path: root/net/core/skbuff.c

/*
 *	Routines having to do with the 'struct sk_buff' memory handlers.
 *
 *	Authors:	Alan Cox <iiitac@pyr.swan.ac.uk>
 *			Florian La Roche <rzsfl@rz.uni-sb.de>
 *
 *	Fixes:	
 *		Alan Cox	:	Fixed the worst of the load balancer bugs.
 *		Dave Platt	:	Interrupt stacking fix.
 *	Richard Kooijman	:	Timestamp fixes.
 *		Alan Cox	:	Changed buffer format.
 *		Alan Cox	:	destructor hook for AF_UNIX etc.
 *		Linus Torvalds	:	Better skb_clone.
 *		Alan Cox	:	Added skb_copy.
 *		Alan Cox	:	Added all the changed routines Linus
 *					only put in the headers
 *		Ray VanTassle	:	Fixed --skb->lock in free
 *		Alan Cox	:	skb_copy copy arp field
 *
 *	NOTE:
 *		The __skb_ routines should be called with interrupts 
 *	disabled, or you better be *real* sure that the operation is atomic 
 *	with respect to whatever list is being frobbed (e.g. via lock_sock()
 *	or via disabling bottom half handlers, etc).
 *
 *	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.
 */

/*
 *	The functions in this file will not compile correctly with gcc 2.4.x
 */

#include <linux/config.h>
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/sched.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/in.h>
#include <linux/inet.h>
#include <linux/malloc.h>
#include <linux/netdevice.h>
#include <linux/string.h>
#include <linux/skbuff.h>

#include <net/ip.h>
#include <net/protocol.h>
#include <net/dst.h>
#include <net/tcp.h>
#include <net/udp.h>
#include <net/sock.h>

#include <asm/uaccess.h>
#include <asm/system.h>

/*
 *	Resource tracking variables
 */

static atomic_t net_skbcount = ATOMIC_INIT(0);
static atomic_t net_allocs = ATOMIC_INIT(0);
static atomic_t net_fails  = ATOMIC_INIT(0);

extern atomic_t ip_frag_mem;

/*
 *	Strings we don't want inline's duplicating
 */
 
char *skb_push_errstr="skpush:under: %p:%d";
char *skb_put_errstr ="skput:over: %p:%d";

void show_net_buffers(void)
{
	printk(KERN_INFO "Networking buffers in use          : %u\n",
	       atomic_read(&net_skbcount));
	printk(KERN_INFO "Total network buffer allocations   : %u\n",
	       atomic_read(&net_allocs));
	printk(KERN_INFO "Total failed network buffer allocs : %u\n",
	       atomic_read(&net_fails));
#ifdef CONFIG_INET
	printk(KERN_INFO "IP fragment buffer size            : %u\n",
	       atomic_read(&ip_frag_mem));
#endif	
}

/*
 *	Free an sk_buff. Release anything attached to the buffer.
 */

void __kfree_skb(struct sk_buff *skb)
{
	if (skb->list)
	 	printk(KERN_WARNING "Warning: kfree_skb passed an skb still "
		       "on a list (from %p).\n", __builtin_return_address(0));

	dst_release(skb->dst);
	if(skb->destructor)
		skb->destructor(skb);
	kfree_skbmem(skb);
}

/*
 *	Allocate a new skbuff. We do this ourselves so we can fill in a few 'private'
 *	fields and also do memory statistics to find all the [BEEP] leaks.
 *
 *	Note: For now we put the header after the data to get better cache
 *	usage. Once we have a good cache aware kmalloc this will cease
 *	to be a good idea.
 */

struct sk_buff *alloc_skb(unsigned int size,int priority)
{
	struct sk_buff *skb;
	unsigned char *bptr;
	int len;

	if (in_interrupt() && priority!=GFP_ATOMIC) {
		static int count = 0;
		if (++count < 5) {
			printk(KERN_ERR "alloc_skb called nonatomically "
			       "from interrupt %p\n", __builtin_return_address(0));
			priority = GFP_ATOMIC;
		}
	}

	/*
	 *	FIXME: We could do with an architecture dependant
	 *	'alignment mask'.
	 */
	 
	/* Allow for alignments. Make a multiple of 16 bytes */
	size = (size + 15) & ~15;
	len = size;
	
	/* And stick the control itself on the end */
	size += sizeof(struct sk_buff);
	
	/*
	 *	Allocate some space
	 */
	 
	bptr = kmalloc(size,priority);
	if (bptr == NULL) {
		atomic_inc(&net_fails);
		return NULL;
	}

	/*
	 *	Now we play a little game with the caches. Linux kmalloc is
	 *	a bit cache dumb, in fact its just about maximally non 
	 *	optimal for typical kernel buffers. We actually run faster
	 *	by doing the following. Which is to deliberately put the
	 *	skb at the _end_ not the start of the memory block.
	 */
	atomic_inc(&net_allocs);
	
	skb = (struct sk_buff *)(bptr + size) - 1;

	atomic_set(&skb->count, 1);		/* only one reference to this */
	skb->data_skb = skb;			/* and we're our own data skb */

	skb->pkt_type = PACKET_HOST;	/* Default type */
	skb->pkt_bridged = 0;		/* Not bridged */
	skb->prev = skb->next = NULL;
	skb->list = NULL;
	skb->sk = NULL;
	skb->truesize=size;
	skb->stamp.tv_sec=0;	/* No idea about time */
	skb->ip_summed = 0;
	skb->security = 0;	/* By default packets are insecure */
	skb->dst = NULL;
	skb->destructor = NULL;
	memset(skb->cb, 0, sizeof(skb->cb));
	skb->priority = SOPRI_NORMAL;
	atomic_inc(&net_skbcount);
	atomic_set(&skb->users, 1);

	/* Load the data pointers. */
	skb->head = bptr;
	skb->data = bptr;
	skb->tail = bptr;
	skb->end = bptr + len;
	skb->len = 0;
	skb->inclone = 0;
	return skb;
}

/*
 *	Free an skbuff by memory
 */

extern inline void __kfree_skbmem(struct sk_buff *skb)
{
	/* don't do anything if somebody still uses us */
	if (atomic_dec_and_test(&skb->count)) {
		kfree(skb->head);
		atomic_dec(&net_skbcount);
	}
}

void kfree_skbmem(struct sk_buff *skb)
{
	void * addr = skb->head;

	/* don't do anything if somebody still uses us */
	if (atomic_dec_and_test(&skb->count)) {
		int free_head = (skb->inclone != SKB_CLONE_INLINE);

		/* free the skb that contains the actual data if we've clone()'d */
		if (skb->data_skb != skb) {
			addr = skb;
			__kfree_skbmem(skb->data_skb);
		}
		if (free_head)
			kfree(addr);
		atomic_dec(&net_skbcount);
	}
}

/*
 *	Duplicate an sk_buff. The new one is not owned by a socket.
 */

struct sk_buff *skb_clone(struct sk_buff *skb, int priority)
{
	struct sk_buff *n;
	int inbuff = 0;
	
	if (!skb->inclone && skb_tailroom(skb) >= sizeof(struct sk_buff)) {
		n = ((struct sk_buff *) skb->end) - 1;
		skb->end -= sizeof(struct sk_buff);
		skb->inclone = SKB_CLONE_ORIG;
		inbuff = SKB_CLONE_INLINE;
	} else {
		n = kmalloc(sizeof(*n), priority);
		if (!n)
			return NULL;
	}
	memcpy(n, skb, sizeof(*n));
	atomic_set(&n->count, 1);
	skb = skb->data_skb;
	atomic_inc(&skb->count);
	atomic_inc(&net_allocs);
	atomic_inc(&net_skbcount);
	dst_clone(n->dst);
	n->data_skb = skb;
	n->next = n->prev = NULL;
	n->list = NULL;
	n->sk = NULL;
	n->tries = 0;
	atomic_set(&n->users, 1);
	n->inclone = inbuff;
	n->destructor = NULL;
	return n;
}

/*
 *	This is slower, and copies the whole data area 
 */
 
struct sk_buff *skb_copy(struct sk_buff *skb, int priority)
{
	struct sk_buff *n;
	unsigned long offset;

	/*
	 *	Allocate the copy buffer
	 */
	 
	n=alloc_skb(skb->end - skb->head, priority);
	if(n==NULL)
		return NULL;

	/*
	 *	Shift between the two data areas in bytes
	 */
	 
	offset=n->head-skb->head;

	/* Set the data pointer */
	skb_reserve(n,skb->data-skb->head);
	/* Set the tail pointer and length */
	skb_put(n,skb->len);
	/* Copy the bytes */
	memcpy(n->head,skb->head,skb->end-skb->head);
	n->list=NULL;
	n->sk=NULL;
	n->when=skb->when;
	n->dev=skb->dev;
	n->priority=skb->priority;
	n->protocol=skb->protocol;
	n->dst=dst_clone(skb->dst);
	n->h.raw=skb->h.raw+offset;
	n->nh.raw=skb->nh.raw+offset;
	n->mac.raw=skb->mac.raw+offset;
	n->seq=skb->seq;
	n->end_seq=skb->end_seq;
	n->ack_seq=skb->ack_seq;
	memcpy(n->cb, skb->cb, sizeof(skb->cb));
	n->used=skb->used;
	n->arp=skb->arp;
	n->tries=0;
	atomic_set(&n->users, 1);
	n->pkt_type=skb->pkt_type;
	n->stamp=skb->stamp;
	n->destructor = NULL;
	n->security=skb->security;
	return n;
}

struct sk_buff *skb_realloc_headroom(struct sk_buff *skb, int newheadroom)
{
	struct sk_buff *n;
	unsigned long offset;
	int headroom = skb_headroom(skb);

	/*
	 *	Allocate the copy buffer
	 */
 	 
	n=alloc_skb(skb->truesize+newheadroom-headroom-sizeof(struct sk_buff), GFP_ATOMIC);
	if(n==NULL)
		return NULL;

	skb_reserve(n,newheadroom);

	/*
	 *	Shift between the two data areas in bytes
	 */
	 
	offset=n->data-skb->data;

	/* Set the tail pointer and length */
	skb_put(n,skb->len);
	/* Copy the bytes */
	memcpy(n->data,skb->data,skb->len);
	n->list=NULL;
	n->sk=NULL;
	n->when=skb->when;
	n->priority=skb->priority;
	n->protocol=skb->protocol;
	n->dev=skb->dev;
	n->dst=dst_clone(skb->dst);
	n->h.raw=skb->h.raw+offset;
	n->nh.raw=skb->nh.raw+offset;
	n->mac.raw=skb->mac.raw+offset;
	memcpy(n->cb, skb->cb, sizeof(skb->cb));
	n->seq=skb->seq;
 	n->end_seq=skb->end_seq;
	n->ack_seq=skb->ack_seq;
	n->used=skb->used;
	n->arp=skb->arp;
	n->tries=0;
	atomic_set(&n->users, 1);
	n->pkt_type=skb->pkt_type;
	n->stamp=skb->stamp;
	n->destructor = NULL;
	n->security=skb->security;

	return n;
}
  
struct sk_buff *dev_alloc_skb(unsigned int length)
{
	struct sk_buff *skb;

	skb = alloc_skb(length+16, GFP_ATOMIC);
	if (skb)
		skb_reserve(skb,16);
	return skb;
}