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[PATCH] SMACK support for mkiss
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SMACK (Stuttgart Modified Amateurradio CRC KISS) is a KISS variant that
uses CRC16 checksums to secure data transfers between the modem and host.
It's also used to communicate over a pty to applications such as Wampes.

Patches for Linux 2.4 by Thomas Osterried DL9SAU, upgraded to the latest
mkiss 2.6 mkiss driver by me.

Signed-off-by: Thomas Osterried DL9SAU <thomas@x-berg.in-berlin.de>
Signed-off-by: Ralf Baechle DL5RB <ralf@linux-mips.org>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>
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Ralf Baechle authored and Jeff Garzik committed Oct 18, 2005
1 parent bc0a743 commit 5793f4b
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Showing 2 changed files with 148 additions and 31 deletions.
1 change: 1 addition & 0 deletions drivers/net/hamradio/Kconfig
View file
Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
config MKISS
tristate "Serial port KISS driver"
depends on AX25
select CRC16
---help---
KISS is a protocol used for the exchange of data between a computer
and a Terminal Node Controller (a small embedded system commonly
Expand Down
178 changes: 147 additions & 31 deletions drivers/net/hamradio/mkiss.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -14,13 +14,14 @@
*
* Copyright (C) Hans Alblas PE1AYX <hans@esrac.ele.tue.nl>
* Copyright (C) 2004, 05 Ralf Baechle DL5RB <ralf@linux-mips.org>
* Copyright (C) 2004, 05 Thomas Osterried DL9SAU <thomas@x-berg.in-berlin.de>
*/

#include <linux/config.h>
#include <linux/module.h>
#include <asm/system.h>
#include <linux/bitops.h>
#include <asm/uaccess.h>
#include <linux/crc16.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
Expand All @@ -39,11 +40,6 @@

#include <net/ax25.h>

#ifdef CONFIG_INET
#include <linux/ip.h>
#include <linux/tcp.h>
#endif

#define AX_MTU 236

/* SLIP/KISS protocol characters. */
Expand Down Expand Up @@ -80,9 +76,13 @@ struct mkiss {

int mode;
int crcmode; /* MW: for FlexNet, SMACK etc. */
#define CRC_MODE_NONE 0
#define CRC_MODE_FLEX 1
#define CRC_MODE_SMACK 2
int crcauto; /* CRC auto mode */

#define CRC_MODE_NONE 0
#define CRC_MODE_FLEX 1
#define CRC_MODE_SMACK 2
#define CRC_MODE_FLEX_TEST 3
#define CRC_MODE_SMACK_TEST 4

atomic_t refcnt;
struct semaphore dead_sem;
Expand Down Expand Up @@ -151,6 +151,21 @@ static int check_crc_flex(unsigned char *cp, int size)
return 0;
}

static int check_crc_16(unsigned char *cp, int size)
{
unsigned short crc = 0x0000;

if (size < 3)
return -1;

crc = crc16(0, cp, size);

if (crc != 0x0000)
return -1;

return 0;
}

/*
* Standard encapsulation
*/
Expand Down Expand Up @@ -237,19 +252,42 @@ static void ax_bump(struct mkiss *ax)

spin_lock_bh(&ax->buflock);
if (ax->rbuff[0] > 0x0f) {
if (ax->rbuff[0] & 0x20) {
ax->crcmode = CRC_MODE_FLEX;
if (ax->rbuff[0] & 0x80) {
if (check_crc_16(ax->rbuff, ax->rcount) < 0) {
ax->stats.rx_errors++;
spin_unlock_bh(&ax->buflock);

return;
}
if (ax->crcmode != CRC_MODE_SMACK && ax->crcauto) {
printk(KERN_INFO
"mkiss: %s: Switchting to crc-smack\n",
ax->dev->name);
ax->crcmode = CRC_MODE_SMACK;
}
ax->rcount -= 2;
*ax->rbuff &= ~0x80;
} else if (ax->rbuff[0] & 0x20) {
if (check_crc_flex(ax->rbuff, ax->rcount) < 0) {
ax->stats.rx_errors++;
ax->stats.rx_errors++;
spin_unlock_bh(&ax->buflock);
return;
}
if (ax->crcmode != CRC_MODE_FLEX && ax->crcauto) {
printk(KERN_INFO
"mkiss: %s: Switchting to crc-flexnet\n",
ax->dev->name);
ax->crcmode = CRC_MODE_FLEX;
}
ax->rcount -= 2;
/* dl9sau bugfix: the trailling two bytes flexnet crc
* will not be passed to the kernel. thus we have
* to correct the kissparm signature, because it
* indicates a crc but there's none

/*
* dl9sau bugfix: the trailling two bytes flexnet crc
* will not be passed to the kernel. thus we have to
* correct the kissparm signature, because it indicates
* a crc but there's none
*/
*ax->rbuff &= ~0x20;
*ax->rbuff &= ~0x20;
}
}
spin_unlock_bh(&ax->buflock);
Expand Down Expand Up @@ -417,20 +455,69 @@ static void ax_encaps(struct net_device *dev, unsigned char *icp, int len)
p = icp;

spin_lock_bh(&ax->buflock);
switch (ax->crcmode) {
unsigned short crc;
if ((*p & 0x0f) != 0) {
/* Configuration Command (kissparms(1).
* Protocol spec says: never append CRC.
* This fixes a very old bug in the linux
* kiss driver. -- dl9sau */
switch (*p & 0xff) {
case 0x85:
/* command from userspace especially for us,
* not for delivery to the tnc */
if (len > 1) {
int cmd = (p[1] & 0xff);
switch(cmd) {
case 3:
ax->crcmode = CRC_MODE_SMACK;
break;
case 2:
ax->crcmode = CRC_MODE_FLEX;
break;
case 1:
ax->crcmode = CRC_MODE_NONE;
break;
case 0:
default:
ax->crcmode = CRC_MODE_SMACK_TEST;
cmd = 0;
}
ax->crcauto = (cmd ? 0 : 1);
printk(KERN_INFO "mkiss: %s: crc mode %s %d\n", ax->dev->name, (len) ? "set to" : "is", cmd);
}
spin_unlock_bh(&ax->buflock);
netif_start_queue(dev);

case CRC_MODE_FLEX:
*p |= 0x20;
crc = calc_crc_flex(p, len);
count = kiss_esc_crc(p, (unsigned char *)ax->xbuff, crc, len+2);
break;
return;
default:
count = kiss_esc(p, (unsigned char *)ax->xbuff, len);
}
} else {
unsigned short crc;
switch (ax->crcmode) {
case CRC_MODE_SMACK_TEST:
ax->crcmode = CRC_MODE_FLEX_TEST;
printk(KERN_INFO "mkiss: %s: Trying crc-smack\n", ax->dev->name);
// fall through
case CRC_MODE_SMACK:
*p |= 0x80;
crc = swab16(crc16(0, p, len));
count = kiss_esc_crc(p, (unsigned char *)ax->xbuff, crc, len+2);
break;
case CRC_MODE_FLEX_TEST:
ax->crcmode = CRC_MODE_NONE;
printk(KERN_INFO "mkiss: %s: Trying crc-flexnet\n", ax->dev->name);
// fall through
case CRC_MODE_FLEX:
*p |= 0x20;
crc = calc_crc_flex(p, len);
count = kiss_esc_crc(p, (unsigned char *)ax->xbuff, crc, len+2);
break;

default:
count = kiss_esc(p, (unsigned char *)ax->xbuff, len);
}
}

default:
count = kiss_esc(p, (unsigned char *)ax->xbuff, len);
break;
}

set_bit(TTY_DO_WRITE_WAKEUP, &ax->tty->flags);
actual = ax->tty->driver->write(ax->tty, ax->xbuff, count);
ax->stats.tx_packets++;
Expand All @@ -439,8 +526,6 @@ static void ax_encaps(struct net_device *dev, unsigned char *icp, int len)
ax->dev->trans_start = jiffies;
ax->xleft = count - actual;
ax->xhead = ax->xbuff + actual;

spin_unlock_bh(&ax->buflock);
}

/* Encapsulate an AX.25 packet and kick it into a TTY queue. */
Expand Down Expand Up @@ -643,6 +728,8 @@ static void mkiss_put(struct mkiss *ax)
up(&ax->dead_sem);
}

static int crc_force = 0; /* Can be overridden with insmod */

static int mkiss_open(struct tty_struct *tty)
{
struct net_device *dev;
Expand Down Expand Up @@ -682,6 +769,33 @@ static int mkiss_open(struct tty_struct *tty)
if (register_netdev(dev))
goto out_free_buffers;

/* after register_netdev() - because else printk smashes the kernel */
switch (crc_force) {
case 3:
ax->crcmode = CRC_MODE_SMACK;
printk(KERN_INFO "mkiss: %s: crc mode smack forced.\n",
ax->dev->name);
break;
case 2:
ax->crcmode = CRC_MODE_FLEX;
printk(KERN_INFO "mkiss: %s: crc mode flexnet forced.\n",
ax->dev->name);
break;
case 1:
ax->crcmode = CRC_MODE_NONE;
printk(KERN_INFO "mkiss: %s: crc mode disabled.\n",
ax->dev->name);
break;
case 0:
/* fall through */
default:
crc_force = 0;
printk(KERN_INFO "mkiss: %s: crc mode is auto.\n",
ax->dev->name);
ax->crcmode = CRC_MODE_SMACK_TEST;
}
ax->crcauto = (crc_force ? 0 : 1);

netif_start_queue(dev);

/* Done. We have linked the TTY line to a channel. */
Expand Down Expand Up @@ -903,6 +1017,8 @@ static void __exit mkiss_exit_driver(void)

MODULE_AUTHOR("Ralf Baechle DL5RB <ralf@linux-mips.org>");
MODULE_DESCRIPTION("KISS driver for AX.25 over TTYs");
MODULE_PARM(crc_force, "i");
MODULE_PARM_DESC(crc_force, "crc [0 = auto | 1 = none | 2 = flexnet | 3 = smack]");
MODULE_LICENSE("GPL");
MODULE_ALIAS_LDISC(N_AX25);

Expand Down

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