/*
   * RFC3927 ZeroConf IPv4 Link-Local addressing
   * (see <http://www.zeroconf.org/>)
   *
   * Copied from BusyBox - networking/zcip.c
   *
   * Copyright (C) 2003 by Arthur van Hoff (avh@strangeberry.com)
   * Copyright (C) 2004 by David Brownell
   * Copyright (C) 2010 by Joe Hershberger
   *
   * Licensed under the GPL v2 or later
   */
  
  #include <common.h>
  #include <net.h>
  #include "arp.h"
  #include "net_rand.h"
  
  /* We don't need more than 32 bits of the counter */
  #define MONOTONIC_MS() ((unsigned)get_timer(0) * (1000 / CONFIG_SYS_HZ))
  
  enum {
  /* 169.254.0.0 */
  	LINKLOCAL_ADDR = 0xa9fe0000,
  
  	IN_CLASSB_NET = 0xffff0000,
  	IN_CLASSB_HOST = 0x0000ffff,
  
  /* protocol timeout parameters, specified in seconds */
  	PROBE_WAIT = 1,
  	PROBE_MIN = 1,
  	PROBE_MAX = 2,
  	PROBE_NUM = 3,
  	MAX_CONFLICTS = 10,
  	RATE_LIMIT_INTERVAL = 60,
  	ANNOUNCE_WAIT = 2,
  	ANNOUNCE_NUM = 2,
  	ANNOUNCE_INTERVAL = 2,
  	DEFEND_INTERVAL = 10
  };
  
  /* States during the configuration process. */
  static enum ll_state_t {
  	PROBE = 0,
  	RATE_LIMIT_PROBE,
  	ANNOUNCE,
  	MONITOR,
  	DEFEND,
  	DISABLED
  } state = DISABLED;
  
  static IPaddr_t ip;
  static int timeout_ms = -1;
  static unsigned deadline_ms;
  static unsigned conflicts;
  static unsigned nprobes;
  static unsigned nclaims;
  static int ready;
  static unsigned int seed;
  
  static void link_local_timeout(void);
  
  /**
   * Pick a random link local IP address on 169.254/16, except that
   * the first and last 256 addresses are reserved.
   */
  static IPaddr_t pick(void)
  {
  	unsigned tmp;
  
  	do {
  		tmp = rand_r(&seed) & IN_CLASSB_HOST;
  	} while (tmp > (IN_CLASSB_HOST - 0x0200));
  	return (IPaddr_t) htonl((LINKLOCAL_ADDR + 0x0100) + tmp);
  }
  
  /**
   * Return milliseconds of random delay, up to "secs" seconds.
   */
  static inline unsigned random_delay_ms(unsigned secs)
  {
  	return rand_r(&seed) % (secs * 1000);
  }
  
  static void configure_wait(void)
  {
  	if (timeout_ms == -1)
  		return;
  
  	/* poll, being ready to adjust current timeout */
  	if (!timeout_ms)
  		timeout_ms = random_delay_ms(PROBE_WAIT);
  
  	/* set deadline_ms to the point in time when we timeout */
  	deadline_ms = MONOTONIC_MS() + timeout_ms;
  
  	debug_cond(DEBUG_DEV_PKT, "...wait %d %s nprobes=%u, nclaims=%u
  ",
  			timeout_ms, eth_get_name(), nprobes, nclaims);
  
  	NetSetTimeout(timeout_ms, link_local_timeout);
  }
  
  void link_local_start(void)
  {
  	ip = getenv_IPaddr("llipaddr");
  	if (ip != 0 && (ntohl(ip) & IN_CLASSB_NET) != LINKLOCAL_ADDR) {
  		puts("invalid link address");
  		net_set_state(NETLOOP_FAIL);
  		return;
  	}
  	NetOurSubnetMask = IN_CLASSB_NET;
  
  	seed = seed_mac();
  	if (ip == 0)
  		ip = pick();
  
  	state = PROBE;
  	timeout_ms = 0;
  	conflicts = 0;
  	nprobes = 0;
  	nclaims = 0;
  	ready = 0;
  
  	configure_wait();
  }
  
  static void link_local_timeout(void)
  {
  	switch (state) {
  	case PROBE:
  		/* timeouts in the PROBE state mean no conflicting ARP packets
  		   have been received, so we can progress through the states */
  		if (nprobes < PROBE_NUM) {
  			nprobes++;
  			debug_cond(DEBUG_LL_STATE, "probe/%u %s@%pI4
  ",
  					nprobes, eth_get_name(), &ip);
  			arp_raw_request(0, NetEtherNullAddr, ip);
  			timeout_ms = PROBE_MIN * 1000;
  			timeout_ms += random_delay_ms(PROBE_MAX - PROBE_MIN);
  		} else {
  			/* Switch to announce state */
  			state = ANNOUNCE;
  			nclaims = 0;
  			debug_cond(DEBUG_LL_STATE, "announce/%u %s@%pI4
  ",
  					nclaims, eth_get_name(), &ip);
  			arp_raw_request(ip, NetOurEther, ip);
  			timeout_ms = ANNOUNCE_INTERVAL * 1000;
  		}
  		break;
  	case RATE_LIMIT_PROBE:
  		/* timeouts in the RATE_LIMIT_PROBE state mean no conflicting
  		   ARP packets have been received, so we can move immediately
  		   to the announce state */
  		state = ANNOUNCE;
  		nclaims = 0;
  		debug_cond(DEBUG_LL_STATE, "announce/%u %s@%pI4
  ",
  				nclaims, eth_get_name(), &ip);
  		arp_raw_request(ip, NetOurEther, ip);
  		timeout_ms = ANNOUNCE_INTERVAL * 1000;
  		break;
  	case ANNOUNCE:
  		/* timeouts in the ANNOUNCE state mean no conflicting ARP
  		   packets have been received, so we can progress through
  		   the states */
  		if (nclaims < ANNOUNCE_NUM) {
  			nclaims++;
  			debug_cond(DEBUG_LL_STATE, "announce/%u %s@%pI4
  ",
  					nclaims, eth_get_name(), &ip);
  			arp_raw_request(ip, NetOurEther, ip);
  			timeout_ms = ANNOUNCE_INTERVAL * 1000;
  		} else {
  			/* Switch to monitor state */
  			state = MONITOR;
  			printf("Successfully assigned %pI4
  ", &ip);
  			NetCopyIP(&NetOurIP, &ip);
  			ready = 1;
  			conflicts = 0;
  			timeout_ms = -1;
  			/* Never timeout in the monitor state */
  			NetSetTimeout(0, NULL);
  
  			/* NOTE: all other exit paths should deconfig ... */
  			net_set_state(NETLOOP_SUCCESS);
  			return;
  		}
  		break;
  	case DEFEND:
  		/* We won!  No ARP replies, so just go back to monitor */
  		state = MONITOR;
  		timeout_ms = -1;
  		conflicts = 0;
  		break;
  	default:
  		/* Invalid, should never happen.  Restart the whole protocol */
  		state = PROBE;
  		ip = pick();
  		timeout_ms = 0;
  		nprobes = 0;
  		nclaims = 0;
  		break;
  	}
  	configure_wait();
  }
  
  void link_local_receive_arp(struct arp_hdr *arp, int len)
  {
  	int source_ip_conflict;
  	int target_ip_conflict;
  	IPaddr_t null_ip = 0;
  
  	if (state == DISABLED)
  		return;
  
  	/* We need to adjust the timeout in case we didn't receive a
  	   conflicting packet. */
  	if (timeout_ms > 0) {
  		unsigned diff = deadline_ms - MONOTONIC_MS();
  		if ((int)(diff) < 0) {
  			/* Current time is greater than the expected timeout
  			   time. This should never happen */
  			debug_cond(DEBUG_LL_STATE,
  				"missed an expected timeout
  ");
  			timeout_ms = 0;
  		} else {
  			debug_cond(DEBUG_INT_STATE, "adjusting timeout
  ");
  			timeout_ms = diff | 1; /* never 0 */
  		}
  	}
  #if 0
   /* XXX Don't bother with ethernet link just yet */
  	if ((fds[0].revents & POLLIN) == 0) {
  		if (fds[0].revents & POLLERR) {
  			/*
  			 * FIXME: links routinely go down;
  			 */
  			bb_error_msg("iface %s is down", eth_get_name());
  			if (ready) {
  				run(argv, "deconfig", &ip);
  			}
  			return EXIT_FAILURE;
  		}
  		continue;
  	}
  #endif
  
  	debug_cond(DEBUG_INT_STATE, "%s recv arp type=%d, op=%d,
  ",
  		eth_get_name(), ntohs(arp->ar_pro),
  		ntohs(arp->ar_op));
  	debug_cond(DEBUG_INT_STATE, "\tsource=%pM %pI4
  ",
  		&arp->ar_sha,
  		&arp->ar_spa);
  	debug_cond(DEBUG_INT_STATE, "\ttarget=%pM %pI4
  ",
  		&arp->ar_tha,
  		&arp->ar_tpa);
  
  	if (arp->ar_op != htons(ARPOP_REQUEST)
  	 && arp->ar_op != htons(ARPOP_REPLY)
  	) {
  		configure_wait();
  		return;
  	}
  
  	source_ip_conflict = 0;
  	target_ip_conflict = 0;
  
  	if (memcmp(&arp->ar_spa, &ip, ARP_PLEN) == 0
  	 && memcmp(&arp->ar_sha, NetOurEther, ARP_HLEN) != 0
  	) {
  		source_ip_conflict = 1;
  	}
  
  	/*
  	 * According to RFC 3927, section 2.2.1:
  	 * Check if packet is an ARP probe by checking for a null source IP
  	 * then check that target IP is equal to ours and source hw addr
  	 * is not equal to ours. This condition should cause a conflict only
  	 * during probe.
  	 */
  	if (arp->ar_op == htons(ARPOP_REQUEST) &&
  	    memcmp(&arp->ar_spa, &null_ip, ARP_PLEN) == 0 &&
  	    memcmp(&arp->ar_tpa, &ip, ARP_PLEN) == 0 &&
  	    memcmp(&arp->ar_sha, NetOurEther, ARP_HLEN) != 0) {
  		target_ip_conflict = 1;
  	}
  
  	debug_cond(DEBUG_NET_PKT,
  		"state = %d, source ip conflict = %d, target ip conflict = "
  		"%d
  ", state, source_ip_conflict, target_ip_conflict);
  	switch (state) {
  	case PROBE:
  	case ANNOUNCE:
  		/* When probing or announcing, check for source IP conflicts
  		   and other hosts doing ARP probes (target IP conflicts). */
  		if (source_ip_conflict || target_ip_conflict) {
  			conflicts++;
  			state = PROBE;
  			if (conflicts >= MAX_CONFLICTS) {
  				debug("%s ratelimit
  ", eth_get_name());
  				timeout_ms = RATE_LIMIT_INTERVAL * 1000;
  				state = RATE_LIMIT_PROBE;
  			}
  
  			/* restart the whole protocol */
  			ip = pick();
  			timeout_ms = 0;
  			nprobes = 0;
  			nclaims = 0;
  		}
  		break;
  	case MONITOR:
  		/* If a conflict, we try to defend with a single ARP probe */
  		if (source_ip_conflict) {
  			debug("monitor conflict -- defending
  ");
  			state = DEFEND;
  			timeout_ms = DEFEND_INTERVAL * 1000;
  			arp_raw_request(ip, NetOurEther, ip);
  		}
  		break;
  	case DEFEND:
  		/* Well, we tried.  Start over (on conflict) */
  		if (source_ip_conflict) {
  			state = PROBE;
  			debug("defend conflict -- starting over
  ");
  			ready = 0;
  			NetOurIP = 0;
  
  			/* restart the whole protocol */
  			ip = pick();
  			timeout_ms = 0;
  			nprobes = 0;
  			nclaims = 0;
  		}
  		break;
  	default:
  		/* Invalid, should never happen.  Restart the whole protocol */
  		debug("invalid state -- starting over
  ");
  		state = PROBE;
  		ip = pick();
  		timeout_ms = 0;
  		nprobes = 0;
  		nclaims = 0;
  		break;
  	}
  	configure_wait();
  }