frag6.c

来自「eCos操作系统源码」· C语言 代码 · 共 737 行 · 第 1/2 页

//==========================================================================
//
//      src/sys/netinet6/frag6.c
//
//==========================================================================
//####BSDCOPYRIGHTBEGIN####
//
// -------------------------------------------
//
// Portions of this software may have been derived from OpenBSD, 
// FreeBSD or other sources, and are covered by the appropriate
// copyright disclaimers included herein.
//
// Portions created by Red Hat are
// Copyright (C) 2002 Red Hat, Inc. All Rights Reserved.
//
// -------------------------------------------
//
//####BSDCOPYRIGHTEND####
//==========================================================================

/*	$KAME: frag6.c,v 1.32 2001/06/21 09:06:29 sumikawa Exp $	*/

/*
 * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the project nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE PROJECT AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE PROJECT OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/param.h>
#include <sys/malloc.h>
#include <sys/mbuf.h>
#include <sys/domain.h>
#include <sys/protosw.h>
#include <sys/socket.h>
#include <sys/errno.h>

#include <net/if.h>
#include <net/route.h>

#include <netinet/in.h>
#include <netinet/in_var.h>
#include <netinet/ip6.h>
#include <netinet6/ip6_var.h>
#if !(defined(__FreeBSD__) && __FreeBSD__ >= 3) && !defined(__OpenBSD__) && !(defined(__bsdi__) && _BSDI_VERSION >= 199802)
#include <netinet6/in6_pcb.h>
#endif
#include <netinet/icmp6.h>

#ifdef __OpenBSD__
#include <dev/rndvar.h>
#endif

/*
 * Define it to get a correct behavior on per-interface statistics.
 * You will need to perform an extra routing table lookup, per fragment,
 * to do it.  This may, or may not be, a performance hit.
 */
#define IN6_IFSTAT_STRICT

static void frag6_enq __P((struct ip6asfrag *, struct ip6asfrag *));
static void frag6_deq __P((struct ip6asfrag *));
static void frag6_insque __P((struct ip6q *, struct ip6q *));
static void frag6_remque __P((struct ip6q *));
static void frag6_freef __P((struct ip6q *));

/* XXX we eventually need splreass6, or some real semaphore */
int frag6_doing_reass;
u_int frag6_nfragpackets;
struct	ip6q ip6q;	/* ip6 reassemble queue */


#ifndef offsetof		/* XXX */
#define	offsetof(type, member)	((size_t)(&((type *)0)->member))
#endif

/*
 * Initialise reassembly queue and fragment identifier.
 */
void
frag6_init()
{
#ifndef __OpenBSD__
	struct timeval tv;

#if defined(__FreeBSD__) && __FreeBSD__ >= 4
	ip6_maxfragpackets = nmbclusters / 4;
#endif

	/*
	 * in many cases, random() here does NOT return random number
	 * as initialization during bootstrap time occur in fixed order.
	 */
	microtime(&tv);
	ip6_id = random() ^ tv.tv_usec;
#else
	ip6_id = arc4random();
#endif
	ip6q.ip6q_next = ip6q.ip6q_prev = &ip6q;
}

/*
 * In RFC2460, fragment and reassembly rule do not agree with each other,
 * in terms of next header field handling in fragment header.
 * While the sender will use the same value for all of the fragmented packets,
 * receiver is suggested not to check the consistency.
 *
 * fragment rule (p20):
 *	(2) A Fragment header containing:
 *	The Next Header value that identifies the first header of
 *	the Fragmentable Part of the original packet.
 *		-> next header field is same for all fragments
 *
 * reassembly rule (p21):
 *	The Next Header field of the last header of the Unfragmentable
 *	Part is obtained from the Next Header field of the first
 *	fragment's Fragment header.
 *		-> should grab it from the first fragment only
 *
 * The following note also contradicts with fragment rule - noone is going to
 * send different fragment with different next header field.
 *
 * additional note (p22):
 *	The Next Header values in the Fragment headers of different
 *	fragments of the same original packet may differ.  Only the value
 *	from the Offset zero fragment packet is used for reassembly.
 *		-> should grab it from the first fragment only
 *
 * There is no explicit reason given in the RFC.  Historical reason maybe?
 */
/*
 * Fragment input
 */
int
frag6_input(mp, offp, proto)
	struct mbuf **mp;
	int *offp, proto;
{
	struct mbuf *m = *mp, *t;
	struct ip6_hdr *ip6;
	struct ip6_frag *ip6f;
	struct ip6q *q6;
	struct ip6asfrag *af6, *ip6af, *af6dwn;
	int offset = *offp, nxt, i, next;
	int first_frag = 0;
	int fragoff, frgpartlen;	/* must be larger than u_int16_t */
	struct ifnet *dstifp;
#ifdef IN6_IFSTAT_STRICT
#ifdef NEW_STRUCT_ROUTE
	static struct route ro;
#else
	static struct route_in6 ro;
#endif
	struct sockaddr_in6 *dst;
#endif

	ip6 = mtod(m, struct ip6_hdr *);
#ifndef PULLDOWN_TEST
	IP6_EXTHDR_CHECK(m, offset, sizeof(struct ip6_frag), IPPROTO_DONE);
	ip6f = (struct ip6_frag *)((caddr_t)ip6 + offset);
#else
	IP6_EXTHDR_GET(ip6f, struct ip6_frag *, m, offset, sizeof(*ip6f));
	if (ip6f == NULL)
		return IPPROTO_DONE;
#endif

	dstifp = NULL;
#ifdef IN6_IFSTAT_STRICT
	/* find the destination interface of the packet. */
	dst = (struct sockaddr_in6 *)&ro.ro_dst;
	if (ro.ro_rt
	 && ((ro.ro_rt->rt_flags & RTF_UP) == 0
	  || !IN6_ARE_ADDR_EQUAL(&dst->sin6_addr, &ip6->ip6_dst))) {
		RTFREE(ro.ro_rt);
		ro.ro_rt = (struct rtentry *)0;
	}
	if (ro.ro_rt == NULL) {
		bzero(dst, sizeof(*dst));
		dst->sin6_family = AF_INET6;
		dst->sin6_len = sizeof(struct sockaddr_in6);
		dst->sin6_addr = ip6->ip6_dst;
	}
#ifndef __bsdi__
	rtalloc((struct route *)&ro);
#else
	rtcalloc((struct route *)&ro);
#endif
	if (ro.ro_rt != NULL && ro.ro_rt->rt_ifa != NULL)
		dstifp = ((struct in6_ifaddr *)ro.ro_rt->rt_ifa)->ia_ifp;
#else
	/* we are violating the spec, this is not the destination interface */
	if ((m->m_flags & M_PKTHDR) != 0)
		dstifp = m->m_pkthdr.rcvif;
#endif

	/* jumbo payload can't contain a fragment header */
	if (ip6->ip6_plen == 0) {
		icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER, offset);
		in6_ifstat_inc(dstifp, ifs6_reass_fail);
		return IPPROTO_DONE;
	}

	/*
	 * check whether fragment packet's fragment length is
	 * multiple of 8 octets.
	 * sizeof(struct ip6_frag) == 8
	 * sizeof(struct ip6_hdr) = 40
	 */
	if ((ip6f->ip6f_offlg & IP6F_MORE_FRAG) &&
	    (((ntohs(ip6->ip6_plen) - offset) & 0x7) != 0)) {
		icmp6_error(m, ICMP6_PARAM_PROB,
			    ICMP6_PARAMPROB_HEADER,
			    offsetof(struct ip6_hdr, ip6_plen));
		in6_ifstat_inc(dstifp, ifs6_reass_fail);
		return IPPROTO_DONE;
	}

	ip6stat.ip6s_fragments++;
	in6_ifstat_inc(dstifp, ifs6_reass_reqd);
	
	/* offset now points to data portion */
	offset += sizeof(struct ip6_frag);

	frag6_doing_reass = 1;

	for (q6 = ip6q.ip6q_next; q6 != &ip6q; q6 = q6->ip6q_next)
		if (ip6f->ip6f_ident == q6->ip6q_ident &&
		    IN6_ARE_ADDR_EQUAL(&ip6->ip6_src, &q6->ip6q_src) &&
		    IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &q6->ip6q_dst))
			break;

	if (q6 == &ip6q) {
		/*
		 * the first fragment to arrive, create a reassembly queue.
		 */
		first_frag = 1;

		/*
		 * Enforce upper bound on number of fragmented packets
		 * for which we attempt reassembly;
		 * If maxfrag is 0, never accept fragments.
		 * If maxfrag is -1, accept all fragments without limitation.
		 */
		if (ip6_maxfragpackets < 0)
			;
		else if (frag6_nfragpackets >= (u_int)ip6_maxfragpackets)
			goto dropfrag;
		frag6_nfragpackets++;
		q6 = (struct ip6q *)malloc(sizeof(struct ip6q), M_FTABLE,
			M_DONTWAIT);
		if (q6 == NULL)
			goto dropfrag;
		bzero(q6, sizeof(*q6));

		frag6_insque(q6, &ip6q);

		/* ip6q_nxt will be filled afterwards, from 1st fragment */
		q6->ip6q_down	= q6->ip6q_up = (struct ip6asfrag *)q6;
#ifdef notyet
		q6->ip6q_nxtp	= (u_char *)nxtp;
#endif
		q6->ip6q_ident	= ip6f->ip6f_ident;
		q6->ip6q_arrive = 0; /* Is it used anywhere? */
		q6->ip6q_ttl 	= IPV6_FRAGTTL;
		q6->ip6q_src	= ip6->ip6_src;
		q6->ip6q_dst	= ip6->ip6_dst;
		q6->ip6q_unfrglen = -1;	/* The 1st fragment has not arrived. */
	}

	/*
	 * If it's the 1st fragment, record the length of the
	 * unfragmentable part and the next header of the fragment header.
	 */
	fragoff = ntohs(ip6f->ip6f_offlg & IP6F_OFF_MASK);
	if (fragoff == 0) {
		q6->ip6q_unfrglen = offset - sizeof(struct ip6_hdr)
			- sizeof(struct ip6_frag);
		q6->ip6q_nxt = ip6f->ip6f_nxt;
	}

	/*
	 * Check that the reassembled packet would not exceed 65535 bytes
	 * in size.
	 * If it would exceed, discard the fragment and return an ICMP error.
	 */
	frgpartlen = sizeof(struct ip6_hdr) + ntohs(ip6->ip6_plen) - offset;
	if (q6->ip6q_unfrglen >= 0) {
		/* The 1st fragment has already arrived. */
		if (q6->ip6q_unfrglen + fragoff + frgpartlen > IPV6_MAXPACKET) {
			icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
				    offset - sizeof(struct ip6_frag) +
					offsetof(struct ip6_frag, ip6f_offlg));
			frag6_doing_reass = 0;
			return(IPPROTO_DONE);
		}
	}
	else if (fragoff + frgpartlen > IPV6_MAXPACKET) {
		icmp6_error(m, ICMP6_PARAM_PROB, ICMP6_PARAMPROB_HEADER,
			    offset - sizeof(struct ip6_frag) +
				offsetof(struct ip6_frag, ip6f_offlg));
		frag6_doing_reass = 0;
		return(IPPROTO_DONE);
	}
	/*
	 * If it's the first fragment, do the above check for each
	 * fragment already stored in the reassembly queue.
	 */
	if (fragoff == 0) {
		for (af6 = q6->ip6q_down; af6 != (struct ip6asfrag *)q6;
		     af6 = af6dwn) {
			af6dwn = af6->ip6af_down;

			if (q6->ip6q_unfrglen + af6->ip6af_off + af6->ip6af_frglen >
			    IPV6_MAXPACKET) {
				struct mbuf *merr = IP6_REASS_MBUF(af6);
				struct ip6_hdr *ip6err;
				int erroff = af6->ip6af_offset;

				/* dequeue the fragment. */
				frag6_deq(af6);
				free(af6, M_FTABLE);

				/* adjust pointer. */
				ip6err = mtod(merr, struct ip6_hdr *);

				/*
				 * Restore source and destination addresses
				 * in the erroneous IPv6 header.
				 */
				ip6err->ip6_src = q6->ip6q_src;
				ip6err->ip6_dst = q6->ip6q_dst;

				icmp6_error(merr, ICMP6_PARAM_PROB,
					    ICMP6_PARAMPROB_HEADER,
					    erroff - sizeof(struct ip6_frag) +
						offsetof(struct ip6_frag, ip6f_offlg));
			}
		}
	}

	ip6af = (struct ip6asfrag *)malloc(sizeof(struct ip6asfrag), M_FTABLE,
	    M_DONTWAIT);
	if (ip6af == NULL)
		goto dropfrag;
	bzero(ip6af, sizeof(*ip6af));
	ip6af->ip6af_head = ip6->ip6_flow;