/** @file
 * @brief IPv4 autoconf related functions
 */

/*
 * Copyright (c) 2017 Matthias Boesl
 * Copyright (c) 2018 Intel Corporation
 *
 * SPDX-License-Identifier: Apache-2.0
 */

#if defined(CONFIG_NET_DEBUG_IPV4_AUTOCONF)
#define SYS_LOG_DOMAIN "net/ipv4ll"
#define NET_LOG_ENABLED 1
#endif

#include "net_private.h"
#include <errno.h>
#include "../l2/ethernet/arp.h"
#include <net/net_pkt.h>
#include <net/net_core.h>
#include <net/net_if.h>

#include "ipv4_autoconf_internal.h"

/* Have only one timer in order to save memory */
static struct k_delayed_work ipv4auto_timer;

/* Track currently active timers */
static sys_slist_t ipv4auto_ifaces;

#define BUF_ALLOC_TIMEOUT K_MSEC(100)

static struct net_pkt *ipv4_autoconf_prepare_arp(struct net_if *iface)
{
	struct net_if_config *cfg = net_if_get_config(iface);
	struct net_pkt *pkt;
	struct net_buf *frag;

	pkt = net_pkt_get_reserve_tx(sizeof(struct net_eth_hdr),
				     BUF_ALLOC_TIMEOUT);
	if (!pkt) {
		goto fail;
	}

	frag = net_pkt_get_frag(pkt, BUF_ALLOC_TIMEOUT);
	if (!frag) {
		goto fail;
	}

	net_pkt_frag_add(pkt, frag);
	net_pkt_set_iface(pkt, iface);
	net_pkt_set_family(pkt, AF_INET);
	net_pkt_set_ipv4_auto(pkt, true);

	return net_arp_prepare(pkt, &cfg->ipv4auto.requested_ip,
			       &cfg->ipv4auto.current_ip);

fail:
	if (pkt) {
		net_pkt_unref(pkt);
	}

	return NULL;
}

static void ipv4_autoconf_send_probe(struct net_if_ipv4_autoconf *ipv4auto)
{
	struct net_pkt *pkt;

	pkt = ipv4_autoconf_prepare_arp(ipv4auto->iface);
	if (!pkt) {
		NET_DBG("Failed to prepare probe %p", ipv4auto->iface);
		return;
	}

	NET_DBG("Probing pkt %p", pkt);

	if (net_if_send_data(ipv4auto->iface, pkt) == NET_DROP) {
		net_pkt_unref(pkt);
	} else {
		ipv4auto->probe_cnt++;
		ipv4auto->state = NET_IPV4_AUTOCONF_PROBE;
	}
}

static void ipv4_autoconf_send_announcement(
	struct net_if_ipv4_autoconf *ipv4auto)
{
	struct net_pkt *pkt;

	pkt = ipv4_autoconf_prepare_arp(ipv4auto->iface);
	if (!pkt) {
		NET_DBG("Failed to prepare announcement %p", ipv4auto->iface);
		return;
	}

	NET_DBG("Announcing pkt %p", pkt);

	if (net_if_send_data(ipv4auto->iface, pkt) == NET_DROP) {
		net_pkt_unref(pkt);
	} else {
		ipv4auto->announce_cnt++;
		ipv4auto->state = NET_IPV4_AUTOCONF_ANNOUNCE;
	}
}

enum net_verdict net_ipv4_autoconf_input(struct net_if *iface,
					 struct net_pkt *pkt)
{
	struct net_if_config *cfg = net_if_get_config(iface);
	struct net_arp_hdr *arp_hdr;

	cfg = net_if_get_config(iface);
	if (!cfg) {
		NET_DBG("Interface %p configuration missing!", iface);
		return NET_DROP;
	}

	if (net_pkt_get_len(pkt) < (sizeof(struct net_arp_hdr) -
				    net_pkt_ll_reserve(pkt))) {
		NET_DBG("Invalid ARP header (len %zu, min %zu bytes)",
			net_pkt_get_len(pkt),
			sizeof(struct net_arp_hdr) -
			net_pkt_ll_reserve(pkt));
		return NET_DROP;
	}

	arp_hdr = NET_ARP_HDR(pkt);

	if (!net_ipv4_addr_cmp(&arp_hdr->dst_ipaddr,
			       &cfg->ipv4auto.requested_ip)) {
		/* No conflict */
		return NET_CONTINUE;
	}

	if (!net_ipv4_addr_cmp(&arp_hdr->src_ipaddr,
			       &cfg->ipv4auto.requested_ip)) {
		/* No need to defend */
		return NET_CONTINUE;
	}

	NET_DBG("Conflict detected from %s for %s, state %d",
		net_sprint_ll_addr((u8_t *)&arp_hdr->src_hwaddr,
				   arp_hdr->hwlen),
		net_sprint_ipv4_addr(&arp_hdr->dst_ipaddr),
		cfg->ipv4auto.state);

	cfg->ipv4auto.conflict_cnt++;

	switch (cfg->ipv4auto.state) {
	case NET_IPV4_AUTOCONF_PROBE:
		/* restart probing with renewed IP */
		net_ipv4_autoconf_start(iface);
		break;
	case NET_IPV4_AUTOCONF_ANNOUNCE:
	case NET_IPV4_AUTOCONF_ASSIGNED:
		if (cfg->ipv4auto.conflict_cnt == 1) {
			/* defend IP */
			ipv4_autoconf_send_announcement(&cfg->ipv4auto);
		} else {
			/* unset host ip */
			if (!net_if_ipv4_addr_rm(iface,
						 &cfg->ipv4auto.requested_ip)) {
				NET_DBG("Failed to remove addr from iface");
			}

			/* restart probing after second conflict */
			net_ipv4_autoconf_start(iface);
		}

		break;
	default:
		break;
	}

	return NET_DROP;
}

static void ipv4_autoconf_send(struct net_if_ipv4_autoconf *ipv4auto)
{
	switch (ipv4auto->state) {
	case NET_IPV4_AUTOCONF_INIT:
		ipv4auto->probe_cnt = 0;
		ipv4auto->announce_cnt = 0;
		ipv4auto->conflict_cnt = 0;
		memset(&ipv4auto->current_ip, 0, sizeof(struct in_addr));
		ipv4auto->requested_ip.s4_addr[0] = 169;
		ipv4auto->requested_ip.s4_addr[1] = 254;
		ipv4auto->requested_ip.s4_addr[2] = sys_rand32_get() % 254;
		ipv4auto->requested_ip.s4_addr[3] = sys_rand32_get() % 254;

		NET_DBG("%s: Starting probe for 169.254.%d.%d", "Init",
			ipv4auto->requested_ip.s4_addr[2],
			ipv4auto->requested_ip.s4_addr[3]);
		ipv4_autoconf_send_probe(ipv4auto);
		break;
	case NET_IPV4_AUTOCONF_RENEW:
		ipv4auto->probe_cnt = 0;
		ipv4auto->announce_cnt = 0;
		ipv4auto->conflict_cnt = 0;
		memset(&ipv4auto->current_ip, 0, sizeof(struct in_addr));
		NET_DBG("%s: Starting probe for 169.254.%d.%d", "Renew",
			ipv4auto->requested_ip.s4_addr[2],
			ipv4auto->requested_ip.s4_addr[3]);
		ipv4_autoconf_send_probe(ipv4auto);
		break;
	case NET_IPV4_AUTOCONF_PROBE:
		/* schedule next probe */
		if (ipv4auto->probe_cnt <= (IPV4_AUTOCONF_PROBE_NUM - 1)) {
			ipv4_autoconf_send_probe(ipv4auto);
			break;
		}
	/* passthrough */
	case NET_IPV4_AUTOCONF_ANNOUNCE:
		if (ipv4auto->announce_cnt <=
		    (IPV4_AUTOCONF_ANNOUNCE_NUM - 1)) {
			net_ipaddr_copy(&ipv4auto->current_ip,
					&ipv4auto->requested_ip);
			ipv4_autoconf_send_announcement(ipv4auto);
			break;
		}

		/* success, add new IPv4 address */
		if (!net_if_ipv4_addr_add(ipv4auto->iface,
					  &ipv4auto->requested_ip,
					  NET_ADDR_AUTOCONF, 0)) {
			NET_DBG("Failed to add IPv4 addr to iface %p",
				ipv4auto->iface);
			return;
		}

		ipv4auto->state = NET_IPV4_AUTOCONF_ASSIGNED;
		break;
	default:
		break;
	}
}

static u32_t ipv4_autoconf_get_timeout(struct net_if_ipv4_autoconf *ipv4auto)
{
	switch (ipv4auto->state) {
	case NET_IPV4_AUTOCONF_PROBE:
		if (ipv4auto->conflict_cnt >= IPV4_AUTOCONF_MAX_CONFLICTS) {
			NET_DBG("Rate limiting");
			return K_SECONDS(IPV4_AUTOCONF_RATE_LIMIT_INTERVAL);

		} else if (ipv4auto->probe_cnt == IPV4_AUTOCONF_PROBE_NUM) {
			return K_SECONDS(IPV4_AUTOCONF_ANNOUNCE_INTERVAL);
		}

		return IPV4_AUTOCONF_PROBE_WAIT * MSEC_PER_SEC +
			(sys_rand32_get() % MSEC_PER_SEC);

	case NET_IPV4_AUTOCONF_ANNOUNCE:
		return K_SECONDS(IPV4_AUTOCONF_ANNOUNCE_INTERVAL);

	default:
		break;
	}

	return 0;
}

static void ipv4_autoconf_submit_work(u32_t timeout)
{
	if (!k_delayed_work_remaining_get(&ipv4auto_timer) ||
	    timeout < k_delayed_work_remaining_get(&ipv4auto_timer)) {
		k_delayed_work_cancel(&ipv4auto_timer);
		k_delayed_work_submit(&ipv4auto_timer, timeout);

		NET_DBG("Next wakeup in %d ms",
			k_delayed_work_remaining_get(&ipv4auto_timer));
	}
}

static bool ipv4_autoconf_check_timeout(s64_t start, u32_t time, s64_t timeout)
{
	start += time;
	if (start < 0) {
		start = -start;
	}

	if (start > timeout) {
		return false;
	}

	return true;
}

static bool ipv4_autoconf_timedout(struct net_if_ipv4_autoconf *ipv4auto,
				   s64_t timeout)
{
	return ipv4_autoconf_check_timeout(ipv4auto->timer_start,
					   ipv4auto->timer_timeout,
					   timeout);
}

static u32_t ipv4_autoconf_manage_timeouts(
	struct net_if_ipv4_autoconf *ipv4auto,
	s64_t timeout)
{
	if (ipv4_autoconf_timedout(ipv4auto, timeout)) {
		ipv4_autoconf_send(ipv4auto);
	}

	ipv4auto->timer_timeout = ipv4_autoconf_get_timeout(ipv4auto);

	return ipv4auto->timer_timeout;
}

static void ipv4_autoconf_timeout(struct k_work *work)
{
	u32_t timeout_update = UINT32_MAX - 1;
	s64_t timeout = k_uptime_get();
	struct net_if_ipv4_autoconf *current, *next;

	ARG_UNUSED(work);

	SYS_SLIST_FOR_EACH_CONTAINER_SAFE(&ipv4auto_ifaces, current, next,
					  node) {
		u32_t next_timeout;

		next_timeout = ipv4_autoconf_manage_timeouts(current, timeout);
		if (next_timeout < timeout_update) {
			timeout_update = next_timeout;
		}
	}

	if (timeout_update != UINT32_MAX && timeout_update > 0) {
		NET_DBG("Waiting for %u ms", timeout_update);

		k_delayed_work_submit(&ipv4auto_timer, timeout_update);
	}
}

static void ipv4_autoconf_start_timer(struct net_if *iface,
				      struct net_if_ipv4_autoconf *ipv4auto)
{
	sys_slist_append(&ipv4auto_ifaces, &ipv4auto->node);

	ipv4auto->timer_start = k_uptime_get();
	ipv4auto->timer_timeout = K_SECONDS(IPV4_AUTOCONF_START_DELAY);
	ipv4auto->iface = iface;

	ipv4_autoconf_submit_work(ipv4auto->timer_timeout);
}

void net_ipv4_autoconf_start(struct net_if *iface)
{
	/* Initialize interface and start probing */
	struct net_if_config *cfg;

	cfg = net_if_get_config(iface);
	if (!cfg) {
		return;
	}

	/* Remove the existing registration if found */
	if (cfg->ipv4auto.iface == iface) {
		net_ipv4_autoconf_reset(iface);
	}

	NET_DBG("Starting IPv4 autoconf for iface %p", iface);

	if (cfg->ipv4auto.state == NET_IPV4_AUTOCONF_ASSIGNED) {
		cfg->ipv4auto.state = NET_IPV4_AUTOCONF_RENEW;
	} else {
		cfg->ipv4auto.state = NET_IPV4_AUTOCONF_INIT;
	}

	ipv4_autoconf_start_timer(iface, &cfg->ipv4auto);
}

void net_ipv4_autoconf_reset(struct net_if *iface)
{
	struct net_if_config *cfg;

	cfg = net_if_get_config(iface);
	if (!cfg) {
		return;
	}

	/* Initialize interface and start probing */
	if (cfg->ipv4auto.state == NET_IPV4_AUTOCONF_ASSIGNED) {
		net_if_ipv4_addr_rm(iface, &cfg->ipv4auto.current_ip);
	}

	NET_DBG("Autoconf reset for %p", iface);

	/* Cancel any ongoing probing/announcing attempt*/
	sys_slist_find_and_remove(&ipv4auto_ifaces, &cfg->ipv4auto.node);

	if (sys_slist_is_empty(&ipv4auto_ifaces)) {
		k_delayed_work_cancel(&ipv4auto_timer);
	}
}

void net_ipv4_autoconf_init(void)
{
	k_delayed_work_init(&ipv4auto_timer, ipv4_autoconf_timeout);
}