300 lines
7.3 KiB
C
300 lines
7.3 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* LAPB release 002
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*
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* This code REQUIRES 2.1.15 or higher/ NET3.038
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*
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* History
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* LAPB 001 Jonathan Naylor Started Coding
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/errno.h>
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#include <linux/types.h>
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#include <linux/socket.h>
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#include <linux/in.h>
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#include <linux/kernel.h>
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#include <linux/timer.h>
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#include <linux/string.h>
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#include <linux/sockios.h>
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#include <linux/net.h>
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#include <linux/inet.h>
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#include <linux/skbuff.h>
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#include <linux/slab.h>
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#include <net/sock.h>
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#include <linux/uaccess.h>
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#include <linux/fcntl.h>
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#include <linux/mm.h>
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#include <linux/interrupt.h>
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#include <net/lapb.h>
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/*
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* This routine purges all the queues of frames.
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*/
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void lapb_clear_queues(struct lapb_cb *lapb)
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{
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skb_queue_purge(&lapb->write_queue);
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skb_queue_purge(&lapb->ack_queue);
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}
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/*
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* This routine purges the input queue of those frames that have been
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* acknowledged. This replaces the boxes labelled "V(a) <- N(r)" on the
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* SDL diagram.
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*/
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void lapb_frames_acked(struct lapb_cb *lapb, unsigned short nr)
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{
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struct sk_buff *skb;
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int modulus;
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modulus = (lapb->mode & LAPB_EXTENDED) ? LAPB_EMODULUS : LAPB_SMODULUS;
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/*
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* Remove all the ack-ed frames from the ack queue.
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*/
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if (lapb->va != nr)
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while (skb_peek(&lapb->ack_queue) && lapb->va != nr) {
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skb = skb_dequeue(&lapb->ack_queue);
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kfree_skb(skb);
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lapb->va = (lapb->va + 1) % modulus;
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}
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}
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void lapb_requeue_frames(struct lapb_cb *lapb)
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{
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struct sk_buff *skb, *skb_prev = NULL;
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/*
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* Requeue all the un-ack-ed frames on the output queue to be picked
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* up by lapb_kick called from the timer. This arrangement handles the
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* possibility of an empty output queue.
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*/
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while ((skb = skb_dequeue(&lapb->ack_queue)) != NULL) {
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if (!skb_prev)
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skb_queue_head(&lapb->write_queue, skb);
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else
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skb_append(skb_prev, skb, &lapb->write_queue);
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skb_prev = skb;
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}
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}
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/*
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* Validate that the value of nr is between va and vs. Return true or
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* false for testing.
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*/
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int lapb_validate_nr(struct lapb_cb *lapb, unsigned short nr)
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{
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unsigned short vc = lapb->va;
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int modulus;
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modulus = (lapb->mode & LAPB_EXTENDED) ? LAPB_EMODULUS : LAPB_SMODULUS;
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while (vc != lapb->vs) {
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if (nr == vc)
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return 1;
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vc = (vc + 1) % modulus;
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}
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return nr == lapb->vs;
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}
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/*
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* This routine is the centralised routine for parsing the control
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* information for the different frame formats.
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*/
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int lapb_decode(struct lapb_cb *lapb, struct sk_buff *skb,
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struct lapb_frame *frame)
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{
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frame->type = LAPB_ILLEGAL;
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lapb_dbg(2, "(%p) S%d RX %3ph\n", lapb->dev, lapb->state, skb->data);
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/* We always need to look at 2 bytes, sometimes we need
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* to look at 3 and those cases are handled below.
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*/
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if (!pskb_may_pull(skb, 2))
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return -1;
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if (lapb->mode & LAPB_MLP) {
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if (lapb->mode & LAPB_DCE) {
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if (skb->data[0] == LAPB_ADDR_D)
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frame->cr = LAPB_COMMAND;
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if (skb->data[0] == LAPB_ADDR_C)
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frame->cr = LAPB_RESPONSE;
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} else {
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if (skb->data[0] == LAPB_ADDR_C)
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frame->cr = LAPB_COMMAND;
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if (skb->data[0] == LAPB_ADDR_D)
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frame->cr = LAPB_RESPONSE;
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}
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} else {
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if (lapb->mode & LAPB_DCE) {
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if (skb->data[0] == LAPB_ADDR_B)
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frame->cr = LAPB_COMMAND;
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if (skb->data[0] == LAPB_ADDR_A)
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frame->cr = LAPB_RESPONSE;
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} else {
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if (skb->data[0] == LAPB_ADDR_A)
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frame->cr = LAPB_COMMAND;
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if (skb->data[0] == LAPB_ADDR_B)
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frame->cr = LAPB_RESPONSE;
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}
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}
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skb_pull(skb, 1);
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if (lapb->mode & LAPB_EXTENDED) {
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if (!(skb->data[0] & LAPB_S)) {
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if (!pskb_may_pull(skb, 2))
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return -1;
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/*
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* I frame - carries NR/NS/PF
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*/
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frame->type = LAPB_I;
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frame->ns = (skb->data[0] >> 1) & 0x7F;
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frame->nr = (skb->data[1] >> 1) & 0x7F;
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frame->pf = skb->data[1] & LAPB_EPF;
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frame->control[0] = skb->data[0];
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frame->control[1] = skb->data[1];
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skb_pull(skb, 2);
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} else if ((skb->data[0] & LAPB_U) == 1) {
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if (!pskb_may_pull(skb, 2))
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return -1;
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/*
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* S frame - take out PF/NR
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*/
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frame->type = skb->data[0] & 0x0F;
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frame->nr = (skb->data[1] >> 1) & 0x7F;
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frame->pf = skb->data[1] & LAPB_EPF;
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frame->control[0] = skb->data[0];
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frame->control[1] = skb->data[1];
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skb_pull(skb, 2);
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} else if ((skb->data[0] & LAPB_U) == 3) {
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/*
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* U frame - take out PF
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*/
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frame->type = skb->data[0] & ~LAPB_SPF;
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frame->pf = skb->data[0] & LAPB_SPF;
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frame->control[0] = skb->data[0];
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frame->control[1] = 0x00;
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skb_pull(skb, 1);
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}
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} else {
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if (!(skb->data[0] & LAPB_S)) {
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/*
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* I frame - carries NR/NS/PF
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*/
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frame->type = LAPB_I;
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frame->ns = (skb->data[0] >> 1) & 0x07;
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frame->nr = (skb->data[0] >> 5) & 0x07;
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frame->pf = skb->data[0] & LAPB_SPF;
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} else if ((skb->data[0] & LAPB_U) == 1) {
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/*
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* S frame - take out PF/NR
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*/
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frame->type = skb->data[0] & 0x0F;
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frame->nr = (skb->data[0] >> 5) & 0x07;
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frame->pf = skb->data[0] & LAPB_SPF;
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} else if ((skb->data[0] & LAPB_U) == 3) {
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/*
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* U frame - take out PF
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*/
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frame->type = skb->data[0] & ~LAPB_SPF;
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frame->pf = skb->data[0] & LAPB_SPF;
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}
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frame->control[0] = skb->data[0];
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skb_pull(skb, 1);
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}
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return 0;
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}
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/*
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* This routine is called when the HDLC layer internally generates a
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* command or response for the remote machine ( eg. RR, UA etc. ).
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* Only supervisory or unnumbered frames are processed, FRMRs are handled
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* by lapb_transmit_frmr below.
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*/
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void lapb_send_control(struct lapb_cb *lapb, int frametype,
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int poll_bit, int type)
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{
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struct sk_buff *skb;
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unsigned char *dptr;
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if ((skb = alloc_skb(LAPB_HEADER_LEN + 3, GFP_ATOMIC)) == NULL)
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return;
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skb_reserve(skb, LAPB_HEADER_LEN + 1);
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if (lapb->mode & LAPB_EXTENDED) {
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if ((frametype & LAPB_U) == LAPB_U) {
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dptr = skb_put(skb, 1);
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*dptr = frametype;
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*dptr |= poll_bit ? LAPB_SPF : 0;
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} else {
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dptr = skb_put(skb, 2);
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dptr[0] = frametype;
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dptr[1] = (lapb->vr << 1);
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dptr[1] |= poll_bit ? LAPB_EPF : 0;
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}
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} else {
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dptr = skb_put(skb, 1);
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*dptr = frametype;
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*dptr |= poll_bit ? LAPB_SPF : 0;
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if ((frametype & LAPB_U) == LAPB_S) /* S frames carry NR */
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*dptr |= (lapb->vr << 5);
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}
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lapb_transmit_buffer(lapb, skb, type);
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}
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/*
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* This routine generates FRMRs based on information previously stored in
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* the LAPB control block.
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*/
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void lapb_transmit_frmr(struct lapb_cb *lapb)
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{
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struct sk_buff *skb;
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unsigned char *dptr;
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if ((skb = alloc_skb(LAPB_HEADER_LEN + 7, GFP_ATOMIC)) == NULL)
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return;
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skb_reserve(skb, LAPB_HEADER_LEN + 1);
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if (lapb->mode & LAPB_EXTENDED) {
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dptr = skb_put(skb, 6);
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*dptr++ = LAPB_FRMR;
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*dptr++ = lapb->frmr_data.control[0];
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*dptr++ = lapb->frmr_data.control[1];
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*dptr++ = (lapb->vs << 1) & 0xFE;
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*dptr = (lapb->vr << 1) & 0xFE;
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if (lapb->frmr_data.cr == LAPB_RESPONSE)
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*dptr |= 0x01;
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dptr++;
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*dptr++ = lapb->frmr_type;
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lapb_dbg(1, "(%p) S%d TX FRMR %5ph\n",
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lapb->dev, lapb->state,
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&skb->data[1]);
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} else {
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dptr = skb_put(skb, 4);
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*dptr++ = LAPB_FRMR;
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*dptr++ = lapb->frmr_data.control[0];
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*dptr = (lapb->vs << 1) & 0x0E;
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*dptr |= (lapb->vr << 5) & 0xE0;
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if (lapb->frmr_data.cr == LAPB_RESPONSE)
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*dptr |= 0x10;
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dptr++;
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*dptr++ = lapb->frmr_type;
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lapb_dbg(1, "(%p) S%d TX FRMR %3ph\n",
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lapb->dev, lapb->state, &skb->data[1]);
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}
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lapb_transmit_buffer(lapb, skb, LAPB_RESPONSE);
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}
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