icmphdr.c

uCLinux下的一个TCP/IP协议栈源码

/* ICMP header conversion routines
 */
#include "global.h"
#include "mbuf.h"
#include "internet.h"
#include "ip.h"
#include "icmp.h"

/* Generate ICMP header in network byte order, link data, compute checksum */
void
htonicmp(
struct icmp *icmp,
struct mbuf **bpp
){
	register uint8 *cp;
	uint16 checksum;

	pushdown(bpp,NULL,ICMPLEN);
	cp = (*bpp)->data;

	*cp++ = icmp->type;
	*cp++ = icmp->code;
	cp = put16(cp,0);		/* Clear checksum */
	switch(icmp->type){
	case ICMP_DEST_UNREACH:
		if(icmp->code == ICMP_FRAG_NEEDED){
			/* Deering/Mogul max MTU indication */
			cp = put16(cp,0);
			cp = put16(cp,icmp->args.mtu);
		} else
			cp = put32(cp,0L);
		break;
	case ICMP_PARAM_PROB:
		*cp++ = icmp->args.pointer;
		*cp++ = 0;
		cp = put16(cp,0);
		break;
	case ICMP_REDIRECT:
		cp = put32(cp,icmp->args.address);
		break;
	case ICMP_ECHO:
	case ICMP_ECHO_REPLY:
	case ICMP_TIMESTAMP:
	case ICMP_TIME_REPLY:
	case ICMP_INFO_RQST:
	case ICMP_INFO_REPLY:
		cp = put16(cp,icmp->args.echo.id);
		cp = put16(cp,icmp->args.echo.seq);
		break;
	default:
		cp = put32(cp,0L);
		break;
	}
	/* Compute checksum, and stash result */
	checksum = cksum(NULL,*bpp,len_p(*bpp));
	cp = &(*bpp)->data[2];
	cp = put16(cp,checksum);
}
/* Pull off ICMP header */
int
ntohicmp(icmp,bpp)
struct icmp *icmp;
struct mbuf **bpp;
{
	uint8 icmpbuf[8];

	if(icmp == (struct icmp *)NULL)
		return -1;
	if(pullup(bpp,icmpbuf,8) != 8)
		return -1;
	icmp->type = icmpbuf[0];
	icmp->code = icmpbuf[1];
	switch(icmp->type){
	case ICMP_DEST_UNREACH:
		/* Retrieve Deering/Mogul MTU value */
		if(icmp->code == ICMP_FRAG_NEEDED)
			icmp->args.mtu = get16(&icmpbuf[6]);
		break;
	case ICMP_PARAM_PROB:
		icmp->args.pointer = icmpbuf[4];
		break;
	case ICMP_REDIRECT:
		icmp->args.address = get32(&icmpbuf[4]);
		break;
	case ICMP_ECHO:
	case ICMP_ECHO_REPLY:
	case ICMP_TIMESTAMP:
	case ICMP_TIME_REPLY:
	case ICMP_INFO_RQST:
	case ICMP_INFO_REPLY:
		icmp->args.echo.id = get16(&icmpbuf[4]);
		icmp->args.echo.seq = get16(&icmpbuf[6]);
		break;
	}
	return 0;
}