ip_input.c

<B>Digital的Unix操作系统VAX 4.2源码</B>

			case IPOPT_TS_TSONLY:
				break;

			case IPOPT_TS_TSANDADDR:
				if (ipt->ipt_ptr + sizeof(n_time) +
				    sizeof(struct in_addr) > ipt->ipt_len)
					goto bad;
				ia = ifptoia(ifp);
				bcopy((caddr_t)&IA_SIN(ia)->sin_addr,
				    (caddr_t)sin, sizeof(struct in_addr));
				ipt->ipt_ptr += sizeof(struct in_addr);
				break;

			case IPOPT_TS_PRESPEC:
				if (ipt->ipt_ptr + sizeof(n_time) +
				    sizeof(struct in_addr) > ipt->ipt_len)
					goto bad;
				bcopy((caddr_t)sin, (caddr_t)&ipaddr.sin_addr,
				    sizeof(struct in_addr));
				if (ifa_ifwithaddr((struct sockaddr *)&ipaddr) == 0)
					continue;
				ipt->ipt_ptr += sizeof(struct in_addr);
				break;

			default:
				goto bad;
			}
			ntime = iptime();
			bcopy((caddr_t)&ntime, (caddr_t)cp + ipt->ipt_ptr - 1,
			    sizeof(n_time));
			ipt->ipt_ptr += sizeof(n_time);
		}
	}
	return (0);
bad:
	ip->ip_len -= sizeof(struct ip);  /* deduct header added by ipintr() */
	icmp_error(ip, type, code, ifp, NULL);
	/* fallthrough */
bad2:
	IPSTAT(ips_badoptions++); /* track number of bad options */
	return (1);
}

/*
 * Given address of next destination (final or next hop),
 * return internet address info of interface to be used to get there.
 */
struct in_ifaddr *
ip_rtaddr(dst)
	 struct in_addr dst;
{
	register struct sockaddr_in *sin;
	register struct in_ifaddr *ia;

	RTLOCK();
	sin = (struct sockaddr_in *) &ipforward_rt.ro_dst;

	if (ipforward_rt.ro_rt == 0 || dst.s_addr != sin->sin_addr.s_addr) {
		if (ipforward_rt.ro_rt) {
			rtfree(ipforward_rt.ro_rt);
			ipforward_rt.ro_rt = 0;
		}
		sin->sin_family = AF_INET;
		sin->sin_addr = dst;
		rtalloc(&ipforward_rt);
	}
	if (ipforward_rt.ro_rt == 0){
		RTUNLOCK();
		return ((struct in_ifaddr *)0);
	}

	/*
	 * Find address associated with outgoing interface.
	 */
	for (ia = in_ifaddr; ia; ia = ia->ia_next)
		if (ia->ia_ifp == ipforward_rt.ro_rt->rt_ifp)
			break;
	RTUNLOCK();
	return (ia);
}

/*
 * Save incoming source route for use in replies,
 * to be picked up later by ip_srcroute if the receiver is interested.
 */
save_rte(option, dst)
	u_char *option;
	struct in_addr dst;
{
	unsigned olen;
	extern ipprintfs;

	olen = option[IPOPT_OLEN];
	if (olen > sizeof(ip_srcrt) - 1) {
		if (ipprintfs)
			printf("save_rte: olen %d\n", olen);
		return;
	}
	bcopy((caddr_t)option, (caddr_t)ip_srcrt.srcopt, olen);
	ip_nhops = (olen - IPOPT_OFFSET - 1) / sizeof(struct in_addr);
	ip_srcrt.route[ip_nhops++] = dst;
}

/*
 * Retrieve incoming source route for use in replies,
 * in the same form used by setsockopt.
 * The first hop is placed before the options, will be removed later.
 */
struct mbuf *
ip_srcroute()
{
	register struct in_addr *p, *q;
	register struct mbuf *m;

	if (ip_nhops == 0)
		return ((struct mbuf *)0);
	m = m_get(M_DONTWAIT, MT_SOOPTS);
	if (m == 0)
		return ((struct mbuf *)0);
	m->m_len = ip_nhops * sizeof(struct in_addr) + IPOPT_OFFSET + 1 + 1;

	/*
	 * First save first hop for return route
	 */
	p = &ip_srcrt.route[ip_nhops - 1];
	*(mtod(m, struct in_addr *)) = *p--;

	/*
	 * Copy option fields and padding (nop) to mbuf.
	 */
	ip_srcrt.nop = IPOPT_NOP;
	bcopy((caddr_t)&ip_srcrt, mtod(m, caddr_t) + sizeof(struct in_addr),
	    IPOPT_OFFSET + 1 + 1);
	q = (struct in_addr *)(mtod(m, caddr_t) +
	    sizeof(struct in_addr) + IPOPT_OFFSET + 1 + 1);
	/*
	 * Record return path as an IP source route,
	 * reversing the path (pointers are now aligned).
	 */
	while (p >= ip_srcrt.route)
		*q++ = *p--;
	return (m);
}

/*
 * Strip out IP options, at higher
 * level protocol in the kernel.
 * Second argument is buffer to which options
 * will be moved, and return value is their length.
 */
ip_stripoptions(ip, mopt)
	struct ip *ip;
	struct mbuf *mopt;
{
	register int i;
	register struct mbuf *m;
	register caddr_t opts;
	int olen, optsoff = 0;

	olen = (ip->ip_hl<<2) - sizeof (struct ip);
	m = dtom(ip);
	opts = (caddr_t)(ip + 1);

	if (mopt) {
		/*
		 * If m_len is 0, we're dealing with an option set which
		 * ip_srcroute found no source routing in.  So, we've got an
		 * empty mbuf, into the * beginning of which we have to coerce
		 * a "first hop" address.  In a packet with no source routing,
		 * this would be the destination * address.  Otherwise, m_len
		 * is real, and we're just appending to the mbuf coming out
		 * of ip_srcroute.
		 */
		if (!mopt->m_len) {
			mopt->m_len = sizeof(struct in_addr);
			bcopy(&ip->ip_dst, mtod(mopt, caddr_t), mopt->m_len);
		}

		/*
		 * Push the rest of the options in.  We don't have to worry
		 * about the other IP level options like we do the source
		 * routing, so just search for them and insert them into the
		 * mbuf.  Notice that anything dealing with source routing is
		 * ignored, since you would want to do that in ip_srcroute
		 * instead.
		 */
		while (optsoff + 1 <= olen) {
			switch(opts[optsoff]) {
			case IPOPT_LSRR:
			case IPOPT_SSRR:
				optsoff += opts[optsoff + IPOPT_OLEN];
				break;
			case IPOPT_EOL:
			case IPOPT_NOP:
				mopt->m_dat[mopt->m_len++] = opts[optsoff++];
				break;
			default:
				bcopy(&opts[optsoff],&mopt->m_dat[mopt->m_len],
					opts[optsoff + IPOPT_OLEN]);
				mopt->m_len += opts[optsoff + IPOPT_OLEN];
				optsoff += opts[optsoff + IPOPT_OLEN];
				break;
			}
		}
		mopt->m_off = MMINOFF;
	}  

	i = m->m_len - (sizeof (struct ip) + olen);
	bcopy(opts  + olen, opts, (unsigned)i);
	m->m_len -= olen;
	ip->ip_hl = sizeof(struct ip) >> 2;
}

u_char inetctlerrmap[PRC_NCMDS] = {
	0,		0,		0,		0,
	0,		0,		EHOSTDOWN,	EHOSTUNREACH,
	ENETUNREACH,	EHOSTUNREACH,	ECONNREFUSED,	ECONNREFUSED,
	EMSGSIZE,	EHOSTUNREACH,	0,		0,
	0,		0,		0,		0,
	ENOPROTOOPT
};

#ifndef IPFORWARDING
#define IPFORWARDING	1
#endif
#ifndef IPSENDREDIRECTS
#define IPSENDREDIRECTS 1
#endif
int	ipprintfs = 0;
int	ipforwarding = IPFORWARDING;
extern int in_interfaces;
int ipsendredirects = IPSENDREDIRECTS;
int ipgateway = 0;

/*
 * Forward a packet.  If some error occurs return the sender
 * an icmp packet.  Note we can't always generate a meaningful
 * icmp message because icmp doesn't have a large enough repertoire
 * of codes and types.
 *
 * If not forwarding (possibly because we have only a single external
 * network), just drop the packet.  This could be confusing if ipforwarding
 * was zero but some routing protocol was advancing us as a gateway
 * to somewhere.  However, we must let the routing protocol deal with that.
 */
/*
 * SMP: No smp locks held coming in.
 * No lock held for call to ip_output. 5.27.87.us
 */
ip_forward(ip, ifp)
	register struct ip *ip;
	struct ifnet *ifp;
{
	register int error, type = 0, code;
	register struct sockaddr_in *sin;
	struct mbuf *mcopy;
	struct in_addr dest;

	dest.s_addr = 0;
	if (ipprintfs)
		printf("forward: src %x dst %x ttl %x\n", ip->ip_src,
			ip->ip_dst, ip->ip_ttl);
	ip->ip_id = htons(ip->ip_id);
	if (ipforwarding == 0 || in_interfaces <= 1) {
		IPSTAT(ips_cantforward++);
		if (ipgateway) {
			/* can't tell difference between net and host */
			type = ICMP_UNREACH, code = ICMP_UNREACH_NET;
			goto sendicmp;
		} else {
			m_freem(dtom(ip));
			return;
		}	
	}
	if (in_canforward(ip->ip_dst) == 0) {
		m_freem(dtom(ip));
		return;
	}
	if (ip->ip_ttl <= IPTTLDEC) {
		type = ICMP_TIMXCEED, code = ICMP_TIMXCEED_INTRANS;
		goto sendicmp;
	}
	ip->ip_ttl -= IPTTLDEC;

	/*
	 * Save at most 64 bytes of the packet in case
	 * we need to generate an ICMP message to the src.
	 */
	mcopy = m_copy(dtom(ip), 0, imin((int)ip->ip_len, 64));
	RTLOCK();
	sin = (struct sockaddr_in *)&ipforward_rt.ro_dst;
	if (ipforward_rt.ro_rt == 0 ||
	    ip->ip_dst.s_addr != sin->sin_addr.s_addr) {
		if (ipforward_rt.ro_rt) {
			rtfree(ipforward_rt.ro_rt);
			ipforward_rt.ro_rt = 0;
		}
		sin->sin_family = AF_INET;
		sin->sin_addr = ip->ip_dst;
		rtalloc(&ipforward_rt);
	}
	/*
	 * If forwarding packet using same interface that it came in on,
	 * perhaps should send a redirect to sender to shortcut a hop.
	 * Only send redirect if source is sending directly to us,
	 * and if packet was not source routed (or has any options).
	 * Also, don't send redirect if forwarding using a default route
	 * or a route modfied by a redirect.
	 */
#define	satosin(sa)	((struct sockaddr_in *)(sa))
	if (ipforward_rt.ro_rt && ipforward_rt.ro_rt->rt_ifp == ifp &&
	    (ipforward_rt.ro_rt->rt_flags & (RTF_DYNAMIC|RTF_MODIFIED)) == 0 &&
	    satosin(&ipforward_rt.ro_rt->rt_dst)->sin_addr.s_addr != 0 &&
	    ipsendredirects && ip->ip_hl == (sizeof(struct ip) >> 2)) {
		struct in_ifaddr *ia;
		u_long src = ntohl(ip->ip_src.s_addr);
		u_long dst = ntohl(ip->ip_dst.s_addr);

		if ((ia = ifptoia(ifp)) &&
		   (src & ia->ia_subnetmask) == ia->ia_subnet) {
		    if (ipforward_rt.ro_rt->rt_flags & RTF_GATEWAY)
			dest = satosin(&ipforward_rt.ro_rt->rt_gateway)->sin_addr;
		    else
			dest = ip->ip_dst;
		    /*
		     * If the destination is reached by a route to host,
		     * is on a subnet of a local net, or is directly
		     * on the attached net (!), use host redirect.
		     * (We may be the correct first hop for other subnets.)
		     */
		    type = ICMP_REDIRECT;
		    code = ICMP_REDIRECT_NET;
		    if ((ipforward_rt.ro_rt->rt_flags & RTF_HOST) ||
		       (ipforward_rt.ro_rt->rt_flags & RTF_GATEWAY) == 0)
			code = ICMP_REDIRECT_HOST;
		    else{ 
		    for (ia = in_ifaddr; ia = ia->ia_next; )
			if ((dst & ia->ia_netmask) == ia->ia_net) {
			    if (ia->ia_subnetmask != ia->ia_netmask)
				    code = ICMP_REDIRECT_HOST;
			    break;
			}
		    }
		    if (ipprintfs)
		        printf("redirect (%d) to %x\n", code, dest);
		}
	}
	RTUNLOCK();
	/* SMP: call ip_output with no smp lock.  4.21.87.us */
	error = ip_output(dtom(ip), (struct mbuf *)0, &ipforward_rt,
		IP_FORWARDING, NULL);
	if (error) { 
		IPSTAT(ips_cantforward++);
	} else if (type) {
		IPSTAT(ips_redirectsent++);
	} else {
		if (mcopy)
			m_freem(mcopy);
		IPSTAT(ips_forward++);
		return;
	}
	if (mcopy == NULL)
		return;
	ip = mtod(mcopy, struct ip *);
	type = ICMP_UNREACH;
	switch (error) {

	case 0:				/* forwarded, but need redirect */
		type = ICMP_REDIRECT;
		/* code set above */
		break;

	case ENETUNREACH:
	case ENETDOWN:
		if (in_localaddr(ip->ip_dst))
			code = ICMP_UNREACH_HOST;
		else
		code = ICMP_UNREACH_NET;
		break;

	case EMSGSIZE:
		code = ICMP_UNREACH_NEEDFRAG;
		break;

	case EPERM:
		code = ICMP_UNREACH_PORT;
		break;

	case ENOBUFS:
		type = ICMP_SOURCEQUENCH;
		break;

	case EHOSTDOWN:
	case EHOSTUNREACH:
		code = ICMP_UNREACH_HOST;
		break;
	}
sendicmp:
	icmp_error(ip, type, code, ifp, dest);
}