if_sl.c

早期freebsd实现

/*
 * Copyright (c) 1987, 1989, 1992, 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.
 *
 *	@(#)if_sl.c	8.6 (Berkeley) 2/1/94
 */

/*
 * Serial Line interface
 *
 * Rick Adams
 * Center for Seismic Studies
 * 1300 N 17th Street, Suite 1450
 * Arlington, Virginia 22209
 * [phone]
 * [e-mail]
 * seismo!rick
 *
 * Pounded on heavily by Chris Torek ([e-mail], umcp-cs!chris).
 * N.B.: this belongs in netinet, not net, the way it stands now.
 * Should have a link-layer type designation, but wouldn't be
 * backwards-compatible.
 *
 * Converted to 4.3BSD Beta by Chris Torek.
 * Other changes made at Berkeley, based in part on code by Kirk Smith.
 * W. Jolitz added slip abort.
 *
 * Hacked almost beyond recognition by Van Jacobson ([e-mail]).
 * Added priority queuing for "interactive" traffic; hooks for TCP
 * header compression; ICMP filtering (at 2400 baud, some cretin
 * pinging you can use up all your bandwidth).  Made low clist behavior
 * more robust and slightly less likely to hang serial line.
 * Sped up a bunch of things.
 * 
 * Note that splimp() is used throughout to block both (tty) input
 * interrupts and network activity; thus, splimp must be >= spltty.
 */

#include "sl.h"
#if NSL > 0

#include "bpfilter.h"

#include <sys/param.h>
#include <sys/proc.h>
#include <sys/mbuf.h>
#include <sys/buf.h>
#include <sys/dkstat.h>
#include <sys/socket.h>
#include <sys/ioctl.h>
#include <sys/file.h>
#include <sys/tty.h>
#include <sys/kernel.h>
#include <sys/conf.h>

#include <machine/cpu.h>

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

#if INET
#include <netinet/in.h>
#include <netinet/in_systm.h>
#include <netinet/in_var.h>
#include <netinet/ip.h>
#else
Huh? Slip without inet?
#endif

#include <net/slcompress.h>
#include <net/if_slvar.h>
#include <net/slip.h>

#if NBPFILTER > 0
#include <sys/time.h>
#include <net/bpf.h>
#endif

/*
 * SLMAX is a hard limit on input packet size.  To simplify the code
 * and improve performance, we require that packets fit in an mbuf
 * cluster, and if we get a compressed packet, there's enough extra
 * room to expand the header into a max length tcp/ip header (128
 * bytes).  So, SLMAX can be at most
 *	MCLBYTES - 128
 *
 * SLMTU is a hard limit on output packet size.  To insure good
 * interactive response, SLMTU wants to be the smallest size that
 * amortizes the header cost.  (Remember that even with
 * type-of-service queuing, we have to wait for any in-progress
 * packet to finish.  I.e., we wait, on the average, 1/2 * mtu /
 * cps, where cps is the line speed in characters per second.
 * E.g., 533ms wait for a 1024 byte MTU on a 9600 baud line.  The
 * average compressed header size is 6-8 bytes so any MTU > 90
 * bytes will give us 90% of the line bandwidth.  A 100ms wait is
 * tolerable (500ms is not), so want an MTU around 296.  (Since TCP
 * will send 256 byte segments (to allow for 40 byte headers), the
 * typical packet size on the wire will be around 260 bytes).  In
 * 4.3tahoe+ systems, we can set an MTU in a route so we do that &
 * leave the interface MTU relatively high (so we don't IP fragment
 * when acting as a gateway to someone using a stupid MTU).
 *
 * Similar considerations apply to SLIP_HIWAT:  It's the amount of
 * data that will be queued 'downstream' of us (i.e., in clists
 * waiting to be picked up by the tty output interrupt).  If we
 * queue a lot of data downstream, it's immune to our t.o.s. queuing.
 * E.g., if SLIP_HIWAT is 1024, the interactive traffic in mixed
 * telnet/ftp will see a 1 sec wait, independent of the mtu (the
 * wait is dependent on the ftp window size but that's typically
 * 1k - 4k).  So, we want SLIP_HIWAT just big enough to amortize
 * the cost (in idle time on the wire) of the tty driver running
 * off the end of its clists & having to call back slstart for a
 * new packet.  For a tty interface with any buffering at all, this
 * cost will be zero.  Even with a totally brain dead interface (like
 * the one on a typical workstation), the cost will be <= 1 character
 * time.  So, setting SLIP_HIWAT to ~100 guarantees that we'll lose
 * at most 1% while maintaining good interactive response.
 */
#if NBPFILTER > 0
#define	BUFOFFSET	(128+sizeof(struct ifnet **)+SLIP_HDRLEN)
#else
#define	BUFOFFSET	(128+sizeof(struct ifnet **))
#endif
#define	SLMAX		(MCLBYTES - BUFOFFSET)
#define	SLBUFSIZE	(SLMAX + BUFOFFSET)
#define	SLMTU		296
#define	SLIP_HIWAT	roundup(50,CBSIZE)
#define	CLISTRESERVE	1024	/* Can't let clists get too low */

/*
 * SLIP ABORT ESCAPE MECHANISM:
 *	(inspired by HAYES modem escape arrangement)
 *	1sec escape 1sec escape 1sec escape { 1sec escape 1sec escape }
 *	within window time signals a "soft" exit from slip mode by remote end
 *	if the IFF_DEBUG flag is on.
 */
#define	ABT_ESC		'\033'	/* can't be t_intr - distant host must know it*/
#define	ABT_IDLE	1	/* in seconds - idle before an escape */
#define	ABT_COUNT	3	/* count of escapes for abort */
#define	ABT_WINDOW	(ABT_COUNT*2+2)	/* in seconds - time to count */

struct sl_softc sl_softc[NSL];

#define FRAME_END	 	0xc0		/* Frame End */
#define FRAME_ESCAPE		0xdb		/* Frame Esc */
#define TRANS_FRAME_END	 	0xdc		/* transposed frame end */
#define TRANS_FRAME_ESCAPE 	0xdd		/* transposed frame esc */

extern struct timeval time;

static int slinit __P((struct sl_softc *));
static struct mbuf *sl_btom __P((struct sl_softc *, int));

/*
 * Called from boot code to establish sl interfaces.
 */
void
slattach()
{
	register struct sl_softc *sc;
	register int i = 0;

	for (sc = sl_softc; i < NSL; sc++) {
		sc->sc_if.if_name = "sl";
		sc->sc_if.if_next = NULL;
		sc->sc_if.if_unit = i++;
		sc->sc_if.if_mtu = SLMTU;
		sc->sc_if.if_flags =
		    IFF_POINTOPOINT | SC_AUTOCOMP | IFF_MULTICAST;
		sc->sc_if.if_type = IFT_SLIP;
		sc->sc_if.if_ioctl = slioctl;
		sc->sc_if.if_output = sloutput;
		sc->sc_if.if_snd.ifq_maxlen = 50;
		sc->sc_fastq.ifq_maxlen = 32;
		if_attach(&sc->sc_if);
#if NBPFILTER > 0
		bpfattach(&sc->sc_bpf, &sc->sc_if, DLT_SLIP, SLIP_HDRLEN);
#endif
	}
}

static int
slinit(sc)
	register struct sl_softc *sc;
{
	register caddr_t p;

	if (sc->sc_ep == (u_char *) 0) {
		MCLALLOC(p, M_WAIT);
		if (p)
			sc->sc_ep = (u_char *)p + SLBUFSIZE;
		else {
			printf("sl%d: can't allocate buffer\n", sc - sl_softc);
			sc->sc_if.if_flags &= ~IFF_UP;
			return (0);
		}
	}
	sc->sc_buf = sc->sc_ep - SLMAX;
	sc->sc_mp = sc->sc_buf;
	sl_compress_init(&sc->sc_comp);
	return (1);
}

/*
 * Line specific open routine.
 * Attach the given tty to the first available sl unit.
 */
/* ARGSUSED */
int
slopen(dev, tp)
	dev_t dev;
	register struct tty *tp;
{
	struct proc *p = curproc;		/* XXX */
	register struct sl_softc *sc;
	register int nsl;
	int error;

	if (error = suser(p->p_ucred, &p->p_acflag))
		return (error);

	if (tp->t_line == SLIPDISC)
		return (0);

	for (nsl = NSL, sc = sl_softc; --nsl >= 0; sc++)
		if (sc->sc_ttyp == NULL) {
			if (slinit(sc) == 0)
				return (ENOBUFS);
			tp->t_sc = (caddr_t)sc;
			sc->sc_ttyp = tp;
			sc->sc_if.if_baudrate = tp->t_ospeed;
			ttyflush(tp, FREAD | FWRITE);
			return (0);
		}
	return (ENXIO);
}

/*
 * Line specific close routine.
 * Detach the tty from the sl unit.
 */
void
slclose(tp)
	struct tty *tp;
{
	register struct sl_softc *sc;
	int s;

	ttywflush(tp);
	s = splimp();		/* actually, max(spltty, splnet) */
	tp->t_line = 0;
	sc = (struct sl_softc *)tp->t_sc;
	if (sc != NULL) {
		if_down(&sc->sc_if);
		sc->sc_ttyp = NULL;
		tp->t_sc = NULL;
		MCLFREE((caddr_t)(sc->sc_ep - SLBUFSIZE));
		sc->sc_ep = 0;
		sc->sc_mp = 0;
		sc->sc_buf = 0;
	}
	splx(s);
}

/*
 * Line specific (tty) ioctl routine.
 * Provide a way to get the sl unit number.
 */
/* ARGSUSED */
int
sltioctl(tp, cmd, data, flag)
	struct tty *tp;
	int cmd;
	caddr_t data;
	int flag;
{
	struct sl_softc *sc = (struct sl_softc *)tp->t_sc;

	switch (cmd) {
	case SLIOCGUNIT:
		*(int *)data = sc->sc_if.if_unit;
		break;

	default:
		return (-1);
	}
	return (0);
}

/*
 * Queue a packet.  Start transmission if not active.
 * Compression happens in slstart; if we do it here, IP TOS
 * will cause us to not compress "background" packets, because
 * ordering gets trashed.  It can be done for all packets in slstart.
 */
int
sloutput(ifp, m, dst, rtp)
	struct ifnet *ifp;
	register struct mbuf *m;
	struct sockaddr *dst;
	struct rtentry *rtp;
{
	register struct sl_softc *sc = &sl_softc[ifp->if_unit];
	register struct ip *ip;
	register struct ifqueue *ifq;
	int s;

	/*
	 * `Cannot happen' (see slioctl).  Someday we will extend
	 * the line protocol to support other address families.
	 */
	if (dst->sa_family != AF_INET) {
		printf("sl%d: af%d not supported\n", sc->sc_if.if_unit,
			dst->sa_family);
		m_freem(m);
		sc->sc_if.if_noproto++;
		return (EAFNOSUPPORT);
	}

	if (sc->sc_ttyp == NULL) {
		m_freem(m);
		return (ENETDOWN);	/* sort of */
	}
	if ((sc->sc_ttyp->t_state & TS_CARR_ON) == 0 &&
	    (sc->sc_ttyp->t_cflag & CLOCAL) == 0) {
		m_freem(m);
		return (EHOSTUNREACH);
	}
	ifq = &sc->sc_if.if_snd;
	ip = mtod(m, struct ip *);
	if (sc->sc_if.if_flags & SC_NOICMP && ip->ip_p == IPPROTO_ICMP) {
		m_freem(m);
		return (ENETRESET);		/* XXX ? */
	}
	if (ip->ip_tos & IPTOS_LOWDELAY)
		ifq = &sc->sc_fastq;
	s = splimp();
	if (IF_QFULL(ifq)) {
		IF_DROP(ifq);
		m_freem(m);
		splx(s);
		sc->sc_if.if_oerrors++;
		return (ENOBUFS);
	}
	IF_ENQUEUE(ifq, m);
	sc->sc_if.if_lastchange = time;
	if (sc->sc_ttyp->t_outq.c_cc == 0)
		slstart(sc->sc_ttyp);
	splx(s);
	return (0);
}

/*
 * Start output on interface.  Get another datagram
 * to send from the interface queue and map it to
 * the interface before starting output.
 */
void
slstart(tp)
	register struct tty *tp;
{
	register struct sl_softc *sc = (struct sl_softc *)tp->t_sc;
	register struct mbuf *m;
	register u_char *cp;
	register struct ip *ip;
	int s;
	struct mbuf *m2;
#if NBPFILTER > 0
	u_char bpfbuf[SLMTU + SLIP_HDRLEN];
	register int len;
#endif
	extern int cfreecount;

	for (;;) {
		/*
		 * If there is more in the output queue, just send it now.
		 * We are being called in lieu of ttstart and must do what
		 * it would.
		 */
		if (tp->t_outq.c_cc != 0) {
			(*tp->t_oproc)(tp);
			if (tp->t_outq.c_cc > SLIP_HIWAT)
				return;
		}
		/*
		 * This happens briefly when the line shuts down.
		 */
		if (sc == NULL)
			return;