patch-2.4.15 linux/net/atm/pppoatm.c

• Lines: 366
• Date: Fri Nov 9 14:11:15 2001
• Orig file: v2.4.14/linux/net/atm/pppoatm.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.4.14/linux/net/atm/pppoatm.c linux/net/atm/pppoatm.c
@@ -0,0 +1,365 @@
+/* net/atm/pppoatm.c - RFC2364 PPP over ATM/AAL5 */
+
+/* Copyright 1999-2000 by Mitchell Blank Jr */
+/* Based on clip.c; 1995-1999 by Werner Almesberger, EPFL LRC/ICA */
+/* And on ppp_async.c; Copyright 1999 Paul Mackerras */
+/* And help from Jens Axboe */
+
+/*
+ *  This program is free software; you can redistribute it and/or
+ *  modify it under the terms of the GNU General Public License
+ *  as published by the Free Software Foundation; either version
+ *  2 of the License, or (at your option) any later version.
+ *
+ * This driver provides the encapsulation and framing for sending
+ * and receiving PPP frames in ATM AAL5 PDUs.
+ */
+
+/*
+ * One shortcoming of this driver is that it does not comply with
+ * section 8 of RFC2364 - we are supposed to detect a change
+ * in encapsulation and immediately abort the connection (in order
+ * to avoid a black-hole being created if our peer loses state
+ * and changes encapsulation unilaterally.  However, since the
+ * ppp_generic layer actually does the decapsulation, we need
+ * a way of notifying it when we _think_ there might be a problem)
+ * There's two cases:
+ *   1.	LLC-encapsulation was missing when it was enabled.  In
+ *	this case, we should tell the upper layer "tear down
+ *	this session if this skb looks ok to you"
+ *   2.	LLC-encapsulation was present when it was disabled.  Then
+ *	we need to tell the upper layer "this packet may be
+ *	ok, but if its in error tear down the session"
+ * These hooks are not yet available in ppp_generic
+ */
+
+#include <linux/module.h>
+#include <linux/config.h>
+#include <linux/init.h>
+#include <linux/skbuff.h>
+#include <linux/atm.h>
+#include <linux/atmdev.h>
+#include <linux/ppp_defs.h>
+#include <linux/if_ppp.h>
+#include <linux/ppp_channel.h>
+#include <linux/atmppp.h>
+
+#if 0
+#define DPRINTK(format, args...) \
+	printk(KERN_DEBUG "pppoatm: " format, ##args)
+#else
+#define DPRINTK(format, args...)
+#endif
+
+enum pppoatm_encaps {
+	e_autodetect = PPPOATM_ENCAPS_AUTODETECT,
+	e_vc = PPPOATM_ENCAPS_VC,
+	e_llc = PPPOATM_ENCAPS_LLC,
+};
+
+struct pppoatm_vcc {
+	struct atm_vcc	*atmvcc;	/* VCC descriptor */
+	void (*old_push)(struct atm_vcc *, struct sk_buff *);
+	void (*old_pop)(struct atm_vcc *, struct sk_buff *);
+					/* keep old push/pop for detaching */
+	enum pppoatm_encaps encaps;
+	int flags;			/* SC_COMP_PROT - compress protocol */
+	struct ppp_channel chan;	/* interface to generic ppp layer */
+	struct tasklet_struct wakeup_tasklet;
+};
+
+/*
+ * Header used for LLC Encapsulated PPP (4 bytes) followed by the LCP protocol
+ * ID (0xC021) used in autodetection
+ */
+static const unsigned char pppllc[6] = { 0xFE, 0xFE, 0x03, 0xCF, 0xC0, 0x21 };
+#define LLC_LEN		(4)
+
+static inline struct pppoatm_vcc *atmvcc_to_pvcc(const struct atm_vcc *atmvcc)
+{
+	return (struct pppoatm_vcc *) (atmvcc->user_back);
+}
+
+static inline struct pppoatm_vcc *chan_to_pvcc(const struct ppp_channel *chan)
+{
+	return (struct pppoatm_vcc *) (chan->private);
+}
+
+/*
+ * We can't do this directly from our _pop handler, since the ppp code
+ * doesn't want to be called in interrupt context, so we do it from
+ * a tasklet
+ */
+static void pppoatm_wakeup_sender(unsigned long arg)
+{
+	ppp_output_wakeup((struct ppp_channel *) arg);
+}
+
+/*
+ * This gets called every time the ATM card has finished sending our
+ * skb.  The ->old_pop will take care up normal atm flow control,
+ * but we also need to wake up the device if we blocked it
+ */
+static void pppoatm_pop(struct atm_vcc *atmvcc, struct sk_buff *skb)
+{
+	struct pppoatm_vcc *pvcc = atmvcc_to_pvcc(atmvcc);
+	pvcc->old_pop(atmvcc, skb);
+	/*
+	 * We don't really always want to do this since it's
+	 * really inefficient - it would be much better if we could
+	 * test if we had actually throttled the generic layer.
+	 * Unfortunately then there would be a nasty SMP race where
+	 * we could clear that flag just as we refuse another packet.
+	 * For now we do the safe thing.
+	 */
+	tasklet_schedule(&pvcc->wakeup_tasklet);
+}
+
+/*
+ * Unbind from PPP - currently we only do this when closing the socket,
+ * but we could put this into an ioctl if need be
+ */
+static void pppoatm_unassign_vcc(struct atm_vcc *atmvcc)
+{
+	struct pppoatm_vcc *pvcc;
+	pvcc = atmvcc_to_pvcc(atmvcc);
+	atmvcc->push = pvcc->old_push;
+	atmvcc->pop = pvcc->old_pop;
+	tasklet_disable(&pvcc->wakeup_tasklet);
+	ppp_unregister_channel(&pvcc->chan);
+	atmvcc->user_back = NULL;
+	kfree(pvcc);
+	/* Gee, I hope we have the big kernel lock here... */
+	MOD_DEC_USE_COUNT;
+}
+
+/* Called when an AAL5 PDU comes in */
+static void pppoatm_push(struct atm_vcc *atmvcc, struct sk_buff *skb)
+{
+	struct pppoatm_vcc *pvcc = atmvcc_to_pvcc(atmvcc);
+	DPRINTK("pppoatm push\n");
+	if (skb == NULL) {			/* VCC was closed */
+		DPRINTK("removing ATMPPP VCC %p\n", pvcc);
+		pppoatm_unassign_vcc(atmvcc);
+		atmvcc->push(atmvcc, NULL);	/* Pass along bad news */
+		return;
+	}
+	atm_return(atmvcc, skb->truesize);
+	switch (pvcc->encaps) {
+	case e_llc:
+		if (skb->len < LLC_LEN ||
+		    memcmp(skb->data, pppllc, LLC_LEN))
+			goto error;
+		skb_pull(skb, LLC_LEN);
+		break;
+	case e_autodetect:
+		if (pvcc->chan.ppp == NULL) {	/* Not bound yet! */
+			kfree_skb(skb);
+			return;
+		}
+		if (skb->len >= sizeof(pppllc) &&
+		    !memcmp(skb->data, pppllc, sizeof(pppllc))) {
+			pvcc->encaps = e_llc;
+			skb_pull(skb, LLC_LEN);
+			break;
+		}
+		if (skb->len >= (sizeof(pppllc) - LLC_LEN) &&
+		    !memcmp(skb->data, &pppllc[LLC_LEN],
+		    sizeof(pppllc) - LLC_LEN)) {
+			pvcc->encaps = e_vc;
+			pvcc->chan.mtu += LLC_LEN;
+			break;
+		}
+		DPRINTK("(unit %d): Couldn't autodetect yet "
+		    "(skb: %02X %02X %02X %02X %02X %02X)\n",
+		    pvcc->chan.unit,
+		    skb->data[0], skb->data[1], skb->data[2],
+		    skb->data[3], skb->data[4], skb->data[5]);
+		goto error;
+	case e_vc:
+		break;
+	}
+	ppp_input(&pvcc->chan, skb);
+	return;
+    error:
+	kfree_skb(skb);
+	ppp_input_error(&pvcc->chan, 0);
+}
+
+/*
+ * Called by the ppp_generic.c to send a packet - returns true if packet
+ * was accepted.  If we return false, then it's our job to call
+ * ppp_output_wakeup(chan) when we're feeling more up to it.
+ * Note that in the ENOMEM case (as opposed to the !atm_may_send case)
+ * we should really drop the packet, but the generic layer doesn't
+ * support this yet.  We just return 'DROP_PACKET' which we actually define
+ * as success, just to be clear what we're really doing.
+ */
+#define DROP_PACKET 1
+static int pppoatm_send(struct ppp_channel *chan, struct sk_buff *skb)
+{
+	struct pppoatm_vcc *pvcc = chan_to_pvcc(chan);
+	ATM_SKB(skb)->vcc = pvcc->atmvcc;
+	DPRINTK("(unit %d): pppoatm_send (skb=0x%p, vcc=0x%p)\n",
+	    pvcc->chan.unit, skb, pvcc->atmvcc);
+	if (skb->data[0] == '\0' && (pvcc->flags & SC_COMP_PROT))
+		(void) skb_pull(skb, 1);
+	switch (pvcc->encaps) {		/* LLC encapsulation needed */
+	case e_llc:
+		if (skb_headroom(skb) < LLC_LEN) {
+			struct sk_buff *n;
+			n = skb_realloc_headroom(skb, LLC_LEN);
+			if (n != NULL &&
+			    !atm_may_send(pvcc->atmvcc, n->truesize)) {
+				kfree_skb(n);
+				goto nospace;
+			}
+			kfree_skb(skb);
+			if ((skb = n) == NULL)
+				return DROP_PACKET;
+		} else if (!atm_may_send(pvcc->atmvcc, skb->truesize))
+			goto nospace;
+		memcpy(skb_push(skb, LLC_LEN), pppllc, LLC_LEN);
+		break;
+	case e_vc:
+		if (!atm_may_send(pvcc->atmvcc, skb->truesize))
+			goto nospace;
+		break;
+	case e_autodetect:
+		DPRINTK("(unit %d): Trying to send without setting encaps!\n",
+		    pvcc->chan.unit);
+		kfree_skb(skb);
+		return 1;
+	}
+	atomic_add(skb->truesize, &ATM_SKB(skb)->vcc->tx_inuse);
+	ATM_SKB(skb)->iovcnt = 0;
+	ATM_SKB(skb)->atm_options = ATM_SKB(skb)->vcc->atm_options;
+	DPRINTK("(unit %d): atm_skb(%p)->vcc(%p)->dev(%p)\n",
+	    pvcc->chan.unit, skb, ATM_SKB(skb)->vcc,
+	    ATM_SKB(skb)->vcc->dev);
+	return ATM_SKB(skb)->vcc->send(ATM_SKB(skb)->vcc, skb)
+	    ? DROP_PACKET : 1;
+    nospace:
+	/*
+	 * 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 &&
+	    skb->data[-1] == '\0')
+		(void) skb_push(skb, 1);
+	return 0;
+}
+
+/* This handles ioctls sent to the /dev/ppp interface */
+static int pppoatm_devppp_ioctl(struct ppp_channel *chan, unsigned int cmd,
+	unsigned long arg)
+{
+	switch (cmd) {
+	case PPPIOCGFLAGS:
+		return put_user(chan_to_pvcc(chan)->flags, (int *) arg)
+		    ? -EFAULT : 0;
+	case PPPIOCSFLAGS:
+		return get_user(chan_to_pvcc(chan)->flags, (int *) arg)
+		    ? -EFAULT : 0;
+	}
+	return -ENOTTY;
+}
+
+static /*const*/ struct ppp_channel_ops pppoatm_ops = {
+	start_xmit: pppoatm_send,
+	ioctl: pppoatm_devppp_ioctl,
+};
+
+static int pppoatm_assign_vcc(struct atm_vcc *atmvcc, unsigned long arg)
+{
+	struct atm_backend_ppp be;
+	struct pppoatm_vcc *pvcc;
+	int err;
+	/*
+	 * Each PPPoATM instance has its own tasklet - this is just a
+	 * prototypical one used to initialize them
+	 */
+	static const DECLARE_TASKLET(tasklet_proto, pppoatm_wakeup_sender, 0);
+	if (copy_from_user(&be, (void *) arg, sizeof be))
+		return -EFAULT;
+	if (be.encaps != PPPOATM_ENCAPS_AUTODETECT &&
+	    be.encaps != PPPOATM_ENCAPS_VC && be.encaps != PPPOATM_ENCAPS_LLC)
+		return -EINVAL;
+	MOD_INC_USE_COUNT;
+	pvcc = kmalloc(sizeof(*pvcc), GFP_KERNEL);
+	if (pvcc == NULL) {
+		MOD_DEC_USE_COUNT;
+		return -ENOMEM;
+	}
+	memset(pvcc, 0, sizeof(*pvcc));
+	pvcc->atmvcc = atmvcc;
+	pvcc->old_push = atmvcc->push;
+	pvcc->old_pop = atmvcc->pop;
+	pvcc->encaps = (enum pppoatm_encaps) be.encaps;
+	pvcc->chan.private = pvcc;
+	pvcc->chan.ops = &pppoatm_ops;
+	pvcc->chan.mtu = atmvcc->qos.txtp.max_sdu - PPP_HDRLEN -
+	    (be.encaps == e_vc ? 0 : LLC_LEN);
+	pvcc->wakeup_tasklet = tasklet_proto;
+	pvcc->wakeup_tasklet.data = (unsigned long) &pvcc->chan;
+	if ((err = ppp_register_channel(&pvcc->chan)) != 0) {
+		kfree(pvcc);
+		return err;
+	}
+	atmvcc->user_back = pvcc;
+	atmvcc->push = pppoatm_push;
+	atmvcc->pop = pppoatm_pop;
+	return 0;
+}
+
+/*
+ * This handles ioctls actually performed on our vcc - we must return
+ * -ENOIOCTLCMD for any unrecognized ioctl
+ */
+static int pppoatm_ioctl(struct atm_vcc *atmvcc, unsigned int cmd,
+	unsigned long 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 *) arg))
+			return -EFAULT;
+		if (b != ATM_BACKEND_PPP)
+			return -ENOIOCTLCMD;
+		if (!capable(CAP_NET_ADMIN))
+			return -EPERM;
+		return pppoatm_assign_vcc(atmvcc, arg);
+		}
+	case PPPIOCGCHAN:
+		return put_user(ppp_channel_index(&atmvcc_to_pvcc(atmvcc)->
+		    chan), (int *) arg) ? -EFAULT : 0;
+	case PPPIOCGUNIT:
+		return put_user(ppp_unit_number(&atmvcc_to_pvcc(atmvcc)->
+		    chan), (int *) arg) ? -EFAULT : 0;
+	}
+	return -ENOIOCTLCMD;
+}
+
+/* the following avoids some spurious warnings from the compiler */
+#define UNUSED __attribute__((unused))
+
+extern int (*pppoatm_ioctl_hook)(struct atm_vcc *, unsigned int, unsigned long);
+
+static int __init UNUSED pppoatm_init(void)
+{
+	pppoatm_ioctl_hook = pppoatm_ioctl;
+	return 0;
+}
+
+static void __exit UNUSED pppoatm_exit(void)
+{
+	pppoatm_ioctl_hook = NULL;
+}
+
+module_init(pppoatm_init);
+module_exit(pppoatm_exit);
+
+MODULE_AUTHOR("Mitchell Blank Jr <mitch@sfgoth.com>");
+MODULE_DESCRIPTION("RFC2364 PPP over ATM/AAL5");