frag6.c

嵌入式操作系统ECOS的网络开发包

	ip6af->ip6af_len = ip6->ip6_plen;
	ip6af->ip6af_nxt = ip6->ip6_nxt;
	ip6af->ip6af_hlim = ip6->ip6_hlim;
	ip6af->ip6af_mff = ip6f->ip6f_offlg & IP6F_MORE_FRAG;
	ip6af->ip6af_off = fragoff;
	ip6af->ip6af_frglen = frgpartlen;
	ip6af->ip6af_offset = offset;
	IP6_REASS_MBUF(ip6af) = m;

	if (first_frag) {
		af6 = (struct ip6asfrag *)q6;
		goto insert;
	}

	/*
	 * Find a segment which begins after this one does.
	 */
	for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
	     af6 = af6->ip6af_down)
		if (af6->ip6af_off > ip6af->ip6af_off)
			break;

#if 0
	/*
	 * If there is a preceding segment, it may provide some of
	 * our data already.  If so, drop the data from the incoming
	 * segment.  If it provides all of our data, drop us.
	 */
	if (af6->ip6af_up != (struct ip6asfrag *)q6) {
		i = af6->ip6af_up->ip6af_off + af6->ip6af_up->ip6af_frglen
			- ip6af->ip6af_off;
		if (i > 0) {
			if (i >= ip6af->ip6af_frglen)
				goto dropfrag;
			m_adj(IP6_REASS_MBUF(ip6af), i);
			ip6af->ip6af_off += i;
			ip6af->ip6af_frglen -= i;
		}
	}

	/*
	 * While we overlap succeeding segments trim them or,
	 * if they are completely covered, dequeue them.
	 */
	while (af6 != (struct ip6asfrag *)q6 &&
	       ip6af->ip6af_off + ip6af->ip6af_frglen > af6->ip6af_off) {
		i = (ip6af->ip6af_off + ip6af->ip6af_frglen) - af6->ip6af_off;
		if (i < af6->ip6af_frglen) {
			af6->ip6af_frglen -= i;
			af6->ip6af_off += i;
			m_adj(IP6_REASS_MBUF(af6), i);
			break;
		}
		af6 = af6->ip6af_down;
		m_freem(IP6_REASS_MBUF(af6->ip6af_up));
		frag6_deq(af6->ip6af_up);
	}
#else
	/*
	 * If the incoming framgent overlaps some existing fragments in
	 * the reassembly queue, drop it, since it is dangerous to override
	 * existing fragments from a security point of view.
	 */
	if (af6->ip6af_up != (struct ip6asfrag *)q6) {
		i = af6->ip6af_up->ip6af_off + af6->ip6af_up->ip6af_frglen
			- ip6af->ip6af_off;
		if (i > 0) {
#if 0				/* suppress the noisy log */
			log(LOG_ERR, "%d bytes of a fragment from %s "
			    "overlaps the previous fragment\n",
			    i, ip6_sprintf(&q6->ip6q_src));
#endif
			free(ip6af, M_FTABLE);
			goto dropfrag;
		}
	}
	if (af6 != (struct ip6asfrag *)q6) {
		i = (ip6af->ip6af_off + ip6af->ip6af_frglen) - af6->ip6af_off;
		if (i > 0) {
#if 0				/* suppress the noisy log */
			log(LOG_ERR, "%d bytes of a fragment from %s "
			    "overlaps the succeeding fragment",
			    i, ip6_sprintf(&q6->ip6q_src));
#endif
			free(ip6af, M_FTABLE);
			goto dropfrag;
		}
	}
#endif

insert:

	/*
	 * Stick new segment in its place;
	 * check for complete reassembly.
	 * Move to front of packet queue, as we are
	 * the most recently active fragmented packet.
	 */
	frag6_enq(ip6af, af6->ip6af_up);
#if 0 /* xxx */
	if (q6 != ip6q.ip6q_next) {
		frag6_remque(q6);
		frag6_insque(q6, &ip6q);
	}
#endif
	next = 0;
	for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
	     af6 = af6->ip6af_down) {
		if (af6->ip6af_off != next) {
			frag6_doing_reass = 0;
			return IPPROTO_DONE;
		}
		next += af6->ip6af_frglen;
	}
	if (af6->ip6af_up->ip6af_mff) {
		frag6_doing_reass = 0;
		return IPPROTO_DONE;
	}

	/*
	 * Reassembly is complete; concatenate fragments.
	 */
	ip6af = q6->ip6q_down;
	t = m = IP6_REASS_MBUF(ip6af);
	af6 = ip6af->ip6af_down;
	frag6_deq(ip6af);
	while (af6 != (struct ip6asfrag *)q6) {
		af6dwn = af6->ip6af_down;
		frag6_deq(af6);
		while (t->m_next)
			t = t->m_next;
		t->m_next = IP6_REASS_MBUF(af6);
		m_adj(t->m_next, af6->ip6af_offset);
		free(af6, M_FTABLE);
		af6 = af6dwn;
	}

	/* adjust offset to point where the original next header starts */
	offset = ip6af->ip6af_offset - sizeof(struct ip6_frag);
	free(ip6af, M_FTABLE);
	ip6 = mtod(m, struct ip6_hdr *);
	ip6->ip6_plen = htons((u_short)next + offset - sizeof(struct ip6_hdr));
	ip6->ip6_src = q6->ip6q_src;
	ip6->ip6_dst = q6->ip6q_dst;
	nxt = q6->ip6q_nxt;
#ifdef notyet
	*q6->ip6q_nxtp = (u_char)(nxt & 0xff);
#endif

	/*
	 * Delete frag6 header with as a few cost as possible.
	 */
	if (offset < m->m_len) {
		ovbcopy((caddr_t)ip6, (caddr_t)ip6 + sizeof(struct ip6_frag),
			offset);
		m->m_data += sizeof(struct ip6_frag);
		m->m_len -= sizeof(struct ip6_frag);
	} else {
		/* this comes with no copy if the boundary is on cluster */
		if ((t = m_split(m, offset, M_DONTWAIT)) == NULL) {
			frag6_remque(q6);
			free(q6, M_FTABLE);
			frag6_nfragpackets--;
			goto dropfrag;
		}
		m_adj(t, sizeof(struct ip6_frag));
		m_cat(m, t);
	}

	/*
	 * Store NXT to the original.
	 */
	{
		char *prvnxtp = ip6_get_prevhdr(m, offset); /* XXX */
		*prvnxtp = nxt;
	}

	frag6_remque(q6);
	free(q6, M_FTABLE);
	frag6_nfragpackets--;

	if (m->m_flags & M_PKTHDR) { /* Isn't it always true? */
		int plen = 0;
		for (t = m; t; t = t->m_next)
			plen += t->m_len;
		m->m_pkthdr.len = plen;
	}
	
	ip6stat.ip6s_reassembled++;
	in6_ifstat_inc(dstifp, ifs6_reass_ok);

	/*
	 * Tell launch routine the next header
	 */

	*mp = m;
	*offp = offset;

	frag6_doing_reass = 0;
	return nxt;

 dropfrag:
	in6_ifstat_inc(dstifp, ifs6_reass_fail);
	ip6stat.ip6s_fragdropped++;
	m_freem(m);
	frag6_doing_reass = 0;
	return IPPROTO_DONE;
}

/*
 * Free a fragment reassembly header and all
 * associated datagrams.
 */
void
frag6_freef(q6)
	struct ip6q *q6;
{
	struct ip6asfrag *af6, *down6;

	for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
	     af6 = down6) {
		struct mbuf *m = IP6_REASS_MBUF(af6);

		down6 = af6->ip6af_down;
		frag6_deq(af6);

		/*
		 * Return ICMP time exceeded error for the 1st fragment.
		 * Just free other fragments.
		 */
		if (af6->ip6af_off == 0) {
			struct ip6_hdr *ip6;

			/* adjust pointer */
			ip6 = mtod(m, struct ip6_hdr *);

			/* restoure source and destination addresses */
			ip6->ip6_src = q6->ip6q_src;
			ip6->ip6_dst = q6->ip6q_dst;

			icmp6_error(m, ICMP6_TIME_EXCEEDED,
				    ICMP6_TIME_EXCEED_REASSEMBLY, 0);
		} else
			m_freem(m);
		free(af6, M_FTABLE);
	}
	frag6_remque(q6);
	free(q6, M_FTABLE);
	frag6_nfragpackets--;
}

/*
 * Put an ip fragment on a reassembly chain.
 * Like insque, but pointers in middle of structure.
 */
void
frag6_enq(af6, up6)
	struct ip6asfrag *af6, *up6;
{
	af6->ip6af_up = up6;
	af6->ip6af_down = up6->ip6af_down;
	up6->ip6af_down->ip6af_up = af6;
	up6->ip6af_down = af6;
}

/*
 * To frag6_enq as remque is to insque.
 */
void
frag6_deq(af6)
	struct ip6asfrag *af6;
{
	af6->ip6af_up->ip6af_down = af6->ip6af_down;
	af6->ip6af_down->ip6af_up = af6->ip6af_up;
}

void
frag6_insque(new, old)
	struct ip6q *new, *old;
{
	new->ip6q_prev = old;
	new->ip6q_next = old->ip6q_next;
	old->ip6q_next->ip6q_prev= new;
	old->ip6q_next = new;
}

void
frag6_remque(p6)
	struct ip6q *p6;
{
	p6->ip6q_prev->ip6q_next = p6->ip6q_next;
	p6->ip6q_next->ip6q_prev = p6->ip6q_prev;
}

/*
 * IPv6 reassembling timer processing;
 * if a timer expires on a reassembly
 * queue, discard it.
 */
void
frag6_slowtimo()
{
	struct ip6q *q6;
#ifdef __NetBSD__
	int s = splsoftnet();
#else
	int s = splnet();
#endif

	frag6_doing_reass = 1;
	q6 = ip6q.ip6q_next;
	if (q6)
		while (q6 != &ip6q) {
			--q6->ip6q_ttl;
			q6 = q6->ip6q_next;
			if (q6->ip6q_prev->ip6q_ttl == 0) {
				ip6stat.ip6s_fragtimeout++;
				/* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
				frag6_freef(q6->ip6q_prev);
			}
		}
	/*
	 * If we are over the maximum number of fragments
	 * (due to the limit being lowered), drain off
	 * enough to get down to the new limit.
	 */
	while (frag6_nfragpackets > (u_int)ip6_maxfragpackets &&
	    ip6q.ip6q_prev) {
		ip6stat.ip6s_fragoverflow++;
		/* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
		frag6_freef(ip6q.ip6q_prev);
	}
	frag6_doing_reass = 0;

#if 0
	/*
	 * Routing changes might produce a better route than we last used;
	 * make sure we notice eventually, even if forwarding only for one
	 * destination and the cache is never replaced.
	 */
	if (ip6_forward_rt.ro_rt) {
		RTFREE(ip6_forward_rt.ro_rt);
		ip6_forward_rt.ro_rt = 0;
	}
	if (ipsrcchk_rt.ro_rt) {
		RTFREE(ipsrcchk_rt.ro_rt);
		ipsrcchk_rt.ro_rt = 0;
	}
#endif

	splx(s);
}

/*
 * Drain off all datagram fragments.
 */
void
frag6_drain()
{
	if (frag6_doing_reass)
		return;
	while (ip6q.ip6q_next != &ip6q) {
		ip6stat.ip6s_fragdropped++;
		/* XXX in6_ifstat_inc(ifp, ifs6_reass_fail) */
		frag6_freef(ip6q.ip6q_next);
	}
}