skbuff.c

Go to the documentation of this file.

/*
 *      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>
 *
 *      Version:        $Id: skbuff.c,v 1.55 1999/02/23 08:12:27 davem Exp $
 *
 *      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
 *              Andi Kleen      :       slabified it.
 *
 *      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 <linux/slab.h>
#include <linux/init.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>

/*
 * Skb list spinlock
 */
spinlock_t skb_queue_lock = SPIN_LOCK_UNLOCKED;

/*
 *      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;

static kmem_cache_t *skbuff_head_cache;

/*
 *      Keep out-of-line to prevent kernel bloat.
 *      __builtin_return_address is not used because it is not always
 *      reliable. 
 */

void skb_over_panic(struct sk_buff *skb, int sz, void *here)
{
        panic("skput:over: %p:%d put:%d dev:%s", 
                here, skb->len, sz, skb->dev ? skb->dev->name : "<NULL>");
}

void skb_under_panic(struct sk_buff *skb, int sz, void *here)
{
        panic("skput:under: %p:%d put:%d dev:%s",
                here, skb->len, sz, skb->dev ? skb->dev->name : "<NULL>");
}

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

/*      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.
 * 
 */

struct sk_buff *alloc_skb(unsigned int size,int gfp_mask)
{
        struct sk_buff *skb;
        u8 *data;

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

        /* Get the HEAD */
        skb = kmem_cache_alloc(skbuff_head_cache, gfp_mask);
        if (skb == NULL) 
                goto nohead;

        /* Get the DATA. Size must match skb_add_mtu(). */
        if (size > 131072 - 32)
                goto nodata;
        size = ((size + 15) & ~15); 
        data = kmalloc(size + sizeof(atomic_t), gfp_mask);
        if (data == NULL)
                goto nodata;

        /* Note that this counter is useless now - you can just look in the
         * skbuff_head entry in /proc/slabinfo. We keep it only for emergency
         * cases.
         */
        atomic_inc(&net_allocs);

        skb->truesize = size;

        atomic_inc(&net_skbcount);

        /* Load the data pointers. */
        skb->head = data;
        skb->data = data;
        skb->tail = data;
        skb->end = data + size;

        /* Set up other state */
        skb->len = 0;
        skb->is_clone = 0;
        skb->cloned = 0;

        atomic_set(&skb->users, 1); 
        atomic_set(skb_datarefp(skb), 1);
        return skb;

nodata:
        kmem_cache_free(skbuff_head_cache, skb);
nohead:
        atomic_inc(&net_fails);
        return NULL;
}


/*
 *      Slab constructor for a skb head. 
 */ 
static inline void skb_headerinit(void *p, kmem_cache_t *cache, 
                                  unsigned long flags)
{
        struct sk_buff *skb = p;

        skb->destructor = NULL;
        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->stamp.tv_sec=0;    /* No idea about time */
        skb->ip_summed = 0;
        skb->security = 0;      /* By default packets are insecure */
        skb->dst = NULL;
#ifdef CONFIG_IP_FIREWALL
        skb->fwmark = 0;
#endif
        memset(skb->cb, 0, sizeof(skb->cb));
        skb->priority = 0;
}

/*
 *      Free an skbuff by memory without cleaning the state. 
 */
void kfree_skbmem(struct sk_buff *skb)
{
        if (!skb->cloned || atomic_dec_and_test(skb_datarefp(skb)))  
                kfree(skb->head);

        kmem_cache_free(skbuff_head_cache, skb);
        atomic_dec(&net_skbcount);
}

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

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);
        skb_headerinit(skb, NULL, 0);  /* clean state */
        kfree_skbmem(skb);
}

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

struct sk_buff *skb_clone(struct sk_buff *skb, int gfp_mask)
{
        struct sk_buff *n;
        
        n = kmem_cache_alloc(skbuff_head_cache, gfp_mask);
        if (!n)
                return NULL;

        memcpy(n, skb, sizeof(*n));
        atomic_inc(skb_datarefp(skb));
        skb->cloned = 1;
       
        atomic_inc(&net_allocs);
        atomic_inc(&net_skbcount);
        dst_clone(n->dst);
        n->cloned = 1;
        n->next = n->prev = NULL;
        n->list = NULL;
        n->sk = NULL;
        n->is_clone = 1;
        atomic_set(&n->users, 1);
        n->destructor = NULL;
        return n;
}

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

        /*
         *      Allocate the copy buffer
         */
         
        n=alloc_skb(skb->end - skb->head, gfp_mask);
        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->csum = skb->csum;
        n->list=NULL;
        n->sk=NULL;
        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;
        memcpy(n->cb, skb->cb, sizeof(skb->cb));
        n->used=skb->used;
        n->is_clone=0;
        atomic_set(&n->users, 1);
        n->pkt_type=skb->pkt_type;
        n->stamp=skb->stamp;
        n->destructor = NULL;
        n->security=skb->security;
#ifdef CONFIG_IP_FIREWALL
        n->fwmark = skb->fwmark;
#endif
        return n;
}

struct sk_buff *skb_copy_grow(struct sk_buff *skb, int pad, int gfp_mask)
{
        struct sk_buff *n;
        unsigned long offset;

        /*
         *      Allocate the copy buffer
         */
         
        n=alloc_skb(skb->end - skb->head + pad, gfp_mask);
        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->csum = skb->csum;
        n->list=NULL;
        n->sk=NULL;
        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;
        memcpy(n->cb, skb->cb, sizeof(skb->cb));
        n->used=skb->used;
        n->is_clone=0;
        atomic_set(&n->users, 1);
        n->pkt_type=skb->pkt_type;
        n->stamp=skb->stamp;
        n->destructor = NULL;
        n->security=skb->security;
#ifdef CONFIG_IP_FIREWALL
        n->fwmark = skb->fwmark;
#endif
        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, 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->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->used=skb->used;
        n->is_clone=0;
        atomic_set(&n->users, 1);
        n->pkt_type=skb->pkt_type;
        n->stamp=skb->stamp;
        n->destructor = NULL;
        n->security=skb->security;
#ifdef CONFIG_IP_FIREWALL
        n->fwmark = skb->fwmark;
#endif

        return n;
}

/**
 *      skb_pad                 -       zero pad the tail of an skb
 *      @skb: buffer to pad
 *      @pad: space to pad
 *
 *      Ensure that a buffer is followed by a padding area that is zero
 *      filled. Used by network drivers which may DMA or transfer data
 *      beyond the buffer end onto the wire.
 *
 *      May return NULL in out of memory cases.
 */
 
struct sk_buff *skb_pad(struct sk_buff *skb, int pad)
{
        struct sk_buff *nskb;
        
        /* If the skbuff is non linear tailroom is always zero.. */
        if(skb_tailroom(skb) >= pad)
        {
                memset(skb->data+skb->len, 0, pad);
                return skb;
        }
        
        nskb = skb_copy_grow(skb, pad, GFP_ATOMIC);
        kfree_skb(skb);
        if(nskb)
                memset(nskb->data+nskb->len, 0, pad);
        return nskb;
}       
 
#if 0
/* 
 *      Tune the memory allocator for a new MTU size.
 */
void skb_add_mtu(int mtu)
{
        /* Must match allocation in alloc_skb */
        mtu = ((mtu + 15) & ~15) + sizeof(atomic_t);

        kmem_add_cache_size(mtu);
}
#endif

void __init skb_init(void)
{
        skbuff_head_cache = kmem_cache_create("skbuff_head_cache",
                                              sizeof(struct sk_buff),
                                              0,
                                              SLAB_HWCACHE_ALIGN,
                                              skb_headerinit, NULL);
        if (!skbuff_head_cache)
                panic("cannot create skbuff cache");
}

---