }
 
 static void
-nftnl_expr_match_build(struct nlmsghdr *nlh, struct nftnl_expr *e)
+nftnl_expr_match_build(struct nlmsghdr *nlh, const struct nftnl_expr *e)
 {
 	struct nftnl_expr_match *mt = nftnl_expr_data(e);
 
@@ -203,7 +203,7 @@ static int nftnl_expr_match_xml_parse(struct nftnl_expr *e, mxml_node_t *tree,
 }
 
 static int nftnl_expr_match_export(char *buf, size_t size,
-				      struct nftnl_expr *e, int type)
+				   const struct nftnl_expr *e, int type)
 {
 	struct nftnl_expr_match *mt = nftnl_expr_data(e);
 	NFTNL_BUF_INIT(b, buf, size);
@@ -216,7 +216,7 @@ static int nftnl_expr_match_export(char *buf, size_t size,
 
 static int
 nftnl_expr_match_snprintf(char *buf, size_t len, uint32_t type,
-			     uint32_t flags, struct nftnl_expr *e)
+			  uint32_t flags, const struct nftnl_expr *e)
 {
 	struct nftnl_expr_match *match = nftnl_expr_data(e);
 
@@ -233,7 +233,7 @@ nftnl_expr_match_snprintf(char *buf, size_t len, uint32_t type,
 	return -1;
 }
 
-static void nftnl_expr_match_free(struct nftnl_expr *e)
+static void nftnl_expr_match_free(const struct nftnl_expr *e)
 {
 	struct nftnl_expr_match *match = nftnl_expr_data(e);
 
diff --git a/src/expr/meta.c b/src/expr/meta.c
index 060c704..a478a89 100644
--- a/src/expr/meta.c
+++ b/src/expr/meta.c
@@ -95,7 +95,7 @@ static int nftnl_expr_meta_cb(const struct nlattr *attr, void *data)
 }
 
 static void
-nftnl_expr_meta_build(struct nlmsghdr *nlh, struct nftnl_expr *e)
+nftnl_expr_meta_build(struct nlmsghdr *nlh, const struct nftnl_expr *e)
 {
 	struct nftnl_expr_meta *meta = nftnl_expr_data(e);
 
@@ -249,7 +249,7 @@ static int nftnl_expr_meta_xml_parse(struct nftnl_expr *e, mxml_node_t *tree,
 
 static int
 nftnl_expr_meta_snprintf_default(char *buf, size_t len,
-				    struct nftnl_expr *e)
+				 const struct nftnl_expr *e)
 {
 	struct nftnl_expr_meta *meta = nftnl_expr_data(e);
 
@@ -265,7 +265,7 @@ nftnl_expr_meta_snprintf_default(char *buf, size_t len,
 }
 
 static int nftnl_expr_meta_export(char *buf, size_t size,
-				     struct nftnl_expr *e, int type)
+				  const struct nftnl_expr *e, int type)
 {
 	struct nftnl_expr_meta *meta = nftnl_expr_data(e);
 	NFTNL_BUF_INIT(b, buf, size);
@@ -282,7 +282,7 @@ static int nftnl_expr_meta_export(char *buf, size_t size,
 
 static int
 nftnl_expr_meta_snprintf(char *buf, size_t len, uint32_t type,
-			    uint32_t flags, struct nftnl_expr *e)
+			 uint32_t flags, const struct nftnl_expr *e)
 {
 	switch (type) {
 	case NFTNL_OUTPUT_DEFAULT:
diff --git a/src/expr/nat.c b/src/expr/nat.c
index 421983f..1ae7f77 100644
--- a/src/expr/nat.c
+++ b/src/expr/nat.c
@@ -172,7 +172,7 @@ nftnl_expr_nat_parse(struct nftnl_expr *e, struct nlattr *attr)
 }
 
 static void
-nftnl_expr_nat_build(struct nlmsghdr *nlh, struct nftnl_expr *e)
+nftnl_expr_nat_build(struct nlmsghdr *nlh, const struct nftnl_expr *e)
 {
 	struct nftnl_expr_nat *nat = nftnl_expr_data(e);
 
@@ -330,7 +330,7 @@ static int nftnl_expr_nat_xml_parse(struct nftnl_expr *e, mxml_node_t *tree,
 }
 
 static int nftnl_expr_nat_export(char *buf, size_t size,
-				    struct nftnl_expr *e, int type)
+				 const struct nftnl_expr *e, int type)
 {
 	struct nftnl_expr_nat *nat = nftnl_expr_data(e);
 	NFTNL_BUF_INIT(b, buf, size);
@@ -355,7 +355,7 @@ static int nftnl_expr_nat_export(char *buf, size_t size,
 
 static int
 nftnl_expr_nat_snprintf_default(char *buf, size_t size,
-				   struct nftnl_expr *e)
+				const struct nftnl_expr *e)
 {
 	struct nftnl_expr_nat *nat = nftnl_expr_data(e);
 	int len = size, offset = 0, ret = 0;
@@ -390,7 +390,7 @@ nftnl_expr_nat_snprintf_default(char *buf, size_t size,
 
 static int
 nftnl_expr_nat_snprintf(char *buf, size_t size, uint32_t type,
-			   uint32_t flags, struct nftnl_expr *e)
+			uint32_t flags, const struct nftnl_expr *e)
 {
 	switch (type) {
 	case NFTNL_OUTPUT_DEFAULT:
diff --git a/src/expr/payload.c b/src/expr/payload.c
index 508f11a..b4fd9c5 100644
--- a/src/expr/payload.c
+++ b/src/expr/payload.c
@@ -126,7 +126,7 @@ static int nftnl_expr_payload_cb(const struct nlattr *attr, void *data)
 }
 
 static void
-nftnl_expr_payload_build(struct nlmsghdr *nlh, struct nftnl_expr *e)
+nftnl_expr_payload_build(struct nlmsghdr *nlh, const struct nftnl_expr *e)
 {
 	struct nftnl_expr_payload *payload = nftnl_expr_data(e);
 
@@ -291,7 +291,7 @@ nftnl_expr_payload_xml_parse(struct nftnl_expr *e, mxml_node_t *tree,
 }
 
 static int nftnl_expr_payload_export(char *buf, size_t size, uint32_t flags,
-					struct nftnl_expr *e, int type)
+				     const struct nftnl_expr *e, int type)
 {
 	struct nftnl_expr_payload *payload = nftnl_expr_data(e);
 	NFTNL_BUF_INIT(b, buf, size);
@@ -310,7 +310,7 @@ static int nftnl_expr_payload_export(char *buf, size_t size, uint32_t flags,
 
 static int
 nftnl_expr_payload_snprintf(char *buf, size_t len, uint32_t type,
-			       uint32_t flags, struct nftnl_expr *e)
+			    uint32_t flags, const struct nftnl_expr *e)
 {
 	struct nftnl_expr_payload *payload = nftnl_expr_data(e);
 
diff --git a/src/expr/queue.c b/src/expr/queue.c
index 21126ed..a2e6ed5 100644
--- a/src/expr/queue.c
+++ b/src/expr/queue.c
@@ -89,7 +89,7 @@ static int nftnl_expr_queue_cb(const struct nlattr *attr, void *data)
 }
 
 static void
-nftnl_expr_queue_build(struct nlmsghdr *nlh, struct nftnl_expr *e)
+nftnl_expr_queue_build(struct nlmsghdr *nlh, const struct nftnl_expr *e)
 {
 	struct nftnl_expr_queue *queue = nftnl_expr_data(e);
 
@@ -181,7 +181,7 @@ nftnl_expr_queue_xml_parse(struct nftnl_expr *e, mxml_node_t *tree,
 }
 
 static int nftnl_expr_queue_snprintf_default(char *buf, size_t len,
-						struct nftnl_expr *e)
+					     const struct nftnl_expr *e)
 {
 	struct nftnl_expr_queue *queue = nftnl_expr_data(e);
 	int ret, size = len, offset = 0;
@@ -211,7 +211,7 @@ static int nftnl_expr_queue_snprintf_default(char *buf, size_t len,
 }
 
 static int nftnl_expr_queue_export(char *buf, size_t size,
-				      struct nftnl_expr *e, int type)
+				   const struct nftnl_expr *e, int type)
 {
 	struct nftnl_expr_queue *queue = nftnl_expr_data(e);
 	NFTNL_BUF_INIT(b, buf, size);
@@ -228,7 +228,7 @@ static int nftnl_expr_queue_export(char *buf, size_t size,
 
 static int
 nftnl_expr_queue_snprintf(char *buf, size_t len, uint32_t type,
-			      uint32_t flags, struct nftnl_expr *e)
+			  uint32_t flags, const struct nftnl_expr *e)
 {
 
 	switch (type) {
diff --git a/src/expr/redir.c b/src/expr/redir.c
index b8fb1fe..c6eedfb 100644
--- a/src/expr/redir.c
+++ b/src/expr/redir.c
@@ -90,7 +90,7 @@ static int nftnl_expr_redir_cb(const struct nlattr *attr, void *data)
 }
 
 static void
-nftnl_expr_redir_build(struct nlmsghdr *nlh, struct nftnl_expr *e)
+nftnl_expr_redir_build(struct nlmsghdr *nlh, const struct nftnl_expr *e)
 {
 	struct nftnl_expr_redir *redir = nftnl_expr_data(e);
 
@@ -184,7 +184,7 @@ nftnl_expr_redir_xml_parse(struct nftnl_expr *e, mxml_node_t *tree,
 }
 
 static int nftnl_expr_redir_export(char *buf, size_t size,
-				      struct nftnl_expr *e, int type)
+				   const struct nftnl_expr *e, int type)
 {
 	struct nftnl_expr_redir *redir = nftnl_expr_data(e);
         NFTNL_BUF_INIT(b, buf, size);
@@ -200,7 +200,7 @@ static int nftnl_expr_redir_export(char *buf, size_t size,
 }
 
 static int nftnl_expr_redir_snprintf_default(char *buf, size_t len,
-						struct nftnl_expr *e)
+					     const struct nftnl_expr *e)
 {
 	int ret, size = len, offset = 0;
 	struct nftnl_expr_redir *redir = nftnl_expr_data(e);
@@ -228,7 +228,7 @@ static int nftnl_expr_redir_snprintf_default(char *buf, size_t len,
 
 static int
 nftnl_expr_redir_snprintf(char *buf, size_t len, uint32_t type,
-			     uint32_t flags, struct nftnl_expr *e)
+			  uint32_t flags, const struct nftnl_expr *e)
 {
 	switch (type) {
 	case NFTNL_OUTPUT_DEFAULT:
diff --git a/src/expr/reject.c b/src/expr/reject.c
index 979817a..1953328 100644
--- a/src/expr/reject.c
+++ b/src/expr/reject.c
@@ -85,7 +85,7 @@ static int nftnl_expr_reject_cb(const struct nlattr *attr, void *data)
 }
 
 static void
-nftnl_expr_reject_build(struct nlmsghdr *nlh, struct nftnl_expr *e)
+nftnl_expr_reject_build(struct nlmsghdr *nlh, const struct nftnl_expr *e)
 {
 	struct nftnl_expr_reject *reject = nftnl_expr_data(e);
 
@@ -161,7 +161,7 @@ nftnl_expr_reject_xml_parse(struct nftnl_expr *e, mxml_node_t *tree,
 }
 
 static int nftnl_expr_reject_snprintf_default(char *buf, size_t len,
-						 struct nftnl_expr *e)
+					      const struct nftnl_expr *e)
 {
 	struct nftnl_expr_reject *reject = nftnl_expr_data(e);
 
@@ -170,7 +170,7 @@ static int nftnl_expr_reject_snprintf_default(char *buf, size_t len,
 }
 
 static int nftnl_expr_reject_export(char *buf, size_t size,
-				       struct nftnl_expr *e, int type)
+				    const struct nftnl_expr *e, int type)
 {
 	struct nftnl_expr_reject *reject = nftnl_expr_data(e);
 	NFTNL_BUF_INIT(b, buf, size);
@@ -185,7 +185,7 @@ static int nftnl_expr_reject_export(char *buf, size_t size,
 
 static int
 nftnl_expr_reject_snprintf(char *buf, size_t len, uint32_t type,
-			      uint32_t flags, struct nftnl_expr *e)
+			   uint32_t flags, const struct nftnl_expr *e)
 {
 	switch (type) {
 	case NFTNL_OUTPUT_DEFAULT:
diff --git a/src/expr/target.c b/src/expr/target.c
index cbbee60..68a7d8a 100644
--- a/src/expr/target.c
+++ b/src/expr/target.c
@@ -109,7 +109,7 @@ static int nftnl_expr_target_cb(const struct nlattr *attr, void *data)
 }
 
 static void
-nftnl_expr_target_build(struct nlmsghdr *nlh, struct nftnl_expr *e)
+nftnl_expr_target_build(struct nlmsghdr *nlh, const struct nftnl_expr *e)
 {
 	struct nftnl_expr_target *tg = nftnl_expr_data(e);
 
@@ -204,7 +204,7 @@ nftnl_expr_target_xml_parse(struct nftnl_expr *e, mxml_node_t *tree,
 }
 
 static int nftnl_rule_exp_target_export(char *buf, size_t size,
-				      struct nftnl_expr *e, int type)
+				        const struct nftnl_expr *e, int type)
 {
 	struct nftnl_expr_target *target = nftnl_expr_data(e);
 	NFTNL_BUF_INIT(b, buf, size);
@@ -217,7 +217,7 @@ static int nftnl_rule_exp_target_export(char *buf, size_t size,
 
 static int
 nftnl_expr_target_snprintf(char *buf, size_t len, uint32_t type,
-			      uint32_t flags, struct nftnl_expr *e)
+			   uint32_t flags, const struct nftnl_expr *e)
 {
 	struct nftnl_expr_target *target = nftnl_expr_data(e);
 
@@ -234,7 +234,7 @@ nftnl_expr_target_snprintf(char *buf, size_t len, uint32_t type,
 	return -1;
 }
 
-static void nftnl_expr_target_free(struct nftnl_expr *e)
+static void nftnl_expr_target_free(const struct nftnl_expr *e)
 {
 	struct nftnl_expr_target *target = nftnl_expr_data(e);