[v4,libnftnl] introduce rt expression

diff --git a/include/libnftnl/expr.h b/include/libnftnl/expr.h
index edf86a9..6245207 100644
--- a/include/libnftnl/expr.h
+++ b/include/libnftnl/expr.h
@@ -64,6 +64,11 @@  enum {
 };
 
 enum {
+	NFTNL_EXPR_RT_KEY	= NFTNL_EXPR_BASE,
+	NFTNL_EXPR_RT_DREG,
+};
+
+enum {
 	NFTNL_EXPR_CMP_SREG	= NFTNL_EXPR_BASE,
 	NFTNL_EXPR_CMP_OP,
 	NFTNL_EXPR_CMP_DATA,
@@ -272,6 +277,11 @@  enum {
 };
 
 enum {
+	NFT_EXPR_RT_KEY		= NFT_RULE_EXPR_ATTR_BASE,
+	NFT_EXPR_RT_DREG,
+};
+
+enum {
 	NFT_EXPR_CMP_SREG	= NFT_RULE_EXPR_ATTR_BASE,
 	NFT_EXPR_CMP_OP,
 	NFT_EXPR_CMP_DATA,
diff --git a/include/linux/netfilter/nf_tables.h b/include/linux/netfilter/nf_tables.h
index 30e3b21..f396293 100644
--- a/include/linux/netfilter/nf_tables.h
+++ b/include/linux/netfilter/nf_tables.h
@@ -753,6 +753,19 @@  enum nft_meta_keys {
 };
 
 /**
+ * enum nft_rt_keys - nf_tables routing expression keys
+ *
+ * @NFT_RT_CLASSID: realm value of packet's route (skb->dst->tclassid)
+ * @NFT_RT_NEXTHOP4: routing nexthop for IPv4
+ * @NFT_RT_NEXTHOP6: routing nexthop for IPv6
+ */
+enum nft_rt_keys {
+	NFT_RT_CLASSID,
+	NFT_RT_NEXTHOP4,
+	NFT_RT_NEXTHOP6,
+};
+
+/**
  * enum nft_hash_attributes - nf_tables hash expression netlink attributes
  *
  * @NFTA_HASH_SREG: source register (NLA_U32)
@@ -791,6 +804,20 @@  enum nft_meta_attributes {
 #define NFTA_META_MAX		(__NFTA_META_MAX - 1)
 
 /**
+ * enum nft_rt_attributes - nf_tables routing expression netlink attributes
+ *
+ * @NFTA_RT_DREG: destination register (NLA_U32)
+ * @NFTA_RT_KEY: routing data item to load (NLA_U32: nft_rt_keys)
+ */
+enum nft_rt_attributes {
+	NFTA_RT_UNSPEC,
+	NFTA_RT_DREG,
+	NFTA_RT_KEY,
+	__NFTA_RT_MAX
+};
+#define NFTA_RT_MAX		(__NFTA_RT_MAX - 1)
+
+/**
  * enum nft_ct_keys - nf_tables ct expression keys
  *
  * @NFT_CT_STATE: conntrack state (bitmask of enum ip_conntrack_info)
diff --git a/src/Makefile.am b/src/Makefile.am
index eac7a56..4b25470 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -44,6 +44,7 @@  libnftnl_la_SOURCES = utils.c		\
 		      expr/queue.c	\
 		      expr/quota.c	\
 		      expr/reject.c	\
+		      expr/rt.c		\
 		      expr/target.c	\
 		      expr/masq.c	\
 		      expr/redir.c	\
diff --git a/src/expr/rt.c b/src/expr/rt.c
new file mode 100644
index 0000000..5088e66
--- /dev/null
+++ b/src/expr/rt.c
@@ -0,0 +1,243 @@ 
+/*
+ * Copyright (c) 2016 Anders K. Pedersen <akp@cohaesio.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 <stdio.h>
+#include <stdint.h>
+#include <string.h>
+#include <arpa/inet.h>
+#include <errno.h>
+#include <linux/netfilter/nf_tables.h>
+
+#include "internal.h"
+#include <libmnl/libmnl.h>
+#include <libnftnl/expr.h>
+#include <libnftnl/rule.h>
+
+#ifndef NFT_RT_MAX
+#define NFT_RT_MAX (NFT_RT_NEXTHOP6 + 1)
+#endif
+
+struct nftnl_expr_rt {
+	enum nft_rt_keys	key;
+	enum nft_registers	dreg;
+};
+
+static int
+nftnl_expr_rt_set(struct nftnl_expr *e, uint16_t type,
+		       const void *data, uint32_t data_len)
+{
+	struct nftnl_expr_rt *rt = nftnl_expr_data(e);
+
+	switch (type) {
+	case NFTNL_EXPR_RT_KEY:
+		rt->key = *((uint32_t *)data);
+		break;
+	case NFTNL_EXPR_RT_DREG:
+		rt->dreg = *((uint32_t *)data);
+		break;
+	default:
+		return -1;
+	}
+	return 0;
+}
+
+static const void *
+nftnl_expr_rt_get(const struct nftnl_expr *e, uint16_t type,
+		       uint32_t *data_len)
+{
+	struct nftnl_expr_rt *rt = nftnl_expr_data(e);
+
+	switch (type) {
+	case NFTNL_EXPR_RT_KEY:
+		*data_len = sizeof(rt->key);
+		return &rt->key;
+	case NFTNL_EXPR_RT_DREG:
+		*data_len = sizeof(rt->dreg);
+		return &rt->dreg;
+	}
+	return NULL;
+}
+
+static int nftnl_expr_rt_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_RT_MAX) < 0)
+		return MNL_CB_OK;
+
+	switch (type) {
+	case NFTA_RT_KEY:
+	case NFTA_RT_DREG:
+		if (mnl_attr_validate(attr, MNL_TYPE_U32) < 0)
+			abi_breakage();
+		break;
+	}
+
+	tb[type] = attr;
+	return MNL_CB_OK;
+}
+
+static void
+nftnl_expr_rt_build(struct nlmsghdr *nlh, const struct nftnl_expr *e)
+{
+	struct nftnl_expr_rt *rt = nftnl_expr_data(e);
+
+	if (e->flags & (1 << NFTNL_EXPR_RT_KEY))
+		mnl_attr_put_u32(nlh, NFTA_RT_KEY, htonl(rt->key));
+	if (e->flags & (1 << NFTNL_EXPR_RT_DREG))
+		mnl_attr_put_u32(nlh, NFTA_RT_DREG, htonl(rt->dreg));
+}
+
+static int
+nftnl_expr_rt_parse(struct nftnl_expr *e, struct nlattr *attr)
+{
+	struct nftnl_expr_rt *rt = nftnl_expr_data(e);
+	struct nlattr *tb[NFTA_RT_MAX+1] = {};
+
+	if (mnl_attr_parse_nested(attr, nftnl_expr_rt_cb, tb) < 0)
+		return -1;
+
+	if (tb[NFTA_RT_KEY]) {
+		rt->key = ntohl(mnl_attr_get_u32(tb[NFTA_RT_KEY]));
+		e->flags |= (1 << NFTNL_EXPR_RT_KEY);
+	}
+	if (tb[NFTA_RT_DREG]) {
+		rt->dreg = ntohl(mnl_attr_get_u32(tb[NFTA_RT_DREG]));
+		e->flags |= (1 << NFTNL_EXPR_RT_DREG);
+	}
+
+	return 0;
+}
+
+static const char *rt_key2str_array[NFT_RT_MAX] = {
+	[NFT_RT_CLASSID]	= "classid",
+	[NFT_RT_NEXTHOP4]	= "nexthop4",
+	[NFT_RT_NEXTHOP6]	= "nexthop6",
+};
+
+static const char *rt_key2str(uint8_t key)
+{
+	if (key < NFT_RT_MAX)
+		return rt_key2str_array[key];
+
+	return "unknown";
+}
+
+static inline int str2rt_key(const char *str)
+{
+	int i;
+
+	for (i = 0; i < NFT_RT_MAX; i++) {
+		if (strcmp(str, rt_key2str_array[i]) == 0)
+			return i;
+	}
+
+	errno = EINVAL;
+	return -1;
+}
+
+static int nftnl_expr_rt_json_parse(struct nftnl_expr *e, json_t *root,
+				    struct nftnl_parse_err *err)
+{
+#ifdef JSON_PARSING
+	const char *val_str;
+	uint32_t reg;
+	int val32;
+
+	val_str = nftnl_jansson_parse_str(root, "key", err);
+	if (val_str != NULL) {
+		val32 = str2rt_key(val_str);
+		if (val32 >= 0)
+			nftnl_expr_set_u32(e, NFTNL_EXPR_RT_KEY, val32);
+	}
+
+	if (nftnl_jansson_node_exist(root, "dreg")) {
+		if (nftnl_jansson_parse_reg(root, "dreg", NFTNL_TYPE_U32, &reg,
+					  err) == 0)
+			nftnl_expr_set_u32(e, NFTNL_EXPR_RT_DREG, reg);
+	}
+
+	return 0;
+#else
+	errno = EOPNOTSUPP;
+	return -1;
+#endif
+}
+
+static int
+nftnl_expr_rt_snprintf_default(char *buf, size_t len,
+			       const struct nftnl_expr *e)
+{
+	struct nftnl_expr_rt *rt = nftnl_expr_data(e);
+
+	if (e->flags & (1 << NFTNL_EXPR_RT_DREG)) {
+		return snprintf(buf, len, "load %s => reg %u ",
+				rt_key2str(rt->key), rt->dreg);
+	}
+	return 0;
+}
+
+static int nftnl_expr_rt_export(char *buf, size_t size,
+				  const struct nftnl_expr *e, int type)
+{
+	struct nftnl_expr_rt *rt = nftnl_expr_data(e);
+	NFTNL_BUF_INIT(b, buf, size);
+
+	if (e->flags & (1 << NFTNL_EXPR_RT_DREG))
+		nftnl_buf_u32(&b, type, rt->dreg, DREG);
+	if (e->flags & (1 << NFTNL_EXPR_RT_KEY))
+		nftnl_buf_str(&b, type, rt_key2str(rt->key), KEY);
+
+	return nftnl_buf_done(&b);
+}
+
+static int
+nftnl_expr_rt_snprintf(char *buf, size_t len, uint32_t type,
+		       uint32_t flags, const struct nftnl_expr *e)
+{
+	switch (type) {
+	case NFTNL_OUTPUT_DEFAULT:
+		return nftnl_expr_rt_snprintf_default(buf, len, e);
+	case NFTNL_OUTPUT_XML:
+	case NFTNL_OUTPUT_JSON:
+		return nftnl_expr_rt_export(buf, len, e, type);
+	default:
+		break;
+	}
+	return -1;
+}
+
+static bool nftnl_expr_rt_cmp(const struct nftnl_expr *e1,
+			      const struct nftnl_expr *e2)
+{
+	struct nftnl_expr_rt *r1 = nftnl_expr_data(e1);
+	struct nftnl_expr_rt *r2 = nftnl_expr_data(e2);
+	bool eq = true;
+
+	if (e1->flags & (1 << NFTNL_EXPR_RT_KEY))
+		eq &= (r1->key == r2->key);
+	if (e1->flags & (1 << NFTNL_EXPR_RT_DREG))
+		eq &= (r1->dreg == r2->dreg);
+
+	return eq;
+}
+
+struct expr_ops expr_ops_rt = {
+	.name		= "rt",
+	.alloc_len	= sizeof(struct nftnl_expr_rt),
+	.max_attr	= NFTA_RT_MAX,
+	.cmp		= nftnl_expr_rt_cmp,
+	.set		= nftnl_expr_rt_set,
+	.get		= nftnl_expr_rt_get,
+	.parse		= nftnl_expr_rt_parse,
+	.build		= nftnl_expr_rt_build,
+	.snprintf	= nftnl_expr_rt_snprintf,
+	.json_parse	= nftnl_expr_rt_json_parse,
+};
diff --git a/src/expr_ops.c b/src/expr_ops.c
index 96b1f8d..a2de9cd 100644
--- a/src/expr_ops.c
+++ b/src/expr_ops.c
@@ -25,6 +25,7 @@  extern struct expr_ops expr_ops_payload;
 extern struct expr_ops expr_ops_range;
 extern struct expr_ops expr_ops_redir;
 extern struct expr_ops expr_ops_reject;
+extern struct expr_ops expr_ops_rt;
 extern struct expr_ops expr_ops_queue;
 extern struct expr_ops expr_ops_quota;
 extern struct expr_ops expr_ops_target;
@@ -58,6 +59,7 @@  static struct expr_ops *expr_ops[] = {
 	&expr_ops_range,
 	&expr_ops_redir,
 	&expr_ops_reject,
+	&expr_ops_rt,
 	&expr_ops_queue,
 	&expr_ops_quota,
 	&expr_ops_target,