mirror of
https://git.FreeBSD.org/src.git
synced 2024-10-19 02:29:40 +00:00
Made SLIP MTU configurable via ifconfig(8). Changed default MTU to 552
as it is a better choice in a day with BTLZ compression modems.
This commit is contained in:
David Greenman
parent
e9512b6c30
commit
fe19c3238d
Notes:
svn2git
2020-12-20 02:59:44 +00:00
svn path=/head/; revision=2735
@ -31,7 +31,7 @@
|
||||
* SUCH DAMAGE.
|
||||
*
|
||||
* @(#)if_sl.c 8.6 (Berkeley) 2/1/94
|
||||
* $Id: if_sl.c,v 1.5 1994/09/09 12:58:10 davidg Exp $
|
||||
* $Id: if_sl.c,v 1.6 1994/09/12 11:49:49 davidg Exp $
|
||||
*/
|
||||
|
||||
/*
|
||||
@ -109,33 +109,30 @@ Huh? Slip without inet?
|
||||
#endif
|
||||
|
||||
/*
|
||||
* SLMAX is a hard limit on input packet size. To simplify the code
|
||||
* SLRMAX 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
|
||||
* bytes). So, SLRMAX 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).
|
||||
* SLMTU is the default transmit MTU. The transmit MTU should be kept
|
||||
* small enough so that interactive use doesn't suffer, but large
|
||||
* enough to provide good performance. 552 is a good choice for SLMTU
|
||||
* because it is high enough to not fragment TCP packets being routed
|
||||
* through this host. Packet fragmentation is bad with SLIP because
|
||||
* fragment headers aren't compressed. The previous assumptions about
|
||||
* the best MTU value don't really hold when using modern modems with
|
||||
* BTLZ data compression because the modem buffers play a much larger
|
||||
* role in interactive performance than the MTU. The MTU can be changed
|
||||
* at any time to suit the specific environment with ifconfig(8), and
|
||||
* its maximum value is defined as SLTMAX. SLTMAX must not be so large
|
||||
* that it would overflow the stack if BPF is configured.
|
||||
*
|
||||
* 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.
|
||||
* SLIP_HIWAT is 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
|
||||
@ -153,13 +150,17 @@ Huh? Slip without inet?
|
||||
#else
|
||||
#define BUFOFFSET (128+sizeof(struct ifnet **))
|
||||
#endif
|
||||
#define SLMAX (MCLBYTES - BUFOFFSET)
|
||||
#define SLBUFSIZE (SLMAX + BUFOFFSET)
|
||||
#define SLRMAX (MCLBYTES - BUFOFFSET)
|
||||
#define SLBUFSIZE (SLRMAX + BUFOFFSET)
|
||||
#ifndef SLMTU
|
||||
#define SLMTU 296
|
||||
#define SLMTU 552 /* default MTU */
|
||||
#endif
|
||||
#define SLTMAX 1500 /* maximum MTU */
|
||||
#define SLIP_HIWAT roundup(50,CBSIZE)
|
||||
#define CLISTRESERVE 1024 /* Can't let clists get too low */
|
||||
#define CLISTRESERVE 1024 /* Can't let clists get too low */
|
||||
|
||||
/* add this many cblocks to the pool */
|
||||
#define CLISTEXTRA ((SLRMAX+SLTMAX) / CBSIZE)
|
||||
|
||||
/*
|
||||
* SLIP ABORT ESCAPE MECHANISM:
|
||||
@ -229,7 +230,7 @@ slinit(sc)
|
||||
return (0);
|
||||
}
|
||||
}
|
||||
sc->sc_buf = sc->sc_ep - SLMAX;
|
||||
sc->sc_buf = sc->sc_ep - SLRMAX;
|
||||
sc->sc_mp = sc->sc_buf;
|
||||
sl_compress_init(&sc->sc_comp);
|
||||
return (1);
|
||||
@ -264,6 +265,9 @@ slopen(dev, tp)
|
||||
sc->sc_ttyp = tp;
|
||||
sc->sc_if.if_baudrate = tp->t_ospeed;
|
||||
ttyflush(tp, FREAD | FWRITE);
|
||||
|
||||
cblock_alloc_cblocks(CLISTEXTRA);
|
||||
|
||||
return (0);
|
||||
}
|
||||
return (ENXIO);
|
||||
@ -292,6 +296,7 @@ slclose(tp)
|
||||
sc->sc_ep = 0;
|
||||
sc->sc_mp = 0;
|
||||
sc->sc_buf = 0;
|
||||
cblock_free_cblocks(CLISTEXTRA);
|
||||
}
|
||||
splx(s);
|
||||
}
|
||||
@ -400,7 +405,7 @@ slstart(tp)
|
||||
int s;
|
||||
struct mbuf *m2;
|
||||
#if NBPFILTER > 0
|
||||
u_char bpfbuf[SLMTU + SLIP_HDRLEN];
|
||||
u_char bpfbuf[SLTMAX + SLIP_HDRLEN];
|
||||
register int len = 0;
|
||||
#endif
|
||||
extern int cfreecount;
|
||||
@ -486,9 +491,12 @@ slstart(tp)
|
||||
/*
|
||||
* If system is getting low on clists, just flush our
|
||||
* output queue (if the stuff was important, it'll get
|
||||
* retransmitted).
|
||||
* retransmitted). Note that SLTMAX is used instead of
|
||||
* the current if_mtu setting because connections that
|
||||
* have already been established still use the original
|
||||
* (possibly larger) mss.
|
||||
*/
|
||||
if (cfreecount < CLISTRESERVE + SLMTU) {
|
||||
if (cfreecount < CLISTRESERVE + SLTMAX) {
|
||||
m_freem(m);
|
||||
sc->sc_if.if_collisions++;
|
||||
continue;
|
||||
@ -784,7 +792,7 @@ slinput(c, tp)
|
||||
error:
|
||||
sc->sc_if.if_ierrors++;
|
||||
newpack:
|
||||
sc->sc_mp = sc->sc_buf = sc->sc_ep - SLMAX;
|
||||
sc->sc_mp = sc->sc_buf = sc->sc_ep - SLRMAX;
|
||||
sc->sc_escape = 0;
|
||||
}
|
||||
|
||||
@ -798,8 +806,10 @@ slioctl(ifp, cmd, data)
|
||||
caddr_t data;
|
||||
{
|
||||
register struct ifaddr *ifa = (struct ifaddr *)data;
|
||||
register struct ifreq *ifr;
|
||||
register int s = splimp(), error = 0;
|
||||
register struct ifreq *ifr = (struct ifreq *)data;
|
||||
register int s, error = 0;
|
||||
|
||||
s = splimp();
|
||||
|
||||
switch (cmd) {
|
||||
|
||||
@ -817,7 +827,6 @@ slioctl(ifp, cmd, data)
|
||||
|
||||
case SIOCADDMULTI:
|
||||
case SIOCDELMULTI:
|
||||
ifr = (struct ifreq *)data;
|
||||
if (ifr == 0) {
|
||||
error = EAFNOSUPPORT; /* XXX */
|
||||
break;
|
||||
@ -835,6 +844,17 @@ slioctl(ifp, cmd, data)
|
||||
}
|
||||
break;
|
||||
|
||||
case SIOCSIFMTU:
|
||||
/*
|
||||
* Set the interface MTU.
|
||||
*/
|
||||
if (ifr->ifr_mtu > SLTMAX) {
|
||||
error = EINVAL;
|
||||
} else {
|
||||
ifp->if_mtu = ifr->ifr_mtu;
|
||||
}
|
||||
break;
|
||||
|
||||
default:
|
||||
error = EINVAL;
|
||||
}
|
||||
|
||||
Loading…
Reference in New Issue
Block a user