ip.c

ARm网口实现的源程序！ 超详细

/************************************************************
 * File name	: Ip.c										*
 * By 			: hugang, [e-mail]			*
 ************************************************************/

#include "armnet.h"
#include "..\inc\44blib.h"
#include <string.h>


extern NODE locnode;       //本机的节点信息结构(mac,ip,mask,port)

/********************************************************************************************************
 * Check frame is IP, checksum & byte-swap, return data len 											*
 ********************************************************************************************************/
short IsIp(ETHERFRAME *efp, short len)
{
    short ver, dlen=0, hlen;
    unsigned short sum;
    IPKT *ip;
    if (efp->e.ptype==PCOL_IP && len>=sizeof(IPHDR))
    {
        ip = (IPKT *)(efp->edata);           		/* Get pointer to IP frame */
        ver = ip->i.vhl >> 4;                		/* Get IP version & hdr len */
        hlen = (ip->i.vhl & 0xf) << 2;
        sum = ~csum((unsigned char *)&ip->i, (unsigned short)hlen);     		/* Do checksum */
        if (ver==4 && len>=hlen && sum==0)   		/* If OK.. */
        {
        	SwapIp(efp);
            dlen =  min(ip->i.len, len);
            dlen -= hlen;
            if (hlen > sizeof(IPHDR))        		/* If IP options present.. */
            {                                		/* ..delete them, move data down */
                memmove((unsigned char *)ip->ipdata, (unsigned char *)&ip->ipdata[hlen-sizeof(IPHDR)], len);
                dlen -= hlen-sizeof(IPHDR);
            }
        }
    }
    return(dlen);
}


/********************************************************************************************************
 * Make an IP packet, if greater than the MTU, also make fragment (subframe) in							*
 * this frame. Return total length of frame and subframes (if any)										*
 ********************************************************************************************************/
short MakeIp(ETHERFRAME *efp, NODE *srcep, NODE *destp, unsigned char pcol, unsigned short dlen)
{
    IPKT *ip;
    static unsigned short ident = 1;
    
    ip = (IPKT *)(efp->edata);           								// Get pointer to IP datagram
    ip->i.ident = ident;               	 								// Set datagram ident
    ip->i.frags = 0;           		 									// Frag offset in units of 8 bytes
    ip->i.vhl = 0x40+(sizeof(IPHDR)>>2);								// Version 4, header len 5 LWORDs
    ip->i.service = 0;                  								// Routine message
    ip->i.ttl = IP_TTL;                 								// Time To Live
    ip->i.pcol = pcol;                  								// Set IP protocol
    ip->i.sip = srcep->ip;              								// Srce, dest IP addrs
    ip->i.dip = destp->ip;
    ip->i.len = dlen + sizeof(IPHDR);    								// Data length
	SwapIp(efp);    
    ip->i.check = 0;                    								// Clear checksum
    ip->i.check = ~csum((unsigned char *)ip, sizeof(IPHDR)); 			// ..then set to calc value
    ident++;                            								// Increment datagram ident
    
    return(MakeFrame(efp, srcep->mac,destp->mac, PCOL_IP, (unsigned short)dlen + sizeof(IPHDR)));
}


/********************************************************************************************************
 * Swap byte order of ints in IP header 																*
 ********************************************************************************************************/
void SwapIp(ETHERFRAME *efp)
{
    IPKT *ip;

    ip = (IPKT *)(efp->edata);      
    ip->i.len = swapw(ip->i.len);
    ip->i.ident = swapw(ip->i.ident);
    ip->i.frags = swapw(ip->i.frags);
    ip->i.sip = swapl(READ_PACKED(ip->i.sip));
    ip->i.dip = swapl(READ_PACKED(ip->i.dip));
}


/********************************************************************************************************
 * Get the frame driver type, source IP and Ethernet addresses											*
 * Returned data does not include port number, netmask or gateway addr 									*
 ********************************************************************************************************/
void GetIpSrce(ETHERFRAME *efp, NODE *np)
{
    IPKT *ip;

	memcpy(np->mac, (unsigned char *)efp->e.srce, MACLEN);
    ip = (IPKT *)efp->edata;
    np->ip = READ_PACKED(ip->i.sip);
}


/********************************************************************************************************
 * Get the frame driver type, destination IP and Ethernet addresses										*
 * Returned data does not include port number, netmask or gateway addr 									*
 ********************************************************************************************************/
void GetIpDest(ETHERFRAME *efp, NODE *np)
{
    IPKT *ip;

 	memcpy(np->mac, (unsigned char *)efp->e.dest, MACLEN);
    ip = (IPKT *)efp->edata;
    np->ip = READ_PACKED(ip->i.dip);
}


/********************************************************************************************************
 * Get local node data corresponding to a frame destination IP address									*
 * Data does not include port number. Return 0 if no matching local node 								*
 ********************************************************************************************************/
unsigned short GetIPLocdest(ETHERFRAME *efp, NODE *np)
{
    IPHDR *iph;
    unsigned short ok = 0;

    iph =(IPHDR *)(efp->edata);
    if (iph->dip==locnode.ip)
    {   
    	*np = locnode;
    	ok = 1;
    }
    return (ok);
}


/********************************************************************************************************
 * Check a remote address to see if it is on the local subnet.											*
 * If so (or no gateway), return it. If not, return the gateway IP address 								*
 ********************************************************************************************************/
unsigned int GateIp(NODE *remp, NODE *locp)
{
    return((locp->gate==0 || OnSubnet(remp->ip, locp)) ? remp->ip : locp->gate);
}


/********************************************************************************************************
 * Check an IP address to see if it is on a subnet, return 0 if not 									*
 ********************************************************************************************************/
short OnSubnet(unsigned int remip, NODE *locp)
{
    return(((remip ^ locp->ip) & locp->mask) == 0);
}