if_ether.c

很好的一个嵌入式linux平台下的bootloader

/* $Id: if_ether.c,v 1.3 1998/12/28 14:13:18 nigel Exp $ */
/*
 * Copyright (c) 1982, 1986, 1988 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.
 *
 *	@(#)if_ether.c	7.13 (Berkeley) 10/31/90
 */

/*
 * Ethernet address resolution protocol.
 * TODO:
 *	run at splnet (add ARP protocol intr.)
 *	link entries onto hash chains, keep free list
 *	add "inuse/lock" bit (or ref. count) along with valid bit
 */

#include "param.h"
#include "systm.h"
#include "malloc.h"
#include "mbuf.h"
#include "socket.h"
#include "time.h"
#include "kernel.h"
#include "errno.h"
#include "ioctl.h"
#include "syslog.h"

#include "../net/if.h"
#include "in.h"
#include "in_systm.h"
#include "in_var.h"
#include "ip.h"
#include "if_ether.h"

#ifdef GATEWAY
#define	ARPTAB_BSIZ	16		/* bucket size */
#define	ARPTAB_NB	37		/* number of buckets */
#else
#ifdef PROM
#define	ARPTAB_BSIZ	3		/* bucket size */
#define	ARPTAB_NB	7		/* number of buckets */
#else
#define	ARPTAB_BSIZ	9		/* bucket size */
#define	ARPTAB_NB	19		/* number of buckets */
#endif
#endif
#define	ARPTAB_SIZE	(ARPTAB_BSIZ * ARPTAB_NB)

struct	arptab arptab[ARPTAB_SIZE];
const int arptab_size = ARPTAB_SIZE;	/* for arp command */

/*
 * ARP trailer negotiation.  Trailer protocol is not IP specific,
 * but ARP request/response use IP addresses.
 */
#define ETHERTYPE_IPTRAILERS ETHERTYPE_TRAIL

#define	ARPTAB_HASH(a) \
	((u_long)(a) % ARPTAB_NB)

#define	ARPTAB_LOOK(at,addr) { \
	register n; \
	at = &arptab[ARPTAB_HASH(addr) * ARPTAB_BSIZ]; \
	for (n = 0 ; n < ARPTAB_BSIZ ; n++,at++) \
		if (at->at_iaddr.s_addr == addr) \
			break; \
	if (n >= ARPTAB_BSIZ) \
		at = 0; \
}

/* timer values */
#define	ARPT_AGE	(60*1)	/* aging timer, 1 min. */
#define	ARPT_KILLC	20	/* kill completed entry in 20 mins. */
#define	ARPT_KILLI	3	/* kill incomplete entry in 3 minutes */

extern struct ifnet loif;

/*
 * Timeout routine.  Age arp_tab entries once a minute.
 */
arptimer()
{
	register struct arptab *at;
	register i;

	timeout(arptimer, (caddr_t)0, ARPT_AGE * hz);
	at = &arptab[0];
	for (i = 0; i < ARPTAB_SIZE; i++, at++) {
		if (at->at_flags == 0 || (at->at_flags & ATF_PERM))
			continue;
		if (++at->at_timer < ((at->at_flags&ATF_COM) ?
		    ARPT_KILLC : ARPT_KILLI))
			continue;
		/* timer has expired, clear entry */
		arptfree(at);
	}
}

/*
 * Broadcast an ARP packet, asking who has addr on interface ac.
 */
arpwhohas(ac, addr)
	register struct arpcom *ac;
	struct in_addr *addr;
{
	register struct mbuf *m;
	register struct ether_header *eh;
	register struct ether_arp *ea;
	struct sockaddr sa;

	if ((m = m_gethdr(M_DONTWAIT, MT_DATA)) == NULL)
		return;
	m->m_len = sizeof(*ea);
	m->m_pkthdr.len = sizeof(*ea);
	MH_ALIGN(m, sizeof(*ea));
	ea = mtod(m, struct ether_arp *);
	eh = (struct ether_header *)sa.sa_data;
	bzero((caddr_t)ea, sizeof (*ea));
	bcopy((caddr_t)etherbroadcastaddr, (caddr_t)eh->ether_dhost,
	    sizeof(eh->ether_dhost));
	eh->ether_type = ETHERTYPE_ARP;		/* if_output will swap */
	ea->arp_hrd = htons(ARPHRD_ETHER);
	ea->arp_pro = htons(ETHERTYPE_IP);
	ea->arp_hln = sizeof(ea->arp_sha);	/* hardware address length */
	ea->arp_pln = sizeof(ea->arp_spa);	/* protocol address length */
	ea->arp_op = htons(ARPOP_REQUEST);
	bcopy((caddr_t)ac->ac_enaddr, (caddr_t)ea->arp_sha,
	   sizeof(ea->arp_sha));
	bcopy((caddr_t)&ac->ac_ipaddr, (caddr_t)ea->arp_spa,
	   sizeof(ea->arp_spa));
	bcopy((caddr_t)addr, (caddr_t)ea->arp_tpa, sizeof(ea->arp_tpa));
	sa.sa_family = AF_UNSPEC;
	sa.sa_len = sizeof(sa);
	(*ac->ac_if.if_output)(&ac->ac_if, m, &sa, (struct rtentry *)0);
}

#ifdef PROM
const int useloopback = 1;	/* use loopback interface for local traffic */
#else
int	useloopback = 1;	/* use loopback interface for local traffic */
#endif

/*
 * Resolve an IP address into an ethernet address.  If success, 
 * desten is filled in.  If there is no entry in arptab,
 * set one up and broadcast a request for the IP address.
 * Hold onto this mbuf and resend it once the address
 * is finally resolved.  A return value of 1 indicates
 * that desten has been filled in and the packet should be sent
 * normally; a 0 return indicates that the packet has been
 * taken over here, either now or for later transmission.
 *
 * We do some (conservative) locking here at splimp, since
 * arptab is also altered from input interrupt service (ecintr/ilintr
 * calls arpinput when ETHERTYPE_ARP packets come in).
 */
arpresolve(ac, m, destip, desten, usetrailers)
	register struct arpcom *ac;
	struct mbuf *m;
	register struct in_addr *destip;
	register u_char *desten;
	int *usetrailers;
{
	register struct arptab *at;
	struct sockaddr_in sin;
	register struct in_ifaddr *ia;
	u_long lna;
	int s;

	*usetrailers = 0;
	if (m->m_flags & M_BCAST) {	/* broadcast */
		bcopy((caddr_t)etherbroadcastaddr, (caddr_t)desten, 
		      sizeof(ac->ac_enaddr));
		return (1);
	}
	lna = in_lnaof(*destip);
	/* if for us, use software loopback driver if up */
	for (ia = in_ifaddr; ia; ia = ia->ia_next)
	    if ((ia->ia_ifp == &ac->ac_if) &&
		(destip->s_addr == ia->ia_addr.sin_addr.s_addr)) {
		/*
		 * This test used to be
		 *	if (loif.if_flags & IFF_UP)
		 * It allowed local traffic to be forced
		 * through the hardware by configuring the loopback down.
		 * However, it causes problems during network configuration
		 * for boards that can't receive packets they send.
		 * It is now necessary to clear "useloopback"
		 * to force traffic out to the hardware.
		 */
		if (useloopback) {
			sin.sin_family = AF_INET;
			sin.sin_addr = *destip;
			(void) looutput(&loif, m, (struct sockaddr *)&sin, 0);
			/*
			 * The packet has already been sent and freed.
			 */
			return (0);
		} else {
			bcopy((caddr_t)ac->ac_enaddr, (caddr_t)desten,
			    sizeof(ac->ac_enaddr));
			return (1);
		}
	}
	s = splimp();
	ARPTAB_LOOK(at, destip->s_addr);
	if (at == 0) {			/* not found */
		if (ac->ac_if.if_flags & IFF_NOARP) {
			bcopy((caddr_t)ac->ac_enaddr, (caddr_t)desten, 3);
			desten[3] = (lna >> 16) & 0x7f;
			desten[4] = (lna >> 8) & 0xff;
			desten[5] = lna & 0xff;
			splx(s);
			return (1);
		} else {
			at = arptnew(destip);
			if (at == 0)
				panic("arpresolve: no free entry");
			at->at_hold = m;
			arpwhohas(ac, destip);
			splx(s);
			return (0);
		}
	}
	at->at_timer = 0;		/* restart the timer */
	if (at->at_flags & ATF_COM) {	/* entry IS complete */
		bcopy((caddr_t)at->at_enaddr, (caddr_t)desten,
		    sizeof(at->at_enaddr));
		if (at->at_flags & ATF_USETRAILERS)
			*usetrailers = 1;
		splx(s);
		return (1);
	}
	/*
	 * There is an arptab entry, but no ethernet address
	 * response yet.  Replace the held mbuf with this
	 * latest one.
	 */
	if (at->at_hold)
		m_freem(at->at_hold);
	at->at_hold = m;
	arpwhohas(ac, destip);		/* ask again */
	splx(s);
	return (0);
}

/*
 * Called from 10 Mb/s Ethernet interrupt handlers
 * when ether packet type ETHERTYPE_ARP
 * is received.  Common length and type checks are done here,
 * then the protocol-specific routine is called.
 */
arpinput(ac, m)
	struct arpcom *ac;
	struct mbuf *m;
{
	register struct arphdr *ar;

	if (ac->ac_if.if_flags & IFF_NOARP)
		goto out;
	if (m->m_len < sizeof(struct arphdr))
		goto out;
	ar = mtod(m, struct arphdr *);
	if (ntohs(ar->ar_hrd) != ARPHRD_ETHER)
		goto out;
	if (m->m_len < sizeof(struct arphdr) + 2 * ar->ar_hln + 2 * ar->ar_pln)
		goto out;

	switch (ntohs(ar->ar_pro)) {

	case ETHERTYPE_IP:
	case ETHERTYPE_IPTRAILERS:
		in_arpinput(ac, m);
		return;

	default:
		break;
	}
out:
	m_freem(m);
}

/*
 * ARP for Internet protocols on 10 Mb/s Ethernet.
 * Algorithm is that given in RFC 826.
 * In addition, a sanity check is performed on the sender
 * protocol address, to catch impersonators.
 * We also handle negotiations for use of trailer protocol: