lapb_subr.c
/*
* LAPB release 002
*
* This code REQUIRES 2.1.15 or higher/ NET3.038
*
* This module:
* This module is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*
* History
* LAPB 001 Jonathan Naylor Started Coding
*/
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/kernel.h>
#include <linux/timer.h>
#include <linux/string.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <linux/inet.h>
#include <linux/skbuff.h>
#include <linux/slab.h>
#include <net/sock.h>
#include <linux/uaccess.h>
#include <linux/fcntl.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <net/lapb.h>
/*
* This routine purges all the queues of frames.
*/
void lapb_clear_queues(struct lapb_cb *lapb)
{
skb_queue_purge(&lapb->write_queue);
skb_queue_purge(&lapb->ack_queue);
}
/*
* This routine purges the input queue of those frames that have been
* acknowledged. This replaces the boxes labelled "V(a) <- N(r)" on the
* SDL diagram.
*/
void lapb_frames_acked(struct lapb_cb *lapb, unsigned short nr)
{
struct sk_buff *skb;
int modulus;
modulus = (lapb->mode & LAPB_EXTENDED) ? LAPB_EMODULUS : LAPB_SMODULUS;
/*
* Remove all the ack-ed frames from the ack queue.
*/
if (lapb->va != nr)
while (skb_peek(&lapb->ack_queue) && lapb->va != nr) {
skb = skb_dequeue(&lapb->ack_queue);
kfree_skb(skb);
lapb->va = (lapb->va + 1) % modulus;
}
}
void lapb_requeue_frames(struct lapb_cb *lapb)
{
struct sk_buff *skb, *skb_prev = NULL;
/*
* Requeue all the un-ack-ed frames on the output queue to be picked
* up by lapb_kick called from the timer. This arrangement handles the
* possibility of an empty output queue.
*/
while ((skb = skb_dequeue(&lapb->ack_queue)) != NULL) {
if (!skb_prev)
skb_queue_head(&lapb->write_queue, skb);
else
skb_append(skb_prev, skb, &lapb->write_queue);
skb_prev = skb;
}
}
/*
* Validate that the value of nr is between va and vs. Return true or
* false for testing.
*/
int lapb_validate_nr(struct lapb_cb *lapb, unsigned short nr)
{
unsigned short vc = lapb->va;
int modulus;
modulus = (lapb->mode & LAPB_EXTENDED) ? LAPB_EMODULUS : LAPB_SMODULUS;
while (vc != lapb->vs) {
if (nr == vc)
return 1;
vc = (vc + 1) % modulus;
}
return nr == lapb->vs;
}
/*
* This routine is the centralised routine for parsing the control
* information for the different frame formats.
*/
int lapb_decode(struct lapb_cb *lapb, struct sk_buff *skb,
struct lapb_frame *frame)
{
frame->type = LAPB_ILLEGAL;
lapb_dbg(2, "(%p) S%d RX %3ph\n", lapb->dev, lapb->state, skb->data);
/* We always need to look at 2 bytes, sometimes we need
* to look at 3 and those cases are handled below.
*/
if (!pskb_may_pull(skb, 2))
return -1;
if (lapb->mode & LAPB_MLP) {
if (lapb->mode & LAPB_DCE) {
if (skb->data[0] == LAPB_ADDR_D)
frame->cr = LAPB_COMMAND;
if (skb->data[0] == LAPB_ADDR_C)
frame->cr = LAPB_RESPONSE;
} else {
if (skb->data[0] == LAPB_ADDR_C)
frame->cr = LAPB_COMMAND;
if (skb->data[0] == LAPB_ADDR_D)
frame->cr = LAPB_RESPONSE;
}
} else {
if (lapb->mode & LAPB_DCE) {
if (skb->data[0] == LAPB_ADDR_B)
frame->cr = LAPB_COMMAND;
if (skb->data[0] == LAPB_ADDR_A)
frame->cr = LAPB_RESPONSE;
} else {
if (skb->data[0] == LAPB_ADDR_A)
frame->cr = LAPB_COMMAND;
if (skb->data[0] == LAPB_ADDR_B)
frame->cr = LAPB_RESPONSE;
}
}
skb_pull(skb, 1);
if (lapb->mode & LAPB_EXTENDED) {
if (!(skb->data[0] & LAPB_S)) {
if (!pskb_may_pull(skb, 2))
return -1;
/*
* I frame - carries NR/NS/PF
*/
frame->type = LAPB_I;
frame->ns = (skb->data[0] >> 1) & 0x7F;
frame->nr = (skb->data[1] >> 1) & 0x7F;
frame->pf = skb->data[1] & LAPB_EPF;
frame->control[0] = skb->data[0];
frame->control[1] = skb->data[1];
skb_pull(skb, 2);
} else if ((skb->data[0] & LAPB_U) == 1) {
if (!pskb_may_pull(skb, 2))
return -1;
/*
* S frame - take out PF/NR
*/
frame->type = skb->data[0] & 0x0F;
frame->nr = (skb->data[1] >> 1) & 0x7F;
frame->pf = skb->data[1] & LAPB_EPF;
frame->control[0] = skb->data[0];
frame->control[1] = skb->data[1];
skb_pull(skb, 2);
} else if ((skb->data[0] & LAPB_U) == 3) {
/*
* U frame - take out PF
*/
frame->type = skb->data[0] & ~LAPB_SPF;
frame->pf = skb->data[0] & LAPB_SPF;
frame->control[0] = skb->data[0];
frame->control[1] = 0x00;
skb_pull(skb, 1);
}
} else {
if (!(skb->data[0] & LAPB_S)) {
/*
* I frame - carries NR/NS/PF
*/
frame->type = LAPB_I;
frame->ns = (skb->data[0] >> 1) & 0x07;
frame->nr = (skb->data[0] >> 5) & 0x07;
frame->pf = skb->data[0] & LAPB_SPF;
} else if ((skb->data[0] & LAPB_U) == 1) {
/*
* S frame - take out PF/NR
*/
frame->type = skb->data[0] & 0x0F;
frame->nr = (skb->data[0] >> 5) & 0x07;
frame->pf = skb->data[0] & LAPB_SPF;
} else if ((skb->data[0] & LAPB_U) == 3) {
/*
* U frame - take out PF
*/
frame->type = skb->data[0] & ~LAPB_SPF;
frame->pf = skb->data[0] & LAPB_SPF;
}
frame->control[0] = skb->data[0];
skb_pull(skb, 1);
}
return 0;
}
/*
* This routine is called when the HDLC layer internally generates a
* command or response for the remote machine ( eg. RR, UA etc. ).
* Only supervisory or unnumbered frames are processed, FRMRs are handled
* by lapb_transmit_frmr below.
*/
void lapb_send_control(struct lapb_cb *lapb, int frametype,
int poll_bit, int type)
{
struct sk_buff *skb;
unsigned char *dptr;
if ((skb = alloc_skb(LAPB_HEADER_LEN + 3, GFP_ATOMIC)) == NULL)
return;
skb_reserve(skb, LAPB_HEADER_LEN + 1);
if (lapb->mode & LAPB_EXTENDED) {
if ((frametype & LAPB_U) == LAPB_U) {
dptr = skb_put(skb, 1);
*dptr = frametype;
*dptr |= poll_bit ? LAPB_SPF : 0;
} else {
dptr = skb_put(skb, 2);
dptr[0] = frametype;
dptr[1] = (lapb->vr << 1);
dptr[1] |= poll_bit ? LAPB_EPF : 0;
}
} else {
dptr = skb_put(skb, 1);
*dptr = frametype;
*dptr |= poll_bit ? LAPB_SPF : 0;
if ((frametype & LAPB_U) == LAPB_S) /* S frames carry NR */
*dptr |= (lapb->vr << 5);
}
lapb_transmit_buffer(lapb, skb, type);
}
/*
* This routine generates FRMRs based on information previously stored in
* the LAPB control block.
*/
void lapb_transmit_frmr(struct lapb_cb *lapb)
{
struct sk_buff *skb;
unsigned char *dptr;
if ((skb = alloc_skb(LAPB_HEADER_LEN + 7, GFP_ATOMIC)) == NULL)
return;
skb_reserve(skb, LAPB_HEADER_LEN + 1);
if (lapb->mode & LAPB_EXTENDED) {
dptr = skb_put(skb, 6);
*dptr++ = LAPB_FRMR;
*dptr++ = lapb->frmr_data.control[0];
*dptr++ = lapb->frmr_data.control[1];
*dptr++ = (lapb->vs << 1) & 0xFE;
*dptr = (lapb->vr << 1) & 0xFE;
if (lapb->frmr_data.cr == LAPB_RESPONSE)
*dptr |= 0x01;
dptr++;
*dptr++ = lapb->frmr_type;
lapb_dbg(1, "(%p) S%d TX FRMR %5ph\n",
lapb->dev, lapb->state,
&skb->data[1]);
} else {
dptr = skb_put(skb, 4);
*dptr++ = LAPB_FRMR;
*dptr++ = lapb->frmr_data.control[0];
*dptr = (lapb->vs << 1) & 0x0E;
*dptr |= (lapb->vr << 5) & 0xE0;
if (lapb->frmr_data.cr == LAPB_RESPONSE)
*dptr |= 0x10;
dptr++;
*dptr++ = lapb->frmr_type;
lapb_dbg(1, "(%p) S%d TX FRMR %3ph\n",
lapb->dev, lapb->state, &skb->data[1]);
}
lapb_transmit_buffer(lapb, skb, LAPB_RESPONSE);
}
