[PATCH libnftnl,v1 1/2] src: add ct expectation support

[PATCH libnftnl,v1 1/2] src: add ct expectation support

[Stéphane Veyret]

Add support for ct expectation objects, used to define specific expectations.

Signed-off-by: Stéphane Veyret <sveyret@gmail.com>
---
 include/libnftnl/object.h           |   7 +
 include/linux/netfilter/nf_tables.h |  13 +-
 include/obj.h                       |   7 +
 src/Makefile.am                     |   1 +
 src/obj/ct_expect.c                 | 193 ++++++++++++++++++++++++++++
 src/object.c                        |   1 +
 6 files changed, 221 insertions(+), 1 deletion(-)
 create mode 100644 src/obj/ct_expect.c

diff --git a/include/libnftnl/object.h b/include/libnftnl/object.h
index 4ce2230..dcb631c 100644
--- a/include/libnftnl/object.h
+++ b/include/libnftnl/object.h
@@ -70,6 +70,13 @@ enum {
 	NFTNL_OBJ_CT_TIMEOUT_ARRAY,
 };
 
+enum {
+	NFTNL_OBJ_CT_EXPECT_L3PROTO = NFTNL_OBJ_BASE,
+	NFTNL_OBJ_CT_EXPECT_L4PROTO,
+	NFTNL_OBJ_CT_EXPECT_DPORT,
+	NFTNL_OBJ_CT_EXPECT_TIMEOUT,
+};
+
 enum {
 	NFTNL_OBJ_LIMIT_RATE	= NFTNL_OBJ_BASE,
 	NFTNL_OBJ_LIMIT_UNIT,
diff --git a/include/linux/netfilter/nf_tables.h b/include/linux/netfilter/nf_tables.h
index fd38cdc..59969f1 100644
--- a/include/linux/netfilter/nf_tables.h
+++ b/include/linux/netfilter/nf_tables.h
@@ -1429,6 +1429,16 @@ enum nft_ct_timeout_attributes {
 };
 #define NFTA_CT_TIMEOUT_MAX	(__NFTA_CT_TIMEOUT_MAX - 1)
 
+enum nft_ct_expectation_attributes {
+	NFTA_CT_EXPECT_UNSPEC,
+	NFTA_CT_EXPECT_L3PROTO,
+	NFTA_CT_EXPECT_L4PROTO,
+	NFTA_CT_EXPECT_DPORT,
+	NFTA_CT_EXPECT_TIMEOUT,
+	__NFTA_CT_EXPECT_MAX,
+};
+#define NFTA_CT_EXPECT_MAX	(__NFTA_CT_EXPECT_MAX - 1)
+
 #define NFT_OBJECT_UNSPEC	0
 #define NFT_OBJECT_COUNTER	1
 #define NFT_OBJECT_QUOTA	2
@@ -1438,7 +1448,8 @@ enum nft_ct_timeout_attributes {
 #define NFT_OBJECT_TUNNEL	6
 #define NFT_OBJECT_CT_TIMEOUT	7
 #define NFT_OBJECT_SECMARK	8
-#define __NFT_OBJECT_MAX	9
+#define NFT_OBJECT_CT_EXPECT	9
+#define __NFT_OBJECT_MAX	10
 #define NFT_OBJECT_MAX		(__NFT_OBJECT_MAX - 1)
 
 /**
diff --git a/include/obj.h b/include/obj.h
index 35b5c40..f5935ab 100644
--- a/include/obj.h
+++ b/include/obj.h
@@ -42,6 +42,12 @@ struct nftnl_obj {
 			uint8_t 	l4proto;
 			uint32_t	timeout[NFTNL_CTTIMEOUT_ARRAY_MAX];
 		} ct_timeout;
+		struct nftnl_obj_ct_expect {
+			uint16_t	l3proto;
+			uint8_t		l4proto;
+			uint16_t	dport;
+			uint32_t	timeout;
+		} ct_expect;
 		struct nftnl_obj_limit {
 			uint64_t	rate;
 			uint64_t	unit;
@@ -99,6 +105,7 @@ extern struct obj_ops obj_ops_counter;
 extern struct obj_ops obj_ops_quota;
 extern struct obj_ops obj_ops_ct_helper;
 extern struct obj_ops obj_ops_ct_timeout;
+extern struct obj_ops obj_ops_ct_expect;
 extern struct obj_ops obj_ops_limit;
 extern struct obj_ops obj_ops_tunnel;
 extern struct obj_ops obj_ops_secmark;
diff --git a/src/Makefile.am b/src/Makefile.am
index 2d5873f..8f9c022 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -65,4 +65,5 @@ libnftnl_la_SOURCES = utils.c		\
 		      obj/limit.c	\
 		      obj/ct_timeout.c 	\
 		      obj/secmark.c	\
+		      obj/ct_expect.c 	\
 		      libnftnl.map
diff --git a/src/obj/ct_expect.c b/src/obj/ct_expect.c
new file mode 100644
index 0000000..16066c4
--- /dev/null
+++ b/src/obj/ct_expect.c
@@ -0,0 +1,193 @@
+/*
+ * (C) 2019 by Stéphane Veyret <sveyret@gmail.com>
+ *
+ * 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 <arpa/inet.h>
+#include <errno.h>
+
+#include <libmnl/libmnl.h>
+
+#include "obj.h"
+
+static int nftnl_obj_ct_expect_set(struct nftnl_obj *e, uint16_t type,
+				   const void *data, uint32_t data_len)
+{
+	struct nftnl_obj_ct_expect *exp = nftnl_obj_data(e);
+
+	switch (type) {
+	case NFTNL_OBJ_CT_EXPECT_L3PROTO:
+		memcpy(&exp->l3proto, data, sizeof(exp->l3proto));
+		break;
+	case NFTNL_OBJ_CT_EXPECT_L4PROTO:
+		memcpy(&exp->l4proto, data, sizeof(exp->l4proto));
+		break;
+	case NFTNL_OBJ_CT_EXPECT_DPORT:
+		memcpy(&exp->dport, data, sizeof(exp->dport));
+		break;
+	case NFTNL_OBJ_CT_EXPECT_TIMEOUT:
+		memcpy(&exp->timeout, data, sizeof(exp->timeout));
+		break;
+	default:
+		return -1;
+	}
+	return 0;
+}
+
+static const void *nftnl_obj_ct_expect_get(const struct nftnl_obj *e,
+					   uint16_t type, uint32_t *data_len)
+{
+	struct nftnl_obj_ct_expect *exp = nftnl_obj_data(e);
+
+	switch (type) {
+	case NFTNL_OBJ_CT_EXPECT_L3PROTO:
+		*data_len = sizeof(exp->l3proto);
+		return &exp->l3proto;
+	case NFTNL_OBJ_CT_EXPECT_L4PROTO:
+		*data_len = sizeof(exp->l4proto);
+		return &exp->l4proto;
+	case NFTNL_OBJ_CT_EXPECT_DPORT:
+		*data_len = sizeof(exp->dport);
+		return &exp->dport;
+	case NFTNL_OBJ_CT_EXPECT_TIMEOUT:
+		*data_len = sizeof(exp->timeout);
+		return &exp->timeout;
+	}
+	return NULL;
+}
+
+static int nftnl_obj_ct_expect_cb(const struct nlattr *attr, void *data)
+{
+	int type = mnl_attr_get_type(attr);
+	const struct nlattr **tb = data;
+
+	if (mnl_attr_type_valid(attr, NFTA_CT_EXPECT_MAX) < 0)
+		return MNL_CB_OK;
+
+	switch (type) {
+	case NFTA_CT_EXPECT_L3PROTO:
+		if (mnl_attr_validate(attr, MNL_TYPE_U16) < 0)
+			abi_breakage();
+		break;
+	case NFTA_CT_EXPECT_L4PROTO:
+		if (mnl_attr_validate(attr, MNL_TYPE_U8) < 0)
+			abi_breakage();
+		break;
+	case NFTA_CT_EXPECT_DPORT:
+		if (mnl_attr_validate(attr, MNL_TYPE_U16) < 0)
+			abi_breakage();
+		break;
+	case NFTA_CT_EXPECT_TIMEOUT:
+		if (mnl_attr_validate(attr, MNL_TYPE_U32) < 0)
+			abi_breakage();
+		break;
+	}
+
+	tb[type] = attr;
+	return MNL_CB_OK;
+}
+
+static void
+nftnl_obj_ct_expect_build(struct nlmsghdr *nlh, const struct nftnl_obj *e)
+{
+	struct nftnl_obj_ct_expect *exp = nftnl_obj_data(e);
+
+	if (e->flags & (1 << NFTNL_OBJ_CT_EXPECT_L3PROTO))
+		mnl_attr_put_u16(nlh, NFTA_CT_EXPECT_L3PROTO, htons(exp->l3proto));
+	if (e->flags & (1 << NFTNL_OBJ_CT_EXPECT_L4PROTO))
+		mnl_attr_put_u8(nlh, NFTA_CT_EXPECT_L4PROTO, exp->l4proto);
+	if (e->flags & (1 << NFTNL_OBJ_CT_EXPECT_DPORT))
+		mnl_attr_put_u16(nlh, NFTA_CT_EXPECT_DPORT, htons(exp->dport));
+	if (e->flags & (1 << NFTNL_OBJ_CT_EXPECT_TIMEOUT))
+		mnl_attr_put_u32(nlh, NFTA_CT_EXPECT_TIMEOUT, exp->timeout);
+}
+
+static int
+nftnl_obj_ct_expect_parse(struct nftnl_obj *e, struct nlattr *attr)
+{
+	struct nftnl_obj_ct_expect *exp = nftnl_obj_data(e);
+	struct nlattr *tb[NFTA_CT_EXPECT_MAX + 1] = {};
+
+	if (mnl_attr_parse_nested(attr, nftnl_obj_ct_expect_cb, tb) < 0)
+		return -1;
+
+	if (tb[NFTA_CT_EXPECT_L3PROTO]) {
+		exp->l3proto = ntohs(mnl_attr_get_u16(tb[NFTA_CT_EXPECT_L3PROTO]));
+		e->flags |= (1 << NFTNL_OBJ_CT_EXPECT_L3PROTO);
+	}
+	if (tb[NFTA_CT_EXPECT_L4PROTO]) {
+		exp->l4proto = mnl_attr_get_u8(tb[NFTA_CT_EXPECT_L4PROTO]);
+		e->flags |= (1 << NFTNL_OBJ_CT_EXPECT_L4PROTO);
+	}
+	if (tb[NFTA_CT_EXPECT_DPORT]) {
+		exp->dport = ntohs(mnl_attr_get_u16(tb[NFTA_CT_EXPECT_DPORT]));
+		e->flags |= (1 << NFTNL_OBJ_CT_EXPECT_DPORT);
+	}
+	if (tb[NFTA_CT_EXPECT_TIMEOUT]) {
+		exp->timeout = mnl_attr_get_u32(tb[NFTA_CT_EXPECT_TIMEOUT]);
+		e->flags |= (1 << NFTNL_OBJ_CT_EXPECT_TIMEOUT);
+	}
+
+	return 0;
+}
+
+static int nftnl_obj_ct_expect_snprintf_default(char *buf, size_t len,
+					       const struct nftnl_obj *e)
+{
+	int ret = 0;
+	int offset = 0, remain = len;
+	struct nftnl_obj_ct_expect *exp = nftnl_obj_data(e);
+
+	if (e->flags & (1 << NFTNL_OBJ_CT_EXPECT_L3PROTO)) {
+		ret = snprintf(buf + offset, len, "family %d ", exp->l3proto);
+		SNPRINTF_BUFFER_SIZE(ret, remain, offset);
+	}
+	if (e->flags & (1 << NFTNL_OBJ_CT_EXPECT_L4PROTO)) {
+		ret = snprintf(buf + offset, len, "protocol %d ", exp->l4proto);
+		SNPRINTF_BUFFER_SIZE(ret, remain, offset);
+	}
+	if (e->flags & (1 << NFTNL_OBJ_CT_EXPECT_DPORT)) {
+		ret = snprintf(buf + offset, len, "dport %d ", exp->dport);
+		SNPRINTF_BUFFER_SIZE(ret, remain, offset);
+	}
+	if (e->flags & (1 << NFTNL_OBJ_CT_EXPECT_TIMEOUT)) {
+		ret = snprintf(buf + offset, len, "timeout %d ", exp->timeout);
+		SNPRINTF_BUFFER_SIZE(ret, remain, offset);
+	}
+
+	buf[offset] = '\0';
+	return offset;
+}
+
+static int nftnl_obj_ct_expect_snprintf(char *buf, size_t len, uint32_t type,
+				       uint32_t flags,
+				       const struct nftnl_obj *e)
+{
+	if (len)
+		buf[0] = '\0';
+
+	switch (type) {
+	case NFTNL_OUTPUT_DEFAULT:
+		return nftnl_obj_ct_expect_snprintf_default(buf, len, e);
+	case NFTNL_OUTPUT_JSON:
+	default:
+		break;
+	}
+	return -1;
+}
+
+struct obj_ops obj_ops_ct_expect = {
+	.name		= "ct_expect",
+	.type		= NFT_OBJECT_CT_EXPECT,
+	.alloc_len	= sizeof(struct nftnl_obj_ct_expect),
+	.max_attr	= NFTA_CT_EXPECT_MAX,
+	.set		= nftnl_obj_ct_expect_set,
+	.get		= nftnl_obj_ct_expect_get,
+	.parse		= nftnl_obj_ct_expect_parse,
+	.build		= nftnl_obj_ct_expect_build,
+	.snprintf	= nftnl_obj_ct_expect_snprintf,
+};
diff --git a/src/object.c b/src/object.c
index 5c8d183..23f8840 100644
--- a/src/object.c
+++ b/src/object.c
@@ -33,6 +33,7 @@ static struct obj_ops *obj_ops[__NFT_OBJECT_MAX] = {
 	[NFT_OBJECT_TUNNEL]	= &obj_ops_tunnel,
 	[NFT_OBJECT_CT_TIMEOUT] = &obj_ops_ct_timeout,
 	[NFT_OBJECT_SECMARK]	= &obj_ops_secmark,
+	[NFT_OBJECT_CT_EXPECT] = &obj_ops_ct_expect,
 };
 
 static struct obj_ops *nftnl_obj_ops_lookup(uint32_t type)
-- 
2.21.0

[PATCH libnftnl,v1 2/2] examples: add ct expectation examples

[Stéphane Veyret]

Add examples for ct expectations.

Add, list and delete ct expectation objects from specified table.
Add expectation object to rule.

Signed-off-by: Stéphane Veyret <sveyret@gmail.com>
---
 examples/Makefile.am                   |  16 +++
 examples/nft-ct-expectation-add.c      | 154 +++++++++++++++++++++++
 examples/nft-ct-expectation-del.c      | 128 +++++++++++++++++++
 examples/nft-ct-expectation-get.c      | 144 ++++++++++++++++++++++
 examples/nft-rule-ct-expectation-add.c | 163 +++++++++++++++++++++++++
 5 files changed, 605 insertions(+)
 create mode 100644 examples/nft-ct-expectation-add.c
 create mode 100644 examples/nft-ct-expectation-del.c
 create mode 100644 examples/nft-ct-expectation-get.c
 create mode 100644 examples/nft-rule-ct-expectation-add.c

diff --git a/examples/Makefile.am b/examples/Makefile.am
index d044b90..db9164d 100644
--- a/examples/Makefile.am
+++ b/examples/Makefile.am
@@ -29,10 +29,14 @@ check_PROGRAMS = nft-table-add		\
 		 nft-flowtable-get	\
 		 nft-ruleset-get	\
 		 nft-compat-get 	\
+		 nft-ct-expectation-add \
+		 nft-ct-expectation-del \
+		 nft-ct-expectation-get \
 		 nft-ct-helper-add	\
 		 nft-ct-helper-get	\
 		 nft-ct-helper-del	\
 		 nft-rule-ct-helper-add \
+		 nft-rule-ct-expectation-add \
 		 nft-rule-ct-timeout-add
 
 nft_table_add_SOURCES = nft-table-add.c
@@ -122,6 +126,15 @@ nft_ruleset_get_LDADD = ../src/libnftnl.la ${LIBMNL_LIBS}
 nft_compat_get_SOURCES = nft-compat-get.c
 nft_compat_get_LDADD = ../src/libnftnl.la ${LIBMNL_LIBS}
 
+nft_ct_expectation_add_SOURCES = nft-ct-expectation-add.c
+nft_ct_expectation_add_LDADD = ../src/libnftnl.la ${LIBMNL_LIBS}
+
+nft_ct_expectation_del_SOURCES = nft-ct-expectation-del.c
+nft_ct_expectation_del_LDADD = ../src/libnftnl.la ${LIBMNL_LIBS}
+
+nft_ct_expectation_get_SOURCES = nft-ct-expectation-get.c
+nft_ct_expectation_get_LDADD = ../src/libnftnl.la ${LIBMNL_LIBS}
+
 nft_ct_helper_add_SOURCES = nft-ct-helper-add.c
 nft_ct_helper_add_LDADD = ../src/libnftnl.la ${LIBMNL_LIBS}
 
@@ -134,5 +147,8 @@ nft_ct_helper_del_LDADD = ../src/libnftnl.la ${LIBMNL_LIBS}
 nft_rule_ct_helper_add_SOURCES = nft-rule-ct-helper-add.c
 nft_rule_ct_helper_add_LDADD = ../src/libnftnl.la ${LIBMNL_LIBS}
 
+nft_rule_ct_expectation_add_SOURCES = nft-rule-ct-expectation-add.c
+nft_rule_ct_expectation_add_LDADD = ../src/libnftnl.la ${LIBMNL_LIBS}
+
 nft_rule_ct_timeout_add_SOURCES = nft-rule-ct-timeout-add.c
 nft_rule_ct_timeout_add_LDADD = ../src/libnftnl.la ${LIBMNL_LIBS}
diff --git a/examples/nft-ct-expectation-add.c b/examples/nft-ct-expectation-add.c
new file mode 100644
index 0000000..eb46418
--- /dev/null
+++ b/examples/nft-ct-expectation-add.c
@@ -0,0 +1,154 @@
+/*
+ * (C) 2019 by Stéphane Veyret <sveyret@gmail.com>
+ *
+ * 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 <time.h>
+#include <string.h>
+#include <netinet/in.h>
+
+#include <linux/netfilter.h>
+
+#include <obj.h>
+#include <libmnl/libmnl.h>
+
+static uint16_t parse_family(char *str, const char *option)
+{
+	if (strcmp(str, "ip") == 0)
+		return NFPROTO_IPV4;
+	else if (strcmp(str, "ip6") == 0)
+		return NFPROTO_IPV6;
+	else if (strcmp(str, "inet") == 0)
+		return NFPROTO_INET;
+	else if (strcmp(str, "arp") == 0)
+		return NFPROTO_INET;
+	else {
+		fprintf(stderr, "Unknown %s: ip, ip6, inet, arp\n", option);
+		exit(EXIT_FAILURE);
+	}
+}
+
+static uint8_t parse_l4proto(char *str)
+{
+	if (strcmp(str, "udp") == 0)
+		return IPPROTO_UDP;
+	else if (strcmp(str, "tcp") == 0)
+		return IPPROTO_TCP;
+	else {
+		fprintf(stderr, "Unknown l4proto: tcp, udp\n");
+		exit(EXIT_FAILURE);
+	}
+	return IPPROTO_TCP;
+}
+
+static struct nftnl_obj *obj_parse(int argc, char *argv[])
+{
+	struct nftnl_obj *t;
+	uint16_t family, l3proto, dport;
+	uint8_t l4proto;
+	uint32_t timeout;
+
+	t = nftnl_obj_alloc();
+	if (t == NULL) {
+			perror("OOM");
+			return NULL;
+	}
+
+	family = parse_family(argv[1], "family");
+	nftnl_obj_set_u32(t, NFTNL_OBJ_FAMILY, family);
+	nftnl_obj_set_u32(t, NFTNL_OBJ_TYPE, NFT_OBJECT_CT_EXPECT);
+	nftnl_obj_set_str(t, NFTNL_OBJ_TABLE, argv[2]);
+	nftnl_obj_set_str(t, NFTNL_OBJ_NAME, argv[3]);
+
+	if (argc > 6) {
+		l3proto = parse_family(argv[6], "l3proto");
+		nftnl_obj_set_u16(t, NFTNL_OBJ_CT_EXPECT_L3PROTO, l3proto);
+	}
+	l4proto = parse_l4proto(argv[4]);
+	nftnl_obj_set_u8(t, NFTNL_OBJ_CT_EXPECT_L4PROTO, l4proto);
+	dport = strtol(argv[5], NULL, 10);
+	nftnl_obj_set_u16(t, NFTNL_OBJ_CT_EXPECT_DPORT, dport);
+	if (argc > 7) {
+		timeout = strtol(argv[7], NULL, 10);
+		nftnl_obj_set_u32(t, NFTNL_OBJ_CT_EXPECT_TIMEOUT, timeout);
+	}
+
+	return t;
+}
+
+int main(int argc, char *argv[])
+{
+	struct mnl_socket *nl;
+	char buf[MNL_SOCKET_BUFFER_SIZE];
+	struct nlmsghdr *nlh;
+	uint32_t portid, seq, obj_seq, family;
+	struct nftnl_obj *t;
+	struct mnl_nlmsg_batch *batch;
+	int ret;
+
+	if (argc < 6 || argc > 8) {
+		fprintf(stderr, "%s <family> <table> <name> <l4proto> <dport> [l3proto [timeout]]\n", argv[0]);
+		exit(EXIT_FAILURE);
+	}
+
+	t = obj_parse(argc, argv);
+	if (t == NULL) {
+		exit(EXIT_FAILURE);
+	}
+
+	seq = time(NULL);
+	batch = mnl_nlmsg_batch_start(buf, sizeof(buf));
+
+	nftnl_batch_begin(mnl_nlmsg_batch_current(batch), seq++);
+	mnl_nlmsg_batch_next(batch);
+
+	obj_seq = seq;
+	family = nftnl_obj_get_u32(t, NFTNL_OBJ_FAMILY);
+	nlh = nftnl_nlmsg_build_hdr(mnl_nlmsg_batch_current(batch),
+					NFT_MSG_NEWOBJ, family, NLM_F_ACK | NLM_F_CREATE, seq++);
+	nftnl_obj_nlmsg_build_payload(nlh, t);
+	nftnl_obj_free(t);
+	mnl_nlmsg_batch_next(batch);
+
+	nftnl_batch_end(mnl_nlmsg_batch_current(batch), seq++);
+	mnl_nlmsg_batch_next(batch);
+
+	nl = mnl_socket_open(NETLINK_NETFILTER);
+	if (nl == NULL) {
+		perror("mnl_socket_open");
+		exit(EXIT_FAILURE);
+	}
+
+	if (mnl_socket_bind(nl, 0, MNL_SOCKET_AUTOPID) < 0) {
+		perror("mnl_socket_bind");
+		exit(EXIT_FAILURE);
+	}
+	portid = mnl_socket_get_portid(nl);
+
+	if (mnl_socket_sendto(nl, mnl_nlmsg_batch_head(batch),
+				  mnl_nlmsg_batch_size(batch)) < 0) {
+		perror("mnl_socket_send");
+		exit(EXIT_FAILURE);
+	}
+
+	mnl_nlmsg_batch_stop(batch);
+
+	ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
+	while (ret > 0) {
+		ret = mnl_cb_run(buf, ret, obj_seq, portid, NULL, NULL);
+		if (ret <= 0)
+			break;
+		ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
+	}
+	if (ret == -1) {
+		perror("error");
+		exit(EXIT_FAILURE);
+	}
+	mnl_socket_close(nl);
+
+	return EXIT_SUCCESS;
+}
diff --git a/examples/nft-ct-expectation-del.c b/examples/nft-ct-expectation-del.c
new file mode 100644
index 0000000..e38b8bd
--- /dev/null
+++ b/examples/nft-ct-expectation-del.c
@@ -0,0 +1,128 @@
+/*
+ * (C) 2019 by Stéphane Veyret <sveyret@gmail.com>
+ *
+ * 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 <stdlib.h>
+#include <time.h>
+#include <string.h>
+#include <netinet/in.h>
+
+#include <linux/netfilter.h>
+#include <linux/netfilter/nf_tables.h>
+
+#include <libmnl/libmnl.h>
+#include <libnftnl/object.h>
+
+static uint16_t parse_family(char *str, const char *option)
+{
+	if (strcmp(str, "ip") == 0)
+		return NFPROTO_IPV4;
+	else if (strcmp(str, "ip6") == 0)
+		return NFPROTO_IPV6;
+	else if (strcmp(str, "inet") == 0)
+		return NFPROTO_INET;
+	else if (strcmp(str, "arp") == 0)
+		return NFPROTO_INET;
+	else {
+		fprintf(stderr, "Unknown %s: ip, ip6, inet, arp\n", option);
+		exit(EXIT_FAILURE);
+	}
+}
+
+static struct nftnl_obj *obj_parse(int argc, char *argv[])
+{
+	struct nftnl_obj *t;
+	uint16_t family;
+
+	t = nftnl_obj_alloc();
+	if (t == NULL) {
+		perror("OOM");
+		return NULL;
+	}
+
+	family = parse_family(argv[1], "family");
+	nftnl_obj_set_u32(t, NFTNL_OBJ_FAMILY, family);
+	nftnl_obj_set_u32(t, NFTNL_OBJ_TYPE, NFT_OBJECT_CT_EXPECT);
+	nftnl_obj_set_str(t, NFTNL_OBJ_TABLE, argv[2]);
+	nftnl_obj_set_str(t, NFTNL_OBJ_NAME, argv[3]);
+
+	return t;
+}
+
+int main(int argc, char *argv[])
+{
+	struct mnl_socket *nl;
+	char buf[MNL_SOCKET_BUFFER_SIZE];
+	struct nlmsghdr *nlh;
+	uint32_t portid, seq, obj_seq, family;
+	struct nftnl_obj *t;
+	struct mnl_nlmsg_batch *batch;
+	int ret;
+
+	if (argc != 4) {
+		fprintf(stderr, "%s <family> <table> <name>\n", argv[0]);
+		exit(EXIT_FAILURE);
+	}
+
+	t = obj_parse(argc, argv);
+	if (t == NULL)
+		exit(EXIT_FAILURE);
+
+	seq = time(NULL);
+	batch = mnl_nlmsg_batch_start(buf, sizeof(buf));
+
+	nftnl_batch_begin(mnl_nlmsg_batch_current(batch), seq++);
+	mnl_nlmsg_batch_next(batch);
+
+	obj_seq = seq;
+	family = nftnl_obj_get_u32(t, NFTNL_OBJ_FAMILY);
+	nlh = nftnl_nlmsg_build_hdr(mnl_nlmsg_batch_current(batch),
+				    NFT_MSG_DELOBJ, family, NLM_F_ACK,
+				    seq++);
+	nftnl_obj_nlmsg_build_payload(nlh, t);
+	mnl_nlmsg_batch_next(batch);
+	nftnl_obj_free(t);
+
+	nftnl_batch_end(mnl_nlmsg_batch_current(batch), seq++);
+	mnl_nlmsg_batch_next(batch);
+
+	nl = mnl_socket_open(NETLINK_NETFILTER);
+	if (nl == NULL) {
+		perror("mnl_socket_open");
+		exit(EXIT_FAILURE);
+	}
+
+	if (mnl_socket_bind(nl, 0, MNL_SOCKET_AUTOPID) < 0) {
+		perror("mnl_socket_bind");
+		exit(EXIT_FAILURE);
+	}
+	portid = mnl_socket_get_portid(nl);
+
+	if (mnl_socket_sendto(nl, mnl_nlmsg_batch_head(batch),
+			      mnl_nlmsg_batch_size(batch)) < 0) {
+		perror("mnl_socket_send");
+		exit(EXIT_FAILURE);
+	}
+
+	mnl_nlmsg_batch_stop(batch);
+
+	ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
+	while (ret > 0) {
+		ret = mnl_cb_run(buf, ret, obj_seq, portid, NULL, NULL);
+		if (ret <= 0)
+			break;
+		ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
+	}
+	if (ret == -1) {
+		perror("error");
+		exit(EXIT_FAILURE);
+	}
+	mnl_socket_close(nl);
+
+	return EXIT_SUCCESS;
+}
diff --git a/examples/nft-ct-expectation-get.c b/examples/nft-ct-expectation-get.c
new file mode 100644
index 0000000..405ba9a
--- /dev/null
+++ b/examples/nft-ct-expectation-get.c
@@ -0,0 +1,144 @@
+/*
+ * (C) 2019 by Stéphane Veyret <sveyret@gmail.com>
+ *
+ * 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 <stdlib.h>
+#include <time.h>
+#include <string.h>
+#include <netinet/in.h>
+
+#include <linux/netfilter.h>
+#include <linux/netfilter/nf_tables.h>
+
+#include <libmnl/libmnl.h>
+#include <libnftnl/object.h>
+
+static uint16_t parse_family(char *str, const char *option)
+{
+	if (strcmp(str, "ip") == 0)
+		return NFPROTO_IPV4;
+	else if (strcmp(str, "ip6") == 0)
+		return NFPROTO_IPV6;
+	else if (strcmp(str, "inet") == 0)
+		return NFPROTO_INET;
+	else if (strcmp(str, "arp") == 0)
+		return NFPROTO_INET;
+	else {
+		fprintf(stderr, "Unknown %s: ip, ip6, inet, arp\n", option);
+		exit(EXIT_FAILURE);
+	}
+}
+
+static struct nftnl_obj *obj_parse(int argc, char *argv[])
+{
+	struct nftnl_obj *t;
+	uint16_t family;
+
+	t = nftnl_obj_alloc();
+	if (t == NULL) {
+		perror("OOM");
+		return NULL;
+	}
+
+	family = parse_family(argv[1], "family");
+	nftnl_obj_set_u32(t, NFTNL_OBJ_FAMILY, family);
+	nftnl_obj_set_u32(t, NFTNL_OBJ_TYPE, NFT_OBJECT_CT_EXPECT);
+	nftnl_obj_set_str(t, NFTNL_OBJ_TABLE, argv[2]);
+
+	if (argc > 3)
+		nftnl_obj_set_str(t, NFTNL_OBJ_NAME, argv[3]);
+
+	return t;
+}
+
+static int obj_cb(const struct nlmsghdr *nlh, void *data)
+{
+	struct nftnl_obj *t;
+	char buf[4096];
+	uint32_t *type = data;
+
+	t = nftnl_obj_alloc();
+	if (t == NULL) {
+		perror("OOM");
+		goto err;
+	}
+
+	if (nftnl_obj_nlmsg_parse(nlh, t) < 0) {
+		perror("nftnl_obj_nlmsg_parse");
+		goto err_free;
+	}
+
+	nftnl_obj_snprintf(buf, sizeof(buf), t, *type, 0);
+	printf("%s\n", buf);
+
+err_free:
+	nftnl_obj_free(t);
+err:
+	return MNL_CB_OK;
+}
+
+int main(int argc, char *argv[])
+{
+	struct mnl_socket *nl;
+	char buf[MNL_SOCKET_BUFFER_SIZE];
+	struct nlmsghdr *nlh;
+	uint32_t portid, seq, family;
+	struct nftnl_obj *t;
+	int ret;
+	uint32_t type = NFTNL_OUTPUT_DEFAULT;
+	uint16_t flags = NLM_F_ACK;
+
+	if (argc < 3 || argc > 4) {
+		fprintf(stderr, "%s <family> <table> [<name>]\n", argv[0]);
+		return EXIT_FAILURE;
+	}
+
+	t = obj_parse(argc, argv);
+	if (t == NULL)
+		exit(EXIT_FAILURE);
+	family = nftnl_obj_get_u32(t, NFTNL_OBJ_FAMILY);
+
+	seq = time(NULL);
+	if (argc < 4)
+		flags = NLM_F_DUMP;
+	nlh = nftnl_nlmsg_build_hdr(buf, NFT_MSG_GETOBJ, family, flags, seq);
+	nftnl_obj_nlmsg_build_payload(nlh, t);
+	nftnl_obj_free(t);
+
+	nl = mnl_socket_open(NETLINK_NETFILTER);
+	if (nl == NULL) {
+		perror("mnl_socket_open");
+		exit(EXIT_FAILURE);
+	}
+
+	if (mnl_socket_bind(nl, 0, MNL_SOCKET_AUTOPID) < 0) {
+		perror("mnl_socket_bind");
+		exit(EXIT_FAILURE);
+	}
+	portid = mnl_socket_get_portid(nl);
+
+	if (mnl_socket_sendto(nl, nlh, nlh->nlmsg_len) < 0) {
+		perror("mnl_socket_send");
+		exit(EXIT_FAILURE);
+	}
+
+	ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
+	while (ret > 0) {
+		ret = mnl_cb_run(buf, ret, seq, portid, obj_cb, &type);
+		if (ret <= 0)
+			break;
+		ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
+	}
+	if (ret == -1) {
+		perror("error");
+		exit(EXIT_FAILURE);
+	}
+	mnl_socket_close(nl);
+
+	return EXIT_SUCCESS;
+}
diff --git a/examples/nft-rule-ct-expectation-add.c b/examples/nft-rule-ct-expectation-add.c
new file mode 100644
index 0000000..794bb2c
--- /dev/null
+++ b/examples/nft-rule-ct-expectation-add.c
@@ -0,0 +1,163 @@
+/*
+ * (C) 2019 by Stéphane Veyret <sveyret@gmail.com>
+ *
+ * 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 <stdlib.h>
+#include <time.h>
+#include <string.h>
+#include <stddef.h>	/* for offsetof */
+#include <netinet/in.h>
+#include <netinet/ip.h>
+#include <netinet/tcp.h>
+#include <arpa/inet.h>
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <errno.h>
+
+#include <linux/netfilter.h>
+#include <linux/netfilter/nfnetlink.h>
+#include <linux/netfilter/nf_tables.h>
+
+#include <libmnl/libmnl.h>
+#include <libnftnl/rule.h>
+#include <libnftnl/expr.h>
+
+static uint16_t parse_family(char *str, const char *option)
+{
+	if (strcmp(str, "ip") == 0)
+		return NFPROTO_IPV4;
+	else if (strcmp(str, "ip6") == 0)
+		return NFPROTO_IPV6;
+	else if (strcmp(str, "inet") == 0)
+		return NFPROTO_INET;
+	else if (strcmp(str, "arp") == 0)
+		return NFPROTO_INET;
+	else {
+		fprintf(stderr, "Unknown %s: ip, ip6, inet, arp\n", option);
+		exit(EXIT_FAILURE);
+	}
+}
+
+static void add_ct_expect(struct nftnl_rule *r, const char *obj_name)
+{
+	struct nftnl_expr *e;
+
+	e = nftnl_expr_alloc("objref");
+	if (e == NULL) {
+		perror("expr objref oom");
+		exit(EXIT_FAILURE);
+	}
+	nftnl_expr_set_str(e, NFTNL_EXPR_OBJREF_IMM_NAME, obj_name);
+	nftnl_expr_set_u32(e, NFTNL_EXPR_OBJREF_IMM_TYPE, NFT_OBJECT_CT_EXPECT);
+
+	nftnl_rule_add_expr(r, e);
+}
+
+static struct nftnl_rule *setup_rule(uint8_t family, const char *table,
+				   const char *chain, const char *handle, const char *obj_name)
+{
+	struct nftnl_rule *r = NULL;
+	uint64_t handle_num;
+
+	r = nftnl_rule_alloc();
+	if (r == NULL) {
+		perror("OOM");
+		exit(EXIT_FAILURE);
+	}
+
+	nftnl_rule_set(r, NFTNL_RULE_TABLE, table);
+	nftnl_rule_set(r, NFTNL_RULE_CHAIN, chain);
+	nftnl_rule_set_u32(r, NFTNL_RULE_FAMILY, family);
+
+	if (handle != NULL) {
+		handle_num = atoll(handle);
+		nftnl_rule_set_u64(r, NFTNL_RULE_POSITION, handle_num);
+	}
+
+	add_ct_expect(r, obj_name);
+
+	return r;
+}
+
+int main(int argc, char *argv[])
+{
+	struct mnl_socket *nl;
+	struct nftnl_rule *r;
+	struct nlmsghdr *nlh;
+	struct mnl_nlmsg_batch *batch;
+	uint8_t family;
+	char buf[MNL_SOCKET_BUFFER_SIZE];
+	uint32_t seq = time(NULL);
+	int ret;
+
+	if (argc < 5 || argc > 6) {
+		fprintf(stderr,
+			"Usage: %s <family> <table> <chain> [<handle>] <name>\n",
+			argv[0]);
+		exit(EXIT_FAILURE);
+	}
+	family = parse_family(argv[1], "family");
+
+	if (argc != 6)
+		r = setup_rule(family, argv[2], argv[3], NULL, argv[4]);
+	else
+		r = setup_rule(family, argv[2], argv[3], argv[4], argv[5]);
+
+	nl = mnl_socket_open(NETLINK_NETFILTER);
+	if (nl == NULL) {
+		perror("mnl_socket_open");
+		exit(EXIT_FAILURE);
+	}
+
+	if (mnl_socket_bind(nl, 0, MNL_SOCKET_AUTOPID) < 0) {
+		perror("mnl_socket_bind");
+		exit(EXIT_FAILURE);
+	}
+
+	batch = mnl_nlmsg_batch_start(buf, sizeof(buf));
+
+	nftnl_batch_begin(mnl_nlmsg_batch_current(batch), seq++);
+	mnl_nlmsg_batch_next(batch);
+
+	nlh = nftnl_rule_nlmsg_build_hdr(mnl_nlmsg_batch_current(batch),
+		NFT_MSG_NEWRULE,
+		nftnl_rule_get_u32(r, NFTNL_RULE_FAMILY),
+		NLM_F_APPEND|NLM_F_CREATE|NLM_F_ACK, seq++);
+
+	nftnl_rule_nlmsg_build_payload(nlh, r);
+	nftnl_rule_free(r);
+	mnl_nlmsg_batch_next(batch);
+
+	nftnl_batch_end(mnl_nlmsg_batch_current(batch), seq++);
+	mnl_nlmsg_batch_next(batch);
+
+	ret = mnl_socket_sendto(nl, mnl_nlmsg_batch_head(batch),
+				mnl_nlmsg_batch_size(batch));
+	if (ret == -1) {
+		perror("mnl_socket_sendto");
+		exit(EXIT_FAILURE);
+	}
+
+	mnl_nlmsg_batch_stop(batch);
+
+	ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
+	if (ret == -1) {
+		perror("mnl_socket_recvfrom");
+		exit(EXIT_FAILURE);
+	}
+
+	ret = mnl_cb_run(buf, ret, 0, mnl_socket_get_portid(nl), NULL, NULL);
+	if (ret < 0) {
+		perror("mnl_cb_run");
+		exit(EXIT_FAILURE);
+	}
+
+	mnl_socket_close(nl);
+
+	return EXIT_SUCCESS;
+}
-- 
2.21.0