cfpkt_skbuff.c

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/*
 * Copyright (C) ST-Ericsson AB 2010
 * Author:  Sjur Brendeland/[email protected]
 * License terms: GNU General Public License (GPL) version 2
 */

#define pr_fmt(fmt) KBUILD_MODNAME ":%s(): " fmt, __func__

#include <linux/string.h>
#include <linux/skbuff.h>
#include <linux/hardirq.h>
#include <linux/export.h>
#include <net/caif/cfpkt.h>

#define PKT_PREFIX  48
#define PKT_POSTFIX 2
#define PKT_LEN_WHEN_EXTENDING 128
#define PKT_ERROR(pkt, errmsg)         \
do {                       \
    cfpkt_priv(pkt)->erronous = true;  \
    skb_reset_tail_pointer(&pkt->skb); \
    pr_warn(errmsg);           \
} while (0)

struct cfpktq {
    struct sk_buff_head head;
    atomic_t count;
    /* Lock protects count updates */
    spinlock_t lock;
};

/*
 * net/caif/ is generic and does not
 * understand SKB, so we do this typecast
 */
struct cfpkt {
    struct sk_buff skb;
};

/* Private data inside SKB */
struct cfpkt_priv_data {
    struct dev_info dev_info;
    bool erronous;
};

static inline struct cfpkt_priv_data *cfpkt_priv(struct cfpkt *pkt)
{
    return (struct cfpkt_priv_data *) pkt->skb.cb;
}

static inline bool is_erronous(struct cfpkt *pkt)
{
    return cfpkt_priv(pkt)->erronous;
}

static inline struct sk_buff *pkt_to_skb(struct cfpkt *pkt)
{
    return &pkt->skb;
}

static inline struct cfpkt *skb_to_pkt(struct sk_buff *skb)
{
    return (struct cfpkt *) skb;
}

struct cfpkt *cfpkt_fromnative(enum caif_direction dir, void *nativepkt)
{
    struct cfpkt *pkt = skb_to_pkt(nativepkt);
    cfpkt_priv(pkt)->erronous = false;
    return pkt;
}
EXPORT_SYMBOL(cfpkt_fromnative);

void *cfpkt_tonative(struct cfpkt *pkt)
{
    return (void *) pkt;
}
EXPORT_SYMBOL(cfpkt_tonative);

static struct cfpkt *cfpkt_create_pfx(u16 len, u16 pfx)
{
    struct sk_buff *skb;

    if (likely(in_interrupt()))
        skb = alloc_skb(len + pfx, GFP_ATOMIC);
    else
        skb = alloc_skb(len + pfx, GFP_KERNEL);

    if (unlikely(skb == NULL))
        return NULL;

    skb_reserve(skb, pfx);
    return skb_to_pkt(skb);
}

inline struct cfpkt *cfpkt_create(u16 len)
{
    return cfpkt_create_pfx(len + PKT_POSTFIX, PKT_PREFIX);
}

void cfpkt_destroy(struct cfpkt *pkt)
{
    struct sk_buff *skb = pkt_to_skb(pkt);
    kfree_skb(skb);
}

inline bool cfpkt_more(struct cfpkt *pkt)
{
    struct sk_buff *skb = pkt_to_skb(pkt);
    return skb->len > 0;
}

int cfpkt_peek_head(struct cfpkt *pkt, void *data, u16 len)
{
    struct sk_buff *skb = pkt_to_skb(pkt);
    if (skb_headlen(skb) >= len) {
        memcpy(data, skb->data, len);
        return 0;
    }
    return !cfpkt_extr_head(pkt, data, len) &&
        !cfpkt_add_head(pkt, data, len);
}

int cfpkt_extr_head(struct cfpkt *pkt, void *data, u16 len)
{
    struct sk_buff *skb = pkt_to_skb(pkt);
    u8 *from;
    if (unlikely(is_erronous(pkt)))
        return -EPROTO;

    if (unlikely(len > skb->len)) {
        PKT_ERROR(pkt, "read beyond end of packet\n");
        return -EPROTO;
    }

    if (unlikely(len > skb_headlen(skb))) {
        if (unlikely(skb_linearize(skb) != 0)) {
            PKT_ERROR(pkt, "linearize failed\n");
            return -EPROTO;
        }
    }
    from = skb_pull(skb, len);
    from -= len;
    if (data)
        memcpy(data, from, len);
    return 0;
}
EXPORT_SYMBOL(cfpkt_extr_head);

int cfpkt_extr_trail(struct cfpkt *pkt, void *dta, u16 len)
{
    struct sk_buff *skb = pkt_to_skb(pkt);
    u8 *data = dta;
    u8 *from;
    if (unlikely(is_erronous(pkt)))
        return -EPROTO;

    if (unlikely(skb_linearize(skb) != 0)) {
        PKT_ERROR(pkt, "linearize failed\n");
        return -EPROTO;
    }
    if (unlikely(skb->data + len > skb_tail_pointer(skb))) {
        PKT_ERROR(pkt, "read beyond end of packet\n");
        return -EPROTO;
    }
    from = skb_tail_pointer(skb) - len;
    skb_trim(skb, skb->len - len);
    memcpy(data, from, len);
    return 0;
}

int cfpkt_pad_trail(struct cfpkt *pkt, u16 len)
{
    return cfpkt_add_body(pkt, NULL, len);
}

int cfpkt_add_body(struct cfpkt *pkt, const void *data, u16 len)
{
    struct sk_buff *skb = pkt_to_skb(pkt);
    struct sk_buff *lastskb;
    u8 *to;
    u16 addlen = 0;


    if (unlikely(is_erronous(pkt)))
        return -EPROTO;

    lastskb = skb;

    /* Check whether we need to add space at the tail */
    if (unlikely(skb_tailroom(skb) < len)) {
        if (likely(len < PKT_LEN_WHEN_EXTENDING))
            addlen = PKT_LEN_WHEN_EXTENDING;
        else
            addlen = len;
    }

    /* Check whether we need to change the SKB before writing to the tail */
    if (unlikely((addlen > 0) || skb_cloned(skb) || skb_shared(skb))) {

        /* Make sure data is writable */
        if (unlikely(skb_cow_data(skb, addlen, &lastskb) < 0)) {
            PKT_ERROR(pkt, "cow failed\n");
            return -EPROTO;
        }
        /*
         * Is the SKB non-linear after skb_cow_data()? If so, we are
         * going to add data to the last SKB, so we need to adjust
         * lengths of the top SKB.
         */
        if (lastskb != skb) {
            pr_warn("Packet is non-linear\n");
            skb->len += len;
            skb->data_len += len;
        }
    }

    /* All set to put the last SKB and optionally write data there. */
    to = skb_put(lastskb, len);
    if (likely(data))
        memcpy(to, data, len);
    return 0;
}

inline int cfpkt_addbdy(struct cfpkt *pkt, u8 data)
{
    return cfpkt_add_body(pkt, &data, 1);
}

int cfpkt_add_head(struct cfpkt *pkt, const void *data2, u16 len)
{
    struct sk_buff *skb = pkt_to_skb(pkt);
    struct sk_buff *lastskb;
    u8 *to;
    const u8 *data = data2;
    int ret;
    if (unlikely(is_erronous(pkt)))
        return -EPROTO;
    if (unlikely(skb_headroom(skb) < len)) {
        PKT_ERROR(pkt, "no headroom\n");
        return -EPROTO;
    }

    /* Make sure data is writable */
    ret = skb_cow_data(skb, 0, &lastskb);
    if (unlikely(ret < 0)) {
        PKT_ERROR(pkt, "cow failed\n");
        return ret;
    }

    to = skb_push(skb, len);
    memcpy(to, data, len);
    return 0;
}
EXPORT_SYMBOL(cfpkt_add_head);

inline int cfpkt_add_trail(struct cfpkt *pkt, const void *data, u16 len)
{
    return cfpkt_add_body(pkt, data, len);
}

inline u16 cfpkt_getlen(struct cfpkt *pkt)
{
    struct sk_buff *skb = pkt_to_skb(pkt);
    return skb->len;
}

inline u16 cfpkt_iterate(struct cfpkt *pkt,
                u16 (*iter_func)(u16, void *, u16),
                u16 data)
{
    /*
     * Don't care about the performance hit of linearizing,
     * Checksum should not be used on high-speed interfaces anyway.
     */
    if (unlikely(is_erronous(pkt)))
        return -EPROTO;
    if (unlikely(skb_linearize(&pkt->skb) != 0)) {
        PKT_ERROR(pkt, "linearize failed\n");
        return -EPROTO;
    }
    return iter_func(data, pkt->skb.data, cfpkt_getlen(pkt));
}

int cfpkt_setlen(struct cfpkt *pkt, u16 len)
{
    struct sk_buff *skb = pkt_to_skb(pkt);


    if (unlikely(is_erronous(pkt)))
        return -EPROTO;

    if (likely(len <= skb->len)) {
        if (unlikely(skb->data_len))
            ___pskb_trim(skb, len);
        else
            skb_trim(skb, len);

            return cfpkt_getlen(pkt);
    }

    /* Need to expand SKB */
    if (unlikely(!cfpkt_pad_trail(pkt, len - skb->len)))
        PKT_ERROR(pkt, "skb_pad_trail failed\n");

    return cfpkt_getlen(pkt);
}

struct cfpkt *cfpkt_append(struct cfpkt *dstpkt,
                 struct cfpkt *addpkt,
                 u16 expectlen)
{
    struct sk_buff *dst = pkt_to_skb(dstpkt);
    struct sk_buff *add = pkt_to_skb(addpkt);
    u16 addlen = skb_headlen(add);
    u16 neededtailspace;
    struct sk_buff *tmp;
    u16 dstlen;
    u16 createlen;
    if (unlikely(is_erronous(dstpkt) || is_erronous(addpkt))) {
        return dstpkt;
    }
    if (expectlen > addlen)
        neededtailspace = expectlen;
    else
        neededtailspace = addlen;

    if (dst->tail + neededtailspace > dst->end) {
        /* Create a dumplicate of 'dst' with more tail space */
        struct cfpkt *tmppkt;
        dstlen = skb_headlen(dst);
        createlen = dstlen + neededtailspace;
        tmppkt = cfpkt_create(createlen + PKT_PREFIX + PKT_POSTFIX);
        if (tmppkt == NULL)
            return NULL;
        tmp = pkt_to_skb(tmppkt);
        skb_set_tail_pointer(tmp, dstlen);
        tmp->len = dstlen;
        memcpy(tmp->data, dst->data, dstlen);
        cfpkt_destroy(dstpkt);
        dst = tmp;
    }
    memcpy(skb_tail_pointer(dst), add->data, skb_headlen(add));
    cfpkt_destroy(addpkt);
    dst->tail += addlen;
    dst->len += addlen;
    return skb_to_pkt(dst);
}

struct cfpkt *cfpkt_split(struct cfpkt *pkt, u16 pos)
{
    struct sk_buff *skb2;
    struct sk_buff *skb = pkt_to_skb(pkt);
    struct cfpkt *tmppkt;
    u8 *split = skb->data + pos;
    u16 len2nd = skb_tail_pointer(skb) - split;

    if (unlikely(is_erronous(pkt)))
        return NULL;

    if (skb->data + pos > skb_tail_pointer(skb)) {
        PKT_ERROR(pkt, "trying to split beyond end of packet\n");
        return NULL;
    }

    /* Create a new packet for the second part of the data */
    tmppkt = cfpkt_create_pfx(len2nd + PKT_PREFIX + PKT_POSTFIX,
                  PKT_PREFIX);
    if (tmppkt == NULL)
        return NULL;
    skb2 = pkt_to_skb(tmppkt);


    if (skb2 == NULL)
        return NULL;

    /* Reduce the length of the original packet */
    skb_set_tail_pointer(skb, pos);
    skb->len = pos;

    memcpy(skb2->data, split, len2nd);
    skb2->tail += len2nd;
    skb2->len += len2nd;
    skb2->priority = skb->priority;
    return skb_to_pkt(skb2);
}

bool cfpkt_erroneous(struct cfpkt *pkt)
{
    return cfpkt_priv(pkt)->erronous;
}

struct caif_payload_info *cfpkt_info(struct cfpkt *pkt)
{
    return (struct caif_payload_info *)&pkt_to_skb(pkt)->cb;
}
EXPORT_SYMBOL(cfpkt_info);

void cfpkt_set_prio(struct cfpkt *pkt, int prio)
{
    pkt_to_skb(pkt)->priority = prio;
}
EXPORT_SYMBOL(cfpkt_set_prio);