cfpkt_skbuff.c

  1// SPDX-License-Identifier: GPL-2.0-only
  2/*
  3 * Copyright (C) ST-Ericsson AB 2010
  4 * Author:	Sjur Brendeland
  5 */
  6
  7#define pr_fmt(fmt) KBUILD_MODNAME ":%s(): " fmt, __func__
  8
  9#include <linux/string.h>
 10#include <linux/skbuff.h>
 11#include <linux/export.h>
 12#include <net/caif/cfpkt.h>
 13
 14#define PKT_PREFIX  48
 15#define PKT_POSTFIX 2
 16#define PKT_LEN_WHEN_EXTENDING 128
 17#define PKT_ERROR(pkt, errmsg)		   \
 18do {					   \
 19	cfpkt_priv(pkt)->erronous = true;  \
 20	skb_reset_tail_pointer(&pkt->skb); \
 21	pr_warn(errmsg);		   \
 22} while (0)
 23
 24/*
 25 * net/caif/ is generic and does not
 26 * understand SKB, so we do this typecast
 27 */
 28struct cfpkt {
 29	struct sk_buff skb;
 30};
 31
 32/* Private data inside SKB */
 33struct cfpkt_priv_data {
 34	struct dev_info dev_info;
 35	bool erronous;
 36};
 37
 38static inline struct cfpkt_priv_data *cfpkt_priv(struct cfpkt *pkt)
 39{
 40	return (struct cfpkt_priv_data *) pkt->skb.cb;
 41}
 42
 43static inline bool is_erronous(struct cfpkt *pkt)
 44{
 45	return cfpkt_priv(pkt)->erronous;
 46}
 47
 48static inline struct sk_buff *pkt_to_skb(struct cfpkt *pkt)
 49{
 50	return &pkt->skb;
 51}
 52
 53static inline struct cfpkt *skb_to_pkt(struct sk_buff *skb)
 54{
 55	return (struct cfpkt *) skb;
 56}
 57
 58struct cfpkt *cfpkt_fromnative(enum caif_direction dir, void *nativepkt)
 59{
 60	struct cfpkt *pkt = skb_to_pkt(nativepkt);
 61	cfpkt_priv(pkt)->erronous = false;
 62	return pkt;
 63}
 64EXPORT_SYMBOL(cfpkt_fromnative);
 65
 66void *cfpkt_tonative(struct cfpkt *pkt)
 67{
 68	return (void *) pkt;
 69}
 70EXPORT_SYMBOL(cfpkt_tonative);
 71
 72static struct cfpkt *cfpkt_create_pfx(u16 len, u16 pfx)
 73{
 74	struct sk_buff *skb;
 75
 76	skb = alloc_skb(len + pfx, GFP_ATOMIC);
 77	if (unlikely(skb == NULL))
 78		return NULL;
 79
 80	skb_reserve(skb, pfx);
 81	return skb_to_pkt(skb);
 82}
 83
 84inline struct cfpkt *cfpkt_create(u16 len)
 85{
 86	return cfpkt_create_pfx(len + PKT_POSTFIX, PKT_PREFIX);
 87}
 88
 89void cfpkt_destroy(struct cfpkt *pkt)
 90{
 91	struct sk_buff *skb = pkt_to_skb(pkt);
 92	kfree_skb(skb);
 93}
 94
 95inline bool cfpkt_more(struct cfpkt *pkt)
 96{
 97	struct sk_buff *skb = pkt_to_skb(pkt);
 98	return skb->len > 0;
 99}
100
101int cfpkt_peek_head(struct cfpkt *pkt, void *data, u16 len)
102{
103	struct sk_buff *skb = pkt_to_skb(pkt);
104	if (skb_headlen(skb) >= len) {
105		memcpy(data, skb->data, len);
106		return 0;
107	}
108	return !cfpkt_extr_head(pkt, data, len) &&
109	    !cfpkt_add_head(pkt, data, len);
110}
111
112int cfpkt_extr_head(struct cfpkt *pkt, void *data, u16 len)
113{
114	struct sk_buff *skb = pkt_to_skb(pkt);
115	u8 *from;
116	if (unlikely(is_erronous(pkt)))
117		return -EPROTO;
118
119	if (unlikely(len > skb->len)) {
120		PKT_ERROR(pkt, "read beyond end of packet\n");
121		return -EPROTO;
122	}
123
124	if (unlikely(len > skb_headlen(skb))) {
125		if (unlikely(skb_linearize(skb) != 0)) {
126			PKT_ERROR(pkt, "linearize failed\n");
127			return -EPROTO;
128		}
129	}
130	from = skb_pull(skb, len);
131	from -= len;
132	if (data)
133		memcpy(data, from, len);
134	return 0;
135}
136EXPORT_SYMBOL(cfpkt_extr_head);
137
138int cfpkt_extr_trail(struct cfpkt *pkt, void *dta, u16 len)
139{
140	struct sk_buff *skb = pkt_to_skb(pkt);
141	u8 *data = dta;
142	u8 *from;
143	if (unlikely(is_erronous(pkt)))
144		return -EPROTO;
145
146	if (unlikely(skb_linearize(skb) != 0)) {
147		PKT_ERROR(pkt, "linearize failed\n");
148		return -EPROTO;
149	}
150	if (unlikely(skb->data + len > skb_tail_pointer(skb))) {
151		PKT_ERROR(pkt, "read beyond end of packet\n");
152		return -EPROTO;
153	}
154	from = skb_tail_pointer(skb) - len;
155	skb_trim(skb, skb->len - len);
156	memcpy(data, from, len);
157	return 0;
158}
159
160int cfpkt_pad_trail(struct cfpkt *pkt, u16 len)
161{
162	return cfpkt_add_body(pkt, NULL, len);
163}
164
165int cfpkt_add_body(struct cfpkt *pkt, const void *data, u16 len)
166{
167	struct sk_buff *skb = pkt_to_skb(pkt);
168	struct sk_buff *lastskb;
169	u8 *to;
170	u16 addlen = 0;
171
172
173	if (unlikely(is_erronous(pkt)))
174		return -EPROTO;
175
176	lastskb = skb;
177
178	/* Check whether we need to add space at the tail */
179	if (unlikely(skb_tailroom(skb) < len)) {
180		if (likely(len < PKT_LEN_WHEN_EXTENDING))
181			addlen = PKT_LEN_WHEN_EXTENDING;
182		else
183			addlen = len;
184	}
185
186	/* Check whether we need to change the SKB before writing to the tail */
187	if (unlikely((addlen > 0) || skb_cloned(skb) || skb_shared(skb))) {
188
189		/* Make sure data is writable */
190		if (unlikely(skb_cow_data(skb, addlen, &lastskb) < 0)) {
191			PKT_ERROR(pkt, "cow failed\n");
192			return -EPROTO;
193		}
194	}
195
196	/* All set to put the last SKB and optionally write data there. */
197	to = pskb_put(skb, lastskb, len);
198	if (likely(data))
199		memcpy(to, data, len);
200	return 0;
201}
202
203inline int cfpkt_addbdy(struct cfpkt *pkt, u8 data)
204{
205	return cfpkt_add_body(pkt, &data, 1);
206}
207
208int cfpkt_add_head(struct cfpkt *pkt, const void *data2, u16 len)
209{
210	struct sk_buff *skb = pkt_to_skb(pkt);
211	struct sk_buff *lastskb;
212	u8 *to;
213	const u8 *data = data2;
214	int ret;
215	if (unlikely(is_erronous(pkt)))
216		return -EPROTO;
217	if (unlikely(skb_headroom(skb) < len)) {
218		PKT_ERROR(pkt, "no headroom\n");
219		return -EPROTO;
220	}
221
222	/* Make sure data is writable */
223	ret = skb_cow_data(skb, 0, &lastskb);
224	if (unlikely(ret < 0)) {
225		PKT_ERROR(pkt, "cow failed\n");
226		return ret;
227	}
228
229	to = skb_push(skb, len);
230	memcpy(to, data, len);
231	return 0;
232}
233EXPORT_SYMBOL(cfpkt_add_head);
234
235inline int cfpkt_add_trail(struct cfpkt *pkt, const void *data, u16 len)
236{
237	return cfpkt_add_body(pkt, data, len);
238}
239
240inline u16 cfpkt_getlen(struct cfpkt *pkt)
241{
242	struct sk_buff *skb = pkt_to_skb(pkt);
243	return skb->len;
244}
245
246int cfpkt_iterate(struct cfpkt *pkt,
247		  u16 (*iter_func)(u16, void *, u16),
248		  u16 data)
249{
250	/*
251	 * Don't care about the performance hit of linearizing,
252	 * Checksum should not be used on high-speed interfaces anyway.
253	 */
254	if (unlikely(is_erronous(pkt)))
255		return -EPROTO;
256	if (unlikely(skb_linearize(&pkt->skb) != 0)) {
257		PKT_ERROR(pkt, "linearize failed\n");
258		return -EPROTO;
259	}
260	return iter_func(data, pkt->skb.data, cfpkt_getlen(pkt));
261}
262
263int cfpkt_setlen(struct cfpkt *pkt, u16 len)
264{
265	struct sk_buff *skb = pkt_to_skb(pkt);
266
267
268	if (unlikely(is_erronous(pkt)))
269		return -EPROTO;
270
271	if (likely(len <= skb->len)) {
272		if (unlikely(skb->data_len))
273			___pskb_trim(skb, len);
274		else
275			skb_trim(skb, len);
276
277		return cfpkt_getlen(pkt);
278	}
279
280	/* Need to expand SKB */
281	if (unlikely(!cfpkt_pad_trail(pkt, len - skb->len)))
282		PKT_ERROR(pkt, "skb_pad_trail failed\n");
283
284	return cfpkt_getlen(pkt);
285}
286
287struct cfpkt *cfpkt_append(struct cfpkt *dstpkt,
288			   struct cfpkt *addpkt,
289			   u16 expectlen)
290{
291	struct sk_buff *dst = pkt_to_skb(dstpkt);
292	struct sk_buff *add = pkt_to_skb(addpkt);
293	u16 addlen = skb_headlen(add);
294	u16 neededtailspace;
295	struct sk_buff *tmp;
296	u16 dstlen;
297	u16 createlen;
298	if (unlikely(is_erronous(dstpkt) || is_erronous(addpkt))) {
299		return dstpkt;
300	}
301
302	neededtailspace = max(expectlen, addlen);
303
304	if (dst->tail + neededtailspace > dst->end) {
305		/* Create a dumplicate of 'dst' with more tail space */
306		struct cfpkt *tmppkt;
307		dstlen = skb_headlen(dst);
308		createlen = dstlen + neededtailspace;
309		tmppkt = cfpkt_create(createlen + PKT_PREFIX + PKT_POSTFIX);
310		if (tmppkt == NULL)
311			return NULL;
312		tmp = pkt_to_skb(tmppkt);
313		skb_put_data(tmp, dst->data, dstlen);
314		cfpkt_destroy(dstpkt);
315		dst = tmp;
316	}
317	skb_put_data(dst, add->data, skb_headlen(add));
318	cfpkt_destroy(addpkt);
319	return skb_to_pkt(dst);
320}
321
322struct cfpkt *cfpkt_split(struct cfpkt *pkt, u16 pos)
323{
324	struct sk_buff *skb2;
325	struct sk_buff *skb = pkt_to_skb(pkt);
326	struct cfpkt *tmppkt;
327	u8 *split = skb->data + pos;
328	u16 len2nd = skb_tail_pointer(skb) - split;
329
330	if (unlikely(is_erronous(pkt)))
331		return NULL;
332
333	if (skb->data + pos > skb_tail_pointer(skb)) {
334		PKT_ERROR(pkt, "trying to split beyond end of packet\n");
335		return NULL;
336	}
337
338	/* Create a new packet for the second part of the data */
339	tmppkt = cfpkt_create_pfx(len2nd + PKT_PREFIX + PKT_POSTFIX,
340				  PKT_PREFIX);
341	if (tmppkt == NULL)
342		return NULL;
343	skb2 = pkt_to_skb(tmppkt);
344
345
346	if (skb2 == NULL)
347		return NULL;
348
349	skb_put_data(skb2, split, len2nd);
350
351	/* Reduce the length of the original packet */
352	skb_trim(skb, pos);
353
354	skb2->priority = skb->priority;
355	return skb_to_pkt(skb2);
356}
357
358bool cfpkt_erroneous(struct cfpkt *pkt)
359{
360	return cfpkt_priv(pkt)->erronous;
361}
362
363struct caif_payload_info *cfpkt_info(struct cfpkt *pkt)
364{
365	return (struct caif_payload_info *)&pkt_to_skb(pkt)->cb;
366}
367EXPORT_SYMBOL(cfpkt_info);
368
369void cfpkt_set_prio(struct cfpkt *pkt, int prio)
370{
371	pkt_to_skb(pkt)->priority = prio;
372}
373EXPORT_SYMBOL(cfpkt_set_prio);