icmp6.c

这是一个同样来自贝尔实验室的和UNIX有着渊源的操作系统, 其简洁的设计和实现易于我们学习和理解

	np->ttl = HOP_LIMIT;
	np->vcf[0] = 0x06 << 4;
	ipriv->out[UnreachableV6]++;

	if(free)
		ipiput6(f, ifc, nbp);
	else {
		ipoput6(f, nbp, 0, MAXTTL, DFLTTOS, nil);
		return;
	}

clean:
	runlock(ifc);
	freeblist(bp);
}

extern void
icmpttlexceeded6(Fs *f, Ipifc *ifc, Block *bp)
{
	Block *nbp;
	IPICMP *np;
	Ip6hdr	*p;
	int osz = BLEN(bp);
	int sz = MIN(sizeof(IPICMP) + osz, v6MINTU);
	Proto	*icmp = f->t2p[ICMPv6];
	Icmppriv6 *ipriv = icmp->priv;

	p = (Ip6hdr *) bp->rp;

	if(isv6mcast(p->src)) 
		return;

	nbp = newIPICMP(sz);
	np = (IPICMP *) nbp->rp;

	if(ipv6anylocal(ifc, np->src)) {
		netlog(f, Logicmp, "send icmpttlexceeded6 -> s%I d%I\n", p->src, p->dst);
	}
	else {
		netlog(f, Logicmp, "icmpttlexceeded6 fail -> s%I d%I\n", p->src, p->dst);
		return;
	}

	memmove(np->dst, p->src, IPaddrlen);
	np->type = TimeExceedV6;
	np->code = 0;
	memmove(nbp->rp + sizeof(IPICMP), bp->rp, sz - sizeof(IPICMP));
	set_cksum(nbp);
	np->ttl = HOP_LIMIT;
	np->vcf[0] = 0x06 << 4;
	ipriv->out[TimeExceedV6]++;
	ipoput6(f, nbp, 0, MAXTTL, DFLTTOS, nil);
}

extern void
icmppkttoobig6(Fs *f, Ipifc *ifc, Block *bp)
{
	Block *nbp;
	IPICMP *np;
	Ip6hdr	*p;
	int osz = BLEN(bp);
	int sz = MIN(sizeof(IPICMP) + osz, v6MINTU);
	Proto	*icmp = f->t2p[ICMPv6];
	Icmppriv6 *ipriv = icmp->priv;

	p = (Ip6hdr *) bp->rp;

	if(isv6mcast(p->src)) 
		return;

	nbp = newIPICMP(sz);
	np = (IPICMP *) nbp->rp;

	if(ipv6anylocal(ifc, np->src)) {
		netlog(f, Logicmp, "send icmppkttoobig6 -> s%I d%I\n", p->src, p->dst);
	}
	else {
		netlog(f, Logicmp, "icmppkttoobig6 fail -> s%I d%I\n", p->src, p->dst);
		return;
	}

	memmove(np->dst, p->src, IPaddrlen);
	np->type = PacketTooBigV6;
	np->code = 0;
	hnputl(np->icmpid, ifc->maxtu - ifc->m->hsize);
	memmove(nbp->rp + sizeof(IPICMP), bp->rp, sz - sizeof(IPICMP));
	set_cksum(nbp);
	np->ttl = HOP_LIMIT;
	np->vcf[0] = 0x06 << 4;
	ipriv->out[PacketTooBigV6]++;
	ipoput6(f, nbp, 0, MAXTTL, DFLTTOS, nil);
}

/*
 * RFC 2461, pages 39-40, pages 57-58.
 */
static int
valid(Proto *icmp, Ipifc *ifc, Block *bp, Icmppriv6 *ipriv) {
	int 	sz, osz, unsp, n, ttl, iplen;
	int 	pktsz = BLEN(bp);
	uchar	*packet = bp->rp;
	IPICMP	*p = (IPICMP *) packet;
	Ndpkt	*np;

	USED(ifc);
	n = blocklen(bp);
	if(n < sizeof(IPICMP)) {
		ipriv->stats[HlenErrs6]++;
		netlog(icmp->f, Logicmp, "icmp hlen %d\n", n);
		goto err;
	}

	iplen = nhgets(p->ploadlen);
	if(iplen > n-IPV6HDR_LEN || (iplen % 1)) {
		ipriv->stats[LenErrs6]++;
		netlog(icmp->f, Logicmp, "icmp length %d\n", iplen);
		goto err;
	}

	// Rather than construct explicit pseudoheader, overwrite IPv6 header
	if(p->proto != ICMPv6) {
		// This code assumes no extension headers!!!
		netlog(icmp->f, Logicmp, "icmp error: extension header\n");
		goto err;
	}
	memset(packet, 0, 4);
	ttl = p->ttl;
	p->ttl = p->proto;
	p->proto = 0;
	if(ptclcsum(bp, 0, iplen + IPV6HDR_LEN)) {
		ipriv->stats[CsumErrs6]++;
		netlog(icmp->f, Logicmp, "icmp checksum error\n");
		goto err;
	}
	p->proto = p->ttl;
	p->ttl = ttl;

	/* additional tests for some pkt types */
	if( (p->type == NbrSolicit) ||
		(p->type == NbrAdvert) ||
		(p->type == RouterAdvert) ||
		(p->type == RouterSolicit) ||
		(p->type == RedirectV6) ) {

		if(p->ttl != HOP_LIMIT) {
			ipriv->stats[HoplimErrs6]++; 
			goto err; 
		}
		if(p->code != 0) {
			ipriv->stats[IcmpCodeErrs6]++; 
			goto err; 
		}

		switch (p->type) {
		case NbrSolicit:
		case NbrAdvert:
			np = (Ndpkt*) p;
			if(isv6mcast(np->target)) {
				ipriv->stats[TargetErrs6]++; 
				goto err; 
			}
			if(optexsts(np) && (np->olen == 0)) {
				ipriv->stats[OptlenErrs6]++; 
				goto err; 
			}
		
			if(p->type == NbrSolicit) {
				if(ipcmp(np->src, v6Unspecified) == 0) { 
					if(!issmcast(np->dst) || optexsts(np))  {
						ipriv->stats[AddrmxpErrs6]++; 
						goto err;
					}
				}
			}
		
			if(p->type == NbrAdvert) {
				if((isv6mcast(np->dst))&&(nhgets(np->icmpid) & Sflag)){
					ipriv->stats[AddrmxpErrs6]++; 
					goto err; 
				}
			}
			break;
	
		case RouterAdvert:
			if(pktsz - sizeof(Ip6hdr) < 16) {
				ipriv->stats[HlenErrs6]++; 
				goto err; 
			}
			if(!islinklocal(p->src)) {
				ipriv->stats[RouterAddrErrs6]++; 
				goto err; 
			}
			sz = sizeof(IPICMP) + 8;
			while ((sz+1) < pktsz) {
				osz = *(packet+sz+1);
				if(osz <= 0) {
					ipriv->stats[OptlenErrs6]++; 
					goto err; 
				}	
				sz += 8*osz;
			}
			break;
	
		case RouterSolicit:
			if(pktsz - sizeof(Ip6hdr) < 8) {
				ipriv->stats[HlenErrs6]++; 
				goto err; 
			}
			unsp = (ipcmp(p->src, v6Unspecified) == 0);
			sz = sizeof(IPICMP) + 8;
			while ((sz+1) < pktsz) {
				osz = *(packet+sz+1);
				if((osz <= 0) ||
					(unsp && (*(packet+sz) == slladd)) ) {
					ipriv->stats[OptlenErrs6]++; 
					goto err; 
				}
				sz += 8*osz;
			}
			break;
	
		case RedirectV6:
			//to be filled in
			break;
	
		default:
			goto err;
		}
	}

	return 1;

err:
	ipriv->stats[InErrors6]++; 
	return 0;
}

static int
targettype(Fs *f, Ipifc *ifc, uchar *target)
{
	Iplifc *lifc;
	int t;

	rlock(ifc);
	if(ipproxyifc(f, ifc, target)) {
		runlock(ifc);
		return t_uniproxy;
	}

	for(lifc = ifc->lifc; lifc; lifc = lifc->next) {
		if(ipcmp(lifc->local, target) == 0) {
			t = (lifc->tentative) ? t_unitent : t_unirany; 
			runlock(ifc);
			return t;
		}
	}

	runlock(ifc);
	return 0;
}

static void
icmpiput6(Proto *icmp, Ipifc *ipifc, Block *bp)
{
	uchar	*packet = bp->rp;
	IPICMP	*p = (IPICMP *)packet;
	Icmppriv6 *ipriv = icmp->priv;
	Block	*r;
	Proto	*pr;
	char	*msg, m2[128];
	Ndpkt* np;
	uchar pktflags;
	uchar lsrc[IPaddrlen];
	int refresh = 1;
	Iplifc *lifc;

	if(!valid(icmp, ipifc, bp, ipriv)) 
		goto raise;

	if(p->type <= Maxtype6)
		ipriv->in[p->type]++;
	else
		goto raise;

	switch(p->type) {
	case EchoRequestV6:
		r = mkechoreply6(bp);
		ipriv->out[EchoReply]++;
		ipoput6(icmp->f, r, 0, MAXTTL, DFLTTOS, nil);
		break;

	case UnreachableV6:
		if(p->code > 4)
			msg = unreachcode[icmp6_unkn_code];
		else
			msg = unreachcode[p->code];

		bp->rp += sizeof(IPICMP);
		if(blocklen(bp) < 8){
			ipriv->stats[LenErrs6]++;
			goto raise;
		}
		p = (IPICMP *)bp->rp;
		pr = Fsrcvpcolx(icmp->f, p->proto);
		if(pr != nil && pr->advise != nil) {
			(*pr->advise)(pr, bp, msg);
			return;
		}

		bp->rp -= sizeof(IPICMP);
		goticmpkt6(icmp, bp, 0);
		break;

	case TimeExceedV6:
		if(p->code == 0){
			sprint(m2, "ttl exceeded at %I", p->src);

			bp->rp += sizeof(IPICMP);
			if(blocklen(bp) < 8){
				ipriv->stats[LenErrs6]++;
				goto raise;
			}
			p = (IPICMP *)bp->rp;
			pr = Fsrcvpcolx(icmp->f, p->proto);
			if(pr != nil && pr->advise != nil) {
				(*pr->advise)(pr, bp, m2);
				return;
			}
			bp->rp -= sizeof(IPICMP);
		}

		goticmpkt6(icmp, bp, 0);
		break;

	case RouterAdvert:
	case RouterSolicit:
		/* using lsrc as a temp, munge hdr for goticmp6 
		memmove(lsrc, p->src, IPaddrlen);
		memmove(p->src, p->dst, IPaddrlen);
		memmove(p->dst, lsrc, IPaddrlen); */

		goticmpkt6(icmp, bp, p->type);
		break;

	case NbrSolicit:
		np = (Ndpkt*) p;
		pktflags = 0;
		switch (targettype(icmp->f, ipifc, np->target)) {
		case t_unirany:
			pktflags |= Oflag;
			/* fall through */

		case t_uniproxy: 
			if(ipcmp(np->src, v6Unspecified) != 0) {
				arpenter(icmp->f, V6, np->src, np->lnaddr, 8*np->olen-2, 0);
				pktflags |= Sflag;
			}
			if(ipv6local(ipifc, lsrc)) {
				icmpna(icmp->f, lsrc, 
				   (ipcmp(np->src, v6Unspecified)==0)?v6allnodesL:np->src,
				   np->target, ipifc->mac, pktflags); 
			}
			else
				freeblist(bp);
			break;

		case t_unitent:
			/* not clear what needs to be done. send up
			 * an icmp mesg saying don't use this address? */

		default:
			freeblist(bp);
		}

		break;

	case NbrAdvert:
		np = (Ndpkt*) p;

		/* if the target address matches one of the local interface 
		 * address and the local interface address has tentative bit set, 
		 * then insert into ARP table. this is so the duplication address 
		 * detection part of ipconfig can discover duplication through 
		 * the arp table
		 */
		lifc = iplocalonifc(ipifc, np->target);
		if(lifc && lifc->tentative)
			refresh = 0;
		arpenter(icmp->f, V6, np->target, np->lnaddr, 8*np->olen-2, refresh);
		freeblist(bp);
		break;

	case PacketTooBigV6:

	default:
		goticmpkt6(icmp, bp, 0);
		break;
	}
	return;

raise:
	freeblist(bp);

}

int
icmpstats6(Proto *icmp6, char *buf, int len)
{
	Icmppriv6 *priv;
	char *p, *e;
	int i;

	priv = icmp6->priv;
	p = buf;
	e = p+len;
	for(i = 0; i < Nstats6; i++)
		p = seprint(p, e, "%s: %lud\n", statnames6[i], priv->stats[i]);
	for(i = 0; i <= Maxtype6; i++){
		if(icmpnames6[i])
			p = seprint(p, e, "%s: %lud %lud\n", icmpnames6[i], priv->in[i], priv->out[i]);
/*		else
			p = seprint(p, e, "%d: %lud %lud\n", i, priv->in[i], priv->out[i]);
*/
	}
	return p - buf;
}


// need to import from icmp.c
extern int	icmpstate(Conv *c, char *state, int n);
extern char*	icmpannounce(Conv *c, char **argv, int argc);
extern char*	icmpconnect(Conv *c, char **argv, int argc);
extern void	icmpclose(Conv *c);

void
icmp6init(Fs *fs)
{
	Proto *icmp6 = smalloc(sizeof(Proto));

	icmp6->priv = smalloc(sizeof(Icmppriv6));
	icmp6->name = "icmpv6";
	icmp6->connect = icmpconnect;
	icmp6->announce = icmpannounce;
	icmp6->state = icmpstate;
	icmp6->create = icmpcreate6;
	icmp6->close = icmpclose;
	icmp6->rcv = icmpiput6;
	icmp6->stats = icmpstats6;
	icmp6->ctl = icmpctl6;
	icmp6->advise = icmpadvise6;
	icmp6->gc = nil;
	icmp6->ipproto = ICMPv6;
	icmp6->nc = 16;
	icmp6->ptclsize = sizeof(Icmpcb6);

	Fsproto(fs, icmp6);
}