isdn_ppp.c

讲述linux的初始化过程

   This looks like a major redesign of the interface would be nice,
   but I don't have an idea how to do it better. */

/* Send a CCP Reset-Request or Reset-Ack directly from the kernel. This is
   getting that lengthy because there is no simple "send-this-frame-out"
   function above but every wrapper does a bit different. Hope I guess
   correct in this hack... */

static void isdn_ppp_ccp_xmit_reset(struct ippp_struct *is, int proto,
				    unsigned char code, unsigned char id,
				    unsigned char *data, int len)
{
	struct sk_buff *skb;
	unsigned char *p;
	int hl;
	int cnt = 0;
	isdn_net_local *lp = is->lp;

	/* Alloc large enough skb */
	hl = dev->drv[lp->isdn_device]->interface->hl_hdrlen;
	skb = alloc_skb(len + hl + 16,GFP_ATOMIC);
	if(!skb) {
		printk(KERN_WARNING
		       "ippp: CCP cannot send reset - out of memory\n");
		return;
	}
	skb_reserve(skb, hl);

	/* We may need to stuff an address and control field first */
	if(!(is->pppcfg & SC_COMP_AC)) {
		p = skb_put(skb, 2);
		*p++ = 0xff;
		*p++ = 0x03;
	}

	/* Stuff proto, code, id and length */
	p = skb_put(skb, 6);
	*p++ = (proto >> 8);
	*p++ = (proto & 0xff);
	*p++ = code;
	*p++ = id;
	cnt = 4 + len;
	*p++ = (cnt >> 8);
	*p++ = (cnt & 0xff);

	/* Now stuff remaining bytes */
	if(len) {
		p = skb_put(skb, len);
		memcpy(p, data, len);
	}

	/* skb is now ready for xmit */
	printk(KERN_DEBUG "Sending CCP Frame:\n");
	isdn_ppp_frame_log("ccp-xmit", skb->data, skb->len, 32, is->unit,lp->ppp_slot);

	isdn_net_write_super(lp, skb);
}

/* Allocate the reset state vector */
static struct ippp_ccp_reset *isdn_ppp_ccp_reset_alloc(struct ippp_struct *is)
{
	struct ippp_ccp_reset *r;
	r = kmalloc(sizeof(struct ippp_ccp_reset), GFP_KERNEL);
	if(!r) {
		printk(KERN_ERR "ippp_ccp: failed to allocate reset data"
		       " structure - no mem\n");
		return NULL;
	}
	memset(r, 0, sizeof(struct ippp_ccp_reset));
	printk(KERN_DEBUG "ippp_ccp: allocated reset data structure %p\n", r);
	is->reset = r;
	return r;
}

/* Destroy the reset state vector. Kill all pending timers first. */
static void isdn_ppp_ccp_reset_free(struct ippp_struct *is)
{
	unsigned int id;

	printk(KERN_DEBUG "ippp_ccp: freeing reset data structure %p\n",
	       is->reset);
	for(id = 0; id < 256; id++) {
		if(is->reset->rs[id]) {
			isdn_ppp_ccp_reset_free_state(is, (unsigned char)id);
		}
	}
	kfree(is->reset);
	is->reset = NULL;
}

/* Free a given state and clear everything up for later reallocation */
static void isdn_ppp_ccp_reset_free_state(struct ippp_struct *is,
					  unsigned char id)
{
	struct ippp_ccp_reset_state *rs;

	if(is->reset->rs[id]) {
		printk(KERN_DEBUG "ippp_ccp: freeing state for id %d\n", id);
		rs = is->reset->rs[id];
		/* Make sure the kernel will not call back later */
		if(rs->ta)
			del_timer(&rs->timer);
		is->reset->rs[id] = NULL;
		kfree(rs);
	} else {
		printk(KERN_WARNING "ippp_ccp: id %d is not allocated\n", id);
	}
}

/* The timer callback function which is called when a ResetReq has timed out,
   aka has never been answered by a ResetAck */
static void isdn_ppp_ccp_timer_callback(unsigned long closure)
{
	struct ippp_ccp_reset_state *rs =
		(struct ippp_ccp_reset_state *)closure;

	if(!rs) {
		printk(KERN_ERR "ippp_ccp: timer cb with zero closure.\n");
		return;
	}
	if(rs->ta && rs->state == CCPResetSentReq) {
		/* We are correct here */
		printk(KERN_DEBUG "ippp_ccp: CCP Reset timed out for id %d\n",
		       rs->id);
		if(!rs->expra) {
			/* Hmm, there is no Ack really expected. We can clean
			   up the state now, it will be reallocated if the
			   decompressor insists on another reset */
			rs->ta = 0;
			isdn_ppp_ccp_reset_free_state(rs->is, rs->id);
			return;
		}
		/* Push it again */
		isdn_ppp_ccp_xmit_reset(rs->is, PPP_CCP, CCP_RESETREQ, rs->id,
					rs->data, rs->dlen);
		/* Restart timer */
		rs->timer.expires = jiffies + HZ*5;
		add_timer(&rs->timer);
	} else {
		printk(KERN_WARNING "ippp_ccp: timer cb in wrong state %d\n",
		       rs->state);
	}
}

/* Allocate a new reset transaction state */
static struct ippp_ccp_reset_state *isdn_ppp_ccp_reset_alloc_state(struct ippp_struct *is,
						      unsigned char id)
{
	struct ippp_ccp_reset_state *rs;
	if(is->reset->rs[id]) {
		printk(KERN_WARNING "ippp_ccp: old state exists for id %d\n",
		       id);
		return NULL;
	} else {
		rs = kmalloc(sizeof(struct ippp_ccp_reset_state), GFP_KERNEL);
		if(!rs)
			return NULL;
		memset(rs, 0, sizeof(struct ippp_ccp_reset_state));
		rs->state = CCPResetIdle;
		rs->is = is;
		rs->id = id;
		rs->timer.data = (unsigned long)rs;
		rs->timer.function = isdn_ppp_ccp_timer_callback;
		is->reset->rs[id] = rs;
	}
	return rs;
}


/* A decompressor wants a reset with a set of parameters - do what is
   necessary to fulfill it */
static void isdn_ppp_ccp_reset_trans(struct ippp_struct *is,
				     struct isdn_ppp_resetparams *rp)
{
	struct ippp_ccp_reset_state *rs;

	if(rp->valid) {
		/* The decompressor defines parameters by itself */
		if(rp->rsend) {
			/* And he wants us to send a request */
			if(!(rp->idval)) {
				printk(KERN_ERR "ippp_ccp: decompressor must"
				       " specify reset id\n");
				return;
			}
			if(is->reset->rs[rp->id]) {
				/* There is already a transaction in existence
				   for this id. May be still waiting for a
				   Ack or may be wrong. */
				rs = is->reset->rs[rp->id];
				if(rs->state == CCPResetSentReq && rs->ta) {
					printk(KERN_DEBUG "ippp_ccp: reset"
					       " trans still in progress"
					       " for id %d\n", rp->id);
				} else {
					printk(KERN_WARNING "ippp_ccp: reset"
					       " trans in wrong state %d for"
					       " id %d\n", rs->state, rp->id);
				}
			} else {
				/* Ok, this is a new transaction */
				printk(KERN_DEBUG "ippp_ccp: new trans for id"
				       " %d to be started\n", rp->id);
				rs = isdn_ppp_ccp_reset_alloc_state(is, rp->id);
				if(!rs) {
					printk(KERN_ERR "ippp_ccp: out of mem"
					       " allocing ccp trans\n");
					return;
				}
				rs->state = CCPResetSentReq;
				rs->expra = rp->expra;
				if(rp->dtval) {
					rs->dlen = rp->dlen;
					memcpy(rs->data, rp->data, rp->dlen);
				}
				/* HACK TODO - add link comp here */
				isdn_ppp_ccp_xmit_reset(is, PPP_CCP,
							CCP_RESETREQ, rs->id,
							rs->data, rs->dlen);
				/* Start the timer */
				rs->timer.expires = jiffies + 5*HZ;
				add_timer(&rs->timer);
				rs->ta = 1;
			}
		} else {
			printk(KERN_DEBUG "ippp_ccp: no reset sent\n");
		}
	} else {
		/* The reset params are invalid. The decompressor does not
		   care about them, so we just send the minimal requests
		   and increase ids only when an Ack is received for a
		   given id */
		if(is->reset->rs[is->reset->lastid]) {
			/* There is already a transaction in existence
			   for this id. May be still waiting for a
			   Ack or may be wrong. */
			rs = is->reset->rs[is->reset->lastid];
			if(rs->state == CCPResetSentReq && rs->ta) {
				printk(KERN_DEBUG "ippp_ccp: reset"
				       " trans still in progress"
				       " for id %d\n", rp->id);
			} else {
				printk(KERN_WARNING "ippp_ccp: reset"
				       " trans in wrong state %d for"
				       " id %d\n", rs->state, rp->id);
			}
		} else {
			printk(KERN_DEBUG "ippp_ccp: new trans for id"
			       " %d to be started\n", is->reset->lastid);
			rs = isdn_ppp_ccp_reset_alloc_state(is,
							    is->reset->lastid);
			if(!rs) {
				printk(KERN_ERR "ippp_ccp: out of mem"
				       " allocing ccp trans\n");
				return;
			}
			rs->state = CCPResetSentReq;
			/* We always expect an Ack if the decompressor doesnt
			   know	better */
			rs->expra = 1;
			rs->dlen = 0;
			/* HACK TODO - add link comp here */
			isdn_ppp_ccp_xmit_reset(is, PPP_CCP, CCP_RESETREQ,
						rs->id, NULL, 0);
			/* Start the timer */
			rs->timer.expires = jiffies + 5*HZ;
			add_timer(&rs->timer);
			rs->ta = 1;
		}
	}
}

/* An Ack was received for this id. This means we stop the timer and clean
   up the state prior to calling the decompressors reset routine. */
static void isdn_ppp_ccp_reset_ack_rcvd(struct ippp_struct *is,
					unsigned char id)
{
	struct ippp_ccp_reset_state *rs = is->reset->rs[id];

	if(rs) {
		if(rs->ta && rs->state == CCPResetSentReq) {
			/* Great, we are correct */
			if(!rs->expra)
				printk(KERN_DEBUG "ippp_ccp: ResetAck received"
				       " for id %d but not expected\n", id);
		} else {
			printk(KERN_INFO "ippp_ccp: ResetAck received out of"
			       "sync for id %d\n", id);
		}
		if(rs->ta) {
			rs->ta = 0;
			del_timer(&rs->timer);
		}
		isdn_ppp_ccp_reset_free_state(is, id);
	} else {
		printk(KERN_INFO "ippp_ccp: ResetAck received for unknown id"
		       " %d\n", id);
	}
	/* Make sure the simple reset stuff uses a new id next time */
	is->reset->lastid++;
}

/* 
 * decompress packet
 *
 * if master = 0, we're trying to uncompress an per-link compressed packet,
 * as opposed to an compressed reconstructed-from-MPPP packet.
 * proto is updated to protocol field of uncompressed packet.
 *
 * retval: decompressed packet,
 *         same packet if uncompressed,
 *	   NULL if decompression error
 */

static struct sk_buff *isdn_ppp_decompress(struct sk_buff *skb,struct ippp_struct *is,struct ippp_struct *master,
	int *proto)
{
	void *stat = NULL;
	struct isdn_ppp_compressor *ipc = NULL;
	struct sk_buff *skb_out;
	int len;
	struct ippp_struct *ri;
	struct isdn_ppp_resetparams rsparm;
	unsigned char rsdata[IPPP_RESET_MAXDATABYTES];

	if(!master) {
		// per-link decompression 
		stat = is->link_decomp_stat;
		ipc = is->link_decompressor;
		ri = is;
	} else {
		stat = master->decomp_stat;
		ipc = master->decompressor;
		ri = master;
	}

	if (!ipc) {
		// no decompressor -> we can't decompress.
		printk(KERN_DEBUG "ippp: no decompressor defined!\n");
		return skb;
	}
	if (!stat) // if we have a compressor, stat has been set as well
		BUG();

	if((master && *proto == PPP_COMP) || (!master && *proto == PPP_COMPFRAG) ) {
		// compressed packets are compressed by their protocol type

		// Set up reset params for the decompressor
  		memset(&rsparm, 0, sizeof(rsparm));
  		rsparm.data = rsdata;
  		rsparm.maxdlen = IPPP_RESET_MAXDATABYTES;
  
		/* !!!HACK,HACK,HACK!!! 2048 is only assumed */
  		skb_out = dev_alloc_skb(2048);
		len = ipc->decompress(stat, skb, skb_out, &rsparm);
		kfree_skb(skb);
		if (len <= 0) {
			switch(len) {
			case DECOMP_ERROR:
				ri->pppcfg |= SC_DC_ERROR;
				printk(KERN_INFO "ippp: decomp wants reset %s params\n",
				       rsparm.valid ? "with" : "without");
				
				isdn_ppp_ccp_reset_trans(ri, &rsparm);
				break;
			case DECOMP_FATALERROR:
				ri->pppcfg |= SC_DC_FERROR;
				/* Kick ipppd to recognize the error */
				isdn_ppp_ccp_kickup(ri);
				break;
			}
			kfree_skb(skb_out);
			return NULL;
		}

		if (isdn_ppp_skip_ac(ri, skb) < 0) {
			kfree_skb(skb);
			return NULL;
		}
		*proto = isdn_ppp_strip_proto(skb);
		if (*proto < 0) {
			kfree_skb(skb);
			return NULL;
		}
		return skb_out;
	} else { 
		// uncompressed packets are fed through the decompressor to
		// update the decompressor state
		ipc->incomp(stat, skb, *proto);
		return skb;
	}
}

/*
 * compress a frame 
 *   type=0: normal/bundle compression
 *       =1: link compression
 * returns original skb if we haven't compressed the frame
 * and a new skb pointer if we've done it
 */
static struct sk_buff *isdn_ppp_compress(struct sk_buff *skb_in,int *proto,
	struct ippp_struct *is,struct ippp_struct *master,int type)
{
    int ret;
    int new_proto;
    struct isdn_ppp_compressor *compressor;
    void *stat;
    struct sk_buff *skb_out;

	/* we do not compress control protocols */
    if(*proto < 0 || *proto > 0x3fff) {
	    return skb_in;
    }

	if(type) { /* type=1 => Link compression */
		return skb_in;
	}
	else {
		if(!master) {
			compressor = is->compressor;
			stat = is->comp_stat;
		}
		else {
			compressor = master->compressor;
			stat = master->comp_stat;
		}
		new_proto = PPP_COMP;
	}

	if(!compressor) {
		printk(KERN_ERR "isdn_ppp: No compressor set!\n");
		return skb_in;
	}
	if(!stat) {
		printk(KERN_ERR "isdn_ppp: Compressor not initialized?\n");
		return skb_in;
	}

	/* Allow for at least 150 % expansion (for now) */
	skb_out = alloc_skb(skb_in->len + skb_in->len/2 + 32 +
		skb_headroom(skb_in), GFP_ATOMIC);
	if(!skb_out)
		return skb_in;
	skb_reserve(skb_out, skb_headroom(skb_in));

	ret = (compressor->compress)(stat,skb_in,skb_out,*proto);
	if(!ret) {
		dev_kfree_skb(skb_out);
		return skb_in;
	}
	
	dev_kfree_skb(skb_in);
	*proto = new_proto;
	return skb_out;
}

/*
 * we received a CCP frame .. 
 * not a clean solution, but we MUST handle a few cases in the kernel
 */
static void isdn_ppp_receive_ccp(isdn_net_dev *net_dev, isdn_net_local *lp,
	 struct sk_buff *skb,int proto)
{
	struct ippp_struct *is = ippp_table[lp->ppp_slot];
	struct ippp_struct *mis;
	int len;
	struct isdn_ppp_resetparams rsparm;
	unsigned char rsdata[IPPP_RESET_MAXDATABYTES];	

	printk(KERN_DEBUG "Received CCP frame from peer\n");
	isdn_ppp_frame_log("ccp-rcv", skb->data, skb->len, 32, is->unit,lp->ppp_slot);

	if(lp->master)
		mis = ippp_table[((isdn_net_local *) (lp->master->priv))->ppp_slot];
	else
		mis = is;

	switch(skb->data[0]) {
	case CCP_CONFREQ:
	case CCP_TERMREQ:
	case CCP_TERMACK:
		if(is->debug & 0x10)
			printk(KERN_DEBUG "Disable (de)compression here!\n");
		if(proto == PPP_CCP)
			mis->compflags &= ~(SC_DECOMP_ON|SC_COMP_ON);		
		else
			is->compflags &= ~(SC_LINK_DECOMP_ON|SC