// SPDX-License-Identifier: GPL-2.0-or-later
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/* net/atm/pppoatm.c - RFC2364 PPP over ATM/AAL5 */
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/* Copyright 1999-2000 by Mitchell Blank Jr */
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/* Based on clip.c; 1995-1999 by Werner Almesberger, EPFL LRC/ICA */
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/* And on ppp_async.c; Copyright 1999 Paul Mackerras */
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/* And help from Jens Axboe */
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/*
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*
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* This driver provides the encapsulation and framing for sending
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* and receiving PPP frames in ATM AAL5 PDUs.
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*/
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/*
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* One shortcoming of this driver is that it does not comply with
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* section 8 of RFC2364 - we are supposed to detect a change
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* in encapsulation and immediately abort the connection (in order
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* to avoid a black-hole being created if our peer loses state
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* and changes encapsulation unilaterally. However, since the
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* ppp_generic layer actually does the decapsulation, we need
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* a way of notifying it when we _think_ there might be a problem)
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* There's two cases:
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* 1. LLC-encapsulation was missing when it was enabled. In
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* this case, we should tell the upper layer "tear down
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* this session if this skb looks ok to you"
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* 2. LLC-encapsulation was present when it was disabled. Then
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* we need to tell the upper layer "this packet may be
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* ok, but if its in error tear down the session"
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* These hooks are not yet available in ppp_generic
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ":%s: " fmt, __func__
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#include <linux/module.h>
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#include <linux/init.h>
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#include <linux/interrupt.h>
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#include <linux/skbuff.h>
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#include <linux/slab.h>
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#include <linux/atm.h>
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#include <linux/atmdev.h>
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#include <linux/capability.h>
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#include <linux/ppp_defs.h>
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#include <linux/ppp-ioctl.h>
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#include <linux/ppp_channel.h>
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#include <linux/atmppp.h>
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#include "common.h"
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enum pppoatm_encaps {
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e_autodetect = PPPOATM_ENCAPS_AUTODETECT,
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e_vc = PPPOATM_ENCAPS_VC,
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e_llc = PPPOATM_ENCAPS_LLC,
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};
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struct pppoatm_vcc {
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struct atm_vcc *atmvcc; /* VCC descriptor */
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void (*old_push)(struct atm_vcc *, struct sk_buff *);
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void (*old_pop)(struct atm_vcc *, struct sk_buff *);
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void (*old_release_cb)(struct atm_vcc *);
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struct module *old_owner;
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/* keep old push/pop for detaching */
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enum pppoatm_encaps encaps;
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atomic_t inflight;
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unsigned long blocked;
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int flags; /* SC_COMP_PROT - compress protocol */
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struct ppp_channel chan; /* interface to generic ppp layer */
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struct tasklet_struct wakeup_tasklet;
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};
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/*
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* We want to allow two packets in the queue. The one that's currently in
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* flight, and *one* queued up ready for the ATM device to send immediately
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* from its TX done IRQ. We want to be able to use atomic_inc_not_zero(), so
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* inflight == -2 represents an empty queue, -1 one packet, and zero means
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* there are two packets in the queue.
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*/
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#define NONE_INFLIGHT -2
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#define BLOCKED 0
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/*
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* Header used for LLC Encapsulated PPP (4 bytes) followed by the LCP protocol
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* ID (0xC021) used in autodetection
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*/
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static const unsigned char pppllc[6] = { 0xFE, 0xFE, 0x03, 0xCF, 0xC0, 0x21 };
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#define LLC_LEN (4)
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static inline struct pppoatm_vcc *atmvcc_to_pvcc(const struct atm_vcc *atmvcc)
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{
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return (struct pppoatm_vcc *) (atmvcc->user_back);
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}
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static inline struct pppoatm_vcc *chan_to_pvcc(const struct ppp_channel *chan)
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{
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return (struct pppoatm_vcc *) (chan->private);
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}
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/*
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* We can't do this directly from our _pop handler, since the ppp code
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* doesn't want to be called in interrupt context, so we do it from
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* a tasklet
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*/
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static void pppoatm_wakeup_sender(unsigned long arg)
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{
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ppp_output_wakeup((struct ppp_channel *) arg);
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}
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static void pppoatm_release_cb(struct atm_vcc *atmvcc)
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{
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struct pppoatm_vcc *pvcc = atmvcc_to_pvcc(atmvcc);
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/*
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* As in pppoatm_pop(), it's safe to clear the BLOCKED bit here because
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* the wakeup *can't* race with pppoatm_send(). They both hold the PPP
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* channel's ->downl lock. And the potential race with *setting* it,
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* which leads to the double-check dance in pppoatm_may_send(), doesn't
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* exist here. In the sock_owned_by_user() case in pppoatm_send(), we
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* set the BLOCKED bit while the socket is still locked. We know that
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* ->release_cb() can't be called until that's done.
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*/
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if (test_and_clear_bit(BLOCKED, &pvcc->blocked))
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tasklet_schedule(&pvcc->wakeup_tasklet);
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if (pvcc->old_release_cb)
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pvcc->old_release_cb(atmvcc);
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}
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/*
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* This gets called every time the ATM card has finished sending our
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* skb. The ->old_pop will take care up normal atm flow control,
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* but we also need to wake up the device if we blocked it
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*/
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static void pppoatm_pop(struct atm_vcc *atmvcc, struct sk_buff *skb)
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{
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struct pppoatm_vcc *pvcc = atmvcc_to_pvcc(atmvcc);
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pvcc->old_pop(atmvcc, skb);
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atomic_dec(&pvcc->inflight);
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/*
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* We always used to run the wakeup tasklet unconditionally here, for
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* fear of race conditions where we clear the BLOCKED flag just as we
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* refuse another packet in pppoatm_send(). This was quite inefficient.
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*
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* In fact it's OK. The PPP core will only ever call pppoatm_send()
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* while holding the channel->downl lock. And ppp_output_wakeup() as
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* called by the tasklet will *also* grab that lock. So even if another
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* CPU is in pppoatm_send() right now, the tasklet isn't going to race
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* with it. The wakeup *will* happen after the other CPU is safely out
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* of pppoatm_send() again.
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*
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* So if the CPU in pppoatm_send() has already set the BLOCKED bit and
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* it about to return, that's fine. We trigger a wakeup which will
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* happen later. And if the CPU in pppoatm_send() *hasn't* set the
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* BLOCKED bit yet, that's fine too because of the double check in
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* pppoatm_may_send() which is commented there.
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*/
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if (test_and_clear_bit(BLOCKED, &pvcc->blocked))
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tasklet_schedule(&pvcc->wakeup_tasklet);
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}
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/*
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* Unbind from PPP - currently we only do this when closing the socket,
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* but we could put this into an ioctl if need be
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*/
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static void pppoatm_unassign_vcc(struct atm_vcc *atmvcc)
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{
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struct pppoatm_vcc *pvcc;
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pvcc = atmvcc_to_pvcc(atmvcc);
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atmvcc->push = pvcc->old_push;
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atmvcc->pop = pvcc->old_pop;
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atmvcc->release_cb = pvcc->old_release_cb;
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tasklet_kill(&pvcc->wakeup_tasklet);
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ppp_unregister_channel(&pvcc->chan);
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atmvcc->user_back = NULL;
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kfree(pvcc);
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}
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/* Called when an AAL5 PDU comes in */
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static void pppoatm_push(struct atm_vcc *atmvcc, struct sk_buff *skb)
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{
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struct pppoatm_vcc *pvcc = atmvcc_to_pvcc(atmvcc);
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pr_debug("\n");
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if (skb == NULL) { /* VCC was closed */
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struct module *module;
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pr_debug("removing ATMPPP VCC %p\n", pvcc);
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module = pvcc->old_owner;
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pppoatm_unassign_vcc(atmvcc);
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atmvcc->push(atmvcc, NULL); /* Pass along bad news */
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module_put(module);
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return;
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}
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atm_return(atmvcc, skb->truesize);
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switch (pvcc->encaps) {
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case e_llc:
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if (skb->len < LLC_LEN ||
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memcmp(skb->data, pppllc, LLC_LEN))
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goto error;
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skb_pull(skb, LLC_LEN);
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break;
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case e_autodetect:
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if (pvcc->chan.ppp == NULL) { /* Not bound yet! */
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kfree_skb(skb);
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return;
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}
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if (skb->len >= sizeof(pppllc) &&
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!memcmp(skb->data, pppllc, sizeof(pppllc))) {
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pvcc->encaps = e_llc;
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skb_pull(skb, LLC_LEN);
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break;
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}
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if (skb->len >= (sizeof(pppllc) - LLC_LEN) &&
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!memcmp(skb->data, &pppllc[LLC_LEN],
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sizeof(pppllc) - LLC_LEN)) {
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pvcc->encaps = e_vc;
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pvcc->chan.mtu += LLC_LEN;
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break;
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}
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pr_debug("Couldn't autodetect yet (skb: %6ph)\n", skb->data);
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goto error;
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case e_vc:
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break;
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}
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ppp_input(&pvcc->chan, skb);
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return;
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error:
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kfree_skb(skb);
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ppp_input_error(&pvcc->chan, 0);
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}
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static int pppoatm_may_send(struct pppoatm_vcc *pvcc, int size)
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{
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/*
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* It's not clear that we need to bother with using atm_may_send()
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* to check we don't exceed sk->sk_sndbuf. If userspace sets a
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* value of sk_sndbuf which is lower than the MTU, we're going to
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* block for ever. But the code always did that before we introduced
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* the packet count limit, so...
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*/
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if (atm_may_send(pvcc->atmvcc, size) &&
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atomic_inc_not_zero(&pvcc->inflight))
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return 1;
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/*
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* We use test_and_set_bit() rather than set_bit() here because
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* we need to ensure there's a memory barrier after it. The bit
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* *must* be set before we do the atomic_inc() on pvcc->inflight.
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* There's no smp_mb__after_set_bit(), so it's this or abuse
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* smp_mb__after_atomic().
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*/
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test_and_set_bit(BLOCKED, &pvcc->blocked);
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/*
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* We may have raced with pppoatm_pop(). If it ran for the
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* last packet in the queue, *just* before we set the BLOCKED
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* bit, then it might never run again and the channel could
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* remain permanently blocked. Cope with that race by checking
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* *again*. If it did run in that window, we'll have space on
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* the queue now and can return success. It's harmless to leave
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* the BLOCKED flag set, since it's only used as a trigger to
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* run the wakeup tasklet. Another wakeup will never hurt.
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* If pppoatm_pop() is running but hasn't got as far as making
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* space on the queue yet, then it hasn't checked the BLOCKED
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* flag yet either, so we're safe in that case too. It'll issue
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* an "immediate" wakeup... where "immediate" actually involves
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* taking the PPP channel's ->downl lock, which is held by the
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* code path that calls pppoatm_send(), and is thus going to
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* wait for us to finish.
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*/
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if (atm_may_send(pvcc->atmvcc, size) &&
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atomic_inc_not_zero(&pvcc->inflight))
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return 1;
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return 0;
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}
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/*
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* Called by the ppp_generic.c to send a packet - returns true if packet
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* was accepted. If we return false, then it's our job to call
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* ppp_output_wakeup(chan) when we're feeling more up to it.
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* Note that in the ENOMEM case (as opposed to the !atm_may_send case)
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* we should really drop the packet, but the generic layer doesn't
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* support this yet. We just return 'DROP_PACKET' which we actually define
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* as success, just to be clear what we're really doing.
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*/
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#define DROP_PACKET 1
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static int pppoatm_send(struct ppp_channel *chan, struct sk_buff *skb)
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{
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struct pppoatm_vcc *pvcc = chan_to_pvcc(chan);
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struct atm_vcc *vcc;
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int ret;
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ATM_SKB(skb)->vcc = pvcc->atmvcc;
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pr_debug("(skb=0x%p, vcc=0x%p)\n", skb, pvcc->atmvcc);
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if (skb->data[0] == '\0' && (pvcc->flags & SC_COMP_PROT))
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(void) skb_pull(skb, 1);
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vcc = ATM_SKB(skb)->vcc;
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bh_lock_sock(sk_atm(vcc));
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if (sock_owned_by_user(sk_atm(vcc))) {
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/*
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* Needs to happen (and be flushed, hence test_and_) before we unlock
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* the socket. It needs to be seen by the time our ->release_cb gets
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* called.
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*/
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test_and_set_bit(BLOCKED, &pvcc->blocked);
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goto nospace;
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}
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if (test_bit(ATM_VF_RELEASED, &vcc->flags) ||
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test_bit(ATM_VF_CLOSE, &vcc->flags) ||
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!test_bit(ATM_VF_READY, &vcc->flags)) {
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bh_unlock_sock(sk_atm(vcc));
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kfree_skb(skb);
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return DROP_PACKET;
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}
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switch (pvcc->encaps) { /* LLC encapsulation needed */
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case e_llc:
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if (skb_headroom(skb) < LLC_LEN) {
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struct sk_buff *n;
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n = skb_realloc_headroom(skb, LLC_LEN);
|
if (n != NULL &&
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!pppoatm_may_send(pvcc, n->truesize)) {
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kfree_skb(n);
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goto nospace;
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}
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consume_skb(skb);
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skb = n;
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if (skb == NULL) {
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bh_unlock_sock(sk_atm(vcc));
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return DROP_PACKET;
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}
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} else if (!pppoatm_may_send(pvcc, skb->truesize))
|
goto nospace;
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memcpy(skb_push(skb, LLC_LEN), pppllc, LLC_LEN);
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break;
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case e_vc:
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if (!pppoatm_may_send(pvcc, skb->truesize))
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goto nospace;
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break;
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case e_autodetect:
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bh_unlock_sock(sk_atm(vcc));
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pr_debug("Trying to send without setting encaps!\n");
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kfree_skb(skb);
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return 1;
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}
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atm_account_tx(vcc, skb);
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pr_debug("atm_skb(%p)->vcc(%p)->dev(%p)\n",
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skb, ATM_SKB(skb)->vcc, ATM_SKB(skb)->vcc->dev);
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ret = ATM_SKB(skb)->vcc->send(ATM_SKB(skb)->vcc, skb)
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? DROP_PACKET : 1;
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bh_unlock_sock(sk_atm(vcc));
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return ret;
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nospace:
|
bh_unlock_sock(sk_atm(vcc));
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/*
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* We don't have space to send this SKB now, but we might have
|
* already applied SC_COMP_PROT compression, so may need to undo
|
*/
|
if ((pvcc->flags & SC_COMP_PROT) && skb_headroom(skb) > 0 &&
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skb->data[-1] == '\0')
|
(void) skb_push(skb, 1);
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return 0;
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}
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/* This handles ioctls sent to the /dev/ppp interface */
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static int pppoatm_devppp_ioctl(struct ppp_channel *chan, unsigned int cmd,
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unsigned long arg)
|
{
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switch (cmd) {
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case PPPIOCGFLAGS:
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return put_user(chan_to_pvcc(chan)->flags, (int __user *) arg)
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? -EFAULT : 0;
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case PPPIOCSFLAGS:
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return get_user(chan_to_pvcc(chan)->flags, (int __user *) arg)
|
? -EFAULT : 0;
|
}
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return -ENOTTY;
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}
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static const struct ppp_channel_ops pppoatm_ops = {
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.start_xmit = pppoatm_send,
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.ioctl = pppoatm_devppp_ioctl,
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};
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static int pppoatm_assign_vcc(struct atm_vcc *atmvcc, void __user *arg)
|
{
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struct atm_backend_ppp be;
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struct pppoatm_vcc *pvcc;
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int err;
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/*
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* Each PPPoATM instance has its own tasklet - this is just a
|
* prototypical one used to initialize them
|
*/
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static const DECLARE_TASKLET_OLD(tasklet_proto, pppoatm_wakeup_sender);
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if (copy_from_user(&be, arg, sizeof be))
|
return -EFAULT;
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if (be.encaps != PPPOATM_ENCAPS_AUTODETECT &&
|
be.encaps != PPPOATM_ENCAPS_VC && be.encaps != PPPOATM_ENCAPS_LLC)
|
return -EINVAL;
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pvcc = kzalloc(sizeof(*pvcc), GFP_KERNEL);
|
if (pvcc == NULL)
|
return -ENOMEM;
|
pvcc->atmvcc = atmvcc;
|
|
/* Maximum is zero, so that we can use atomic_inc_not_zero() */
|
atomic_set(&pvcc->inflight, NONE_INFLIGHT);
|
pvcc->old_push = atmvcc->push;
|
pvcc->old_pop = atmvcc->pop;
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pvcc->old_owner = atmvcc->owner;
|
pvcc->old_release_cb = atmvcc->release_cb;
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pvcc->encaps = (enum pppoatm_encaps) be.encaps;
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pvcc->chan.private = pvcc;
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pvcc->chan.ops = &pppoatm_ops;
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pvcc->chan.mtu = atmvcc->qos.txtp.max_sdu - PPP_HDRLEN -
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(be.encaps == e_vc ? 0 : LLC_LEN);
|
pvcc->wakeup_tasklet = tasklet_proto;
|
pvcc->wakeup_tasklet.data = (unsigned long) &pvcc->chan;
|
err = ppp_register_channel(&pvcc->chan);
|
if (err != 0) {
|
kfree(pvcc);
|
return err;
|
}
|
atmvcc->user_back = pvcc;
|
atmvcc->push = pppoatm_push;
|
atmvcc->pop = pppoatm_pop;
|
atmvcc->release_cb = pppoatm_release_cb;
|
__module_get(THIS_MODULE);
|
atmvcc->owner = THIS_MODULE;
|
|
/* re-process everything received between connection setup and
|
backend setup */
|
vcc_process_recv_queue(atmvcc);
|
return 0;
|
}
|
|
/*
|
* This handles ioctls actually performed on our vcc - we must return
|
* -ENOIOCTLCMD for any unrecognized ioctl
|
*/
|
static int pppoatm_ioctl(struct socket *sock, unsigned int cmd,
|
unsigned long arg)
|
{
|
struct atm_vcc *atmvcc = ATM_SD(sock);
|
void __user *argp = (void __user *)arg;
|
|
if (cmd != ATM_SETBACKEND && atmvcc->push != pppoatm_push)
|
return -ENOIOCTLCMD;
|
switch (cmd) {
|
case ATM_SETBACKEND: {
|
atm_backend_t b;
|
if (get_user(b, (atm_backend_t __user *) argp))
|
return -EFAULT;
|
if (b != ATM_BACKEND_PPP)
|
return -ENOIOCTLCMD;
|
if (!capable(CAP_NET_ADMIN))
|
return -EPERM;
|
if (sock->state != SS_CONNECTED)
|
return -EINVAL;
|
return pppoatm_assign_vcc(atmvcc, argp);
|
}
|
case PPPIOCGCHAN:
|
return put_user(ppp_channel_index(&atmvcc_to_pvcc(atmvcc)->
|
chan), (int __user *) argp) ? -EFAULT : 0;
|
case PPPIOCGUNIT:
|
return put_user(ppp_unit_number(&atmvcc_to_pvcc(atmvcc)->
|
chan), (int __user *) argp) ? -EFAULT : 0;
|
}
|
return -ENOIOCTLCMD;
|
}
|
|
static struct atm_ioctl pppoatm_ioctl_ops = {
|
.owner = THIS_MODULE,
|
.ioctl = pppoatm_ioctl,
|
};
|
|
static int __init pppoatm_init(void)
|
{
|
register_atm_ioctl(&pppoatm_ioctl_ops);
|
return 0;
|
}
|
|
static void __exit pppoatm_exit(void)
|
{
|
deregister_atm_ioctl(&pppoatm_ioctl_ops);
|
}
|
|
module_init(pppoatm_init);
|
module_exit(pppoatm_exit);
|
|
MODULE_AUTHOR("Mitchell Blank Jr <mitch@sfgoth.com>");
|
MODULE_DESCRIPTION("RFC2364 PPP over ATM/AAL5");
|
MODULE_LICENSE("GPL");
|
