clnp_frag.c

早期freebsd实现

/*-
 * Copyright (c) 1991, 1993
 *	The Regents of the University of California.  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. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University 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 REGENTS 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 REGENTS 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.
 *
 *	@(#)clnp_frag.c	8.1 (Berkeley) 6/10/93
 */

/***********************************************************
		Copyright IBM Corporation 1987

                      All Rights Reserved

Permission to use, copy, modify, and distribute this software and its 
documentation for any purpose and without fee is hereby granted, 
provided that the above copyright notice appear in all copies and that
both that copyright notice and this permission notice appear in 
supporting documentation, and that the name of IBM not be
used in advertising or publicity pertaining to distribution of the
software without specific, written prior permission.  

IBM DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE, INCLUDING
ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO EVENT SHALL
IBM BE LIABLE FOR ANY SPECIAL, INDIRECT OR CONSEQUENTIAL DAMAGES OR
ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS,
WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION,
ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS
SOFTWARE.

******************************************************************/

/*
 * ARGO Project, Computer Sciences Dept., University of Wisconsin - Madison
 */
/* $Header: /var/src/sys/netiso/RCS/clnp_frag.c,v 5.1 89/02/09 16:20:26 hagens Exp $ */
/* $Source: /var/src/sys/netiso/RCS/clnp_frag.c,v $ */

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

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

#include <netiso/iso.h>
#include <netiso/iso_var.h>
#include <netiso/clnp.h>
#include <netiso/clnp_stat.h>
#include <netiso/argo_debug.h>

/* all fragments are hung off this list */
struct clnp_fragl	*clnp_frags = NULL;

struct mbuf	*clnp_comp_pdu();


/*
 * FUNCTION:		clnp_fragment
 *
 * PURPOSE:			Fragment a datagram, and send the itty bitty pieces
 *					out over an interface.
 *
 * RETURNS:			success - 0
 *					failure - unix error code
 *
 * SIDE EFFECTS:	
 *
 * NOTES:			If there is an error sending the packet, clnp_discard
 *					is called to discard the packet and send an ER. If
 *					clnp_fragment was called from clnp_output, then
 *					we generated the packet, and should not send an 
 *					ER -- clnp_emit_er will check for this. Otherwise,
 *					the packet was fragmented during forwarding. In this
 *					case, we ought to send an ER back.
 */
clnp_fragment(ifp, m, first_hop, total_len, segoff, flags, rt)
struct ifnet	*ifp;		/* ptr to outgoing interface */
struct mbuf		*m;			/* ptr to packet */
struct sockaddr	*first_hop;	/* ptr to first hop */
int				total_len;	/* length of datagram */
int				segoff;		/* offset of segpart in hdr */
int				flags;		/* flags passed to clnp_output */
struct rtentry *rt;			/* route if direct ether */
{
	struct clnp_fixed		*clnp = mtod(m, struct clnp_fixed *);
	int						hdr_len = (int)clnp->cnf_hdr_len;
	int						frag_size = (SN_MTU(ifp, rt) - hdr_len) & ~7;

	total_len -= hdr_len;
	if ((clnp->cnf_type & CNF_SEG_OK) &&
		(total_len >= 8) &&
		(frag_size > 8 || (frag_size == 8 && !(total_len & 7)))) {

		struct mbuf			*hdr = NULL;		/* save copy of clnp hdr */
		struct mbuf			*frag_hdr = NULL;
		struct mbuf			*frag_data = NULL;
		struct clnp_segment	seg_part;			/* segmentation header */
		int					frag_base;
		int					error = 0;


		INCSTAT(cns_fragmented);
        (void) bcopy(segoff + mtod(m, caddr_t), (caddr_t)&seg_part,
            sizeof(seg_part));
		frag_base = ntohs(seg_part.cng_off);
		/*
		 *	Duplicate header, and remove from packet
		 */
		if ((hdr = m_copy(m, 0, hdr_len)) == NULL) {
			clnp_discard(m, GEN_CONGEST);
			return(ENOBUFS);
		}
		m_adj(m, hdr_len);

		while (total_len > 0) {
			int		remaining, last_frag;

			IFDEBUG(D_FRAG)
				struct mbuf *mdump = frag_hdr;
				int tot_mlen = 0;
				printf("clnp_fragment: total_len %d:\n", total_len);
				while (mdump != NULL) {
					printf("\tmbuf x%x, m_len %d\n", 
						mdump, mdump->m_len);
					tot_mlen += mdump->m_len;
					mdump = mdump->m_next;
				}
				printf("clnp_fragment: sum of mbuf chain %d:\n", tot_mlen);
			ENDDEBUG
			
			frag_size = min(total_len, frag_size);
			if ((remaining = total_len - frag_size) == 0)
				last_frag = 1;
			else {
				/*
				 *  If this fragment will cause the last one to 
				 *	be less than 8 bytes, shorten this fragment a bit.
				 *  The obscure test on frag_size above ensures that
				 *  frag_size will be positive.
				 */
				last_frag = 0;
				if (remaining < 8)
						frag_size -= 8;
			}
			

			IFDEBUG(D_FRAG)
				printf("clnp_fragment: seg off %d, size %d, remaining %d\n", 
					ntohs(seg_part.cng_off), frag_size, total_len-frag_size);
				if (last_frag)
					printf("clnp_fragment: last fragment\n");
			ENDDEBUG

			if (last_frag) {
				/* 
				 *	this is the last fragment; we don't need to get any other
				 *	mbufs.
				 */
				frag_hdr = hdr;
				frag_data = m;
			} else {
				/* duplicate header and data mbufs */
				if ((frag_hdr = m_copy(hdr, 0, (int)M_COPYALL)) == NULL) {
					clnp_discard(hdr, GEN_CONGEST);
					m_freem(m);
					return(ENOBUFS);
				}
				if ((frag_data = m_copy(m, 0, frag_size)) == NULL) {
					clnp_discard(hdr, GEN_CONGEST);
					m_freem(m);
					m_freem(frag_hdr);
					return(ENOBUFS);
				}
				INCSTAT(cns_fragments);
			}
			clnp = mtod(frag_hdr, struct clnp_fixed *);

			if (!last_frag)
				clnp->cnf_type |= CNF_MORE_SEGS;
			
			/* link together */
			m_cat(frag_hdr, frag_data);

			/* insert segmentation part; updated below */
			bcopy((caddr_t)&seg_part, mtod(frag_hdr, caddr_t) + segoff,
				sizeof(struct clnp_segment));

			{
				int	derived_len = hdr_len + frag_size;
				HTOC(clnp->cnf_seglen_msb, clnp->cnf_seglen_lsb, derived_len);
				if ((frag_hdr->m_flags & M_PKTHDR) == 0)
					panic("clnp_frag:lost header");
				frag_hdr->m_pkthdr.len = derived_len;
			}
			/* compute clnp checksum (on header only) */
			if (flags & CLNP_NO_CKSUM) {
				HTOC(clnp->cnf_cksum_msb, clnp->cnf_cksum_lsb, 0);
			} else {
				iso_gen_csum(frag_hdr, CLNP_CKSUM_OFF, hdr_len);
			}

			IFDEBUG(D_DUMPOUT)
				struct mbuf *mdump = frag_hdr;
				printf("clnp_fragment: sending dg:\n");
				while (mdump != NULL) {
					printf("\tmbuf x%x, m_len %d\n", mdump, mdump->m_len);
					mdump = mdump->m_next;
				}
			ENDDEBUG

#ifdef	TROLL
			error = troll_output(ifp, frag_hdr, first_hop, rt);
#else
			error = (*ifp->if_output)(ifp, frag_hdr, first_hop, rt);
#endif	/* TROLL */

			/*
			 *	Tough situation: if the error occured on the last 
			 *	fragment, we can not send an ER, as the if_output
			 *	routine consumed the packet. If the error occured
			 *	on any intermediate packets, we can send an ER
			 *	because we still have the original header in (m).
			 */
			if (error) {
				if (frag_hdr != hdr) {
					/* 
					 *	The error was not on the last fragment. We must
					 *	free hdr and m before returning
					 */
					clnp_discard(hdr, GEN_NOREAS);
					m_freem(m);
				}
				return(error);
			}

			/* bump segment offset, trim data mbuf, and decrement count left */
#ifdef	TROLL
			/*
			 *	Decrement frag_size by some fraction. This will cause the
			 *	next fragment to start 'early', thus duplicating the end
			 *	of the current fragment.  troll.tr_dup_size controls
			 *	the fraction. If positive, it specifies the fraction. If
			 *	negative, a random fraction is used.
			 */
			if ((trollctl.tr_ops & TR_DUPEND) && (!last_frag)) {
				int num_bytes = frag_size;

				if (trollctl.tr_dup_size > 0) 
					num_bytes *= trollctl.tr_dup_size;
				else
					num_bytes *= troll_random();
				frag_size -= num_bytes;
			}
#endif	/* TROLL */
			total_len -= frag_size;
			if (!last_frag) {
				frag_base += frag_size;
				seg_part.cng_off = htons(frag_base);
				m_adj(m, frag_size);
			}
		}
		return(0);
	} else {
	cantfrag:
		INCSTAT(cns_cantfrag);
		clnp_discard(m, GEN_SEGNEEDED);
		return(EMSGSIZE);
	}
}

/*
 * FUNCTION:		clnp_reass
 *
 * PURPOSE:			Attempt to reassemble a clnp packet given the current
 *					fragment. If reassembly succeeds (all the fragments
 *					are present), then return a pointer to an mbuf chain
 *					containing the reassembled packet. This packet will
 *					appear in the mbufs as if it had just arrived in
 *					one piece. 
 *
 *					If reassembly fails, then save this fragment and
 *					return 0.
 *
 * RETURNS:			Ptr to assembled packet, or 0
 *
 * SIDE EFFECTS:	
 *
 * NOTES:			
 *		clnp_slowtimo can not affect this code because clnpintr, and thus
 *		this code, is called at a higher priority than clnp_slowtimo.
 */
struct mbuf *
clnp_reass(m, src, dst, seg)
struct mbuf 		*m;		/* new fragment */
struct iso_addr		*src;	/* src of new fragment */
struct iso_addr		*dst; 	/* dst of new fragment */
struct clnp_segment	*seg;	/* segment part of fragment header */
{
	register struct clnp_fragl		*cfh;

	/* look for other fragments of this datagram */
	for (cfh = clnp_frags; cfh != NULL; cfh = cfh->cfl_next) {
		if (seg->cng_id == cfh->cfl_id &&
		    iso_addrmatch1(src, &cfh->cfl_src) && 
			iso_addrmatch1(dst, &cfh->cfl_dst)) {
			IFDEBUG(D_REASS)
				printf("clnp_reass: found packet\n");
			ENDDEBUG
			/*
			 *	There are other fragments here already. Lets see if
			 *	this fragment is of any help
			 */
			clnp_insert_frag(cfh, m, seg);
			if (m = clnp_comp_pdu(cfh)) {
				register struct clnp_fixed *clnp = mtod(m, struct clnp_fixed *);
				HTOC(clnp->cnf_seglen_msb, clnp->cnf_seglen_lsb,
					 seg->cng_tot_len);
			}
			return (m);
		}
	}

	IFDEBUG(D_REASS)
		printf("clnp_reass: new packet!\n");
	ENDDEBUG

	/*
	 *	This is the first fragment. If src is not consuming too many
	 *	resources, then create a new fragment list and add
	 *	this fragment to the list.
	 */
	/* TODO: don't let one src hog all the reassembly buffers */
	if (!clnp_newpkt(m, src, dst, seg) /* || this src is a hog */) {
		INCSTAT(cns_fragdropped);
		clnp_discard(m, GEN_CONGEST);
	}

	return(NULL);
}

/*
 * FUNCTION:		clnp_newpkt
 *
 * PURPOSE:			Create the necessary structures to handle a new
 *					fragmented clnp packet.
 *
 * RETURNS:			non-zero if it succeeds, zero if fails.
 *
 * SIDE EFFECTS:	
 *
 * NOTES:			Failure is only due to insufficient resources.
 */
clnp_newpkt(m, src, dst, seg)
struct mbuf 		*m;		/* new fragment */
struct iso_addr		*src;	/* src of new fragment */
struct iso_addr		*dst; 	/* dst of new fragment */
struct clnp_segment	*seg;	/* segment part of fragment header */
{
	register struct clnp_fragl		*cfh;
	register struct clnp_fixed		*clnp;
	struct mbuf 					*m0;
	
	clnp = mtod(m, struct clnp_fixed *);

	/* 
	 *	Allocate new clnp fragl structure to act as header of all fragments
	 *	for this datagram.
	 */
	MGET(m0, M_DONTWAIT, MT_FTABLE);
	if (m0 == NULL) {
		return (0);
	}
	cfh = mtod(m0, struct clnp_fragl *);

	/* 
	 *	Duplicate the header of this fragment, and save in cfh.
	 *	Free m0 and return if m_copy does not succeed.
	 */
	if ((cfh->cfl_orighdr = m_copy(m, 0, (int)clnp->cnf_hdr_len)) == NULL) {
		m_freem(m0);
		return (0);
	}
	
	/* Fill in rest of fragl structure */
	bcopy((caddr_t)src, (caddr_t)&cfh->cfl_src, sizeof(struct iso_addr));
	bcopy((caddr_t)dst, (caddr_t)&cfh->cfl_dst, sizeof(struct iso_addr));
	cfh->cfl_id = seg->cng_id;
	cfh->cfl_ttl = clnp->cnf_ttl;
	cfh->cfl_last = (seg->cng_tot_len - clnp->cnf_hdr_len) - 1;
	cfh->cfl_frags = NULL;
	cfh->cfl_next = NULL;

	/* Insert into list of packets */
	cfh->cfl_next = clnp_frags;
	clnp_frags = cfh;

	/* Insert this fragment into list headed by cfh */
	clnp_insert_frag(cfh, m, seg);