Exemple #1
0
int
ip_vs_icmp_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
                   struct ip_vs_protocol *pp, int offset)
{
    struct rt6_info	*rt;	/* Route to the other host */
    int mtu;
    int rc;
    int local;

    EnterFunction(10);

    /* The ICMP packet for VS/TUN, VS/DR and LOCALNODE will be
       forwarded directly here, because there is no need to
       translate address/port back */
    if (IP_VS_FWD_METHOD(cp) != IP_VS_CONN_F_MASQ) {
        if (cp->packet_xmit)
            rc = cp->packet_xmit(skb, cp, pp);
        else
            rc = NF_ACCEPT;
        /* do not touch skb anymore */
        atomic_inc_unchecked(&cp->in_pkts);
        goto out;
    }

    /*
     * mangle and send the packet here (only for VS/NAT)
     */

    if (!(rt = __ip_vs_get_out_rt_v6(skb, cp->dest, &cp->daddr.in6, NULL,
                                     0, 1|2|4)))
        goto tx_error_icmp;

    local = __ip_vs_is_local_route6(rt);
    /*
     * Avoid duplicate tuple in reply direction for NAT traffic
     * to local address when connection is sync-ed
     */
#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
    if (cp->flags & IP_VS_CONN_F_SYNC && local) {
        enum ip_conntrack_info ctinfo;
        struct nf_conn *ct = ct = nf_ct_get(skb, &ctinfo);

        if (ct && !nf_ct_is_untracked(ct)) {
            IP_VS_DBG(10, "%s(): "
                      "stopping DNAT to local address %pI6\n",
                      __func__, &cp->daddr.in6);
            goto tx_error_put;
        }
    }
#endif

    /* From world but DNAT to loopback address? */
    if (local && skb->dev && !(skb->dev->flags & IFF_LOOPBACK) &&
            ipv6_addr_type(&rt->rt6i_dst.addr) & IPV6_ADDR_LOOPBACK) {
        IP_VS_DBG(1, "%s(): "
                  "stopping DNAT to loopback %pI6\n",
                  __func__, &cp->daddr.in6);
        goto tx_error_put;
    }

    /* MTU checking */
    mtu = dst_mtu(&rt->dst);
    if (skb->len > mtu && !skb_is_gso(skb)) {
        if (!skb->dev) {
            struct net *net = dev_net(skb_dst(skb)->dev);

            skb->dev = net->loopback_dev;
        }
        icmpv6_send(skb, ICMPV6_PKT_TOOBIG, 0, mtu);
        IP_VS_DBG_RL("%s(): frag needed\n", __func__);
        goto tx_error_put;
    }

    /* copy-on-write the packet before mangling it */
    if (!skb_make_writable(skb, offset))
        goto tx_error_put;

    if (skb_cow(skb, rt->dst.dev->hard_header_len))
        goto tx_error_put;

    ip_vs_nat_icmp_v6(skb, pp, cp, 0);

    if (!local || !skb->dev) {
        /* drop the old route when skb is not shared */
        skb_dst_drop(skb);
        skb_dst_set(skb, &rt->dst);
    } else {
        /* destined to loopback, do we need to change route? */
        dst_release(&rt->dst);
    }

    /* Another hack: avoid icmp_send in ip_fragment */
    skb->local_df = 1;

    IP_VS_XMIT_NAT(NFPROTO_IPV6, skb, cp, local);

    rc = NF_STOLEN;
    goto out;

tx_error_icmp:
    dst_link_failure(skb);
tx_error:
    dev_kfree_skb(skb);
    rc = NF_STOLEN;
out:
    LeaveFunction(10);
    return rc;
tx_error_put:
    dst_release(&rt->dst);
    goto tx_error;
}
Exemple #2
0
/*
 *	ICMP packet transmitter
 *	called by the ip_vs_in_icmp
 */
int
ip_vs_icmp_xmit(struct sk_buff *skb, struct ip_vs_conn *cp,
                struct ip_vs_protocol *pp, int offset)
{
    struct rtable	*rt;	/* Route to the other host */
    int mtu;
    int rc;
    int local;

    EnterFunction(10);

    /* The ICMP packet for VS/TUN, VS/DR and LOCALNODE will be
       forwarded directly here, because there is no need to
       translate address/port back */
    if (IP_VS_FWD_METHOD(cp) != IP_VS_CONN_F_MASQ) {
        if (cp->packet_xmit)
            rc = cp->packet_xmit(skb, cp, pp);
        else
            rc = NF_ACCEPT;
        /* do not touch skb anymore */
        atomic_inc_unchecked(&cp->in_pkts);
        goto out;
    }

    /*
     * mangle and send the packet here (only for VS/NAT)
     */

    if (!(rt = __ip_vs_get_out_rt(skb, cp->dest, cp->daddr.ip,
                                  RT_TOS(ip_hdr(skb)->tos),
                                  IP_VS_RT_MODE_LOCAL |
                                  IP_VS_RT_MODE_NON_LOCAL |
                                  IP_VS_RT_MODE_RDR)))
        goto tx_error_icmp;
    local = rt->rt_flags & RTCF_LOCAL;

    /*
     * Avoid duplicate tuple in reply direction for NAT traffic
     * to local address when connection is sync-ed
     */
#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
    if (cp->flags & IP_VS_CONN_F_SYNC && local) {
        enum ip_conntrack_info ctinfo;
        struct nf_conn *ct = ct = nf_ct_get(skb, &ctinfo);

        if (ct && !nf_ct_is_untracked(ct)) {
            IP_VS_DBG(10, "%s(): "
                      "stopping DNAT to local address %pI4\n",
                      __func__, &cp->daddr.ip);
            goto tx_error_put;
        }
    }
#endif

    /* From world but DNAT to loopback address? */
    if (local && ipv4_is_loopback(rt->rt_dst) &&
            rt_is_input_route(skb_rtable(skb))) {
        IP_VS_DBG(1, "%s(): "
                  "stopping DNAT to loopback %pI4\n",
                  __func__, &cp->daddr.ip);
        goto tx_error_put;
    }

    /* MTU checking */
    mtu = dst_mtu(&rt->dst);
    if ((skb->len > mtu) && (ip_hdr(skb)->frag_off & htons(IP_DF)) &&
            !skb_is_gso(skb)) {
        icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, htonl(mtu));
        IP_VS_DBG_RL("%s(): frag needed\n", __func__);
        goto tx_error_put;
    }

    /* copy-on-write the packet before mangling it */
    if (!skb_make_writable(skb, offset))
        goto tx_error_put;

    if (skb_cow(skb, rt->dst.dev->hard_header_len))
        goto tx_error_put;

    ip_vs_nat_icmp(skb, pp, cp, 0);

    if (!local) {
        /* drop the old route when skb is not shared */
        skb_dst_drop(skb);
        skb_dst_set(skb, &rt->dst);
    } else {
        ip_rt_put(rt);
        /*
         * Some IPv4 replies get local address from routes,
         * not from iph, so while we DNAT after routing
         * we need this second input/output route.
         */
        if (!__ip_vs_reroute_locally(skb))
            goto tx_error;
    }

    /* Another hack: avoid icmp_send in ip_fragment */
    skb->local_df = 1;

    IP_VS_XMIT_NAT(NFPROTO_IPV4, skb, cp, local);

    rc = NF_STOLEN;
    goto out;

tx_error_icmp:
    dst_link_failure(skb);
tx_error:
    dev_kfree_skb(skb);
    rc = NF_STOLEN;
out:
    LeaveFunction(10);
    return rc;
tx_error_put:
    ip_rt_put(rt);
    goto tx_error;
}
Exemple #3
0
int
ip_vs_icmp_xmit_v6(struct sk_buff *skb, struct ip_vs_conn *cp,
		struct ip_vs_protocol *pp, int offset, unsigned int hooknum,
		struct ip_vs_iphdr *ipvsh)
{
	struct rt6_info	*rt;	/* Route to the other host */
	int rc;
	int local;
	int rt_mode;

	EnterFunction(10);

	/* The ICMP packet for VS/TUN, VS/DR and LOCALNODE will be
	   forwarded directly here, because there is no need to
	   translate address/port back */
	if (IP_VS_FWD_METHOD(cp) != IP_VS_CONN_F_MASQ) {
		if (cp->packet_xmit)
			rc = cp->packet_xmit(skb, cp, pp, ipvsh);
		else
			rc = NF_ACCEPT;
		/* do not touch skb anymore */
		atomic_inc_unchecked(&cp->in_pkts);
		goto out;
	}

	/*
	 * mangle and send the packet here (only for VS/NAT)
	 */

	/* LOCALNODE from FORWARD hook is not supported */
	rt_mode = (hooknum != NF_INET_FORWARD) ?
		  IP_VS_RT_MODE_LOCAL | IP_VS_RT_MODE_NON_LOCAL |
		  IP_VS_RT_MODE_RDR : IP_VS_RT_MODE_NON_LOCAL;
	rcu_read_lock();
	local = __ip_vs_get_out_rt_v6(skb, cp->dest, &cp->daddr.in6, NULL,
				      ipvsh, 0, rt_mode);
	if (local < 0)
		goto tx_error;
	rt = (struct rt6_info *) skb_dst(skb);
	/*
	 * Avoid duplicate tuple in reply direction for NAT traffic
	 * to local address when connection is sync-ed
	 */
#if IS_ENABLED(CONFIG_NF_CONNTRACK)
	if (cp->flags & IP_VS_CONN_F_SYNC && local) {
		enum ip_conntrack_info ctinfo;
		struct nf_conn *ct = nf_ct_get(skb, &ctinfo);

		if (ct && !nf_ct_is_untracked(ct)) {
			IP_VS_DBG(10, "%s(): "
				  "stopping DNAT to local address %pI6\n",
				  __func__, &cp->daddr.in6);
			goto tx_error;
		}
	}
#endif

	/* From world but DNAT to loopback address? */
	if (local && skb->dev && !(skb->dev->flags & IFF_LOOPBACK) &&
	    ipv6_addr_type(&rt->rt6i_dst.addr) & IPV6_ADDR_LOOPBACK) {
		IP_VS_DBG(1, "%s(): "
			  "stopping DNAT to loopback %pI6\n",
			  __func__, &cp->daddr.in6);
		goto tx_error;
	}

	/* copy-on-write the packet before mangling it */
	if (!skb_make_writable(skb, offset))
		goto tx_error;

	if (skb_cow(skb, rt->dst.dev->hard_header_len))
		goto tx_error;

	ip_vs_nat_icmp_v6(skb, pp, cp, 0);

	/* Another hack: avoid icmp_send in ip_fragment */
	skb->local_df = 1;

	rc = ip_vs_nat_send_or_cont(NFPROTO_IPV6, skb, cp, local);
	rcu_read_unlock();
	goto out;

tx_error:
	kfree_skb(skb);
	rcu_read_unlock();
	rc = NF_STOLEN;
out:
	LeaveFunction(10);
	return rc;
}
Exemple #4
0
/*
 *	Handle ICMP messages in the inside-to-outside direction (outgoing).
 *	Find any that might be relevant, check against existing connections,
 *	forward to the right destination host if relevant.
 *	Currently handles error types - unreachable, quench, ttl exceeded.
 *	(Only used in VS/NAT)
 */
static int ip_vs_out_icmp(struct sk_buff **pskb, int *related)
{
	struct sk_buff *skb = *pskb;
	struct iphdr *iph;
	struct icmphdr	_icmph, *ic;
	struct iphdr	_ciph, *cih;	/* The ip header contained within the ICMP */
	struct ip_vs_conn *cp;
	struct ip_vs_protocol *pp;
	unsigned int offset, ihl, verdict;

	*related = 1;

	/* reassemble IP fragments */
	if (ip_hdr(skb)->frag_off & htons(IP_MF | IP_OFFSET)) {
		skb = ip_vs_gather_frags(skb, IP_DEFRAG_VS_OUT);
		if (!skb)
			return NF_STOLEN;
		*pskb = skb;
	}

	iph = ip_hdr(skb);
	offset = ihl = iph->ihl * 4;
	ic = skb_header_pointer(skb, offset, sizeof(_icmph), &_icmph);
	if (ic == NULL)
		return NF_DROP;

	IP_VS_DBG(12, "Outgoing ICMP (%d,%d) %u.%u.%u.%u->%u.%u.%u.%u\n",
		  ic->type, ntohs(icmp_id(ic)),
		  NIPQUAD(iph->saddr), NIPQUAD(iph->daddr));

	/*
	 * Work through seeing if this is for us.
	 * These checks are supposed to be in an order that means easy
	 * things are checked first to speed up processing.... however
	 * this means that some packets will manage to get a long way
	 * down this stack and then be rejected, but that's life.
	 */
	if ((ic->type != ICMP_DEST_UNREACH) &&
	    (ic->type != ICMP_SOURCE_QUENCH) &&
	    (ic->type != ICMP_TIME_EXCEEDED)) {
		*related = 0;
		return NF_ACCEPT;
	}

	/* Now find the contained IP header */
	offset += sizeof(_icmph);
	cih = skb_header_pointer(skb, offset, sizeof(_ciph), &_ciph);
	if (cih == NULL)
		return NF_ACCEPT; /* The packet looks wrong, ignore */

	pp = ip_vs_proto_get(cih->protocol);
	if (!pp)
		return NF_ACCEPT;

	/* Is the embedded protocol header present? */
	if (unlikely(cih->frag_off & htons(IP_OFFSET) &&
		     pp->dont_defrag))
		return NF_ACCEPT;

	IP_VS_DBG_PKT(11, pp, skb, offset, "Checking outgoing ICMP for");

	offset += cih->ihl * 4;

	/* The embedded headers contain source and dest in reverse order */
	cp = pp->conn_out_get(skb, pp, cih, offset, 1);
	if (!cp)
		return NF_ACCEPT;

	verdict = NF_DROP;

	if (IP_VS_FWD_METHOD(cp) != 0) {
		IP_VS_ERR("shouldn't reach here, because the box is on the"
			  "half connection in the tun/dr module.\n");
	}

	/* Ensure the checksum is correct */
	if (!skb_csum_unnecessary(skb) && ip_vs_checksum_complete(skb, ihl)) {
		/* Failed checksum! */
		IP_VS_DBG(1, "Forward ICMP: failed checksum from %d.%d.%d.%d!\n",
			  NIPQUAD(iph->saddr));
		goto out;
	}

	if (IPPROTO_TCP == cih->protocol || IPPROTO_UDP == cih->protocol)
		offset += 2 * sizeof(__u16);
	if (!ip_vs_make_skb_writable(pskb, offset))
		goto out;
	skb = *pskb;

	ip_vs_nat_icmp(skb, pp, cp, 1);

	/* do the statistics and put it back */
	ip_vs_out_stats(cp, skb);

	skb->ipvs_property = 1;
	verdict = NF_ACCEPT;

  out:
	__ip_vs_conn_put(cp);

	return verdict;
}
Exemple #5
0
/*
 *	Handle ICMP messages in the outside-to-inside direction (incoming)
 *	and sometimes in outgoing direction from ip_vs_forward_icmp.
 *	Find any that might be relevant, check against existing connections,
 *	forward to the right destination host if relevant.
 *	Currently handles error types - unreachable, quench, ttl exceeded.
 */
static int ip_vs_in_icmp(struct sk_buff **skb_p)
{
	struct sk_buff	*skb   = *skb_p;
	struct iphdr    *iph;
	struct icmphdr  *icmph;
	struct iphdr    *ciph;	/* The ip header contained within the ICMP */
	__u16	        *pptr;	/* port numbers from TCP/UDP contained header */
	unsigned short   len;
	unsigned short	clen, csize;
	struct ip_vs_conn *cp;
	struct rtable *rt;			/* Route to the other host */
	int    mtu;

	if (skb_is_nonlinear(skb)) {
		if (skb_linearize(skb, GFP_ATOMIC) != 0)
			return NF_DROP;
	}

	iph = skb->nh.iph;
	ip_send_check(iph);
	icmph = (struct icmphdr *)((char *)iph + (iph->ihl << 2));
	len = ntohs(iph->tot_len) - (iph->ihl<<2);
	if (len < sizeof(struct icmphdr))
		return NF_DROP;

	IP_VS_DBG(12, "icmp in (%d,%d) %u.%u.%u.%u -> %u.%u.%u.%u\n",
		  icmph->type, ntohs(icmp_id(icmph)),
		  NIPQUAD(iph->saddr), NIPQUAD(iph->daddr));

	if ((icmph->type != ICMP_DEST_UNREACH) &&
	    (icmph->type != ICMP_SOURCE_QUENCH) &&
	    (icmph->type != ICMP_TIME_EXCEEDED))
		return NF_ACCEPT;

	/*
	 * If we get here we have an ICMP error of one of the above 3 types
	 * Now find the contained IP header
	 */
	clen = len - sizeof(struct icmphdr);
	if (clen < sizeof(struct iphdr))
		return NF_DROP;
	ciph = (struct iphdr *) (icmph + 1);
	csize = ciph->ihl << 2;
	if (clen < csize)
		return NF_DROP;

	/* We are only interested ICMPs generated from TCP or UDP packets */
	if (ciph->protocol != IPPROTO_UDP && ciph->protocol != IPPROTO_TCP)
		return NF_ACCEPT;

	/* Skip non-first embedded TCP/UDP fragments */
	if (ciph->frag_off & __constant_htons(IP_OFFSET))
		return NF_ACCEPT;

	/* We need at least TCP/UDP ports here */
	if (clen < csize + sizeof(struct udphdr))
		return NF_DROP;

	/* Ensure the checksum is correct */
	if (ip_compute_csum((unsigned char *) icmph, len)) {
		/* Failed checksum! */
		IP_VS_ERR_RL("incoming ICMP: failed checksum from "
			     "%d.%d.%d.%d!\n", NIPQUAD(iph->saddr));
		return NF_DROP;
	}

	pptr = (__u16 *)&(((char *)ciph)[csize]);

	IP_VS_DBG(11, "Handling incoming ICMP for "
		  "%u.%u.%u.%u:%d -> %u.%u.%u.%u:%d\n",
		  NIPQUAD(ciph->saddr), ntohs(pptr[0]),
		  NIPQUAD(ciph->daddr), ntohs(pptr[1]));

	/* This is pretty much what ip_vs_conn_in_get() does,
	   except parameters are in the reverse order */
	cp = ip_vs_conn_in_get(ciph->protocol,
			       ciph->daddr, pptr[1],
			       ciph->saddr, pptr[0]);
	if (cp == NULL)
		return NF_ACCEPT;

	ip_vs_in_stats(cp, skb);

	/* The ICMP packet for VS/TUN, VS/DR and LOCALNODE will be
	   forwarded directly here, because there is no need to
	   translate address/port back */
	if (IP_VS_FWD_METHOD(cp) != IP_VS_CONN_F_MASQ) {
		int ret;
		if (cp->packet_xmit)
			ret = cp->packet_xmit(skb, cp);
		else
			ret = NF_ACCEPT;
		atomic_inc(&cp->in_pkts);
		ip_vs_conn_put(cp);
		return ret;
	}

	/*
	 * mangle and send the packet here
	 */
	if (!(rt = __ip_vs_get_out_rt(cp, RT_TOS(iph->tos))))
		goto tx_error_icmp;

	/* MTU checking */
	mtu = rt->u.dst.pmtu;
	if ((skb->len > mtu) && (iph->frag_off&__constant_htons(IP_DF))) {
		ip_rt_put(rt);
		icmp_send(skb, ICMP_DEST_UNREACH,ICMP_FRAG_NEEDED, htonl(mtu));
		IP_VS_DBG_RL("ip_vs_in_icmp(): frag needed\n");
		goto tx_error;
	}

	/* drop old route */
	dst_release(skb->dst);
	skb->dst = &rt->u.dst;

	/* copy-on-write the packet before mangling it */
	if (ip_vs_skb_cow(skb, rt->u.dst.dev->hard_header_len,
			  &iph, (unsigned char**)&icmph)) {
		ip_vs_conn_put(cp);
		return NF_DROP;
	}
	ciph = (struct iphdr *) (icmph + 1);
	pptr = (__u16 *)&(((char *)ciph)[csize]);

	/* The ICMP packet for VS/NAT must be written to correct addresses
	   before being forwarded to the right server */

	/* First change the dest IP address, and recalc checksum */
	iph->daddr = cp->daddr;
	ip_send_check(iph);

	/* Now change the *source* address in the contained IP */
	ciph->saddr = cp->daddr;
	ip_send_check(ciph);

	/* the TCP/UDP source port - cannot redo check */
	pptr[0] = cp->dport;

	/* And finally the ICMP checksum */
	icmph->checksum = 0;
	icmph->checksum = ip_compute_csum((unsigned char *) icmph, len);
	skb->ip_summed = CHECKSUM_UNNECESSARY;

	IP_VS_DBG(11, "Forwarding incoming ICMP to "
		  "%u.%u.%u.%u:%d -> %u.%u.%u.%u:%d\n",
		  NIPQUAD(ciph->saddr), ntohs(pptr[0]),
		  NIPQUAD(ciph->daddr), ntohs(pptr[1]));

#ifdef CONFIG_NETFILTER_DEBUG
	skb->nf_debug = 1 << NF_IP_LOCAL_OUT;
#endif /* CONFIG_NETFILTER_DEBUG */
	ip_send(skb);
	ip_vs_conn_put(cp);
	return NF_STOLEN;

  tx_error_icmp:
	dst_link_failure(skb);
  tx_error:
	dev_kfree_skb(skb);
	ip_vs_conn_put(cp);
	return NF_STOLEN;
}
Exemple #6
0
/*
 *	Handle ICMP messages in the inside-to-outside direction (outgoing).
 *	Find any that might be relevant, check against existing connections,
 *	forward to the right destination host if relevant.
 *	Currently handles error types - unreachable, quench, ttl exceeded.
 *      (Only used in VS/NAT)
 */
static int ip_vs_out_icmp(struct sk_buff **skb_p)
{
	struct sk_buff	*skb   = *skb_p;
	struct iphdr	*iph;
	struct icmphdr	*icmph;
	struct iphdr	*ciph;	/* The ip header contained within the ICMP */
	__u16		*pptr;	/* port numbers from TCP/UDP contained header */
	unsigned short	ihl;
	unsigned short	len;
	unsigned short	clen, csize;
	struct ip_vs_conn *cp;

	/* reassemble IP fragments, but will it happen in ICMP packets?? */
	if (skb->nh.iph->frag_off & __constant_htons(IP_MF|IP_OFFSET)) {
		skb = ip_defrag(skb, IP_DEFRAG_VS_OUT);
		if (!skb)
			return NF_STOLEN;
		*skb_p = skb;
	}

	if (skb_is_nonlinear(skb)) {
		if (skb_linearize(skb, GFP_ATOMIC) != 0)
			return NF_DROP;
		ip_send_check(skb->nh.iph);
	}

	iph = skb->nh.iph;
	ihl = iph->ihl << 2;
	icmph = (struct icmphdr *)((char *)iph + ihl);
	len   = ntohs(iph->tot_len) - ihl;
	if (len < sizeof(struct icmphdr))
		return NF_DROP;

	IP_VS_DBG(12, "outgoing ICMP (%d,%d) %u.%u.%u.%u->%u.%u.%u.%u\n",
		  icmph->type, ntohs(icmp_id(icmph)),
		  NIPQUAD(iph->saddr), NIPQUAD(iph->daddr));

	/*
	 * Work through seeing if this is for us.
	 * These checks are supposed to be in an order that means easy
	 * things are checked first to speed up processing.... however
	 * this means that some packets will manage to get a long way
	 * down this stack and then be rejected, but that's life.
	 */
	if ((icmph->type != ICMP_DEST_UNREACH) &&
	    (icmph->type != ICMP_SOURCE_QUENCH) &&
	    (icmph->type != ICMP_TIME_EXCEEDED))
		return NF_ACCEPT;

	/* Now find the contained IP header */
	clen = len - sizeof(struct icmphdr);
	if (clen < sizeof(struct iphdr))
		return NF_DROP;
	ciph = (struct iphdr *) (icmph + 1);
	csize = ciph->ihl << 2;
	if (clen < csize)
		return NF_DROP;

	/* We are only interested ICMPs generated from TCP or UDP packets */
	if (ciph->protocol != IPPROTO_UDP && ciph->protocol != IPPROTO_TCP)
		return NF_ACCEPT;

	/* Skip non-first embedded TCP/UDP fragments */
	if (ciph->frag_off & __constant_htons(IP_OFFSET))
		return NF_ACCEPT;

	/* We need at least TCP/UDP ports here */
	if (clen < csize + sizeof(struct udphdr))
		return NF_DROP;

	/*
	 * Find the ports involved - this packet was
	 * incoming so the ports are right way round
	 * (but reversed relative to outer IP header!)
	 */
	pptr = (__u16 *)&(((char *)ciph)[csize]);

	/* Ensure the checksum is correct */
	if (ip_compute_csum((unsigned char *) icmph, len)) {
		/* Failed checksum! */
		IP_VS_DBG(1, "forward ICMP: failed checksum from %d.%d.%d.%d!\n",
			  NIPQUAD(iph->saddr));
		return NF_DROP;
	}

	IP_VS_DBG(11, "Handling outgoing ICMP for "
		  "%u.%u.%u.%u:%d -> %u.%u.%u.%u:%d\n",
		  NIPQUAD(ciph->saddr), ntohs(pptr[0]),
		  NIPQUAD(ciph->daddr), ntohs(pptr[1]));

	/* ciph content is actually <protocol, caddr, cport, daddr, dport> */
	cp = ip_vs_conn_out_get(ciph->protocol, ciph->daddr, pptr[1],
				ciph->saddr, pptr[0]);
	if (!cp)
		return NF_ACCEPT;

	if (IP_VS_FWD_METHOD(cp) != 0) {
		IP_VS_ERR("shouldn't reach here, because the box is on the"
			  "half connection in the tun/dr module.\n");
	}

	/* Now we do real damage to this packet...! */
	/* First change the source IP address, and recalc checksum */
	iph->saddr = cp->vaddr;
	ip_send_check(iph);

	/* Now change the *dest* address in the contained IP */
	ciph->daddr = cp->vaddr;
	ip_send_check(ciph);

	/* the TCP/UDP dest port - cannot redo check */
	pptr[1] = cp->vport;

	/* And finally the ICMP checksum */
	icmph->checksum = 0;
	icmph->checksum = ip_compute_csum((unsigned char *) icmph, len);
	skb->ip_summed = CHECKSUM_UNNECESSARY;

	/* do the statistics and put it back */
	ip_vs_out_stats(cp, skb);
	ip_vs_conn_put(cp);

	IP_VS_DBG(11, "Forwarding correct outgoing ICMP to "
		  "%u.%u.%u.%u:%d -> %u.%u.%u.%u:%d\n",
		  NIPQUAD(ciph->saddr), ntohs(pptr[0]),
		  NIPQUAD(ciph->daddr), ntohs(pptr[1]));

	skb->nfcache |= NFC_IPVS_PROPERTY;

	return NF_ACCEPT;
}