/*
 * Code for encoding/decoding FPM messages that are in netlink format.
 *
 * Copyright (C) 1997, 98, 99 Kunihiro Ishiguro
 * Copyright (C) 2012 by Open Source Routing.
 * Copyright (C) 2012 by Internet Systems Consortium, Inc. ("ISC")
 *
 * This file is part of GNU Zebra.
 *
 * GNU Zebra 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, or (at your option) any
 * later version.
 *
 * GNU Zebra is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; see the file COPYING; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
 */

#include <zebra.h>

#ifdef HAVE_NETLINK

#include "log.h"
#include "rib.h"
#include "vty.h"
#include "prefix.h"

#include "zebra/zserv.h"
#include "zebra/zebra_dplane.h"
#include "zebra/zebra_ns.h"
#include "zebra/zebra_vrf.h"
#include "zebra/kernel_netlink.h"
#include "zebra/rt_netlink.h"
#include "nexthop.h"

#include "zebra/zebra_fpm_private.h"

/*
 * addr_to_a
 *
 * Returns string representation of an address of the given AF.
 */
static inline const char *addr_to_a(uint8_t af, void *addr)
{
	if (!addr)
		return "<No address>";

	switch (af) {

	case AF_INET:
		return inet_ntoa(*((struct in_addr *)addr));
		break;
	case AF_INET6:
		return inet6_ntoa(*((struct in6_addr *)addr));
		break;
	default:
		return "<Addr in unknown AF>";
		break;
	}
}

/*
 * prefix_addr_to_a
 *
 * Convience wrapper that returns a human-readable string for the
 * address in a prefix.
 */
static const char *prefix_addr_to_a(struct prefix *prefix)
{
	if (!prefix)
		return "<No address>";

	return addr_to_a(prefix->family, &prefix->u.prefix);
}

/*
 * af_addr_size
 *
 * The size of an address in a given address family.
 */
static size_t af_addr_size(uint8_t af)
{
	switch (af) {

	case AF_INET:
		return 4;
		break;
	case AF_INET6:
		return 16;
		break;
	default:
		assert(0);
		return 16;
	}
}

/*
 * netlink_nh_info_t
 *
 * Holds information about a single nexthop for netlink. These info
 * structures are transient and may contain pointers into rib
 * data structures for convenience.
 */
typedef struct netlink_nh_info_t_ {
	uint32_t if_index;
	union g_addr *gateway;

	/*
	 * Information from the struct nexthop from which this nh was
	 * derived. For debug purposes only.
	 */
	int recursive;
	enum nexthop_types_t type;
} netlink_nh_info_t;

/*
 * netlink_route_info_t
 *
 * A structure for holding information for a netlink route message.
 */
typedef struct netlink_route_info_t_ {
	uint16_t nlmsg_type;
	uint8_t rtm_type;
	uint32_t rtm_table;
	uint8_t rtm_protocol;
	uint8_t af;
	struct prefix *prefix;
	uint32_t *metric;
	unsigned int num_nhs;

	/*
	 * Nexthop structures
	 */
	netlink_nh_info_t nhs[MULTIPATH_NUM];
	union g_addr *pref_src;
} netlink_route_info_t;

/*
 * netlink_route_info_add_nh
 *
 * Add information about the given nexthop to the given route info
 * structure.
 *
 * Returns TRUE if a nexthop was added, FALSE otherwise.
 */
static int netlink_route_info_add_nh(netlink_route_info_t *ri,
				     struct nexthop *nexthop)
{
	netlink_nh_info_t nhi;
	union g_addr *src;

	memset(&nhi, 0, sizeof(nhi));
	src = NULL;

	if (ri->num_nhs >= (int)ZEBRA_NUM_OF(ri->nhs))
		return 0;

	nhi.recursive = nexthop->rparent ? 1 : 0;
	nhi.type = nexthop->type;
	nhi.if_index = nexthop->ifindex;

	if (nexthop->type == NEXTHOP_TYPE_IPV4
	    || nexthop->type == NEXTHOP_TYPE_IPV4_IFINDEX) {
		nhi.gateway = &nexthop->gate;
		if (nexthop->src.ipv4.s_addr)
			src = &nexthop->src;
	}

	if (nexthop->type == NEXTHOP_TYPE_IPV6
	    || nexthop->type == NEXTHOP_TYPE_IPV6_IFINDEX) {
		nhi.gateway = &nexthop->gate;
	}

	if (nexthop->type == NEXTHOP_TYPE_IFINDEX) {
		if (nexthop->src.ipv4.s_addr)
			src = &nexthop->src;
	}

	if (!nhi.gateway && nhi.if_index == 0)
		return 0;

	/*
	 * We have a valid nhi. Copy the structure over to the route_info.
	 */
	ri->nhs[ri->num_nhs] = nhi;
	ri->num_nhs++;

	if (src && !ri->pref_src)
		ri->pref_src = src;

	return 1;
}

/*
 * netlink_proto_from_route_type
 */
static uint8_t netlink_proto_from_route_type(int type)
{
	switch (type) {
	case ZEBRA_ROUTE_KERNEL:
	case ZEBRA_ROUTE_CONNECT:
		return RTPROT_KERNEL;

	default:
		return RTPROT_ZEBRA;
	}
}

/*
 * netlink_route_info_fill
 *
 * Fill out the route information object from the given route.
 *
 * Returns TRUE on success and FALSE on failure.
 */
static int netlink_route_info_fill(netlink_route_info_t *ri, int cmd,
				   rib_dest_t *dest, struct route_entry *re)
{
	struct nexthop *nexthop;

	memset(ri, 0, sizeof(*ri));

	ri->prefix = rib_dest_prefix(dest);
	ri->af = rib_dest_af(dest);

	ri->nlmsg_type = cmd;
	ri->rtm_table = zvrf_id(rib_dest_vrf(dest));
	ri->rtm_protocol = RTPROT_UNSPEC;

	/*
	 * An RTM_DELROUTE need not be accompanied by any nexthops,
	 * particularly in our communication with the FPM.
	 */
	if (cmd == RTM_DELROUTE && !re)
		return 1;

	if (!re) {
		zfpm_debug("%s: Expected non-NULL re pointer",
			   __PRETTY_FUNCTION__);
		return 0;
	}

	ri->rtm_protocol = netlink_proto_from_route_type(re->type);
	ri->rtm_type = RTN_UNICAST;
	ri->metric = &re->metric;

	for (ALL_NEXTHOPS(re->ng, nexthop)) {
		if (ri->num_nhs >= multipath_num)
			break;

		if (CHECK_FLAG(nexthop->flags, NEXTHOP_FLAG_RECURSIVE))
			continue;

		if (nexthop->type == NEXTHOP_TYPE_BLACKHOLE) {
			switch (nexthop->bh_type) {
			case BLACKHOLE_ADMINPROHIB:
				ri->rtm_type = RTN_PROHIBIT;
				break;
			case BLACKHOLE_REJECT:
				ri->rtm_type = RTN_UNREACHABLE;
				break;
			case BLACKHOLE_NULL:
			default:
				ri->rtm_type = RTN_BLACKHOLE;
				break;
			}
			return 1;
		}

		if ((cmd == RTM_NEWROUTE
		     && CHECK_FLAG(nexthop->flags, NEXTHOP_FLAG_ACTIVE))
		    || (cmd == RTM_DELROUTE
			&& CHECK_FLAG(nexthop->flags, NEXTHOP_FLAG_FIB))) {
			netlink_route_info_add_nh(ri, nexthop);
		}
	}

	/* If there is no useful nexthop then return. */
	if (ri->num_nhs == 0) {
		zfpm_debug("netlink_encode_route(): No useful nexthop.");
		return 0;
	}

	return 1;
}

/*
 * netlink_route_info_encode
 *
 * Returns the number of bytes written to the buffer. 0 or a negative
 * value indicates an error.
 */
static int netlink_route_info_encode(netlink_route_info_t *ri, char *in_buf,
				     size_t in_buf_len)
{
	size_t bytelen;
	unsigned int nexthop_num = 0;
	size_t buf_offset;
	netlink_nh_info_t *nhi;

	struct {
		struct nlmsghdr n;
		struct rtmsg r;
		char buf[1];
	} * req;

	req = (void *)in_buf;

	buf_offset = ((char *)req->buf) - ((char *)req);

	if (in_buf_len < buf_offset) {
		assert(0);
		return 0;
	}

	memset(req, 0, buf_offset);

	bytelen = af_addr_size(ri->af);

	req->n.nlmsg_len = NLMSG_LENGTH(sizeof(struct rtmsg));
	req->n.nlmsg_flags = NLM_F_CREATE | NLM_F_REQUEST;
	req->n.nlmsg_type = ri->nlmsg_type;
	req->r.rtm_family = ri->af;
	req->r.rtm_table = ri->rtm_table;
	req->r.rtm_dst_len = ri->prefix->prefixlen;
	req->r.rtm_protocol = ri->rtm_protocol;
	req->r.rtm_scope = RT_SCOPE_UNIVERSE;

	addattr_l(&req->n, in_buf_len, RTA_DST, &ri->prefix->u.prefix, bytelen);

	req->r.rtm_type = ri->rtm_type;

	/* Metric. */
	if (ri->metric)
		addattr32(&req->n, in_buf_len, RTA_PRIORITY, *ri->metric);

	if (ri->num_nhs == 0)
		goto done;

	if (ri->num_nhs == 1) {
		nhi = &ri->nhs[0];

		if (nhi->gateway) {
			addattr_l(&req->n, in_buf_len, RTA_GATEWAY,
				  nhi->gateway, bytelen);
		}

		if (nhi->if_index) {
			addattr32(&req->n, in_buf_len, RTA_OIF, nhi->if_index);
		}

		goto done;
	}

	/*
	 * Multipath case.
	 */
	char buf[NL_PKT_BUF_SIZE];
	struct rtattr *rta = (void *)buf;
	struct rtnexthop *rtnh;

	rta->rta_type = RTA_MULTIPATH;
	rta->rta_len = RTA_LENGTH(0);
	rtnh = RTA_DATA(rta);

	for (nexthop_num = 0; nexthop_num < ri->num_nhs; nexthop_num++) {
		nhi = &ri->nhs[nexthop_num];

		rtnh->rtnh_len = sizeof(*rtnh);
		rtnh->rtnh_flags = 0;
		rtnh->rtnh_hops = 0;
		rtnh->rtnh_ifindex = 0;
		rta->rta_len += rtnh->rtnh_len;

		if (nhi->gateway) {
			rta_addattr_l(rta, sizeof(buf), RTA_GATEWAY,
				      nhi->gateway, bytelen);
			rtnh->rtnh_len += sizeof(struct rtattr) + bytelen;
		}

		if (nhi->if_index) {
			rtnh->rtnh_ifindex = nhi->if_index;
		}

		rtnh = RTNH_NEXT(rtnh);
	}

	assert(rta->rta_len > RTA_LENGTH(0));
	addattr_l(&req->n, in_buf_len, RTA_MULTIPATH, RTA_DATA(rta),
		  RTA_PAYLOAD(rta));

done:

	if (ri->pref_src) {
		addattr_l(&req->n, in_buf_len, RTA_PREFSRC, &ri->pref_src,
			  bytelen);
	}

	assert(req->n.nlmsg_len < in_buf_len);
	return req->n.nlmsg_len;
}

/*
 * zfpm_log_route_info
 *
 * Helper function to log the information in a route_info structure.
 */
static void zfpm_log_route_info(netlink_route_info_t *ri, const char *label)
{
	netlink_nh_info_t *nhi;
	unsigned int i;

	zfpm_debug("%s : %s %s/%d, Proto: %s, Metric: %u", label,
		   nl_msg_type_to_str(ri->nlmsg_type),
		   prefix_addr_to_a(ri->prefix), ri->prefix->prefixlen,
		   nl_rtproto_to_str(ri->rtm_protocol),
		   ri->metric ? *ri->metric : 0);

	for (i = 0; i < ri->num_nhs; i++) {
		nhi = &ri->nhs[i];
		zfpm_debug("  Intf: %u, Gateway: %s, Recursive: %s, Type: %s",
			   nhi->if_index, addr_to_a(ri->af, nhi->gateway),
			   nhi->recursive ? "yes" : "no",
			   nexthop_type_to_str(nhi->type));
	}
}

/*
 * zfpm_netlink_encode_route
 *
 * Create a netlink message corresponding to the given route in the
 * given buffer space.
 *
 * Returns the number of bytes written to the buffer. 0 or a negative
 * value indicates an error.
 */
int zfpm_netlink_encode_route(int cmd, rib_dest_t *dest, struct route_entry *re,
			      char *in_buf, size_t in_buf_len)
{
	netlink_route_info_t ri_space, *ri;

	ri = &ri_space;

	if (!netlink_route_info_fill(ri, cmd, dest, re))
		return 0;

	zfpm_log_route_info(ri, __FUNCTION__);

	return netlink_route_info_encode(ri, in_buf, in_buf_len);
}

#endif /* HAVE_NETLINK */