#include "include/zicmp.h"int icmp_input(znetif_t *pnetif, zbuffer_t *pbuffer){	ip_header_t	*pipheader;	icmp_echo_header_t *picmp_echo_header;	eth_header_t *pethheader;	ipaddr_t tmpipaddr;	u8_t	i;	u16_t	hlen;	u8_t	type;		pipheader =(ip_header_t *) (( u8_t*)pbuffer->pdata + ETH_HEAD_LEN);	/*remenber buffer is whole PACKET*/	pethheader = (eth_header_t *) (( u8_t*)pbuffer->pdata );		hlen = IPH_HL(pipheader) * 4 + ETH_HEAD_LEN;			/*must jump ETH and IP */		type = *(u8_t *)((u8_t *)pbuffer->pdata + hlen );		/*move to the ICMP header*/		switch(type)	{	case ICMP_ECHO:			if ( pbuffer->tot_len <  ( sizeof(ip_header_t) + sizeof( icmp_echo_header_t) ) )				return -1;			picmp_echo_header = (icmp_echo_header_t *)((u8_t *)pbuffer->pdata + hlen );			/*change src and dest ip*/			tmpipaddr = pipheader->src_ipaddr;		    pipheader->src_ipaddr = pipheader->dest_ipaddr;		    pipheader->dest_ipaddr = tmpipaddr;			/*change ICMP type*/			ICMPH_TYPE_SET(picmp_echo_header, ICMP_ER);			/*change ICMP checksum*/			if( picmp_echo_header->chksum >= htons(0xffff - (ICMP_ECHO << 8))) 			{				picmp_echo_header->chksum += htons(ICMP_ECHO << 8) + 1;			}			else			{				picmp_echo_header->chksum += htons(ICMP_ECHO << 8);			}			/*setup ETH addr */			for ( i=0 ; i < 6 ; i++)			{				pethheader->dest_hwaddr.addr[i] = pethheader->src_hwaddr.addr[i];				pethheader->src_hwaddr.addr[i] = pnetif->hwaddr.addr[i];			}					pnetif->netif_tx(pnetif, pbuffer);						zbuffer_delete(pbuffer);			return 0;			break;	}	zbuffer_delete(pbuffer);	return -1;}void icmp_dest_unreach(znetif_t *pnetif, zbuffer_t * pbuffer, enum icmp_dur_type t){	ip_header_t	* pipheader;	u16_t	offset;	u8_t	i;	icmp_dur_header_t	*pdur;	eth_header_t		*pethheader;	ipaddr_t		tmpipaddr;						pethheader = (eth_header_t *)(pbuffer->pdata);	pipheader =(ip_header_t *) (( u8_t*)pbuffer->pdata + ETH_HEAD_LEN);	/*remenber buffer is whole PACKET*/	offset = IPH_HL(pipheader) * 4 + ETH_HEAD_LEN;	pdur = (icmp_dur_header_t *)((u8_t *)pbuffer->pdata + offset);	pbuffer = zbuffer_adjust(pbuffer, 0, (offset + 8 + IP_HEAD_LEN + 8 - pbuffer->tot_len) );		if (pbuffer == NULL )		return;	for ( i = 0; i < 8 + IP_HEAD_LEN; i++)	{		*(u8_t *)((u8_t *)pbuffer->pdata + offset + i + 8) = *(u8_t *)((u8_t *)pbuffer->pdata + ETH_HEAD_LEN  + i);	}		for ( i = 0; i < 4; i++)	{		*(u8_t *)((u8_t *)pbuffer->pdata + offset + i + 4) = 0x00;	}	ICMPH_TYPE_SET(pdur, ICMP_DUR);	ICMPH_CODE_SET(pdur, t);	pdur->chksum = 0;	pdur->chksum = inet_chksum(pdur, 8 + IP_HEAD_LEN + 8);	/*change src and dest ip and proto and checksum*/	tmpipaddr = pipheader->src_ipaddr;	pipheader->src_ipaddr = pipheader->dest_ipaddr;	pipheader->dest_ipaddr = tmpipaddr;	pipheader->_len = offset + 8 + IP_HEAD_LEN + 8 - ETH_HEAD_LEN;	/*updata length*/	pipheader->_ttl_proto &= (0xff00 &  IP_PROTO_ICMP);	pipheader->_chksum = 0;	pipheader->_chksum = inet_chksum(pipheader, IPH_HL(pipheader) * 4);	for ( i=0 ; i < 6 ; i++)	{		pethheader->dest_hwaddr.addr[i] = pethheader->src_hwaddr.addr[i];		pethheader->src_hwaddr.addr[i] = pnetif->hwaddr.addr[i];	}		pnetif->netif_tx(pnetif, pbuffer);	zbuffer_delete(pbuffer);}