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491 lines
15 KiB
491 lines
15 KiB
// 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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|
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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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* |
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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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/* |
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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(struct tasklet_struct *t) |
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{ |
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struct pppoatm_vcc *pvcc = from_tasklet(pvcc, t, wakeup_tasklet); |
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ppp_output_wakeup(&pvcc->chan); |
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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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/* |
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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); |
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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)) |
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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: |
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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 |
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* already applied SC_COMP_PROT compression, so may need to undo |
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*/ |
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if ((pvcc->flags & SC_COMP_PROT) && skb_headroom(skb) > 0 && |
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skb->data[-1] == '\0') |
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(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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{ |
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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) |
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? -EFAULT : 0; |
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} |
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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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{ |
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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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if (copy_from_user(&be, arg, sizeof be)) |
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return -EFAULT; |
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if (be.encaps != PPPOATM_ENCAPS_AUTODETECT && |
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be.encaps != PPPOATM_ENCAPS_VC && be.encaps != PPPOATM_ENCAPS_LLC) |
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return -EINVAL; |
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pvcc = kzalloc(sizeof(*pvcc), GFP_KERNEL); |
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if (pvcc == NULL) |
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return -ENOMEM; |
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pvcc->atmvcc = atmvcc; |
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/* Maximum is zero, so that we can use atomic_inc_not_zero() */ |
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atomic_set(&pvcc->inflight, NONE_INFLIGHT); |
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pvcc->old_push = atmvcc->push; |
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pvcc->old_pop = atmvcc->pop; |
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pvcc->old_owner = atmvcc->owner; |
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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); |
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tasklet_setup(&pvcc->wakeup_tasklet, pppoatm_wakeup_sender); |
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err = ppp_register_channel(&pvcc->chan); |
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if (err != 0) { |
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kfree(pvcc); |
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return err; |
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} |
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atmvcc->user_back = pvcc; |
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atmvcc->push = pppoatm_push; |
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atmvcc->pop = pppoatm_pop; |
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atmvcc->release_cb = pppoatm_release_cb; |
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__module_get(THIS_MODULE); |
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atmvcc->owner = THIS_MODULE; |
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|
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/* re-process everything received between connection setup and |
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backend setup */ |
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vcc_process_recv_queue(atmvcc); |
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return 0; |
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} |
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|
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/* |
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* This handles ioctls actually performed on our vcc - we must return |
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* -ENOIOCTLCMD for any unrecognized ioctl |
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*/ |
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static int pppoatm_ioctl(struct socket *sock, unsigned int cmd, |
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unsigned long arg) |
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{ |
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struct atm_vcc *atmvcc = ATM_SD(sock); |
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void __user *argp = (void __user *)arg; |
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if (cmd != ATM_SETBACKEND && atmvcc->push != pppoatm_push) |
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return -ENOIOCTLCMD; |
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switch (cmd) { |
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case ATM_SETBACKEND: { |
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atm_backend_t b; |
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if (get_user(b, (atm_backend_t __user *) argp)) |
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return -EFAULT; |
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if (b != ATM_BACKEND_PPP) |
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return -ENOIOCTLCMD; |
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if (!capable(CAP_NET_ADMIN)) |
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return -EPERM; |
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if (sock->state != SS_CONNECTED) |
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return -EINVAL; |
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return pppoatm_assign_vcc(atmvcc, argp); |
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} |
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case PPPIOCGCHAN: |
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return put_user(ppp_channel_index(&atmvcc_to_pvcc(atmvcc)-> |
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chan), (int __user *) argp) ? -EFAULT : 0; |
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case PPPIOCGUNIT: |
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return put_user(ppp_unit_number(&atmvcc_to_pvcc(atmvcc)-> |
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chan), (int __user *) argp) ? -EFAULT : 0; |
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} |
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return -ENOIOCTLCMD; |
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} |
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static struct atm_ioctl pppoatm_ioctl_ops = { |
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.owner = THIS_MODULE, |
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.ioctl = pppoatm_ioctl, |
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}; |
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|
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static int __init pppoatm_init(void) |
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{ |
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register_atm_ioctl(&pppoatm_ioctl_ops); |
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return 0; |
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} |
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|
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static void __exit pppoatm_exit(void) |
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{ |
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deregister_atm_ioctl(&pppoatm_ioctl_ops); |
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} |
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|
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module_init(pppoatm_init); |
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module_exit(pppoatm_exit); |
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|
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MODULE_AUTHOR("Mitchell Blank Jr <[email protected]>"); |
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MODULE_DESCRIPTION("RFC2364 PPP over ATM/AAL5"); |
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MODULE_LICENSE("GPL");
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