/** @file
 * @brief ICMPv6 related functions
 */

/*
 * Copyright (c) 2016 Intel Corporation
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#include <logging/log.h>
LOG_MODULE_REGISTER(net_icmpv6, CONFIG_NET_ICMPV6_LOG_LEVEL);

#include <errno.h>
#include <misc/slist.h>
#include <misc/byteorder.h>
#include <net/net_core.h>
#include <net/net_pkt.h>
#include <net/net_if.h>
#include "net_private.h"
#include "icmpv6.h"
#include "ipv6.h"
#include "net_stats.h"

#define PKT_WAIT_TIME K_SECONDS(1)

static sys_slist_t handlers;

const char *net_icmpv6_type2str(int icmpv6_type)
{
	switch (icmpv6_type) {
	case NET_ICMPV6_DST_UNREACH:
		return "Destination Unreachable";
	case NET_ICMPV6_PACKET_TOO_BIG:
		return "Packet Too Big";
	case NET_ICMPV6_TIME_EXCEEDED:
		return "Time Exceeded";
	case NET_ICMPV6_PARAM_PROBLEM:
		return "IPv6 Bad Header";
	case NET_ICMPV6_ECHO_REQUEST:
		return "Echo Request";
	case NET_ICMPV6_ECHO_REPLY:
		return "Echo Reply";
	case NET_ICMPV6_MLD_QUERY:
		return "Multicast Listener Query";
	case NET_ICMPV6_RS:
		return "Router Solicitation";
	case NET_ICMPV6_RA:
		return "Router Advertisement";
	case NET_ICMPV6_NS:
		return "Neighbor Solicitation";
	case NET_ICMPV6_NA:
		return "Neighbor Advertisement";
	case NET_ICMPV6_MLDv2:
		return "Multicast Listener Report v2";
	}

	return "?";
}

void net_icmpv6_register_handler(struct net_icmpv6_handler *handler)
{
	sys_slist_prepend(&handlers, &handler->node);
}

void net_icmpv6_unregister_handler(struct net_icmpv6_handler *handler)
{
	sys_slist_find_and_remove(&handlers, &handler->node);
}

int net_icmpv6_set_chksum(struct net_pkt *pkt)
{
	u16_t chksum = 0U;
	struct net_buf *frag;
	struct net_buf *temp_frag;
	u16_t temp_pos;
	u16_t pos;

	/* Skip to the position of checksum */
	frag = net_frag_skip(pkt->frags, 0, &pos,
			     net_pkt_ip_hdr_len(pkt) +
			     net_pkt_ipv6_ext_len(pkt) +
			     1 + 1 /* type + code */);
	if (pos > 0 && !frag) {
		return -EINVAL;
	}

	/* Cache checksum fragment and postion, to be safe side first
	 * write 0's in checksum position and calculate checksum and
	 * write checksum in the packet.
	 */
	temp_frag = frag;
	temp_pos = pos;

	frag = net_pkt_write(pkt, frag, pos, &pos, sizeof(chksum),
			     (u8_t *)&chksum, PKT_WAIT_TIME);
	if (pos > 0 && !frag) {
		return -EINVAL;
	}

	chksum = net_calc_chksum_icmpv6(pkt);

	temp_frag = net_pkt_write(pkt, temp_frag, temp_pos, &temp_pos,
				  sizeof(chksum), (u8_t *)&chksum,
				  PKT_WAIT_TIME);
	if (temp_pos > 0 && !temp_frag) {
		return -EINVAL;
	}

	return 0;
}

int net_icmpv6_finalize(struct net_pkt *pkt)
{
	NET_PKT_DATA_ACCESS_CONTIGUOUS_DEFINE(icmp_access,
					      struct net_icmp_hdr);
	struct net_icmp_hdr *icmp_hdr;

	icmp_hdr = (struct net_icmp_hdr *)net_pkt_get_data_new(pkt,
							       &icmp_access);
	if (!icmp_hdr) {
		return -ENOBUFS;
	}

	icmp_hdr->chksum = net_calc_chksum_icmpv6(pkt);

	return net_pkt_set_data(pkt, &icmp_access);
}

int net_icmpv6_create(struct net_pkt *pkt, u8_t icmp_type, u8_t icmp_code)
{
	NET_PKT_DATA_ACCESS_CONTIGUOUS_DEFINE(icmp_access,
					      struct net_icmp_hdr);
	struct net_icmp_hdr *icmp_hdr;

	icmp_hdr = (struct net_icmp_hdr *)net_pkt_get_data_new(pkt,
							       &icmp_access);
	if (!icmp_hdr) {
		return -ENOBUFS;
	}

	icmp_hdr->type   = icmp_type;
	icmp_hdr->code   = icmp_code;
	icmp_hdr->chksum = 0;

	return net_pkt_set_data(pkt, &icmp_access);
}

static
enum net_verdict icmpv6_handle_echo_request(struct net_pkt *pkt,
					    struct net_ipv6_hdr *ip_hdr,
					    struct net_icmp_hdr *icmp_hdr)
{
	struct net_pkt *reply = NULL;
	const struct in6_addr *src;
	s16_t payload_len;

	ARG_UNUSED(icmp_hdr);

	NET_DBG("Received Echo Request from %s to %s",
		log_strdup(net_sprint_ipv6_addr(&ip_hdr->src)),
		log_strdup(net_sprint_ipv6_addr(&ip_hdr->dst)));

	payload_len = ntohs(ip_hdr->len) -
		net_pkt_ipv6_ext_len(pkt) - NET_ICMPH_LEN;
	if (payload_len < NET_ICMPV6_UNUSED_LEN) {
		/* No identifier or sequence number present */
		goto drop;
	}

	reply = net_pkt_alloc_with_buffer(net_pkt_iface(pkt), payload_len,
					  AF_INET6, IPPROTO_ICMPV6,
					  PKT_WAIT_TIME);
	if (!reply) {
		NET_DBG("DROP: No buffer");
		goto drop;
	}

	if (net_ipv6_is_addr_mcast(&ip_hdr->dst)) {
		src = net_if_ipv6_select_src_addr(net_pkt_iface(pkt),
						  &ip_hdr->dst);
	} else {
		src = &ip_hdr->dst;
	}

	/* We must not set the destination ll address here but trust
	 * that it is set properly using a value from neighbor cache.
	 * Same for source as it points to original pkt ll src address.
	 */
	net_pkt_lladdr_dst(reply)->addr = NULL;
	net_pkt_lladdr_src(reply)->addr = NULL;

	if (net_ipv6_create_new(reply, src, &ip_hdr->src)) {
		NET_DBG("DROP: wrong buffer");
		goto drop;
	}

	if (net_icmpv6_create(reply, NET_ICMPV6_ECHO_REPLY, 0) ||
	    net_pkt_copy_new(reply, pkt, payload_len)) {
		NET_DBG("DROP: wrong buffer");
		goto drop;
	}

	net_pkt_cursor_init(reply);
	net_ipv6_finalize_new(reply, IPPROTO_ICMPV6);

	NET_DBG("Sending Echo Reply from %s to %s",
		log_strdup(net_sprint_ipv6_addr(src)),
		log_strdup(net_sprint_ipv6_addr(&ip_hdr->src)));

	if (net_send_data(reply) < 0) {
		goto drop;
	}

	net_stats_update_icmp_sent(net_pkt_iface(reply));

	net_pkt_unref(pkt);

	return NET_OK;

drop:
	if (reply) {
		net_pkt_unref(reply);
	}

	net_stats_update_icmp_drop(net_pkt_iface(pkt));

	return NET_DROP;
}

int net_icmpv6_send_error(struct net_pkt *orig, u8_t type, u8_t code,
			  u32_t param)
{
	NET_PKT_DATA_ACCESS_CONTIGUOUS_DEFINE(ipv6_access, struct net_ipv6_hdr);
	int err = -EIO;
	struct net_ipv6_hdr *ip_hdr;
	const struct in6_addr *src;
	struct net_pkt *pkt;
	size_t copy_len;

	net_pkt_cursor_init(orig);

	ip_hdr = (struct net_ipv6_hdr *)net_pkt_get_data_new(orig,
							     &ipv6_access);
	if (!ip_hdr) {
		goto drop_no_pkt;
	}

	if (ip_hdr->nexthdr == IPPROTO_ICMPV6) {
		NET_PKT_DATA_ACCESS_CONTIGUOUS_DEFINE(icmpv6_access,
						      struct net_icmp_hdr);
		struct net_icmp_hdr *icmp_hdr;

		net_pkt_acknowledge_data(orig, &ipv6_access);

		icmp_hdr = (struct net_icmp_hdr *)net_pkt_get_data_new(
							orig, &icmpv6_access);
		if (!icmp_hdr || icmp_hdr->code < 128) {
			/* We must not send ICMP errors back */
			err = -EINVAL;
			goto drop_no_pkt;
		}

		net_pkt_cursor_init(orig);
	}

	if (ip_hdr->nexthdr == IPPROTO_UDP) {
		copy_len = sizeof(struct net_ipv6_hdr) +
			sizeof(struct net_udp_hdr);
	} else if (ip_hdr->nexthdr == IPPROTO_TCP) {
		copy_len = sizeof(struct net_ipv6_hdr) +
			sizeof(struct net_tcp_hdr);
	} else {
		copy_len = net_pkt_get_len(orig);
	}

	pkt = net_pkt_alloc_with_buffer(net_pkt_iface(orig),
					copy_len + NET_ICMPV6_UNUSED_LEN,
					AF_INET6, IPPROTO_ICMPV6,
					PKT_WAIT_TIME);
	if (!pkt) {
		err = -ENOMEM;
		goto drop_no_pkt;
	}

	if (net_ipv6_is_addr_mcast(&ip_hdr->dst)) {
		src = net_if_ipv6_select_src_addr(net_pkt_iface(pkt),
						  &ip_hdr->dst);
	} else {
		src = &ip_hdr->dst;
	}

	if (net_ipv6_create_new(pkt, src, &ip_hdr->src) ||
	    net_icmpv6_create(pkt, type, code)) {
		goto drop;
	}

	/* Depending on error option, we store the param into the ICMP message.
	 */
	if (type == NET_ICMPV6_PARAM_PROBLEM) {
		err = net_pkt_write_be32_new(pkt, param);
	} else {
		err = net_pkt_memset(pkt, 0, NET_ICMPV6_UNUSED_LEN);
	}

	/* Allocator might not have been able to allocate all requested space,
	 * so let's copy as much as we can.
	 */
	copy_len = net_pkt_available_buffer(pkt);

	if (err || net_pkt_copy_new(pkt, orig, copy_len)) {
		goto drop;
	}

	net_pkt_lladdr_src(pkt)->addr = net_pkt_lladdr_dst(orig)->addr;
	net_pkt_lladdr_src(pkt)->len = net_pkt_lladdr_dst(orig)->len;
	net_pkt_lladdr_dst(pkt)->addr = net_pkt_lladdr_src(orig)->addr;
	net_pkt_lladdr_dst(pkt)->len = net_pkt_lladdr_src(orig)->len;

	net_pkt_cursor_init(pkt);
	net_ipv6_finalize_new(pkt, IPPROTO_ICMPV6);

	NET_DBG("Sending ICMPv6 Error Message type %d code %d param %d"
		" from %s to %s", type, code, param,
		log_strdup(net_sprint_ipv6_addr(src)),
		log_strdup(net_sprint_ipv6_addr(&ip_hdr->src)));

	if (net_send_data(pkt) >= 0) {
		net_stats_update_icmp_sent(net_pkt_iface(pkt));
		return 0;
	}

drop:
	net_pkt_unref(pkt);

drop_no_pkt:
	net_stats_update_icmp_drop(net_pkt_iface(orig));

	return err;
}

int net_icmpv6_send_echo_request(struct net_if *iface,
				 struct in6_addr *dst,
				 u16_t identifier,
				 u16_t sequence)
{
	NET_PKT_DATA_ACCESS_CONTIGUOUS_DEFINE(icmpv6_access,
					      struct net_icmpv6_echo_req);
	int ret = -ENOBUFS;
	struct net_icmpv6_echo_req *echo_req;
	const struct in6_addr *src;
	struct net_pkt *pkt;

	src = net_if_ipv6_select_src_addr(iface, dst);

	pkt = net_pkt_alloc_with_buffer(iface,
					sizeof(struct net_icmpv6_echo_req),
					AF_INET6, IPPROTO_ICMPV6,
					PKT_WAIT_TIME);
	if (!pkt) {
		return -ENOMEM;
	}

	if (net_ipv6_create_new(pkt, src, dst) ||
	    net_icmpv6_create(pkt, NET_ICMPV6_ECHO_REQUEST, 0)) {
		goto drop;
	}

	echo_req = (struct net_icmpv6_echo_req *)net_pkt_get_data_new(
							pkt, &icmpv6_access);
	if (!echo_req) {
		goto drop;
	}

	echo_req->identifier = htons(identifier);
	echo_req->sequence   = htons(sequence);

	net_pkt_set_data(pkt, &icmpv6_access);

	net_ipv6_finalize_new(pkt, IPPROTO_ICMPV6);

	NET_DBG("Sending ICMPv6 Echo Request type %d from %s to %s",
		NET_ICMPV6_ECHO_REQUEST,
		log_strdup(net_sprint_ipv6_addr(src)),
		log_strdup(net_sprint_ipv6_addr(dst)));

	if (net_send_data(pkt) >= 0) {
		net_stats_update_icmp_sent(iface);
		return 0;
	}

	net_stats_update_icmp_drop(iface);

	ret = -EIO;

drop:
	net_pkt_unref(pkt);

	return ret;
}

enum net_verdict net_icmpv6_input(struct net_pkt *pkt,
				  struct net_ipv6_hdr *ip_hdr)
{
	NET_PKT_DATA_ACCESS_CONTIGUOUS_DEFINE(icmp_access,
					      struct net_icmp_hdr);
	struct net_icmp_hdr *icmp_hdr;
	struct net_icmpv6_handler *cb;

	icmp_hdr = (struct net_icmp_hdr *)net_pkt_get_data_new(pkt,
							       &icmp_access);
	if (!icmp_hdr) {
		NET_DBG("DROP: NULL ICMPv6 header");
		return NET_DROP;
	}

	if (net_calc_chksum_icmpv6(pkt) != 0) {
		NET_DBG("DROP: invalid checksum");
		goto drop;
	}

	net_pkt_acknowledge_data(pkt, &icmp_access);

	NET_DBG("ICMPv6 %s received type %d code %d",
		net_icmpv6_type2str(icmp_hdr->type),
		icmp_hdr->type, icmp_hdr->code);

	net_stats_update_icmp_recv(net_pkt_iface(pkt));

	SYS_SLIST_FOR_EACH_CONTAINER(&handlers, cb, node) {
		if (cb->type == icmp_hdr->type &&
		    (cb->code == icmp_hdr->code || cb->code == 0)) {
			return cb->handler(pkt, ip_hdr, icmp_hdr);
		}
	}
drop:
	net_stats_update_icmp_drop(net_pkt_iface(pkt));

	return NET_DROP;
}

static struct net_icmpv6_handler echo_request_handler = {
	.type = NET_ICMPV6_ECHO_REQUEST,
	.code = 0,
	.handler = icmpv6_handle_echo_request,
};

void net_icmpv6_init(void)
{
	net_icmpv6_register_handler(&echo_request_handler);
}