src/ip6_icmp.c - libslirp - Git at Google

 /* SPDX-License-Identifier: BSD-3-Clause */
 /*
  * Copyright (c) 2013
  * Guillaume Subiron, Yann Bordenave, Serigne Modou Wagne.
  */

 #include "slirp.h"
 #include "ip6_icmp.h"

 #define NDP_Interval \
     g_rand_int_range(slirp->grand, NDP_MinRtrAdvInterval, NDP_MaxRtrAdvInterval)

 static void ra_timer_handler(void *opaque)
 {
     Slirp *slirp = opaque;

     slirp->cb->timer_mod(slirp->ra_timer,
                          slirp->cb->clock_get_ns(slirp->opaque) / SCALE_MS +
                              NDP_Interval,
                          slirp->opaque);
     ndp_send_ra(slirp);
 }

 void icmp6_init(Slirp *slirp)
 {
     if (!slirp->in6_enabled) {
         return;
     }

     slirp->ra_timer =
         slirp->cb->timer_new(ra_timer_handler, slirp, slirp->opaque);
     slirp->cb->timer_mod(slirp->ra_timer,
                          slirp->cb->clock_get_ns(slirp->opaque) / SCALE_MS +
                              NDP_Interval,
                          slirp->opaque);
 }

 void icmp6_cleanup(Slirp *slirp)
 {
     if (!slirp->in6_enabled) {
         return;
     }

     slirp->cb->timer_free(slirp->ra_timer, slirp->opaque);
 }

 static void icmp6_send_echoreply(struct mbuf *m, Slirp *slirp, struct ip6 *ip,
                                  struct icmp6 *icmp)
 {
     struct mbuf *t = m_get(slirp);
     t->m_len = sizeof(struct ip6) + ntohs(ip->ip_pl);
     memcpy(t->m_data, m->m_data, t->m_len);

     /* IPv6 Packet */
     struct ip6 *rip = mtod(t, struct ip6 *);
     rip->ip_dst = ip->ip_src;
     rip->ip_src = ip->ip_dst;

     /* ICMPv6 packet */
     t->m_data += sizeof(struct ip6);
     struct icmp6 *ricmp = mtod(t, struct icmp6 *);
     ricmp->icmp6_type = ICMP6_ECHO_REPLY;
     ricmp->icmp6_cksum = 0;

     /* Checksum */
     t->m_data -= sizeof(struct ip6);
     ricmp->icmp6_cksum = ip6_cksum(t);

     ip6_output(NULL, t, 0);
 }

 void icmp6_forward_error(struct mbuf *m, uint8_t type, uint8_t code, struct in6_addr *src)
 {
     Slirp *slirp = m->slirp;
     struct mbuf *t;
     struct ip6 *ip = mtod(m, struct ip6 *);
     char addrstr[INET6_ADDRSTRLEN];

     DEBUG_CALL("icmp6_send_error");
     DEBUG_ARG("type = %d, code = %d", type, code);

     if (IN6_IS_ADDR_MULTICAST(&ip->ip_src) || in6_zero(&ip->ip_src)) {
         /* TODO icmp error? */
         return;
     }

     t = m_get(slirp);

     /* IPv6 packet */
     struct ip6 *rip = mtod(t, struct ip6 *);
     rip->ip_src = *src;
     rip->ip_dst = ip->ip_src;
     inet_ntop(AF_INET6, &rip->ip_dst, addrstr, INET6_ADDRSTRLEN);
     DEBUG_ARG("target = %s", addrstr);

     rip->ip_nh = IPPROTO_ICMPV6;
     const int error_data_len = MIN(
         m->m_len, slirp->if_mtu - (sizeof(struct ip6) + ICMP6_ERROR_MINLEN));
     rip->ip_pl = htons(ICMP6_ERROR_MINLEN + error_data_len);
     t->m_len = sizeof(struct ip6) + ntohs(rip->ip_pl);

     /* ICMPv6 packet */
     t->m_data += sizeof(struct ip6);
     struct icmp6 *ricmp = mtod(t, struct icmp6 *);
     ricmp->icmp6_type = type;
     ricmp->icmp6_code = code;
     ricmp->icmp6_cksum = 0;

     switch (type) {
     case ICMP6_UNREACH:
     case ICMP6_TIMXCEED:
         ricmp->icmp6_err.unused = 0;
         break;
     case ICMP6_TOOBIG:
         ricmp->icmp6_err.mtu = htonl(slirp->if_mtu);
         break;
     case ICMP6_PARAMPROB:
         /* TODO: Handle this case */
         break;
     default:
         g_assert_not_reached();
     }
     t->m_data += ICMP6_ERROR_MINLEN;
     memcpy(t->m_data, m->m_data, error_data_len);

     /* Checksum */
     t->m_data -= ICMP6_ERROR_MINLEN;
     t->m_data -= sizeof(struct ip6);
     ricmp->icmp6_cksum = ip6_cksum(t);

     ip6_output(NULL, t, 0);
 }

 void icmp6_send_error(struct mbuf *m, uint8_t type, uint8_t code)
 {
     struct in6_addr src = LINKLOCAL_ADDR;
     icmp6_forward_error(m, type, code, &src);
 }

 /*
  * Send NDP Router Advertisement
  */
 void ndp_send_ra(Slirp *slirp)
 {
     DEBUG_CALL("ndp_send_ra");

     /* Build IPv6 packet */
     struct mbuf *t = m_get(slirp);
     struct ip6 *rip = mtod(t, struct ip6 *);
     size_t pl_size = 0;
     struct in6_addr addr;
     uint32_t scope_id;

     rip->ip_src = (struct in6_addr)LINKLOCAL_ADDR;
     rip->ip_dst = (struct in6_addr)ALLNODES_MULTICAST;
     rip->ip_nh = IPPROTO_ICMPV6;

     /* Build ICMPv6 packet */
     t->m_data += sizeof(struct ip6);
     struct icmp6 *ricmp = mtod(t, struct icmp6 *);
     ricmp->icmp6_type = ICMP6_NDP_RA;
     ricmp->icmp6_code = 0;
     ricmp->icmp6_cksum = 0;

     /* NDP */
     ricmp->icmp6_nra.chl = NDP_AdvCurHopLimit;
     ricmp->icmp6_nra.M = NDP_AdvManagedFlag;
     ricmp->icmp6_nra.O = NDP_AdvOtherConfigFlag;
     ricmp->icmp6_nra.reserved = 0;
     ricmp->icmp6_nra.lifetime = htons(NDP_AdvDefaultLifetime);
     ricmp->icmp6_nra.reach_time = htonl(NDP_AdvReachableTime);
     ricmp->icmp6_nra.retrans_time = htonl(NDP_AdvRetransTime);
     t->m_data += ICMP6_NDP_RA_MINLEN;
     pl_size += ICMP6_NDP_RA_MINLEN;

     /* Source link-layer address (NDP option) */
     struct ndpopt *opt = mtod(t, struct ndpopt *);
     opt->ndpopt_type = NDPOPT_LINKLAYER_SOURCE;
     opt->ndpopt_len = NDPOPT_LINKLAYER_LEN / 8;
     in6_compute_ethaddr(rip->ip_src, opt->ndpopt_linklayer);
     t->m_data += NDPOPT_LINKLAYER_LEN;
     pl_size += NDPOPT_LINKLAYER_LEN;

     /* Prefix information (NDP option) */
     struct ndpopt *opt2 = mtod(t, struct ndpopt *);
     opt2->ndpopt_type = NDPOPT_PREFIX_INFO;
     opt2->ndpopt_len = NDPOPT_PREFIXINFO_LEN / 8;
     opt2->ndpopt_prefixinfo.prefix_length = slirp->vprefix_len;
     opt2->ndpopt_prefixinfo.L = 1;
     opt2->ndpopt_prefixinfo.A = 1;
     opt2->ndpopt_prefixinfo.reserved1 = 0;
     opt2->ndpopt_prefixinfo.valid_lt = htonl(NDP_AdvValidLifetime);
     opt2->ndpopt_prefixinfo.pref_lt = htonl(NDP_AdvPrefLifetime);
     opt2->ndpopt_prefixinfo.reserved2 = 0;
     opt2->ndpopt_prefixinfo.prefix = slirp->vprefix_addr6;
     t->m_data += NDPOPT_PREFIXINFO_LEN;
     pl_size += NDPOPT_PREFIXINFO_LEN;

     /* Prefix information (NDP option) */
     if (get_dns6_addr(&addr, &scope_id) >= 0) {
         /* Host system does have an IPv6 DNS server, announce our proxy.  */
         struct ndpopt *opt3 = mtod(t, struct ndpopt *);
         opt3->ndpopt_type = NDPOPT_RDNSS;
         opt3->ndpopt_len = NDPOPT_RDNSS_LEN / 8;
         opt3->ndpopt_rdnss.reserved = 0;
         opt3->ndpopt_rdnss.lifetime = htonl(2 * NDP_MaxRtrAdvInterval);
         opt3->ndpopt_rdnss.addr = slirp->vnameserver_addr6;
         t->m_data += NDPOPT_RDNSS_LEN;
         pl_size += NDPOPT_RDNSS_LEN;
     }

     rip->ip_pl = htons(pl_size);
     t->m_data -= sizeof(struct ip6) + pl_size;
     t->m_len = sizeof(struct ip6) + pl_size;

     /* ICMPv6 Checksum */
     ricmp->icmp6_cksum = ip6_cksum(t);

     ip6_output(NULL, t, 0);
 }

 /*
  * Send NDP Neighbor Solitication
  */
 void ndp_send_ns(Slirp *slirp, struct in6_addr addr)
 {
     char addrstr[INET6_ADDRSTRLEN];

     inet_ntop(AF_INET6, &addr, addrstr, INET6_ADDRSTRLEN);

     DEBUG_CALL("ndp_send_ns");
     DEBUG_ARG("target = %s", addrstr);

     /* Build IPv6 packet */
     struct mbuf *t = m_get(slirp);
     struct ip6 *rip = mtod(t, struct ip6 *);
     rip->ip_src = slirp->vhost_addr6;
     rip->ip_dst = (struct in6_addr)SOLICITED_NODE_PREFIX;
     memcpy(&rip->ip_dst.s6_addr[13], &addr.s6_addr[13], 3);
     rip->ip_nh = IPPROTO_ICMPV6;
     rip->ip_pl = htons(ICMP6_NDP_NS_MINLEN + NDPOPT_LINKLAYER_LEN);
     t->m_len = sizeof(struct ip6) + ntohs(rip->ip_pl);

     /* Build ICMPv6 packet */
     t->m_data += sizeof(struct ip6);
     struct icmp6 *ricmp = mtod(t, struct icmp6 *);
     ricmp->icmp6_type = ICMP6_NDP_NS;
     ricmp->icmp6_code = 0;
     ricmp->icmp6_cksum = 0;

     /* NDP */
     ricmp->icmp6_nns.reserved = 0;
     ricmp->icmp6_nns.target = addr;

     /* Build NDP option */
     t->m_data += ICMP6_NDP_NS_MINLEN;
     struct ndpopt *opt = mtod(t, struct ndpopt *);
     opt->ndpopt_type = NDPOPT_LINKLAYER_SOURCE;
     opt->ndpopt_len = NDPOPT_LINKLAYER_LEN / 8;
     in6_compute_ethaddr(slirp->vhost_addr6, opt->ndpopt_linklayer);

     /* ICMPv6 Checksum */
     t->m_data -= ICMP6_NDP_NA_MINLEN;
     t->m_data -= sizeof(struct ip6);
     ricmp->icmp6_cksum = ip6_cksum(t);

     ip6_output(NULL, t, 1);
 }

 /*
  * Send NDP Neighbor Advertisement
  */
 static void ndp_send_na(Slirp *slirp, struct ip6 *ip, struct icmp6 *icmp)
 {
     /* Build IPv6 packet */
     struct mbuf *t = m_get(slirp);
     struct ip6 *rip = mtod(t, struct ip6 *);
     rip->ip_src = icmp->icmp6_nns.target;
     if (in6_zero(&ip->ip_src)) {
         rip->ip_dst = (struct in6_addr)ALLNODES_MULTICAST;
     } else {
         rip->ip_dst = ip->ip_src;
     }
     rip->ip_nh = IPPROTO_ICMPV6;
     rip->ip_pl = htons(ICMP6_NDP_NA_MINLEN + NDPOPT_LINKLAYER_LEN);
     t->m_len = sizeof(struct ip6) + ntohs(rip->ip_pl);

     /* Build ICMPv6 packet */
     t->m_data += sizeof(struct ip6);
     struct icmp6 *ricmp = mtod(t, struct icmp6 *);
     ricmp->icmp6_type = ICMP6_NDP_NA;
     ricmp->icmp6_code = 0;
     ricmp->icmp6_cksum = 0;

     /* NDP */
     ricmp->icmp6_nna.R = NDP_IsRouter;
     ricmp->icmp6_nna.S = !IN6_IS_ADDR_MULTICAST(&rip->ip_dst);
     ricmp->icmp6_nna.O = 1;
     ricmp->icmp6_nna.reserved_hi = 0;
     ricmp->icmp6_nna.reserved_lo = 0;
     ricmp->icmp6_nna.target = icmp->icmp6_nns.target;

     /* Build NDP option */
     t->m_data += ICMP6_NDP_NA_MINLEN;
     struct ndpopt *opt = mtod(t, struct ndpopt *);
     opt->ndpopt_type = NDPOPT_LINKLAYER_TARGET;
     opt->ndpopt_len = NDPOPT_LINKLAYER_LEN / 8;
     in6_compute_ethaddr(ricmp->icmp6_nna.target, opt->ndpopt_linklayer);

     /* ICMPv6 Checksum */
     t->m_data -= ICMP6_NDP_NA_MINLEN;
     t->m_data -= sizeof(struct ip6);
     ricmp->icmp6_cksum = ip6_cksum(t);

     ip6_output(NULL, t, 0);
 }

 /*
  * Process a NDP message
  */
 static void ndp_input(struct mbuf *m, Slirp *slirp, struct ip6 *ip,
                       struct icmp6 *icmp)
 {
     g_assert(M_ROOMBEFORE(m) >= ETH_HLEN);

     m->m_len += ETH_HLEN;
     m->m_data -= ETH_HLEN;
     struct ethhdr *eth = mtod(m, struct ethhdr *);
     m->m_len -= ETH_HLEN;
     m->m_data += ETH_HLEN;

     switch (icmp->icmp6_type) {
     case ICMP6_NDP_RS:
         DEBUG_CALL(" type = Router Solicitation");
         if (ip->ip_hl == 255 && icmp->icmp6_code == 0 &&
             ntohs(ip->ip_pl) >= ICMP6_NDP_RS_MINLEN) {
             /* Gratuitous NDP */
             ndp_table_add(slirp, ip->ip_src, eth->h_source);

             ndp_send_ra(slirp);
         }
         break;

     case ICMP6_NDP_RA:
         DEBUG_CALL(" type = Router Advertisement");
         slirp->cb->guest_error("Warning: guest sent NDP RA, but shouldn't",
                                slirp->opaque);
         break;

     case ICMP6_NDP_NS:
         DEBUG_CALL(" type = Neighbor Solicitation");
         if (ip->ip_hl == 255 && icmp->icmp6_code == 0 &&
             !IN6_IS_ADDR_MULTICAST(&icmp->icmp6_nns.target) &&
             ntohs(ip->ip_pl) >= ICMP6_NDP_NS_MINLEN &&
             (!in6_zero(&ip->ip_src) ||
              in6_solicitednode_multicast(&ip->ip_dst))) {
             if (in6_equal_host(&icmp->icmp6_nns.target)) {
                 /* Gratuitous NDP */
                 ndp_table_add(slirp, ip->ip_src, eth->h_source);
                 ndp_send_na(slirp, ip, icmp);
             }
         }
         break;

     case ICMP6_NDP_NA:
         DEBUG_CALL(" type = Neighbor Advertisement");
         if (ip->ip_hl == 255 && icmp->icmp6_code == 0 &&
             ntohs(ip->ip_pl) >= ICMP6_NDP_NA_MINLEN &&
             !IN6_IS_ADDR_MULTICAST(&icmp->icmp6_nna.target) &&
             (!IN6_IS_ADDR_MULTICAST(&ip->ip_dst) || icmp->icmp6_nna.S == 0)) {
             ndp_table_add(slirp, ip->ip_src, eth->h_source);
         }
         break;

     case ICMP6_NDP_REDIRECT:
         DEBUG_CALL(" type = Redirect");
         slirp->cb->guest_error(
             "Warning: guest sent NDP REDIRECT, but shouldn't", slirp->opaque);
         break;
     }
 }

 /*
  * Process a received ICMPv6 message.
  */
 void icmp6_input(struct mbuf *m)
 {
     Slirp *slirp = m->slirp;
     /* NDP reads the ethernet header for gratuitous NDP */
     M_DUP_DEBUG(slirp, m, 1, ETH_HLEN);

     struct icmp6 *icmp;
     struct ip6 *ip = mtod(m, struct ip6 *);
     int hlen = sizeof(struct ip6);

     DEBUG_CALL("icmp6_input");
     DEBUG_ARG("m = %p", m);
     DEBUG_ARG("m_len = %d", m->m_len);

     if (ntohs(ip->ip_pl) < ICMP6_MINLEN) {
         goto end;
     }

     if (ip6_cksum(m)) {
         goto end;
     }

     m->m_len -= hlen;
     m->m_data += hlen;
     icmp = mtod(m, struct icmp6 *);
     m->m_len += hlen;
     m->m_data -= hlen;

     DEBUG_ARG("icmp6_type = %d", icmp->icmp6_type);
     switch (icmp->icmp6_type) {
     case ICMP6_ECHO_REQUEST:
         if (in6_equal_host(&ip->ip_dst)) {
             icmp6_send_echoreply(m, slirp, ip, icmp);
         } else {
             /* TODO */
             g_critical("external icmpv6 not supported yet");
         }
         break;

     case ICMP6_NDP_RS:
     case ICMP6_NDP_RA:
     case ICMP6_NDP_NS:
     case ICMP6_NDP_NA:
     case ICMP6_NDP_REDIRECT:
         ndp_input(m, slirp, ip, icmp);
         break;

     case ICMP6_UNREACH:
     case ICMP6_TOOBIG:
     case ICMP6_TIMXCEED:
     case ICMP6_PARAMPROB:
         /* XXX? report error? close socket? */
     default:
         break;
     }

 end:
     m_free(m);
 }
	/* SPDX-License-Identifier: BSD-3-Clause */
	/*
	* Copyright (c) 2013
	* Guillaume Subiron, Yann Bordenave, Serigne Modou Wagne.
	*/

	#include "slirp.h"
	#include "ip6_icmp.h"

	#define NDP_Interval \
	g_rand_int_range(slirp->grand, NDP_MinRtrAdvInterval, NDP_MaxRtrAdvInterval)

	static void ra_timer_handler(void *opaque)
	{
	Slirp *slirp = opaque;

	slirp->cb->timer_mod(slirp->ra_timer,
	slirp->cb->clock_get_ns(slirp->opaque) / SCALE_MS +
	NDP_Interval,
	slirp->opaque);
	ndp_send_ra(slirp);
	}

	void icmp6_init(Slirp *slirp)
	{
	if (!slirp->in6_enabled) {
	return;
	}

	slirp->ra_timer =
	slirp->cb->timer_new(ra_timer_handler, slirp, slirp->opaque);
	slirp->cb->timer_mod(slirp->ra_timer,
	slirp->cb->clock_get_ns(slirp->opaque) / SCALE_MS +
	NDP_Interval,
	slirp->opaque);
	}

	void icmp6_cleanup(Slirp *slirp)
	{
	if (!slirp->in6_enabled) {
	return;
	}

	slirp->cb->timer_free(slirp->ra_timer, slirp->opaque);
	}

	static void icmp6_send_echoreply(struct mbuf m, Slirp slirp, struct ip6 *ip,
	struct icmp6 *icmp)
	{
	struct mbuf *t = m_get(slirp);
	t->m_len = sizeof(struct ip6) + ntohs(ip->ip_pl);
	memcpy(t->m_data, m->m_data, t->m_len);

	/* IPv6 Packet */
	struct ip6 rip = mtod(t, struct ip6 );
	rip->ip_dst = ip->ip_src;
	rip->ip_src = ip->ip_dst;

	/* ICMPv6 packet */
	t->m_data += sizeof(struct ip6);
	struct icmp6 ricmp = mtod(t, struct icmp6 );
	ricmp->icmp6_type = ICMP6_ECHO_REPLY;
	ricmp->icmp6_cksum = 0;

	/* Checksum */
	t->m_data -= sizeof(struct ip6);
	ricmp->icmp6_cksum = ip6_cksum(t);

	ip6_output(NULL, t, 0);
	}

	void icmp6_forward_error(struct mbuf m, uint8_t type, uint8_t code, struct in6_addr src)
	{
	Slirp *slirp = m->slirp;
	struct mbuf *t;
	struct ip6 ip = mtod(m, struct ip6 );
	char addrstr[INET6_ADDRSTRLEN];

	DEBUG_CALL("icmp6_send_error");
	DEBUG_ARG("type = %d, code = %d", type, code);

	if (IN6_IS_ADDR_MULTICAST(&ip->ip_src) \|\| in6_zero(&ip->ip_src)) {
	/* TODO icmp error? */
	return;
	}

	t = m_get(slirp);

	/* IPv6 packet */
	struct ip6 rip = mtod(t, struct ip6 );
	rip->ip_src = *src;
	rip->ip_dst = ip->ip_src;
	inet_ntop(AF_INET6, &rip->ip_dst, addrstr, INET6_ADDRSTRLEN);
	DEBUG_ARG("target = %s", addrstr);

	rip->ip_nh = IPPROTO_ICMPV6;
	const int error_data_len = MIN(
	m->m_len, slirp->if_mtu - (sizeof(struct ip6) + ICMP6_ERROR_MINLEN));
	rip->ip_pl = htons(ICMP6_ERROR_MINLEN + error_data_len);
	t->m_len = sizeof(struct ip6) + ntohs(rip->ip_pl);

	/* ICMPv6 packet */
	t->m_data += sizeof(struct ip6);
	struct icmp6 ricmp = mtod(t, struct icmp6 );
	ricmp->icmp6_type = type;
	ricmp->icmp6_code = code;
	ricmp->icmp6_cksum = 0;

	switch (type) {
	case ICMP6_UNREACH:
	case ICMP6_TIMXCEED:
	ricmp->icmp6_err.unused = 0;
	break;
	case ICMP6_TOOBIG:
	ricmp->icmp6_err.mtu = htonl(slirp->if_mtu);
	break;
	case ICMP6_PARAMPROB:
	/* TODO: Handle this case */
	break;
	default:
	g_assert_not_reached();
	}
	t->m_data += ICMP6_ERROR_MINLEN;
	memcpy(t->m_data, m->m_data, error_data_len);

	/* Checksum */
	t->m_data -= ICMP6_ERROR_MINLEN;
	t->m_data -= sizeof(struct ip6);
	ricmp->icmp6_cksum = ip6_cksum(t);

	ip6_output(NULL, t, 0);
	}

	void icmp6_send_error(struct mbuf *m, uint8_t type, uint8_t code)
	{
	struct in6_addr src = LINKLOCAL_ADDR;
	icmp6_forward_error(m, type, code, &src);
	}

	/*
	* Send NDP Router Advertisement
	*/
	void ndp_send_ra(Slirp *slirp)
	{
	DEBUG_CALL("ndp_send_ra");

	/* Build IPv6 packet */
	struct mbuf *t = m_get(slirp);
	struct ip6 rip = mtod(t, struct ip6 );
	size_t pl_size = 0;
	struct in6_addr addr;
	uint32_t scope_id;

	rip->ip_src = (struct in6_addr)LINKLOCAL_ADDR;
	rip->ip_dst = (struct in6_addr)ALLNODES_MULTICAST;
	rip->ip_nh = IPPROTO_ICMPV6;

	/* Build ICMPv6 packet */
	t->m_data += sizeof(struct ip6);
	struct icmp6 ricmp = mtod(t, struct icmp6 );
	ricmp->icmp6_type = ICMP6_NDP_RA;
	ricmp->icmp6_code = 0;
	ricmp->icmp6_cksum = 0;

	/* NDP */
	ricmp->icmp6_nra.chl = NDP_AdvCurHopLimit;
	ricmp->icmp6_nra.M = NDP_AdvManagedFlag;
	ricmp->icmp6_nra.O = NDP_AdvOtherConfigFlag;
	ricmp->icmp6_nra.reserved = 0;
	ricmp->icmp6_nra.lifetime = htons(NDP_AdvDefaultLifetime);
	ricmp->icmp6_nra.reach_time = htonl(NDP_AdvReachableTime);
	ricmp->icmp6_nra.retrans_time = htonl(NDP_AdvRetransTime);
	t->m_data += ICMP6_NDP_RA_MINLEN;
	pl_size += ICMP6_NDP_RA_MINLEN;

	/* Source link-layer address (NDP option) */
	struct ndpopt opt = mtod(t, struct ndpopt );
	opt->ndpopt_type = NDPOPT_LINKLAYER_SOURCE;
	opt->ndpopt_len = NDPOPT_LINKLAYER_LEN / 8;
	in6_compute_ethaddr(rip->ip_src, opt->ndpopt_linklayer);
	t->m_data += NDPOPT_LINKLAYER_LEN;
	pl_size += NDPOPT_LINKLAYER_LEN;

	/* Prefix information (NDP option) */
	struct ndpopt opt2 = mtod(t, struct ndpopt );
	opt2->ndpopt_type = NDPOPT_PREFIX_INFO;
	opt2->ndpopt_len = NDPOPT_PREFIXINFO_LEN / 8;
	opt2->ndpopt_prefixinfo.prefix_length = slirp->vprefix_len;
	opt2->ndpopt_prefixinfo.L = 1;
	opt2->ndpopt_prefixinfo.A = 1;
	opt2->ndpopt_prefixinfo.reserved1 = 0;
	opt2->ndpopt_prefixinfo.valid_lt = htonl(NDP_AdvValidLifetime);
	opt2->ndpopt_prefixinfo.pref_lt = htonl(NDP_AdvPrefLifetime);
	opt2->ndpopt_prefixinfo.reserved2 = 0;
	opt2->ndpopt_prefixinfo.prefix = slirp->vprefix_addr6;
	t->m_data += NDPOPT_PREFIXINFO_LEN;
	pl_size += NDPOPT_PREFIXINFO_LEN;

	/* Prefix information (NDP option) */
	if (get_dns6_addr(&addr, &scope_id) >= 0) {
	/* Host system does have an IPv6 DNS server, announce our proxy. */
	struct ndpopt opt3 = mtod(t, struct ndpopt );
	opt3->ndpopt_type = NDPOPT_RDNSS;
	opt3->ndpopt_len = NDPOPT_RDNSS_LEN / 8;
	opt3->ndpopt_rdnss.reserved = 0;
	opt3->ndpopt_rdnss.lifetime = htonl(2 * NDP_MaxRtrAdvInterval);
	opt3->ndpopt_rdnss.addr = slirp->vnameserver_addr6;
	t->m_data += NDPOPT_RDNSS_LEN;
	pl_size += NDPOPT_RDNSS_LEN;
	}

	rip->ip_pl = htons(pl_size);
	t->m_data -= sizeof(struct ip6) + pl_size;
	t->m_len = sizeof(struct ip6) + pl_size;

	/* ICMPv6 Checksum */
	ricmp->icmp6_cksum = ip6_cksum(t);

	ip6_output(NULL, t, 0);
	}

	/*
	* Send NDP Neighbor Solitication
	*/
	void ndp_send_ns(Slirp *slirp, struct in6_addr addr)
	{
	char addrstr[INET6_ADDRSTRLEN];

	inet_ntop(AF_INET6, &addr, addrstr, INET6_ADDRSTRLEN);

	DEBUG_CALL("ndp_send_ns");
	DEBUG_ARG("target = %s", addrstr);

	/* Build IPv6 packet */
	struct mbuf *t = m_get(slirp);
	struct ip6 rip = mtod(t, struct ip6 );
	rip->ip_src = slirp->vhost_addr6;
	rip->ip_dst = (struct in6_addr)SOLICITED_NODE_PREFIX;
	memcpy(&rip->ip_dst.s6_addr[13], &addr.s6_addr[13], 3);
	rip->ip_nh = IPPROTO_ICMPV6;
	rip->ip_pl = htons(ICMP6_NDP_NS_MINLEN + NDPOPT_LINKLAYER_LEN);
	t->m_len = sizeof(struct ip6) + ntohs(rip->ip_pl);

	/* Build ICMPv6 packet */
	t->m_data += sizeof(struct ip6);
	struct icmp6 ricmp = mtod(t, struct icmp6 );
	ricmp->icmp6_type = ICMP6_NDP_NS;
	ricmp->icmp6_code = 0;
	ricmp->icmp6_cksum = 0;

	/* NDP */
	ricmp->icmp6_nns.reserved = 0;
	ricmp->icmp6_nns.target = addr;

	/* Build NDP option */
	t->m_data += ICMP6_NDP_NS_MINLEN;
	struct ndpopt opt = mtod(t, struct ndpopt );
	opt->ndpopt_type = NDPOPT_LINKLAYER_SOURCE;
	opt->ndpopt_len = NDPOPT_LINKLAYER_LEN / 8;
	in6_compute_ethaddr(slirp->vhost_addr6, opt->ndpopt_linklayer);

	/* ICMPv6 Checksum */
	t->m_data -= ICMP6_NDP_NA_MINLEN;
	t->m_data -= sizeof(struct ip6);
	ricmp->icmp6_cksum = ip6_cksum(t);

	ip6_output(NULL, t, 1);
	}

	/*
	* Send NDP Neighbor Advertisement
	*/
	static void ndp_send_na(Slirp slirp, struct ip6 ip, struct icmp6 *icmp)
	{
	/* Build IPv6 packet */
	struct mbuf *t = m_get(slirp);
	struct ip6 rip = mtod(t, struct ip6 );
	rip->ip_src = icmp->icmp6_nns.target;
	if (in6_zero(&ip->ip_src)) {
	rip->ip_dst = (struct in6_addr)ALLNODES_MULTICAST;
	} else {
	rip->ip_dst = ip->ip_src;
	}
	rip->ip_nh = IPPROTO_ICMPV6;
	rip->ip_pl = htons(ICMP6_NDP_NA_MINLEN + NDPOPT_LINKLAYER_LEN);
	t->m_len = sizeof(struct ip6) + ntohs(rip->ip_pl);

	/* Build ICMPv6 packet */
	t->m_data += sizeof(struct ip6);
	struct icmp6 ricmp = mtod(t, struct icmp6 );
	ricmp->icmp6_type = ICMP6_NDP_NA;
	ricmp->icmp6_code = 0;
	ricmp->icmp6_cksum = 0;

	/* NDP */
	ricmp->icmp6_nna.R = NDP_IsRouter;
	ricmp->icmp6_nna.S = !IN6_IS_ADDR_MULTICAST(&rip->ip_dst);
	ricmp->icmp6_nna.O = 1;
	ricmp->icmp6_nna.reserved_hi = 0;
	ricmp->icmp6_nna.reserved_lo = 0;
	ricmp->icmp6_nna.target = icmp->icmp6_nns.target;

	/* Build NDP option */
	t->m_data += ICMP6_NDP_NA_MINLEN;
	struct ndpopt opt = mtod(t, struct ndpopt );
	opt->ndpopt_type = NDPOPT_LINKLAYER_TARGET;
	opt->ndpopt_len = NDPOPT_LINKLAYER_LEN / 8;
	in6_compute_ethaddr(ricmp->icmp6_nna.target, opt->ndpopt_linklayer);

	/* ICMPv6 Checksum */
	t->m_data -= ICMP6_NDP_NA_MINLEN;
	t->m_data -= sizeof(struct ip6);
	ricmp->icmp6_cksum = ip6_cksum(t);

	ip6_output(NULL, t, 0);
	}

	/*
	* Process a NDP message
	*/
	static void ndp_input(struct mbuf m, Slirp slirp, struct ip6 *ip,
	struct icmp6 *icmp)
	{
	g_assert(M_ROOMBEFORE(m) >= ETH_HLEN);

	m->m_len += ETH_HLEN;
	m->m_data -= ETH_HLEN;
	struct ethhdr eth = mtod(m, struct ethhdr );
	m->m_len -= ETH_HLEN;
	m->m_data += ETH_HLEN;

	switch (icmp->icmp6_type) {
	case ICMP6_NDP_RS:
	DEBUG_CALL(" type = Router Solicitation");
	if (ip->ip_hl == 255 && icmp->icmp6_code == 0 &&
	ntohs(ip->ip_pl) >= ICMP6_NDP_RS_MINLEN) {
	/* Gratuitous NDP */
	ndp_table_add(slirp, ip->ip_src, eth->h_source);

	ndp_send_ra(slirp);
	}
	break;

	case ICMP6_NDP_RA:
	DEBUG_CALL(" type = Router Advertisement");
	slirp->cb->guest_error("Warning: guest sent NDP RA, but shouldn't",
	slirp->opaque);
	break;

	case ICMP6_NDP_NS:
	DEBUG_CALL(" type = Neighbor Solicitation");
	if (ip->ip_hl == 255 && icmp->icmp6_code == 0 &&
	!IN6_IS_ADDR_MULTICAST(&icmp->icmp6_nns.target) &&
	ntohs(ip->ip_pl) >= ICMP6_NDP_NS_MINLEN &&
	(!in6_zero(&ip->ip_src) \|\|
	in6_solicitednode_multicast(&ip->ip_dst))) {
	if (in6_equal_host(&icmp->icmp6_nns.target)) {
	/* Gratuitous NDP */
	ndp_table_add(slirp, ip->ip_src, eth->h_source);
	ndp_send_na(slirp, ip, icmp);
	}
	}
	break;

	case ICMP6_NDP_NA:
	DEBUG_CALL(" type = Neighbor Advertisement");
	if (ip->ip_hl == 255 && icmp->icmp6_code == 0 &&
	ntohs(ip->ip_pl) >= ICMP6_NDP_NA_MINLEN &&
	!IN6_IS_ADDR_MULTICAST(&icmp->icmp6_nna.target) &&
	(!IN6_IS_ADDR_MULTICAST(&ip->ip_dst) \|\| icmp->icmp6_nna.S == 0)) {
	ndp_table_add(slirp, ip->ip_src, eth->h_source);
	}
	break;

	case ICMP6_NDP_REDIRECT:
	DEBUG_CALL(" type = Redirect");
	slirp->cb->guest_error(
	"Warning: guest sent NDP REDIRECT, but shouldn't", slirp->opaque);
	break;
	}
	}

	/*
	* Process a received ICMPv6 message.
	*/
	void icmp6_input(struct mbuf *m)
	{
	Slirp *slirp = m->slirp;
	/* NDP reads the ethernet header for gratuitous NDP */
	M_DUP_DEBUG(slirp, m, 1, ETH_HLEN);

	struct icmp6 *icmp;
	struct ip6 ip = mtod(m, struct ip6 );
	int hlen = sizeof(struct ip6);

	DEBUG_CALL("icmp6_input");
	DEBUG_ARG("m = %p", m);
	DEBUG_ARG("m_len = %d", m->m_len);

	if (ntohs(ip->ip_pl) < ICMP6_MINLEN) {
	goto end;
	}

	if (ip6_cksum(m)) {
	goto end;
	}

	m->m_len -= hlen;
	m->m_data += hlen;
	icmp = mtod(m, struct icmp6 *);
	m->m_len += hlen;
	m->m_data -= hlen;

	DEBUG_ARG("icmp6_type = %d", icmp->icmp6_type);
	switch (icmp->icmp6_type) {
	case ICMP6_ECHO_REQUEST:
	if (in6_equal_host(&ip->ip_dst)) {
	icmp6_send_echoreply(m, slirp, ip, icmp);
	} else {
	/* TODO */
	g_critical("external icmpv6 not supported yet");
	}
	break;

	case ICMP6_NDP_RS:
	case ICMP6_NDP_RA:
	case ICMP6_NDP_NS:
	case ICMP6_NDP_NA:
	case ICMP6_NDP_REDIRECT:
	ndp_input(m, slirp, ip, icmp);
	break;

	case ICMP6_UNREACH:
	case ICMP6_TOOBIG:
	case ICMP6_TIMXCEED:
	case ICMP6_PARAMPROB:
	/* XXX? report error? close socket? */
	default:
	break;
	}

	end:
	m_free(m);
	}