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 * @truesize: Buffer size
187 * @head: Head of buffer
188 * @data: Data head pointer
189 * @tail: Tail pointer
191 * @destructor: Destruct function
192 * @nfmark: Can be used for communication between hooks
193 * @nfcache: Cache info
194 * @nfct: Associated connection, if any
195 * @nfctinfo: Relationship of this skb to the connection
196 * @nf_bridge: Saved data about a bridged frame - see br_netfilter.c
197 * @private: Data which is private to the HIPPI implementation
198 * @tc_index: Traffic control index
199 * @tc_verd: traffic control verdict
200 * @tc_classid: traffic control classid
204 /* These two members must be first. */
205 struct sk_buff *next;
206 struct sk_buff *prev;
208 struct sk_buff_head *list;
210 struct timeval stamp;
211 struct net_device *dev;
212 struct net_device *input_dev;
213 struct net_device *real_dev;
218 struct icmphdr *icmph;
219 struct igmphdr *igmph;
221 struct ipv6hdr *ipv6h;
227 struct ipv6hdr *ipv6h;
236 struct dst_entry *dst;
240 * This is the control buffer. It is free to use for every
241 * layer. Please put your private variables there. If you
242 * want to keep them across layers you have to do a skb_clone()
243 * first. This is owned by whoever has the skb queued ATM.
251 unsigned char local_df,
257 unsigned short protocol;
259 void (*destructor)(struct sk_buff *skb);
260 #ifdef CONFIG_NETFILTER
261 unsigned long nfmark;
264 struct nf_conntrack *nfct;
265 #ifdef CONFIG_BRIDGE_NETFILTER
266 struct nf_bridge_info *nf_bridge;
268 #endif /* CONFIG_NETFILTER */
269 #if defined(CONFIG_HIPPI)
274 #ifdef CONFIG_NET_SCHED
275 __u32 tc_index; /* traffic control index */
276 #ifdef CONFIG_NET_CLS_ACT
277 __u32 tc_verd; /* traffic control verdict */
278 __u32 tc_classid; /* traffic control classid */
284 /* These elements must be at the end, see alloc_skb() for details. */
285 unsigned int truesize;
295 * Handling routines are only of interest to the kernel
297 #include <linux/slab.h>
299 #include <asm/system.h>
301 extern void __kfree_skb(struct sk_buff *skb);
302 extern struct sk_buff *alloc_skb(unsigned int size, int priority);
303 extern struct sk_buff *alloc_skb_from_cache(kmem_cache_t *cp,
304 unsigned int size, int priority);
305 extern void kfree_skbmem(struct sk_buff *skb);
306 extern struct sk_buff *skb_clone(struct sk_buff *skb, int priority);
307 extern struct sk_buff *skb_copy(const struct sk_buff *skb, int priority);
308 extern struct sk_buff *pskb_copy(struct sk_buff *skb, int gfp_mask);
309 extern int pskb_expand_head(struct sk_buff *skb,
310 int nhead, int ntail, int gfp_mask);
311 extern struct sk_buff *skb_realloc_headroom(struct sk_buff *skb,
312 unsigned int headroom);
313 extern struct sk_buff *skb_copy_expand(const struct sk_buff *skb,
314 int newheadroom, int newtailroom,
316 extern struct sk_buff * skb_pad(struct sk_buff *skb, int pad);
317 #define dev_kfree_skb(a) kfree_skb(a)
318 extern void skb_over_panic(struct sk_buff *skb, int len,
320 extern void skb_under_panic(struct sk_buff *skb, int len,
328 __u32 stepped_offset;
329 struct sk_buff *root_skb;
330 struct sk_buff *cur_skb;
334 extern void skb_prepare_seq_read(struct sk_buff *skb,
335 unsigned int from, unsigned int to,
336 struct skb_seq_state *st);
337 extern unsigned int skb_seq_read(unsigned int consumed, const u8 **data,
338 struct skb_seq_state *st);
339 extern void skb_abort_seq_read(struct skb_seq_state *st);
341 extern unsigned int skb_find_text(struct sk_buff *skb, unsigned int from,
342 unsigned int to, struct ts_config *config,
343 struct ts_state *state);
346 #define skb_shinfo(SKB) ((struct skb_shared_info *)((SKB)->end))
349 * skb_queue_empty - check if a queue is empty
352 * Returns true if the queue is empty, false otherwise.
354 static inline int skb_queue_empty(const struct sk_buff_head *list)
356 return list->next == (struct sk_buff *)list;
360 * skb_get - reference buffer
361 * @skb: buffer to reference
363 * Makes another reference to a socket buffer and returns a pointer
366 static inline struct sk_buff *skb_get(struct sk_buff *skb)
368 atomic_inc(&skb->users);
373 * If users == 1, we are the only owner and are can avoid redundant
378 * kfree_skb - free an sk_buff
379 * @skb: buffer to free
381 * Drop a reference to the buffer and free it if the usage count has
384 static inline void kfree_skb(struct sk_buff *skb)
386 if (likely(atomic_read(&skb->users) == 1))
388 else if (likely(!atomic_dec_and_test(&skb->users)))
394 * skb_cloned - is the buffer a clone
395 * @skb: buffer to check
397 * Returns true if the buffer was generated with skb_clone() and is
398 * one of multiple shared copies of the buffer. Cloned buffers are
399 * shared data so must not be written to under normal circumstances.
401 static inline int skb_cloned(const struct sk_buff *skb)
403 return skb->cloned &&
404 (atomic_read(&skb_shinfo(skb)->dataref) & SKB_DATAREF_MASK) != 1;
408 * skb_header_cloned - is the header a clone
409 * @skb: buffer to check
411 * Returns true if modifying the header part of the buffer requires
412 * the data to be copied.
414 static inline int skb_header_cloned(const struct sk_buff *skb)
421 dataref = atomic_read(&skb_shinfo(skb)->dataref);
422 dataref = (dataref & SKB_DATAREF_MASK) - (dataref >> SKB_DATAREF_SHIFT);
427 * skb_header_release - release reference to header
428 * @skb: buffer to operate on
430 * Drop a reference to the header part of the buffer. This is done
431 * by acquiring a payload reference. You must not read from the header
432 * part of skb->data after this.
434 static inline void skb_header_release(struct sk_buff *skb)
438 atomic_add(1 << SKB_DATAREF_SHIFT, &skb_shinfo(skb)->dataref);
442 * skb_shared - is the buffer shared
443 * @skb: buffer to check
445 * Returns true if more than one person has a reference to this
448 static inline int skb_shared(const struct sk_buff *skb)
450 return atomic_read(&skb->users) != 1;
454 * skb_share_check - check if buffer is shared and if so clone it
455 * @skb: buffer to check
456 * @pri: priority for memory allocation
458 * If the buffer is shared the buffer is cloned and the old copy
459 * drops a reference. A new clone with a single reference is returned.
460 * If the buffer is not shared the original buffer is returned. When
461 * being called from interrupt status or with spinlocks held pri must
464 * NULL is returned on a memory allocation failure.
466 static inline struct sk_buff *skb_share_check(struct sk_buff *skb, int pri)
468 might_sleep_if(pri & __GFP_WAIT);
469 if (skb_shared(skb)) {
470 struct sk_buff *nskb = skb_clone(skb, pri);
478 * Copy shared buffers into a new sk_buff. We effectively do COW on
479 * packets to handle cases where we have a local reader and forward
480 * and a couple of other messy ones. The normal one is tcpdumping
481 * a packet thats being forwarded.
485 * skb_unshare - make a copy of a shared buffer
486 * @skb: buffer to check
487 * @pri: priority for memory allocation
489 * If the socket buffer is a clone then this function creates a new
490 * copy of the data, drops a reference count on the old copy and returns
491 * the new copy with the reference count at 1. If the buffer is not a clone
492 * the original buffer is returned. When called with a spinlock held or
493 * from interrupt state @pri must be %GFP_ATOMIC
495 * %NULL is returned on a memory allocation failure.
497 static inline struct sk_buff *skb_unshare(struct sk_buff *skb, int pri)
499 might_sleep_if(pri & __GFP_WAIT);
500 if (skb_cloned(skb)) {
501 struct sk_buff *nskb = skb_copy(skb, pri);
502 kfree_skb(skb); /* Free our shared copy */
510 * @list_: list to peek at
512 * Peek an &sk_buff. Unlike most other operations you _MUST_
513 * be careful with this one. A peek leaves the buffer on the
514 * list and someone else may run off with it. You must hold
515 * the appropriate locks or have a private queue to do this.
517 * Returns %NULL for an empty list or a pointer to the head element.
518 * The reference count is not incremented and the reference is therefore
519 * volatile. Use with caution.
521 static inline struct sk_buff *skb_peek(struct sk_buff_head *list_)
523 struct sk_buff *list = ((struct sk_buff *)list_)->next;
524 if (list == (struct sk_buff *)list_)
531 * @list_: list to peek at
533 * Peek an &sk_buff. Unlike most other operations you _MUST_
534 * be careful with this one. A peek leaves the buffer on the
535 * list and someone else may run off with it. You must hold
536 * the appropriate locks or have a private queue to do this.
538 * Returns %NULL for an empty list or a pointer to the tail element.
539 * The reference count is not incremented and the reference is therefore
540 * volatile. Use with caution.
542 static inline struct sk_buff *skb_peek_tail(struct sk_buff_head *list_)
544 struct sk_buff *list = ((struct sk_buff *)list_)->prev;
545 if (list == (struct sk_buff *)list_)
551 * skb_queue_len - get queue length
552 * @list_: list to measure
554 * Return the length of an &sk_buff queue.
556 static inline __u32 skb_queue_len(const struct sk_buff_head *list_)
561 static inline void skb_queue_head_init(struct sk_buff_head *list)
563 spin_lock_init(&list->lock);
564 list->prev = list->next = (struct sk_buff *)list;
569 * Insert an sk_buff at the start of a list.
571 * The "__skb_xxxx()" functions are the non-atomic ones that
572 * can only be called with interrupts disabled.
576 * __skb_queue_head - queue a buffer at the list head
578 * @newsk: buffer to queue
580 * Queue a buffer at the start of a list. This function takes no locks
581 * and you must therefore hold required locks before calling it.
583 * A buffer cannot be placed on two lists at the same time.
585 extern void skb_queue_head(struct sk_buff_head *list, struct sk_buff *newsk);
586 static inline void __skb_queue_head(struct sk_buff_head *list,
587 struct sk_buff *newsk)
589 struct sk_buff *prev, *next;
593 prev = (struct sk_buff *)list;
597 next->prev = prev->next = newsk;
601 * __skb_queue_tail - queue a buffer at the list tail
603 * @newsk: buffer to queue
605 * Queue a buffer at the end of a list. This function takes no locks
606 * and you must therefore hold required locks before calling it.
608 * A buffer cannot be placed on two lists at the same time.
610 extern void skb_queue_tail(struct sk_buff_head *list, struct sk_buff *newsk);
611 static inline void __skb_queue_tail(struct sk_buff_head *list,
612 struct sk_buff *newsk)
614 struct sk_buff *prev, *next;
618 next = (struct sk_buff *)list;
622 next->prev = prev->next = newsk;
627 * __skb_dequeue - remove from the head of the queue
628 * @list: list to dequeue from
630 * Remove the head of the list. This function does not take any locks
631 * so must be used with appropriate locks held only. The head item is
632 * returned or %NULL if the list is empty.
634 extern struct sk_buff *skb_dequeue(struct sk_buff_head *list);
635 static inline struct sk_buff *__skb_dequeue(struct sk_buff_head *list)
637 struct sk_buff *next, *prev, *result;
639 prev = (struct sk_buff *) list;
648 result->next = result->prev = NULL;
656 * Insert a packet on a list.
658 extern void skb_insert(struct sk_buff *old, struct sk_buff *newsk);
659 static inline void __skb_insert(struct sk_buff *newsk,
660 struct sk_buff *prev, struct sk_buff *next,
661 struct sk_buff_head *list)
665 next->prev = prev->next = newsk;
671 * Place a packet after a given packet in a list.
673 extern void skb_append(struct sk_buff *old, struct sk_buff *newsk);
674 static inline void __skb_append(struct sk_buff *old, struct sk_buff *newsk)
676 __skb_insert(newsk, old, old->next, old->list);
680 * remove sk_buff from list. _Must_ be called atomically, and with
683 extern void skb_unlink(struct sk_buff *skb);
684 static inline void __skb_unlink(struct sk_buff *skb, struct sk_buff_head *list)
686 struct sk_buff *next, *prev;
691 skb->next = skb->prev = NULL;
698 /* XXX: more streamlined implementation */
701 * __skb_dequeue_tail - remove from the tail of the queue
702 * @list: list to dequeue from
704 * Remove the tail of the list. This function does not take any locks
705 * so must be used with appropriate locks held only. The tail item is
706 * returned or %NULL if the list is empty.
708 extern struct sk_buff *skb_dequeue_tail(struct sk_buff_head *list);
709 static inline struct sk_buff *__skb_dequeue_tail(struct sk_buff_head *list)
711 struct sk_buff *skb = skb_peek_tail(list);
713 __skb_unlink(skb, list);
718 static inline int skb_is_nonlinear(const struct sk_buff *skb)
720 return skb->data_len;
723 static inline unsigned int skb_headlen(const struct sk_buff *skb)
725 return skb->len - skb->data_len;
728 static inline int skb_pagelen(const struct sk_buff *skb)
732 for (i = (int)skb_shinfo(skb)->nr_frags - 1; i >= 0; i--)
733 len += skb_shinfo(skb)->frags[i].size;
734 return len + skb_headlen(skb);
737 static inline void skb_fill_page_desc(struct sk_buff *skb, int i,
738 struct page *page, int off, int size)
740 skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
743 frag->page_offset = off;
745 skb_shinfo(skb)->nr_frags = i + 1;
748 #define SKB_PAGE_ASSERT(skb) BUG_ON(skb_shinfo(skb)->nr_frags)
749 #define SKB_FRAG_ASSERT(skb) BUG_ON(skb_shinfo(skb)->frag_list)
750 #define SKB_LINEAR_ASSERT(skb) BUG_ON(skb_is_nonlinear(skb))
753 * Add data to an sk_buff
755 static inline unsigned char *__skb_put(struct sk_buff *skb, unsigned int len)
757 unsigned char *tmp = skb->tail;
758 SKB_LINEAR_ASSERT(skb);
765 * skb_put - add data to a buffer
766 * @skb: buffer to use
767 * @len: amount of data to add
769 * This function extends the used data area of the buffer. If this would
770 * exceed the total buffer size the kernel will panic. A pointer to the
771 * first byte of the extra data is returned.
773 static inline unsigned char *skb_put(struct sk_buff *skb, unsigned int len)
775 unsigned char *tmp = skb->tail;
776 SKB_LINEAR_ASSERT(skb);
779 if (unlikely(skb->tail>skb->end))
780 skb_over_panic(skb, len, current_text_addr());
784 static inline unsigned char *__skb_push(struct sk_buff *skb, unsigned int len)
792 * skb_push - add data to the start of a buffer
793 * @skb: buffer to use
794 * @len: amount of data to add
796 * This function extends the used data area of the buffer at the buffer
797 * start. If this would exceed the total buffer headroom the kernel will
798 * panic. A pointer to the first byte of the extra data is returned.
800 static inline unsigned char *skb_push(struct sk_buff *skb, unsigned int len)
804 if (unlikely(skb->data<skb->head))
805 skb_under_panic(skb, len, current_text_addr());
809 static inline unsigned char *__skb_pull(struct sk_buff *skb, unsigned int len)
812 BUG_ON(skb->len < skb->data_len);
813 return skb->data += len;
817 * skb_pull - remove data from the start of a buffer
818 * @skb: buffer to use
819 * @len: amount of data to remove
821 * This function removes data from the start of a buffer, returning
822 * the memory to the headroom. A pointer to the next data in the buffer
823 * is returned. Once the data has been pulled future pushes will overwrite
826 static inline unsigned char *skb_pull(struct sk_buff *skb, unsigned int len)
828 return unlikely(len > skb->len) ? NULL : __skb_pull(skb, len);
831 extern unsigned char *__pskb_pull_tail(struct sk_buff *skb, int delta);
833 static inline unsigned char *__pskb_pull(struct sk_buff *skb, unsigned int len)
835 if (len > skb_headlen(skb) &&
836 !__pskb_pull_tail(skb, len-skb_headlen(skb)))
839 return skb->data += len;
842 static inline unsigned char *pskb_pull(struct sk_buff *skb, unsigned int len)
844 return unlikely(len > skb->len) ? NULL : __pskb_pull(skb, len);
847 static inline int pskb_may_pull(struct sk_buff *skb, unsigned int len)
849 if (likely(len <= skb_headlen(skb)))
851 if (unlikely(len > skb->len))
853 return __pskb_pull_tail(skb, len-skb_headlen(skb)) != NULL;
857 * skb_headroom - bytes at buffer head
858 * @skb: buffer to check
860 * Return the number of bytes of free space at the head of an &sk_buff.
862 static inline int skb_headroom(const struct sk_buff *skb)
864 return skb->data - skb->head;
868 * skb_tailroom - bytes at buffer end
869 * @skb: buffer to check
871 * Return the number of bytes of free space at the tail of an sk_buff
873 static inline int skb_tailroom(const struct sk_buff *skb)
875 return skb_is_nonlinear(skb) ? 0 : skb->end - skb->tail;
879 * skb_reserve - adjust headroom
880 * @skb: buffer to alter
881 * @len: bytes to move
883 * Increase the headroom of an empty &sk_buff by reducing the tail
884 * room. This is only allowed for an empty buffer.
886 static inline void skb_reserve(struct sk_buff *skb, unsigned int len)
893 * CPUs often take a performance hit when accessing unaligned memory
894 * locations. The actual performance hit varies, it can be small if the
895 * hardware handles it or large if we have to take an exception and fix it
898 * Since an ethernet header is 14 bytes network drivers often end up with
899 * the IP header at an unaligned offset. The IP header can be aligned by
900 * shifting the start of the packet by 2 bytes. Drivers should do this
903 * skb_reserve(NET_IP_ALIGN);
905 * The downside to this alignment of the IP header is that the DMA is now
906 * unaligned. On some architectures the cost of an unaligned DMA is high
907 * and this cost outweighs the gains made by aligning the IP header.
909 * Since this trade off varies between architectures, we allow NET_IP_ALIGN
913 #define NET_IP_ALIGN 2
916 extern int ___pskb_trim(struct sk_buff *skb, unsigned int len, int realloc);
918 static inline void __skb_trim(struct sk_buff *skb, unsigned int len)
920 if (!skb->data_len) {
922 skb->tail = skb->data + len;
924 ___pskb_trim(skb, len, 0);
928 * skb_trim - remove end from a buffer
929 * @skb: buffer to alter
932 * Cut the length of a buffer down by removing data from the tail. If
933 * the buffer is already under the length specified it is not modified.
935 static inline void skb_trim(struct sk_buff *skb, unsigned int len)
938 __skb_trim(skb, len);
942 static inline int __pskb_trim(struct sk_buff *skb, unsigned int len)
944 if (!skb->data_len) {
946 skb->tail = skb->data+len;
949 return ___pskb_trim(skb, len, 1);
952 static inline int pskb_trim(struct sk_buff *skb, unsigned int len)
954 return (len < skb->len) ? __pskb_trim(skb, len) : 0;
958 * skb_orphan - orphan a buffer
959 * @skb: buffer to orphan
961 * If a buffer currently has an owner then we call the owner's
962 * destructor function and make the @skb unowned. The buffer continues
963 * to exist but is no longer charged to its former owner.
965 static inline void skb_orphan(struct sk_buff *skb)
968 skb->destructor(skb);
969 skb->destructor = NULL;
974 * __skb_queue_purge - empty a list
975 * @list: list to empty
977 * Delete all buffers on an &sk_buff list. Each buffer is removed from
978 * the list and one reference dropped. This function does not take the
979 * list lock and the caller must hold the relevant locks to use it.
981 extern void skb_queue_purge(struct sk_buff_head *list);
982 static inline void __skb_queue_purge(struct sk_buff_head *list)
985 while ((skb = __skb_dequeue(list)) != NULL)
989 #ifndef CONFIG_HAVE_ARCH_DEV_ALLOC_SKB
991 * __dev_alloc_skb - allocate an skbuff for sending
992 * @length: length to allocate
993 * @gfp_mask: get_free_pages mask, passed to alloc_skb
995 * Allocate a new &sk_buff and assign it a usage count of one. The
996 * buffer has unspecified headroom built in. Users should allocate
997 * the headroom they think they need without accounting for the
998 * built in space. The built in space is used for optimisations.
1000 * %NULL is returned in there is no free memory.
1002 static inline struct sk_buff *__dev_alloc_skb(unsigned int length,
1005 struct sk_buff *skb = alloc_skb(length + 16, gfp_mask);
1007 skb_reserve(skb, 16);
1011 extern struct sk_buff *__dev_alloc_skb(unsigned int length, int gfp_mask);
1015 * dev_alloc_skb - allocate an skbuff for sending
1016 * @length: length to allocate
1018 * Allocate a new &sk_buff and assign it a usage count of one. The
1019 * buffer has unspecified headroom built in. Users should allocate
1020 * the headroom they think they need without accounting for the
1021 * built in space. The built in space is used for optimisations.
1023 * %NULL is returned in there is no free memory. Although this function
1024 * allocates memory it can be called from an interrupt.
1026 static inline struct sk_buff *dev_alloc_skb(unsigned int length)
1028 return __dev_alloc_skb(length, GFP_ATOMIC);
1032 * skb_cow - copy header of skb when it is required
1033 * @skb: buffer to cow
1034 * @headroom: needed headroom
1036 * If the skb passed lacks sufficient headroom or its data part
1037 * is shared, data is reallocated. If reallocation fails, an error
1038 * is returned and original skb is not changed.
1040 * The result is skb with writable area skb->head...skb->tail
1041 * and at least @headroom of space at head.
1043 static inline int skb_cow(struct sk_buff *skb, unsigned int headroom)
1045 int delta = (headroom > 16 ? headroom : 16) - skb_headroom(skb);
1050 if (delta || skb_cloned(skb))
1051 return pskb_expand_head(skb, (delta + 15) & ~15, 0, GFP_ATOMIC);
1056 * skb_padto - pad an skbuff up to a minimal size
1057 * @skb: buffer to pad
1058 * @len: minimal length
1060 * Pads up a buffer to ensure the trailing bytes exist and are
1061 * blanked. If the buffer already contains sufficient data it
1062 * is untouched. Returns the buffer, which may be a replacement
1063 * for the original, or NULL for out of memory - in which case
1064 * the original buffer is still freed.
1067 static inline struct sk_buff *skb_padto(struct sk_buff *skb, unsigned int len)
1069 unsigned int size = skb->len;
1070 if (likely(size >= len))
1072 return skb_pad(skb, len-size);
1075 static inline int skb_add_data(struct sk_buff *skb,
1076 char __user *from, int copy)
1078 const int off = skb->len;
1080 if (skb->ip_summed == CHECKSUM_NONE) {
1082 unsigned int csum = csum_and_copy_from_user(from,
1086 skb->csum = csum_block_add(skb->csum, csum, off);
1089 } else if (!copy_from_user(skb_put(skb, copy), from, copy))
1092 __skb_trim(skb, off);
1096 static inline int skb_can_coalesce(struct sk_buff *skb, int i,
1097 struct page *page, int off)
1100 struct skb_frag_struct *frag = &skb_shinfo(skb)->frags[i - 1];
1102 return page == frag->page &&
1103 off == frag->page_offset + frag->size;
1109 * skb_linearize - convert paged skb to linear one
1110 * @skb: buffer to linarize
1111 * @gfp: allocation mode
1113 * If there is no free memory -ENOMEM is returned, otherwise zero
1114 * is returned and the old skb data released.
1116 extern int __skb_linearize(struct sk_buff *skb, int gfp);
1117 static inline int skb_linearize(struct sk_buff *skb, int gfp)
1119 return __skb_linearize(skb, gfp);
1123 * skb_postpull_rcsum - update checksum for received skb after pull
1124 * @skb: buffer to update
1125 * @start: start of data before pull
1126 * @len: length of data pulled
1128 * After doing a pull on a received packet, you need to call this to
1129 * update the CHECKSUM_HW checksum, or set ip_summed to CHECKSUM_NONE
1130 * so that it can be recomputed from scratch.
1133 static inline void skb_postpull_rcsum(struct sk_buff *skb,
1134 const void *start, int len)
1136 if (skb->ip_summed == CHECKSUM_HW)
1137 skb->csum = csum_sub(skb->csum, csum_partial(start, len, 0));
1141 * pskb_trim_rcsum - trim received skb and update checksum
1142 * @skb: buffer to trim
1145 * This is exactly the same as pskb_trim except that it ensures the
1146 * checksum of received packets are still valid after the operation.
1149 static inline int pskb_trim_rcsum(struct sk_buff *skb, unsigned int len)
1151 if (len >= skb->len)
1153 if (skb->ip_summed == CHECKSUM_HW)
1154 skb->ip_summed = CHECKSUM_NONE;
1155 return __pskb_trim(skb, len);
1158 static inline void *kmap_skb_frag(const skb_frag_t *frag)
1160 #ifdef CONFIG_HIGHMEM
1165 return kmap_atomic(frag->page, KM_SKB_DATA_SOFTIRQ);
1168 static inline void kunmap_skb_frag(void *vaddr)
1170 kunmap_atomic(vaddr, KM_SKB_DATA_SOFTIRQ);
1171 #ifdef CONFIG_HIGHMEM
1176 #define skb_queue_walk(queue, skb) \
1177 for (skb = (queue)->next; \
1178 prefetch(skb->next), (skb != (struct sk_buff *)(queue)); \
1182 extern struct sk_buff *skb_recv_datagram(struct sock *sk, unsigned flags,
1183 int noblock, int *err);
1184 extern unsigned int datagram_poll(struct file *file, struct socket *sock,
1185 struct poll_table_struct *wait);
1186 extern int skb_copy_datagram_iovec(const struct sk_buff *from,
1187 int offset, struct iovec *to,
1189 extern int skb_copy_and_csum_datagram_iovec(const
1190 struct sk_buff *skb,
1193 extern void skb_free_datagram(struct sock *sk, struct sk_buff *skb);
1194 extern unsigned int skb_checksum(const struct sk_buff *skb, int offset,
1195 int len, unsigned int csum);
1196 extern int skb_copy_bits(const struct sk_buff *skb, int offset,
1198 extern int skb_store_bits(const struct sk_buff *skb, int offset,
1199 void *from, int len);
1200 extern unsigned int skb_copy_and_csum_bits(const struct sk_buff *skb,
1201 int offset, u8 *to, int len,
1203 extern void skb_copy_and_csum_dev(const struct sk_buff *skb, u8 *to);
1204 extern void skb_split(struct sk_buff *skb,
1205 struct sk_buff *skb1, const u32 len);
1207 static inline void *skb_header_pointer(const struct sk_buff *skb, int offset,
1208 int len, void *buffer)
1210 int hlen = skb_headlen(skb);
1212 if (hlen - offset >= len)
1213 return skb->data + offset;
1215 if (skb_copy_bits(skb, offset, buffer, len) < 0)
1221 extern void skb_init(void);
1222 extern void skb_add_mtu(int mtu);
1224 #ifdef CONFIG_NETFILTER
1225 static inline void nf_conntrack_put(struct nf_conntrack *nfct)
1227 if (nfct && atomic_dec_and_test(&nfct->use))
1228 nfct->destroy(nfct);
1230 static inline void nf_conntrack_get(struct nf_conntrack *nfct)
1233 atomic_inc(&nfct->use);
1235 static inline void nf_reset(struct sk_buff *skb)
1237 nf_conntrack_put(skb->nfct);
1241 #ifdef CONFIG_BRIDGE_NETFILTER
1242 static inline void nf_bridge_put(struct nf_bridge_info *nf_bridge)
1244 if (nf_bridge && atomic_dec_and_test(&nf_bridge->use))
1247 static inline void nf_bridge_get(struct nf_bridge_info *nf_bridge)
1250 atomic_inc(&nf_bridge->use);
1252 #endif /* CONFIG_BRIDGE_NETFILTER */
1253 #else /* CONFIG_NETFILTER */
1254 static inline void nf_reset(struct sk_buff *skb) {}
1255 #endif /* CONFIG_NETFILTER */
1257 #endif /* __KERNEL__ */
1258 #endif /* _LINUX_SKBUFF_H */