/*
 * File:        arp.c
 * Purpose:     Address Resolution Protocol routines.
 *
 * Notes:
 */

#include "net.h"
#include <stdbool.h>
#include <stddef.h>

#define TIMER_NETWORK 0

static uint8_t *arp_find_pair(ARP_INFO *arptab, uint16_t protocol, uint8_t *hwa, uint8_t *pa)
{
	/*
	 * This function searches through the ARP table for the
	 * specified <protocol,hwa> or <protocol,pa> address pair.
	 * If it is found, then a a pointer to the non-specified
	 * address is returned.  Otherwise NULL is returned.
	 * If you pass in <protocol,pa> then you get <hwa> out.
	 * If you pass in <protocol,hwa> then you get <pa> out.
	 */
	int slot, i, match = false;
	uint8_t *rvalue;

	if (((hwa == 0) && (pa == 0)) || (arptab == 0))
		return NULL;

	rvalue = NULL;

	/* 
	 * Check each protocol address for a match 
	 */
	for (slot = 0; slot < arptab->tab_size; slot++)
	{
		if ((arptab->table[slot].longevity != ARP_ENTRY_EMPTY) &&
				(arptab->table[slot].protocol == protocol))
		{
			match = true;
			if (hwa != 0)
			{
				/* 
				 * Check the Hardware Address field 
				 */
				rvalue = &arptab->table[slot].pa[0];
				for (i = 0; i < arptab->table[slot].hwa_size; i++)
				{
					if (arptab->table[slot].hwa[i] != hwa[i])
					{
						match = false;
						break;
					}
				}
			}
			else
			{
				/* 
				 * Check the Protocol Address field 
				 */
				rvalue = &arptab->table[slot].hwa[0];
				for (i = 0; i < arptab->table[slot].pa_size; i++)
				{
					if (arptab->table[slot].pa[i] != pa[i])
					{
						match = false;
						break;
					}
				}
			}
			if (match)
			{
				break;
			}
		}
	}

	if (match)
		return rvalue;
	else
		return NULL;
}

void arp_merge(ARP_INFO *arptab, uint16_t protocol, int hwa_size, uint8_t *hwa,
		int pa_size, uint8_t *pa, int longevity)
{
	/*
	 * This function merges an entry into the ARP table.  If
	 * either piece is NULL, the function exits, otherwise
	 * the entry is merged or added, provided there is space.
	 */
	int i, slot;
	uint8_t *ta;

	if ((hwa == NULL) || (pa == NULL) || (arptab == NULL) ||
			((longevity != ARP_ENTRY_TEMP) &&
			 (longevity != ARP_ENTRY_PERM)))
	{
		return;
	}

	/* First search ARP table for existing entry */
	if ((ta = arp_find_pair(arptab,protocol,NULL,pa)) != 0)
	{
		/* Update hardware address */
		for (i = 0; i < hwa_size; i++)
			ta[i] = hwa[i];
		return;
	}

	/* Next try to find an empty slot */
	slot = -1;
	for (i = 0; i < MAX_ARP_ENTRY; i++)
	{
		if (arptab->table[i].longevity == ARP_ENTRY_EMPTY)
		{
			slot = i;
			break;
		}
	}

	/* if no empty slot was found, pick a temp slot */
	if (slot == -1)
	{
		for (i = 0; i < MAX_ARP_ENTRY; i++)
		{
			if (arptab->table[i].longevity == ARP_ENTRY_TEMP)
			{
				slot = i;
				break;
			}
		}
	}

	/* if after all this, still no slot found, add in last slot */
	if (slot == -1)
		slot = (MAX_ARP_ENTRY - 1);

	/* add the entry into the slot */
	arptab->table[slot].protocol = protocol;

	arptab->table[slot].hwa_size = (uint8_t) hwa_size;
	for (i = 0; i < hwa_size; i++)
		arptab->table[slot].hwa[i] = hwa[i];

	arptab->table[slot].pa_size = (uint8_t) pa_size;
	for (i = 0; i < pa_size; i++)
		arptab->table[slot].pa[i] = pa[i];

	arptab->table[slot].longevity = longevity;
}


void arp_remove(ARP_INFO *arptab, uint16_t protocol, uint8_t *hwa, uint8_t *pa)
{
	/*
	 * This function removes an entry from the ARP table.  The
	 * ARP table is searched according to the non-NULL address
	 * that is provided.
	 */
	int slot, i, match;

	if (((hwa == 0) && (pa == 0)) || (arptab == 0))
		return;

	/* check each hardware adress for a match */
	for (slot = 0; slot < arptab->tab_size; slot++)
	{
		if ((arptab->table[slot].longevity != ARP_ENTRY_EMPTY) &&
				(arptab->table[slot].protocol == protocol))
		{
			match = true;
			if (hwa != 0)
			{
				/* Check Hardware Address field */
				for (i = 0; i < arptab->table[slot].hwa_size; i++)
				{
					if (arptab->table[slot].hwa[i] != hwa[i])
					{
						match = false;
						break;
					}
				}
			}
			else
			{
				/* Check Protocol Address field */
				for (i = 0; i < arptab->table[slot].pa_size; i++)
				{
					if (arptab->table[slot].pa[i] != pa[i])
					{
						match = false;
						break;
					}
				}
			}
			if (match)
			{
				for (i = 0; i < arptab->table[slot].hwa_size; i++)
					arptab->table[slot].hwa[i] = 0;
				for (i = 0; i < arptab->table[slot].pa_size; i++)
					arptab->table[slot].pa[i] = 0;
				arptab->table[slot].longevity = ARP_ENTRY_EMPTY;
				break;
			}
		}
	}
}

void arp_request(NIF *nif, uint8_t *pa)
{
	/*
	 * This function broadcasts an ARP request for the protocol
	 * address "pa"
	 */
	uint8_t *addr;
	NBUF *pNbuf;
	arp_frame_hdr *arpframe;
	int i, result;


	xprintf("%s\r\n", __FUNCTION__);

	pNbuf = nbuf_alloc();
	if (pNbuf == NULL)
	{
		xprintf("ARP: arp_request couldn't allocate Tx buffer\n");
		return;
	}

	arpframe = (arp_frame_hdr *)&pNbuf->data[ARP_HDR_OFFSET];

	/* Build the ARP request packet */
	arpframe->ar_hrd = ETHERNET;
	arpframe->ar_pro = ETH_FRM_IP;
	arpframe->ar_hln = 6;
	arpframe->ar_pln = 4;
	arpframe->opcode = ARP_REQUEST;

	addr = &nif->hwa[0];
	for (i = 0; i < 6; i++)
		arpframe->ar_sha[i] = addr[i];

	addr = ip_get_myip(nif_get_protocol_info(nif,ETH_FRM_IP));
	for (i = 0; i < 4; i++)
		arpframe->ar_spa[i] = addr[i];

	for (i = 0; i < 6; i++)
		arpframe->ar_tha[i] = 0x00;

	for (i = 0; i < 4; i++)
		arpframe->ar_tpa[i] = pa[i];

	pNbuf->length = ARP_HDR_LEN;

	/* Send the ARP request */
	result = nif->send(nif, nif->broadcast, nif->hwa, ETH_FRM_ARP, pNbuf);

	if (result == 0)
		nbuf_free(pNbuf);
}

static int arp_resolve_pa(NIF *nif, uint16_t protocol, uint8_t *pa, uint8_t **ha)
{
	/*
	 * This function accepts a pointer to a protocol address and
	 * searches the ARP table for a hardware address match.  If no
	 * no match found, false is returned.
	 */
	ARP_INFO *arptab;

	if ((pa == NULL) || (nif == NULL) || (protocol == 0))
		return 0;

	arptab = nif_get_protocol_info (nif,ETH_FRM_ARP);
	*ha = arp_find_pair(arptab,protocol,0,pa);

	if (*ha == NULL)
		return 0;
	else
		return 1;
}

uint8_t *arp_resolve(NIF *nif, uint16_t protocol, uint8_t *pa)
{
	int i;
	uint8_t *hwa;

	/* 
	 * Check to see if the necessary MAC-to-IP translation information
	 * is in table already 
	 */
	if (arp_resolve_pa (nif, protocol, pa, &hwa))
		return hwa;

	/* 
	 * Ok, it's not, so we need to try to obtain it by broadcasting
	 * an ARP request.  Hopefully the desired host is listening and
	 * will respond with it's MAC address
	 */
	for (i = 0; i < 3; i++)
	{
		arp_request (nif, pa);

		timer_set_secs(TIMER_NETWORK, ARP_TIMEOUT);
		while (timer_get_reference(TIMER_NETWORK))
		{
			if (arp_resolve_pa (nif, protocol, pa, &hwa))
				return hwa;
		}
	}

	return NULL;
}

void arp_init(ARP_INFO *arptab)
{
	int slot, i;

	arptab->tab_size = MAX_ARP_ENTRY;
	for (slot = 0; slot < arptab->tab_size; slot++)
	{
		for (i = 0; i < MAX_HWA_SIZE; i++)
			arptab->table[slot].hwa[i] = 0;
		for (i = 0; i < MAX_PA_SIZE; i++)
			arptab->table[slot].pa[i] = 0;
		arptab->table[slot].longevity = ARP_ENTRY_EMPTY;
		arptab->table[slot].hwa_size = 0;
		arptab->table[slot].pa_size = 0;
	}
}

void arp_handler(NIF *nif, NBUF *pNbuf)
{
	/* 
	 * ARP protocol handler 
	 */
	uint8_t *addr;
	ARP_INFO *arptab;
	int longevity;
	arp_frame_hdr *rx_arpframe, *tx_arpframe;

	arptab = nif_get_protocol_info(nif, ETH_FRM_ARP);
	rx_arpframe = (arp_frame_hdr *) &pNbuf->data[pNbuf->offset];

	/* 
	 * Check for an appropriate ARP packet 
	 */
	if ((pNbuf->length < ARP_HDR_LEN)       ||  
			(rx_arpframe->ar_hrd != ETHERNET)   ||
			(rx_arpframe->ar_hln != 6)          ||
			(rx_arpframe->ar_pro != ETH_FRM_IP) ||
			(rx_arpframe->ar_pln != 4))
	{
		nbuf_free(pNbuf);
		return;
	}

	/* 
	 * Check to see if it was addressed to me - if it was, keep this
	 * ARP entry in the table permanently; if not, mark it so that it
	 * can be displaced later if necessary
	 */
	addr = ip_get_myip(nif_get_protocol_info(nif,ETH_FRM_IP));
	if ((rx_arpframe->ar_tpa[0] == addr[0]) &&
			(rx_arpframe->ar_tpa[1] == addr[1]) &&
			(rx_arpframe->ar_tpa[2] == addr[2]) &&
			(rx_arpframe->ar_tpa[3] == addr[3]) )
	{
		longevity = ARP_ENTRY_PERM;
	}
	else 
		longevity = ARP_ENTRY_TEMP;

	/* 
	 * Add ARP info into the table
	 */
	arp_merge(arptab,
			rx_arpframe->ar_pro,
			rx_arpframe->ar_hln,
			&rx_arpframe->ar_sha[0],
			rx_arpframe->ar_pln,
			&rx_arpframe->ar_spa[0],
			longevity
			);

	switch (rx_arpframe->opcode)
	{
		case ARP_REQUEST:
			/* 
			 * Check to see if request is directed to me
			 */
			if ((rx_arpframe->ar_tpa[0] == addr[0]) &&
					(rx_arpframe->ar_tpa[1] == addr[1]) &&
					(rx_arpframe->ar_tpa[2] == addr[2]) &&
					(rx_arpframe->ar_tpa[3] == addr[3]) )
			{
				/*
				 * Reuse the current network buffer to assemble an ARP reply
				 */
				tx_arpframe = (arp_frame_hdr *)&pNbuf->data[ARP_HDR_OFFSET];

				/*
				 * Build new ARP frame from the received data
				 */
				tx_arpframe->ar_hrd = ETHERNET;
				tx_arpframe->ar_pro = ETH_FRM_IP;
				tx_arpframe->ar_hln = 6;
				tx_arpframe->ar_pln = 4;
				tx_arpframe->opcode = ARP_REPLY;
				tx_arpframe->ar_tha[0] = rx_arpframe->ar_sha[0];
				tx_arpframe->ar_tha[1] = rx_arpframe->ar_sha[1];
				tx_arpframe->ar_tha[2] = rx_arpframe->ar_sha[2];
				tx_arpframe->ar_tha[3] = rx_arpframe->ar_sha[3];
				tx_arpframe->ar_tha[4] = rx_arpframe->ar_sha[4];
				tx_arpframe->ar_tha[5] = rx_arpframe->ar_sha[5];
				tx_arpframe->ar_tpa[0] = rx_arpframe->ar_spa[0];
				tx_arpframe->ar_tpa[1] = rx_arpframe->ar_spa[1];
				tx_arpframe->ar_tpa[2] = rx_arpframe->ar_spa[2];
				tx_arpframe->ar_tpa[3] = rx_arpframe->ar_spa[3];

				/* 
				 * Now copy in the new information 
				 */
				addr = &nif->hwa[0];
				tx_arpframe->ar_sha[0] = addr[0];
				tx_arpframe->ar_sha[1] = addr[1];
				tx_arpframe->ar_sha[2] = addr[2];
				tx_arpframe->ar_sha[3] = addr[3];
				tx_arpframe->ar_sha[4] = addr[4];
				tx_arpframe->ar_sha[5] = addr[5];

				addr = ip_get_myip(nif_get_protocol_info(nif,ETH_FRM_IP));
				tx_arpframe->ar_spa[0] = addr[0];
				tx_arpframe->ar_spa[1] = addr[1];
				tx_arpframe->ar_spa[2] = addr[2];
				tx_arpframe->ar_spa[3] = addr[3];

				/* 
				 * Save the length of my packet in the buffer structure 
				 */
				pNbuf->length = ARP_HDR_LEN;

				nif->send(nif, 
						&tx_arpframe->ar_tha[0], 
						&tx_arpframe->ar_sha[0], 
						ETH_FRM_ARP, 
						pNbuf);
			}
			else 
				nbuf_free(pNbuf);
			break;
		case ARP_REPLY:
			/*
			 * The ARP Reply case is already taken care of
			 */
		default:
			nbuf_free(pNbuf);
			break;
	}

	return;
}