2 * Definitions for the 'struct sk_buff' memory handlers.
5 * Alan Cox, <gw4pts@gw4pts.ampr.org>
6 * Florian La Roche, <rzsfl@rz.uni-sb.de>
8 * This program is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU General Public License
10 * as published by the Free Software Foundation; either version
11 * 2 of the License, or (at your option) any later version.
14 #ifndef _LINUX_SKBUFF_H
15 #define _LINUX_SKBUFF_H
17 #include <linux/config.h>
18 #include <linux/kernel.h>
19 #include <linux/compiler.h>
20 #include <linux/time.h>
21 #include <linux/cache.h>
23 #include <asm/atomic.h>
24 #include <asm/types.h>
25 #include <linux/spinlock.h>
27 #include <linux/highmem.h>
28 #include <linux/poll.h>
29 #include <linux/net.h>
30 #include <linux/textsearch.h>
31 #include <net/checksum.h>
33 #define HAVE_ALLOC_SKB /* For the drivers to know */
34 #define HAVE_ALIGNABLE_SKB /* Ditto 8) */
35 #define SLAB_SKB /* Slabified skbuffs */
37 #define CHECKSUM_NONE 0
39 #define CHECKSUM_UNNECESSARY 2
41 #define SKB_DATA_ALIGN(X) (((X) + (SMP_CACHE_BYTES - 1)) & \
42 ~(SMP_CACHE_BYTES - 1))
43 #define SKB_MAX_ORDER(X, ORDER) (((PAGE_SIZE << (ORDER)) - (X) - \
44 sizeof(struct skb_shared_info)) & \
45 ~(SMP_CACHE_BYTES - 1))
46 #define SKB_MAX_HEAD(X) (SKB_MAX_ORDER((X), 0))
47 #define SKB_MAX_ALLOC (SKB_MAX_ORDER(0, 2))
49 /* A. Checksumming of received packets by device.
51 * NONE: device failed to checksum this packet.
52 * skb->csum is undefined.
54 * UNNECESSARY: device parsed packet and wouldbe verified checksum.
55 * skb->csum is undefined.
56 * It is bad option, but, unfortunately, many of vendors do this.
57 * Apparently with secret goal to sell you new device, when you
58 * will add new protocol to your host. F.e. IPv6. 8)
60 * HW: the most generic way. Device supplied checksum of _all_
61 * the packet as seen by netif_rx in skb->csum.
62 * NOTE: Even if device supports only some protocols, but
63 * is able to produce some skb->csum, it MUST use HW,
66 * B. Checksumming on output.
68 * NONE: skb is checksummed by protocol or csum is not required.
70 * HW: device is required to csum packet as seen by hard_start_xmit
71 * from skb->h.raw to the end and to record the checksum
72 * at skb->h.raw+skb->csum.
74 * Device must show its capabilities in dev->features, set
75 * at device setup time.
76 * NETIF_F_HW_CSUM - it is clever device, it is able to checksum
78 * NETIF_F_NO_CSUM - loopback or reliable single hop media.
79 * NETIF_F_IP_CSUM - device is dumb. It is able to csum only
80 * TCP/UDP over IPv4. Sigh. Vendors like this
81 * way by an unknown reason. Though, see comment above
82 * about CHECKSUM_UNNECESSARY. 8)
84 * Any questions? No questions, good. --ANK
89 #ifdef CONFIG_NETFILTER
92 void (*destroy
)(struct nf_conntrack
*);
95 #ifdef CONFIG_BRIDGE_NETFILTER
96 struct nf_bridge_info
{
98 struct net_device
*physindev
;
99 struct net_device
*physoutdev
;
100 #if defined(CONFIG_VLAN_8021Q) || defined(CONFIG_VLAN_8021Q_MODULE)
101 struct net_device
*netoutdev
;
104 unsigned long data
[32 / sizeof(unsigned long)];
110 struct sk_buff_head
{
111 /* These two members must be first. */
112 struct sk_buff
*next
;
113 struct sk_buff
*prev
;
121 /* To allow 64K frame to be packed as single skb without frag_list */
122 #define MAX_SKB_FRAGS (65536/PAGE_SIZE + 2)
124 typedef struct skb_frag_struct skb_frag_t
;
126 struct skb_frag_struct
{
132 /* This data is invariant across clones and lives at
133 * the end of the header data, ie. at skb->end.
135 struct skb_shared_info
{
137 unsigned int nr_frags
;
138 unsigned short tso_size
;
139 unsigned short tso_segs
;
140 struct sk_buff
*frag_list
;
141 skb_frag_t frags
[MAX_SKB_FRAGS
];
144 /* We divide dataref into two halves. The higher 16 bits hold references
145 * to the payload part of skb->data. The lower 16 bits hold references to
146 * the entire skb->data. It is up to the users of the skb to agree on
147 * where the payload starts.
149 * All users must obey the rule that the skb->data reference count must be
150 * greater than or equal to the payload reference count.
152 * Holding a reference to the payload part means that the user does not
153 * care about modifications to the header part of skb->data.
155 #define SKB_DATAREF_SHIFT 16
156 #define SKB_DATAREF_MASK ((1 << SKB_DATAREF_SHIFT) - 1)
159 * struct sk_buff - socket buffer
160 * @next: Next buffer in list
161 * @prev: Previous buffer in list
162 * @list: List we are on
163 * @sk: Socket we are owned by
164 * @stamp: Time we arrived
165 * @dev: Device we arrived on/are leaving by
166 * @input_dev: Device we arrived on
167 * @real_dev: The real device we are using
168 * @h: Transport layer header
169 * @nh: Network layer header
170 * @mac: Link layer header
171 * @dst: destination entry
172 * @sp: the security path, used for xfrm
173 * @cb: Control buffer. Free for use by every layer. Put private vars here
174 * @len: Length of actual data
175 * @data_len: Data length
176 * @mac_len: Length of link layer header
178 * @local_df: allow local fragmentation
179 * @cloned: Head may be cloned (check refcnt to be sure)
180 * @nohdr: Payload reference only, must not modify header
181 * @pkt_type: Packet class
182 * @ip_summed: Driver fed us an IP checksum
183 * @priority: Packet queueing priority
184 * @users: User count - see {datagram,tcp}.c
185 * @protocol: Packet protocol from driver
186 * @security: Security level of packet
187 * @truesize: Buffer size
188 * @head: Head of buffer
189 * @data: Data head pointer
190 * @tail: Tail pointer
192 * @destructor: Destruct function
193 * @nfmark: Can be used for communication between hooks
194 * @nfcache: Cache info
195 * @nfct: Associated connection, if any
196 * @nfctinfo: Relationship of this skb to the connection
197 * @nf_bridge: Saved data about a bridged frame - see br_netfilter.c
198 * @private: Data which is private to the HIPPI implementation
199 * @tc_index: Traffic control index
200 * @tc_verd: traffic control verdict
201 * @tc_classid: traffic control classid
205 /* These two members must be first. */
206 struct sk_buff
*next
;
207 struct sk_buff
*prev
;
209 struct sk_buff_head
*list
;
211 struct timeval stamp
;
212 struct net_device
*dev
;
213 struct net_device
*input_dev
;
214 struct net_device
*real_dev
;
219 struct icmphdr
*icmph
;
220 struct igmphdr
*igmph
;
222 struct ipv6hdr
*ipv6h
;
228 struct ipv6hdr
*ipv6h
;
237 struct dst_entry
*dst
;
241 * This is the control buffer. It is free to use for every
242 * layer. Please put your private variables there. If you
243 * want to keep them across layers you have to do a skb_clone()
244 * first. This is owned by whoever has the skb queued ATM.
252 unsigned char local_df
,
258 unsigned short protocol
,
261 void (*destructor
)(struct sk_buff
*skb
);
262 #ifdef CONFIG_NETFILTER
263 unsigned long nfmark
;
266 struct nf_conntrack
*nfct
;
267 #ifdef CONFIG_BRIDGE_NETFILTER
268 struct nf_bridge_info
*nf_bridge
;
270 #endif /* CONFIG_NETFILTER */
271 #if defined(CONFIG_HIPPI)
276 #ifdef CONFIG_NET_SCHED
277 __u32 tc_index
; /* traffic control index */
278 #ifdef CONFIG_NET_CLS_ACT
279 __u32 tc_verd
; /* traffic control verdict */
280 __u32 tc_classid
; /* traffic control classid */
286 /* These elements must be at the end, see alloc_skb() for details. */
287 unsigned int truesize
;
297 * Handling routines are only of interest to the kernel
299 #include <linux/slab.h>
301 #include <asm/system.h>
303 extern void __kfree_skb(struct sk_buff
*skb
);
304 extern struct sk_buff
*alloc_skb(unsigned int size
, int priority
);
305 extern struct sk_buff
*alloc_skb_from_cache(kmem_cache_t
*cp
,
306 unsigned int size
, int priority
);
307 extern void kfree_skbmem(struct sk_buff
*skb
);
308 extern struct sk_buff
*skb_clone(struct sk_buff
*skb
, int priority
);
309 extern struct sk_buff
*skb_copy(const struct sk_buff
*skb
, int priority
);
310 extern struct sk_buff
*pskb_copy(struct sk_buff
*skb
, int gfp_mask
);
311 extern int pskb_expand_head(struct sk_buff
*skb
,
312 int nhead
, int ntail
, int gfp_mask
);
313 extern struct sk_buff
*skb_realloc_headroom(struct sk_buff
*skb
,
314 unsigned int headroom
);
315 extern struct sk_buff
*skb_copy_expand(const struct sk_buff
*skb
,
316 int newheadroom
, int newtailroom
,
318 extern struct sk_buff
* skb_pad(struct sk_buff
*skb
, int pad
);
319 #define dev_kfree_skb(a) kfree_skb(a)
320 extern void skb_over_panic(struct sk_buff
*skb
, int len
,
322 extern void skb_under_panic(struct sk_buff
*skb
, int len
,
330 __u32 stepped_offset
;
331 struct sk_buff
*root_skb
;
332 struct sk_buff
*cur_skb
;
336 extern void skb_prepare_seq_read(struct sk_buff
*skb
,
337 unsigned int from
, unsigned int to
,
338 struct skb_seq_state
*st
);
339 extern unsigned int skb_seq_read(unsigned int consumed
, const u8
**data
,
340 struct skb_seq_state
*st
);
341 extern void skb_abort_seq_read(struct skb_seq_state
*st
);
343 extern unsigned int skb_find_text(struct sk_buff
*skb
, unsigned int from
,
344 unsigned int to
, struct ts_config
*config
,
345 struct ts_state
*state
);
348 #define skb_shinfo(SKB) ((struct skb_shared_info *)((SKB)->end))
351 * skb_queue_empty - check if a queue is empty
354 * Returns true if the queue is empty, false otherwise.
356 static inline int skb_queue_empty(const struct sk_buff_head
*list
)
358 return list
->next
== (struct sk_buff
*)list
;
362 * skb_get - reference buffer
363 * @skb: buffer to reference
365 * Makes another reference to a socket buffer and returns a pointer
368 static inline struct sk_buff
*skb_get(struct sk_buff
*skb
)
370 atomic_inc(&skb
->users
);
375 * If users == 1, we are the only owner and are can avoid redundant
380 * kfree_skb - free an sk_buff
381 * @skb: buffer to free
383 * Drop a reference to the buffer and free it if the usage count has
386 static inline void kfree_skb(struct sk_buff
*skb
)
388 if (likely(atomic_read(&skb
->users
) == 1))
390 else if (likely(!atomic_dec_and_test(&skb
->users
)))
396 * skb_cloned - is the buffer a clone
397 * @skb: buffer to check
399 * Returns true if the buffer was generated with skb_clone() and is
400 * one of multiple shared copies of the buffer. Cloned buffers are
401 * shared data so must not be written to under normal circumstances.
403 static inline int skb_cloned(const struct sk_buff
*skb
)
405 return skb
->cloned
&&
406 (atomic_read(&skb_shinfo(skb
)->dataref
) & SKB_DATAREF_MASK
) != 1;
410 * skb_header_cloned - is the header a clone
411 * @skb: buffer to check
413 * Returns true if modifying the header part of the buffer requires
414 * the data to be copied.
416 static inline int skb_header_cloned(const struct sk_buff
*skb
)
423 dataref
= atomic_read(&skb_shinfo(skb
)->dataref
);
424 dataref
= (dataref
& SKB_DATAREF_MASK
) - (dataref
>> SKB_DATAREF_SHIFT
);
429 * skb_header_release - release reference to header
430 * @skb: buffer to operate on
432 * Drop a reference to the header part of the buffer. This is done
433 * by acquiring a payload reference. You must not read from the header
434 * part of skb->data after this.
436 static inline void skb_header_release(struct sk_buff
*skb
)
440 atomic_add(1 << SKB_DATAREF_SHIFT
, &skb_shinfo(skb
)->dataref
);
444 * skb_shared - is the buffer shared
445 * @skb: buffer to check
447 * Returns true if more than one person has a reference to this
450 static inline int skb_shared(const struct sk_buff
*skb
)
452 return atomic_read(&skb
->users
) != 1;
456 * skb_share_check - check if buffer is shared and if so clone it
457 * @skb: buffer to check
458 * @pri: priority for memory allocation
460 * If the buffer is shared the buffer is cloned and the old copy
461 * drops a reference. A new clone with a single reference is returned.
462 * If the buffer is not shared the original buffer is returned. When
463 * being called from interrupt status or with spinlocks held pri must
466 * NULL is returned on a memory allocation failure.
468 static inline struct sk_buff
*skb_share_check(struct sk_buff
*skb
, int pri
)
470 might_sleep_if(pri
& __GFP_WAIT
);
471 if (skb_shared(skb
)) {
472 struct sk_buff
*nskb
= skb_clone(skb
, pri
);
480 * Copy shared buffers into a new sk_buff. We effectively do COW on
481 * packets to handle cases where we have a local reader and forward
482 * and a couple of other messy ones. The normal one is tcpdumping
483 * a packet thats being forwarded.
487 * skb_unshare - make a copy of a shared buffer
488 * @skb: buffer to check
489 * @pri: priority for memory allocation
491 * If the socket buffer is a clone then this function creates a new
492 * copy of the data, drops a reference count on the old copy and returns
493 * the new copy with the reference count at 1. If the buffer is not a clone
494 * the original buffer is returned. When called with a spinlock held or
495 * from interrupt state @pri must be %GFP_ATOMIC
497 * %NULL is returned on a memory allocation failure.
499 static inline struct sk_buff
*skb_unshare(struct sk_buff
*skb
, int pri
)
501 might_sleep_if(pri
& __GFP_WAIT
);
502 if (skb_cloned(skb
)) {
503 struct sk_buff
*nskb
= skb_copy(skb
, pri
);
504 kfree_skb(skb
); /* Free our shared copy */
512 * @list_: list to peek at
514 * Peek an &sk_buff. Unlike most other operations you _MUST_
515 * be careful with this one. A peek leaves the buffer on the
516 * list and someone else may run off with it. You must hold
517 * the appropriate locks or have a private queue to do this.
519 * Returns %NULL for an empty list or a pointer to the head element.
520 * The reference count is not incremented and the reference is therefore
521 * volatile. Use with caution.
523 static inline struct sk_buff
*skb_peek(struct sk_buff_head
*list_
)
525 struct sk_buff
*list
= ((struct sk_buff
*)list_
)->next
;
526 if (list
== (struct sk_buff
*)list_
)
533 * @list_: list to peek at
535 * Peek an &sk_buff. Unlike most other operations you _MUST_
536 * be careful with this one. A peek leaves the buffer on the
537 * list and someone else may run off with it. You must hold
538 * the appropriate locks or have a private queue to do this.
540 * Returns %NULL for an empty list or a pointer to the tail element.
541 * The reference count is not incremented and the reference is therefore
542 * volatile. Use with caution.
544 static inline struct sk_buff
*skb_peek_tail(struct sk_buff_head
*list_
)
546 struct sk_buff
*list
= ((struct sk_buff
*)list_
)->prev
;
547 if (list
== (struct sk_buff
*)list_
)
553 * skb_queue_len - get queue length
554 * @list_: list to measure
556 * Return the length of an &sk_buff queue.
558 static inline __u32
skb_queue_len(const struct sk_buff_head
*list_
)
563 static inline void skb_queue_head_init(struct sk_buff_head
*list
)
565 spin_lock_init(&list
->lock
);
566 list
->prev
= list
->next
= (struct sk_buff
*)list
;
571 * Insert an sk_buff at the start of a list.
573 * The "__skb_xxxx()" functions are the non-atomic ones that
574 * can only be called with interrupts disabled.
578 * __skb_queue_head - queue a buffer at the list head
580 * @newsk: buffer to queue
582 * Queue a buffer at the start of a list. This function takes no locks
583 * and you must therefore hold required locks before calling it.
585 * A buffer cannot be placed on two lists at the same time.
587 extern void skb_queue_head(struct sk_buff_head
*list
, struct sk_buff
*newsk
);
588 static inline void __skb_queue_head(struct sk_buff_head
*list
,
589 struct sk_buff
*newsk
)
591 struct sk_buff
*prev
, *next
;
595 prev
= (struct sk_buff
*)list
;
599 next
->prev
= prev
->next
= newsk
;
603 * __skb_queue_tail - queue a buffer at the list tail
605 * @newsk: buffer to queue
607 * Queue a buffer at the end of a list. This function takes no locks
608 * and you must therefore hold required locks before calling it.
610 * A buffer cannot be placed on two lists at the same time.
612 extern void skb_queue_tail(struct sk_buff_head
*list
, struct sk_buff
*newsk
);
613 static inline void __skb_queue_tail(struct sk_buff_head
*list
,
614 struct sk_buff
*newsk
)
616 struct sk_buff
*prev
, *next
;
620 next
= (struct sk_buff
*)list
;
624 next
->prev
= prev
->next
= newsk
;
629 * __skb_dequeue - remove from the head of the queue
630 * @list: list to dequeue from
632 * Remove the head of the list. This function does not take any locks
633 * so must be used with appropriate locks held only. The head item is
634 * returned or %NULL if the list is empty.
636 extern struct sk_buff
*skb_dequeue(struct sk_buff_head
*list
);
637 static inline struct sk_buff
*__skb_dequeue(struct sk_buff_head
*list
)
639 struct sk_buff
*next
, *prev
, *result
;
641 prev
= (struct sk_buff
*) list
;
650 result
->next
= result
->prev
= NULL
;
658 * Insert a packet on a list.
660 extern void skb_insert(struct sk_buff
*old
, struct sk_buff
*newsk
);
661 static inline void __skb_insert(struct sk_buff
*newsk
,
662 struct sk_buff
*prev
, struct sk_buff
*next
,
663 struct sk_buff_head
*list
)
667 next
->prev
= prev
->next
= newsk
;
673 * Place a packet after a given packet in a list.
675 extern void skb_append(struct sk_buff
*old
, struct sk_buff
*newsk
);
676 static inline void __skb_append(struct sk_buff
*old
, struct sk_buff
*newsk
)
678 __skb_insert(newsk
, old
, old
->next
, old
->list
);
682 * remove sk_buff from list. _Must_ be called atomically, and with
685 extern void skb_unlink(struct sk_buff
*skb
);
686 static inline void __skb_unlink(struct sk_buff
*skb
, struct sk_buff_head
*list
)
688 struct sk_buff
*next
, *prev
;
693 skb
->next
= skb
->prev
= NULL
;
700 /* XXX: more streamlined implementation */
703 * __skb_dequeue_tail - remove from the tail of the queue
704 * @list: list to dequeue from
706 * Remove the tail of the list. This function does not take any locks
707 * so must be used with appropriate locks held only. The tail item is
708 * returned or %NULL if the list is empty.
710 extern struct sk_buff
*skb_dequeue_tail(struct sk_buff_head
*list
);
711 static inline struct sk_buff
*__skb_dequeue_tail(struct sk_buff_head
*list
)
713 struct sk_buff
*skb
= skb_peek_tail(list
);
715 __skb_unlink(skb
, list
);
720 static inline int skb_is_nonlinear(const struct sk_buff
*skb
)
722 return skb
->data_len
;
725 static inline unsigned int skb_headlen(const struct sk_buff
*skb
)
727 return skb
->len
- skb
->data_len
;
730 static inline int skb_pagelen(const struct sk_buff
*skb
)
734 for (i
= (int)skb_shinfo(skb
)->nr_frags
- 1; i
>= 0; i
--)
735 len
+= skb_shinfo(skb
)->frags
[i
].size
;
736 return len
+ skb_headlen(skb
);
739 static inline void skb_fill_page_desc(struct sk_buff
*skb
, int i
,
740 struct page
*page
, int off
, int size
)
742 skb_frag_t
*frag
= &skb_shinfo(skb
)->frags
[i
];
745 frag
->page_offset
= off
;
747 skb_shinfo(skb
)->nr_frags
= i
+ 1;
750 #define SKB_PAGE_ASSERT(skb) BUG_ON(skb_shinfo(skb)->nr_frags)
751 #define SKB_FRAG_ASSERT(skb) BUG_ON(skb_shinfo(skb)->frag_list)
752 #define SKB_LINEAR_ASSERT(skb) BUG_ON(skb_is_nonlinear(skb))
755 * Add data to an sk_buff
757 static inline unsigned char *__skb_put(struct sk_buff
*skb
, unsigned int len
)
759 unsigned char *tmp
= skb
->tail
;
760 SKB_LINEAR_ASSERT(skb
);
767 * skb_put - add data to a buffer
768 * @skb: buffer to use
769 * @len: amount of data to add
771 * This function extends the used data area of the buffer. If this would
772 * exceed the total buffer size the kernel will panic. A pointer to the
773 * first byte of the extra data is returned.
775 static inline unsigned char *skb_put(struct sk_buff
*skb
, unsigned int len
)
777 unsigned char *tmp
= skb
->tail
;
778 SKB_LINEAR_ASSERT(skb
);
781 if (unlikely(skb
->tail
>skb
->end
))
782 skb_over_panic(skb
, len
, current_text_addr());
786 static inline unsigned char *__skb_push(struct sk_buff
*skb
, unsigned int len
)
794 * skb_push - add data to the start of a buffer
795 * @skb: buffer to use
796 * @len: amount of data to add
798 * This function extends the used data area of the buffer at the buffer
799 * start. If this would exceed the total buffer headroom the kernel will
800 * panic. A pointer to the first byte of the extra data is returned.
802 static inline unsigned char *skb_push(struct sk_buff
*skb
, unsigned int len
)
806 if (unlikely(skb
->data
<skb
->head
))
807 skb_under_panic(skb
, len
, current_text_addr());
811 static inline unsigned char *__skb_pull(struct sk_buff
*skb
, unsigned int len
)
814 BUG_ON(skb
->len
< skb
->data_len
);
815 return skb
->data
+= len
;
819 * skb_pull - remove data from the start of a buffer
820 * @skb: buffer to use
821 * @len: amount of data to remove
823 * This function removes data from the start of a buffer, returning
824 * the memory to the headroom. A pointer to the next data in the buffer
825 * is returned. Once the data has been pulled future pushes will overwrite
828 static inline unsigned char *skb_pull(struct sk_buff
*skb
, unsigned int len
)
830 return unlikely(len
> skb
->len
) ? NULL
: __skb_pull(skb
, len
);
833 extern unsigned char *__pskb_pull_tail(struct sk_buff
*skb
, int delta
);
835 static inline unsigned char *__pskb_pull(struct sk_buff
*skb
, unsigned int len
)
837 if (len
> skb_headlen(skb
) &&
838 !__pskb_pull_tail(skb
, len
-skb_headlen(skb
)))
841 return skb
->data
+= len
;
844 static inline unsigned char *pskb_pull(struct sk_buff
*skb
, unsigned int len
)
846 return unlikely(len
> skb
->len
) ? NULL
: __pskb_pull(skb
, len
);
849 static inline int pskb_may_pull(struct sk_buff
*skb
, unsigned int len
)
851 if (likely(len
<= skb_headlen(skb
)))
853 if (unlikely(len
> skb
->len
))
855 return __pskb_pull_tail(skb
, len
-skb_headlen(skb
)) != NULL
;
859 * skb_headroom - bytes at buffer head
860 * @skb: buffer to check
862 * Return the number of bytes of free space at the head of an &sk_buff.
864 static inline int skb_headroom(const struct sk_buff
*skb
)
866 return skb
->data
- skb
->head
;
870 * skb_tailroom - bytes at buffer end
871 * @skb: buffer to check
873 * Return the number of bytes of free space at the tail of an sk_buff
875 static inline int skb_tailroom(const struct sk_buff
*skb
)
877 return skb_is_nonlinear(skb
) ? 0 : skb
->end
- skb
->tail
;
881 * skb_reserve - adjust headroom
882 * @skb: buffer to alter
883 * @len: bytes to move
885 * Increase the headroom of an empty &sk_buff by reducing the tail
886 * room. This is only allowed for an empty buffer.
888 static inline void skb_reserve(struct sk_buff
*skb
, unsigned int len
)
895 * CPUs often take a performance hit when accessing unaligned memory
896 * locations. The actual performance hit varies, it can be small if the
897 * hardware handles it or large if we have to take an exception and fix it
900 * Since an ethernet header is 14 bytes network drivers often end up with
901 * the IP header at an unaligned offset. The IP header can be aligned by
902 * shifting the start of the packet by 2 bytes. Drivers should do this
905 * skb_reserve(NET_IP_ALIGN);
907 * The downside to this alignment of the IP header is that the DMA is now
908 * unaligned. On some architectures the cost of an unaligned DMA is high
909 * and this cost outweighs the gains made by aligning the IP header.
911 * Since this trade off varies between architectures, we allow NET_IP_ALIGN
915 #define NET_IP_ALIGN 2
918 extern int ___pskb_trim(struct sk_buff
*skb
, unsigned int len
, int realloc
);
920 static inline void __skb_trim(struct sk_buff
*skb
, unsigned int len
)
922 if (!skb
->data_len
) {
924 skb
->tail
= skb
->data
+ len
;
926 ___pskb_trim(skb
, len
, 0);
930 * skb_trim - remove end from a buffer
931 * @skb: buffer to alter
934 * Cut the length of a buffer down by removing data from the tail. If
935 * the buffer is already under the length specified it is not modified.
937 static inline void skb_trim(struct sk_buff
*skb
, unsigned int len
)
940 __skb_trim(skb
, len
);
944 static inline int __pskb_trim(struct sk_buff
*skb
, unsigned int len
)
946 if (!skb
->data_len
) {
948 skb
->tail
= skb
->data
+len
;
951 return ___pskb_trim(skb
, len
, 1);
954 static inline int pskb_trim(struct sk_buff
*skb
, unsigned int len
)
956 return (len
< skb
->len
) ? __pskb_trim(skb
, len
) : 0;
960 * skb_orphan - orphan a buffer
961 * @skb: buffer to orphan
963 * If a buffer currently has an owner then we call the owner's
964 * destructor function and make the @skb unowned. The buffer continues
965 * to exist but is no longer charged to its former owner.
967 static inline void skb_orphan(struct sk_buff
*skb
)
970 skb
->destructor(skb
);
971 skb
->destructor
= NULL
;
976 * __skb_queue_purge - empty a list
977 * @list: list to empty
979 * Delete all buffers on an &sk_buff list. Each buffer is removed from
980 * the list and one reference dropped. This function does not take the
981 * list lock and the caller must hold the relevant locks to use it.
983 extern void skb_queue_purge(struct sk_buff_head
*list
);
984 static inline void __skb_queue_purge(struct sk_buff_head
*list
)
987 while ((skb
= __skb_dequeue(list
)) != NULL
)
991 #ifndef CONFIG_HAVE_ARCH_DEV_ALLOC_SKB
993 * __dev_alloc_skb - allocate an skbuff for sending
994 * @length: length to allocate
995 * @gfp_mask: get_free_pages mask, passed to alloc_skb
997 * Allocate a new &sk_buff and assign it a usage count of one. The
998 * buffer has unspecified headroom built in. Users should allocate
999 * the headroom they think they need without accounting for the
1000 * built in space. The built in space is used for optimisations.
1002 * %NULL is returned in there is no free memory.
1004 static inline struct sk_buff
*__dev_alloc_skb(unsigned int length
,
1007 struct sk_buff
*skb
= alloc_skb(length
+ 16, gfp_mask
);
1009 skb_reserve(skb
, 16);
1013 extern struct sk_buff
*__dev_alloc_skb(unsigned int length
, int gfp_mask
);
1017 * dev_alloc_skb - allocate an skbuff for sending
1018 * @length: length to allocate
1020 * Allocate a new &sk_buff and assign it a usage count of one. The
1021 * buffer has unspecified headroom built in. Users should allocate
1022 * the headroom they think they need without accounting for the
1023 * built in space. The built in space is used for optimisations.
1025 * %NULL is returned in there is no free memory. Although this function
1026 * allocates memory it can be called from an interrupt.
1028 static inline struct sk_buff
*dev_alloc_skb(unsigned int length
)
1030 return __dev_alloc_skb(length
, GFP_ATOMIC
);
1034 * skb_cow - copy header of skb when it is required
1035 * @skb: buffer to cow
1036 * @headroom: needed headroom
1038 * If the skb passed lacks sufficient headroom or its data part
1039 * is shared, data is reallocated. If reallocation fails, an error
1040 * is returned and original skb is not changed.
1042 * The result is skb with writable area skb->head...skb->tail
1043 * and at least @headroom of space at head.
1045 static inline int skb_cow(struct sk_buff
*skb
, unsigned int headroom
)
1047 int delta
= (headroom
> 16 ? headroom
: 16) - skb_headroom(skb
);
1052 if (delta
|| skb_cloned(skb
))
1053 return pskb_expand_head(skb
, (delta
+ 15) & ~15, 0, GFP_ATOMIC
);
1058 * skb_padto - pad an skbuff up to a minimal size
1059 * @skb: buffer to pad
1060 * @len: minimal length
1062 * Pads up a buffer to ensure the trailing bytes exist and are
1063 * blanked. If the buffer already contains sufficient data it
1064 * is untouched. Returns the buffer, which may be a replacement
1065 * for the original, or NULL for out of memory - in which case
1066 * the original buffer is still freed.
1069 static inline struct sk_buff
*skb_padto(struct sk_buff
*skb
, unsigned int len
)
1071 unsigned int size
= skb
->len
;
1072 if (likely(size
>= len
))
1074 return skb_pad(skb
, len
-size
);
1077 static inline int skb_add_data(struct sk_buff
*skb
,
1078 char __user
*from
, int copy
)
1080 const int off
= skb
->len
;
1082 if (skb
->ip_summed
== CHECKSUM_NONE
) {
1084 unsigned int csum
= csum_and_copy_from_user(from
,
1088 skb
->csum
= csum_block_add(skb
->csum
, csum
, off
);
1091 } else if (!copy_from_user(skb_put(skb
, copy
), from
, copy
))
1094 __skb_trim(skb
, off
);
1098 static inline int skb_can_coalesce(struct sk_buff
*skb
, int i
,
1099 struct page
*page
, int off
)
1102 struct skb_frag_struct
*frag
= &skb_shinfo(skb
)->frags
[i
- 1];
1104 return page
== frag
->page
&&
1105 off
== frag
->page_offset
+ frag
->size
;
1111 * skb_linearize - convert paged skb to linear one
1112 * @skb: buffer to linarize
1113 * @gfp: allocation mode
1115 * If there is no free memory -ENOMEM is returned, otherwise zero
1116 * is returned and the old skb data released.
1118 extern int __skb_linearize(struct sk_buff
*skb
, int gfp
);
1119 static inline int skb_linearize(struct sk_buff
*skb
, int gfp
)
1121 return __skb_linearize(skb
, gfp
);
1125 * skb_postpull_rcsum - update checksum for received skb after pull
1126 * @skb: buffer to update
1127 * @start: start of data before pull
1128 * @len: length of data pulled
1130 * After doing a pull on a received packet, you need to call this to
1131 * update the CHECKSUM_HW checksum, or set ip_summed to CHECKSUM_NONE
1132 * so that it can be recomputed from scratch.
1135 static inline void skb_postpull_rcsum(struct sk_buff
*skb
,
1136 const void *start
, int len
)
1138 if (skb
->ip_summed
== CHECKSUM_HW
)
1139 skb
->csum
= csum_sub(skb
->csum
, csum_partial(start
, len
, 0));
1143 * pskb_trim_rcsum - trim received skb and update checksum
1144 * @skb: buffer to trim
1147 * This is exactly the same as pskb_trim except that it ensures the
1148 * checksum of received packets are still valid after the operation.
1151 static inline int pskb_trim_rcsum(struct sk_buff
*skb
, unsigned int len
)
1153 if (len
>= skb
->len
)
1155 if (skb
->ip_summed
== CHECKSUM_HW
)
1156 skb
->ip_summed
= CHECKSUM_NONE
;
1157 return __pskb_trim(skb
, len
);
1160 static inline void *kmap_skb_frag(const skb_frag_t
*frag
)
1162 #ifdef CONFIG_HIGHMEM
1167 return kmap_atomic(frag
->page
, KM_SKB_DATA_SOFTIRQ
);
1170 static inline void kunmap_skb_frag(void *vaddr
)
1172 kunmap_atomic(vaddr
, KM_SKB_DATA_SOFTIRQ
);
1173 #ifdef CONFIG_HIGHMEM
1178 #define skb_queue_walk(queue, skb) \
1179 for (skb = (queue)->next; \
1180 prefetch(skb->next), (skb != (struct sk_buff *)(queue)); \
1184 extern struct sk_buff
*skb_recv_datagram(struct sock
*sk
, unsigned flags
,
1185 int noblock
, int *err
);
1186 extern unsigned int datagram_poll(struct file
*file
, struct socket
*sock
,
1187 struct poll_table_struct
*wait
);
1188 extern int skb_copy_datagram_iovec(const struct sk_buff
*from
,
1189 int offset
, struct iovec
*to
,
1191 extern int skb_copy_and_csum_datagram_iovec(const
1192 struct sk_buff
*skb
,
1195 extern void skb_free_datagram(struct sock
*sk
, struct sk_buff
*skb
);
1196 extern unsigned int skb_checksum(const struct sk_buff
*skb
, int offset
,
1197 int len
, unsigned int csum
);
1198 extern int skb_copy_bits(const struct sk_buff
*skb
, int offset
,
1200 extern int skb_store_bits(const struct sk_buff
*skb
, int offset
,
1201 void *from
, int len
);
1202 extern unsigned int skb_copy_and_csum_bits(const struct sk_buff
*skb
,
1203 int offset
, u8
*to
, int len
,
1205 extern void skb_copy_and_csum_dev(const struct sk_buff
*skb
, u8
*to
);
1206 extern void skb_split(struct sk_buff
*skb
,
1207 struct sk_buff
*skb1
, const u32 len
);
1209 static inline void *skb_header_pointer(const struct sk_buff
*skb
, int offset
,
1210 int len
, void *buffer
)
1212 int hlen
= skb_headlen(skb
);
1214 if (offset
+ len
<= hlen
)
1215 return skb
->data
+ offset
;
1217 if (skb_copy_bits(skb
, offset
, buffer
, len
) < 0)
1223 extern void skb_init(void);
1224 extern void skb_add_mtu(int mtu
);
1226 #ifdef CONFIG_NETFILTER
1227 static inline void nf_conntrack_put(struct nf_conntrack
*nfct
)
1229 if (nfct
&& atomic_dec_and_test(&nfct
->use
))
1230 nfct
->destroy(nfct
);
1232 static inline void nf_conntrack_get(struct nf_conntrack
*nfct
)
1235 atomic_inc(&nfct
->use
);
1237 static inline void nf_reset(struct sk_buff
*skb
)
1239 nf_conntrack_put(skb
->nfct
);
1243 #ifdef CONFIG_BRIDGE_NETFILTER
1244 static inline void nf_bridge_put(struct nf_bridge_info
*nf_bridge
)
1246 if (nf_bridge
&& atomic_dec_and_test(&nf_bridge
->use
))
1249 static inline void nf_bridge_get(struct nf_bridge_info
*nf_bridge
)
1252 atomic_inc(&nf_bridge
->use
);
1254 #endif /* CONFIG_BRIDGE_NETFILTER */
1255 #else /* CONFIG_NETFILTER */
1256 static inline void nf_reset(struct sk_buff
*skb
) {}
1257 #endif /* CONFIG_NETFILTER */
1259 #endif /* __KERNEL__ */
1260 #endif /* _LINUX_SKBUFF_H */