C++ skb_realloc_headroom函数代码示例

/*
 * CFG802.11 network device handler for data transmission.
 */
static int
mwifiex_hard_start_xmit(struct sk_buff *skb, struct net_device *dev)
{
	struct mwifiex_private *priv = mwifiex_netdev_get_priv(dev);
	struct sk_buff *new_skb;
	struct mwifiex_txinfo *tx_info;
	struct timeval tv;

	dev_dbg(priv->adapter->dev, "data: %lu BSS(%d-%d): Data <= kernel\n",
		jiffies, priv->bss_type, priv->bss_num);

	if (priv->adapter->surprise_removed) {
		kfree_skb(skb);
		priv->stats.tx_dropped++;
		return 0;
	}
	if (!skb->len || (skb->len > ETH_FRAME_LEN)) {
		dev_err(priv->adapter->dev, "Tx: bad skb len %d\n", skb->len);
		kfree_skb(skb);
		priv->stats.tx_dropped++;
		return 0;
	}
	if (skb_headroom(skb) < MWIFIEX_MIN_DATA_HEADER_LEN) {
		dev_dbg(priv->adapter->dev,
			"data: Tx: insufficient skb headroom %d\n",
			skb_headroom(skb));
		/* Insufficient skb headroom - allocate a new skb */
		new_skb =
			skb_realloc_headroom(skb, MWIFIEX_MIN_DATA_HEADER_LEN);
		if (unlikely(!new_skb)) {
			dev_err(priv->adapter->dev, "Tx: cannot alloca new_skb\n");
			kfree_skb(skb);
			priv->stats.tx_dropped++;
			return 0;
		}
		kfree_skb(skb);
		skb = new_skb;
		dev_dbg(priv->adapter->dev, "info: new skb headroomd %d\n",
			skb_headroom(skb));
	}

	tx_info = MWIFIEX_SKB_TXCB(skb);
	memset(tx_info, 0, sizeof(*tx_info));
	tx_info->bss_num = priv->bss_num;
	tx_info->bss_type = priv->bss_type;

	/* Record the current time the packet was queued; used to
	 * determine the amount of time the packet was queued in
	 * the driver before it was sent to the firmware.
	 * The delay is then sent along with the packet to the
	 * firmware for aggregate delay calculation for stats and
	 * MSDU lifetime expiry.
	 */
	do_gettimeofday(&tv);
	skb->tstamp = timeval_to_ktime(tv);

	mwifiex_queue_tx_pkt(priv, skb);

	return 0;
}

void ax25_transmit_buffer(ax25_cb *ax25, struct sk_buff *skb, int type)
{
	struct sk_buff *skbn;
	unsigned char *ptr;
	int headroom;

	if (ax25->ax25_dev == NULL) {
		ax25_disconnect(ax25, ENETUNREACH);
		return;
	}

	headroom = ax25_addr_size(ax25->digipeat);

	if (skb_headroom(skb) < headroom) {
		if ((skbn = skb_realloc_headroom(skb, headroom)) == NULL) {
			printk(KERN_CRIT "AX.25: ax25_transmit_buffer - out of memory\n");
			kfree_skb(skb);
			return;
		}

		if (skb->sk != NULL)
			skb_set_owner_w(skbn, skb->sk);

		consume_skb(skb);
		skb = skbn;
	}

	ptr = skb_push(skb, headroom);

	ax25_addr_build(ptr, &ax25->source_addr, &ax25->dest_addr, ax25->digipeat, type, ax25->modulus);

	ax25_queue_xmit(skb, ax25->ax25_dev->dev);
}

struct sk_buff *ax25_rt_build_path(struct sk_buff *skb, ax25_address *src, ax25_address *dest, ax25_digi *digi)
{
	struct sk_buff *skbn;
	unsigned char *bp;
	int len;

	len = digi->ndigi * AX25_ADDR_LEN;

	if (skb_headroom(skb) < len) {
		if ((skbn = skb_realloc_headroom(skb, len)) == NULL) {
			printk(KERN_CRIT "AX.25: ax25_dg_build_path - out of memory\n");
			return NULL;
		}

		if (skb->sk != NULL)
			skb_set_owner_w(skbn, skb->sk);

		kfree_skb(skb);

		skb = skbn;
	}

	bp = skb_push(skb, len);

	ax25_addr_build(bp, src, dest, digi, AX25_COMMAND, AX25_MODULUS);

	return skb;
}

static struct sk_buff *rndis_add_header(struct gether *port,
					struct sk_buff *skb)
{
	struct sk_buff *skb2;
	struct rndis_packet_msg_type *header = NULL;
	struct f_rndis *rndis = func_to_rndis(&port->func);
	struct usb_composite_dev *cdev = port->func.config->cdev;

	if (rndis->port.multi_pkt_xfer || cdev->gadget->sg_supported) {
		if (port->header) {
			header = port->header;
			header->MessageType = cpu_to_le32(RNDIS_MSG_PACKET);
			header->MessageLength = cpu_to_le32(skb->len +
							sizeof(*header));
			header->DataOffset = cpu_to_le32(36);
			header->DataLength = cpu_to_le32(skb->len);
			pr_debug("MessageLength:%d DataLength:%d\n",
						header->MessageLength,
						header->DataLength);
			return skb;
		} else {
			dev_kfree_skb_any(skb);
			pr_err("RNDIS header is NULL.\n");
			return NULL;
		}
	} else {
		skb2 = skb_realloc_headroom(skb,
				sizeof(struct rndis_packet_msg_type));
		if (skb2)
			rndis_add_hdr(skb2);

		dev_kfree_skb_any(skb);
		return skb2;
	}
}

static int ipmr_cache_report(struct sk_buff *pkt, vifi_t vifi, int assert)
{
	struct sk_buff *skb;
	int ihl = pkt->nh.iph->ihl<<2;
	struct igmphdr *igmp;
	struct igmpmsg *msg;
	int ret;

#ifdef CONFIG_IP_PIMSM
	if (assert == IGMPMSG_WHOLEPKT)
		skb = skb_realloc_headroom(pkt, sizeof(struct iphdr));
	else
#endif
		skb = alloc_skb(128, GFP_ATOMIC);

	if(!skb)
		return -ENOBUFS;

#ifdef CONFIG_IP_PIMSM
	if (assert == IGMPMSG_WHOLEPKT) {
		/* Ugly, but we have no choice with this interface.
		   Duplicate old header, fix ihl, length etc.
		   And all this only to mangle msg->im_msgtype and
		   to set msg->im_mbz to "mbz" :-)
		 */
		msg = (struct igmpmsg*)skb_push(skb, sizeof(struct iphdr));
		skb->nh.raw = skb->h.raw = (u8*)msg;
		memcpy(msg, pkt->nh.raw, sizeof(struct iphdr));
		msg->im_msgtype = IGMPMSG_WHOLEPKT;
		msg->im_mbz = 0;
 		msg->im_vif = reg_vif_num;
		skb->nh.iph->ihl = sizeof(struct iphdr) >> 2;
		skb->nh.iph->tot_len = htons(ntohs(pkt->nh.iph->tot_len) + sizeof(struct iphdr));
	} else 

/* When forwarding a packet, we must ensure that we've got enough headroom
 * for the encapsulation packet in the skb.  This also gives us an
 * opportunity to figure out what the payload_len, dsfield, ttl, and df
 * values should be, so that we won't need to look at the old ip header
 * again
 */
static struct sk_buff *
ip_vs_prepare_tunneled_skb(struct sk_buff *skb, int skb_af,
			   unsigned int max_headroom, __u8 *next_protocol,
			   __u32 *payload_len, __u8 *dsfield, __u8 *ttl,
			   __be16 *df)
{
	struct sk_buff *new_skb = NULL;
	struct iphdr *old_iph = NULL;
#ifdef CONFIG_IP_VS_IPV6
	struct ipv6hdr *old_ipv6h = NULL;
#endif

	ip_vs_drop_early_demux_sk(skb);

	if (skb_headroom(skb) < max_headroom || skb_cloned(skb)) {
		new_skb = skb_realloc_headroom(skb, max_headroom);
		if (!new_skb)
			goto error;
		if (skb->sk)
			skb_set_owner_w(new_skb, skb->sk);
		consume_skb(skb);
		skb = new_skb;
	}

#ifdef CONFIG_IP_VS_IPV6
	if (skb_af == AF_INET6) {
		old_ipv6h = ipv6_hdr(skb);
		*next_protocol = IPPROTO_IPV6;
		if (payload_len)
			*payload_len =
				ntohs(old_ipv6h->payload_len) +
				sizeof(*old_ipv6h);
		*dsfield = ipv6_get_dsfield(old_ipv6h);
		*ttl = old_ipv6h->hop_limit;
		if (df)
			*df = 0;
	} else
#endif
	{
		old_iph = ip_hdr(skb);
		/* Copy DF, reset fragment offset and MF */
		if (df)
			*df = (old_iph->frag_off & htons(IP_DF));
		*next_protocol = IPPROTO_IPIP;

		/* fix old IP header checksum */
		ip_send_check(old_iph);
		*dsfield = ipv4_get_dsfield(old_iph);
		*ttl = old_iph->ttl;
		if (payload_len)
			*payload_len = ntohs(old_iph->tot_len);
	}

	return skb;
error:
	kfree_skb(skb);
	return ERR_PTR(-ENOMEM);
}

static int ethertap_start_xmit(struct sk_buff *skb, struct net_device *dev)
{
	struct net_local *lp = (struct net_local *)dev->priv;
#ifdef CONFIG_ETHERTAP_MC
	struct ethhdr *eth = (struct ethhdr*)skb->data;
#endif

	if (skb_headroom(skb) < 2) {
		static int once;
	  	struct sk_buff *skb2;

		if (!once) {
			once = 1;
			printk(KERN_DEBUG "%s: not aligned xmit by protocol %04x\n", dev->name, skb->protocol);
		}

		skb2 = skb_realloc_headroom(skb, 2);
		dev_kfree_skb(skb);
		if (skb2 == NULL)
			return 0;
		skb = skb2;
	}
	__skb_push(skb, 2);

	/* Make the same thing, which loopback does. */
	if (skb_shared(skb)) {
	  	struct sk_buff *skb2 = skb;
	  	skb = skb_clone(skb, GFP_ATOMIC);	/* Clone the buffer */
	  	if (skb==NULL) {
			dev_kfree_skb(skb2);
			return 0;
		}
	  	dev_kfree_skb(skb2);
	}
	/* ... but do not orphan it here, netlink does it in any case. */

	lp->stats.tx_bytes+=skb->len;
	lp->stats.tx_packets++;

#ifndef CONFIG_ETHERTAP_MC
	netlink_broadcast(lp->nl, skb, 0, ~0, GFP_ATOMIC);
#else
	if (dev->flags&IFF_NOARP) {
		netlink_broadcast(lp->nl, skb, 0, ~0, GFP_ATOMIC);
		return 0;
	}

	if (!(eth->h_dest[0]&1)) {
		/* Unicast packet */
		__u32 pid;
		memcpy(&pid, eth->h_dest+2, 4);
		netlink_unicast(lp->nl, skb, ntohl(pid), MSG_DONTWAIT);
	} else
		netlink_broadcast(lp->nl, skb, 0, ethertap_mc_hash(eth->h_dest), GFP_ATOMIC);
#endif
	return 0;
}

/*
 * Function irlan_eth_tx (skb)
 *
 *    Transmits ethernet frames over IrDA link.
 *
 */
static netdev_tx_t irlan_eth_xmit(struct sk_buff *skb,
					struct net_device *dev)
{
	struct irlan_cb *self = netdev_priv(dev);
	int ret;
	unsigned int len;

	/* skb headroom large enough to contain all IrDA-headers? */
	if ((skb_headroom(skb) < self->max_header_size) || (skb_shared(skb))) {
		struct sk_buff *new_skb =
			skb_realloc_headroom(skb, self->max_header_size);

		/*  We have to free the original skb anyway */
		dev_kfree_skb(skb);

		/* Did the realloc succeed? */
		if (new_skb == NULL)
			return NETDEV_TX_OK;

		/* Use the new skb instead */
		skb = new_skb;
	}

	dev->trans_start = jiffies;

	len = skb->len;
	/* Now queue the packet in the transport layer */
	if (self->use_udata)
		ret = irttp_udata_request(self->tsap_data, skb);
	else
		ret = irttp_data_request(self->tsap_data, skb);

	if (ret < 0) {
		/*
		 * IrTTPs tx queue is full, so we just have to
		 * drop the frame! You might think that we should
		 * just return -1 and don't deallocate the frame,
		 * but that is dangerous since it's possible that
		 * we have replaced the original skb with a new
		 * one with larger headroom, and that would really
		 * confuse do_dev_queue_xmit() in dev.c! I have
		 * tried :-) DB
		 */
		/* irttp_data_request already free the packet */
		dev->stats.tx_dropped++;
	} else {
		dev->stats.tx_packets++;
		dev->stats.tx_bytes += len;
	}

	return NETDEV_TX_OK;
}

static int pppoatm_send(struct ppp_channel *chan, struct sk_buff *skb)
{
	struct pppoatm_vcc *pvcc = chan_to_pvcc(chan);
	ATM_SKB(skb)->vcc = pvcc->atmvcc;
	pr_debug("(skb=0x%p, vcc=0x%p)\n", skb, pvcc->atmvcc);
	if (skb->data[0] == '\0' && (pvcc->flags & SC_COMP_PROT))
		(void) skb_pull(skb, 1);
	switch (pvcc->encaps) {		/* LLC encapsulation needed */
	case e_llc:
		if (skb_headroom(skb) < LLC_LEN) {
			struct sk_buff *n;
			n = skb_realloc_headroom(skb, LLC_LEN);
			if (n != NULL &&
			    !atm_may_send(pvcc->atmvcc, n->truesize)) {
				kfree_skb(n);
				goto nospace;
			}
			kfree_skb(skb);
			skb = n;
			if (skb == NULL)
				return DROP_PACKET;
		} else if (!atm_may_send(pvcc->atmvcc, skb->truesize))
			goto nospace;
		memcpy(skb_push(skb, LLC_LEN), pppllc, LLC_LEN);
		break;
	case e_vc:
		if (!atm_may_send(pvcc->atmvcc, skb->truesize))
			goto nospace;
		break;
	case e_autodetect:
		pr_debug("Trying to send without setting encaps!\n");
		kfree_skb(skb);
		return 1;
	}

	atomic_add(skb->truesize, &sk_atm(ATM_SKB(skb)->vcc)->sk_wmem_alloc);
	ATM_SKB(skb)->atm_options = ATM_SKB(skb)->vcc->atm_options;
	pr_debug("atm_skb(%p)->vcc(%p)->dev(%p)\n",
		 skb, ATM_SKB(skb)->vcc, ATM_SKB(skb)->vcc->dev);
	return ATM_SKB(skb)->vcc->send(ATM_SKB(skb)->vcc, skb)
	    ? DROP_PACKET : 1;
nospace:
	/*
	 * We don't have space to send this SKB now, but we might have
	 * already applied SC_COMP_PROT compression, so may need to undo
	 */
	if ((pvcc->flags & SC_COMP_PROT) && skb_headroom(skb) > 0 &&
	    skb->data[-1] == '\0')
		(void) skb_push(skb, 1);
	return 0;
}

static struct sk_buff *_rmnet_add_headroom(struct sk_buff **skb,
					   struct net_device *dev)
{
	struct sk_buff *skbn;

	if (skb_headroom(*skb) < dev->needed_headroom) {
		msm_rmnet_bam_headroom_check_failure++;
		skbn = skb_realloc_headroom(*skb, dev->needed_headroom);
		kfree_skb(*skb);
		*skb = skbn;
	} else {
		skbn = *skb;
	}

	return skbn;
}

/* modelled after ip_finish_output2 */
static int vrf_finish_output(struct net *net, struct sock *sk, struct sk_buff *skb)
{
	struct dst_entry *dst = skb_dst(skb);
	struct rtable *rt = (struct rtable *)dst;
	struct net_device *dev = dst->dev;
	unsigned int hh_len = LL_RESERVED_SPACE(dev);
	struct neighbour *neigh;
	u32 nexthop;
	int ret = -EINVAL;

	nf_reset(skb);

	/* Be paranoid, rather than too clever. */
	if (unlikely(skb_headroom(skb) < hh_len && dev->header_ops)) {
		struct sk_buff *skb2;

		skb2 = skb_realloc_headroom(skb, LL_RESERVED_SPACE(dev));
		if (!skb2) {
			ret = -ENOMEM;
			goto err;
		}
		if (skb->sk)
			skb_set_owner_w(skb2, skb->sk);

		consume_skb(skb);
		skb = skb2;
	}

	rcu_read_lock_bh();

	nexthop = (__force u32)rt_nexthop(rt, ip_hdr(skb)->daddr);
	neigh = __ipv4_neigh_lookup_noref(dev, nexthop);
	if (unlikely(!neigh))
		neigh = __neigh_create(&arp_tbl, &nexthop, dev, false);
	if (!IS_ERR(neigh)) {
		sock_confirm_neigh(skb, neigh);
		ret = neigh_output(neigh, skb);
		rcu_read_unlock_bh();
		return ret;
	}

	rcu_read_unlock_bh();
err:
	vrf_tx_error(skb->dev, skb);
	return ret;
}

static int dn_long_output(struct sk_buff *skb)
{
    struct dst_entry *dst = skb->dst;
    struct neighbour *neigh = dst->neighbour;
    struct net_device *dev = neigh->dev;
    int headroom = dev->hard_header_len + sizeof(struct dn_long_packet) + 3;
    unsigned char *data;
    struct dn_long_packet *lp;
    struct dn_skb_cb *cb = DN_SKB_CB(skb);


    if (skb_headroom(skb) < headroom) {
        struct sk_buff *skb2 = skb_realloc_headroom(skb, headroom);
        if (skb2 == NULL) {
            if (net_ratelimit())
                printk(KERN_CRIT "dn_long_output: no memory\n");
            kfree_skb(skb);
            return -ENOBUFS;
        }
        kfree_skb(skb);
        skb = skb2;
        if (net_ratelimit())
            printk(KERN_INFO "dn_long_output: Increasing headroom\n");
    }

    data = skb_push(skb, sizeof(struct dn_long_packet) + 3);
    lp = (struct dn_long_packet *)(data+3);

    *((unsigned short *)data) = dn_htons(skb->len - 2);
    *(data + 2) = 1 | DN_RT_F_PF; /* Padding */

    lp->msgflg   = DN_RT_PKT_LONG|(cb->rt_flags&(DN_RT_F_IE|DN_RT_F_RQR|DN_RT_F_RTS));
    lp->d_area   = lp->d_subarea = 0;
    dn_dn2eth(lp->d_id, dn_ntohs(cb->dst));
    lp->s_area   = lp->s_subarea = 0;
    dn_dn2eth(lp->s_id, dn_ntohs(cb->src));
    lp->nl2      = 0;
    lp->visit_ct = cb->hops & 0x3f;
    lp->s_class  = 0;
    lp->pt       = 0;

    skb->nh.raw = skb->data;

    return NF_HOOK(PF_DECnet, NF_DN_POST_ROUTING, skb, NULL, neigh->dev, dn_neigh_output_packet);
}

static int btmrvl_tx_pkt(struct btmrvl_private *priv, struct sk_buff *skb)
{
	int ret = 0;

	if (!skb || !skb->data)
		return -EINVAL;

	if (!skb->len || ((skb->len + BTM_HEADER_LEN) > BTM_UPLD_SIZE)) {
		BT_ERR("Tx Error: Bad skb length %d : %d",
						skb->len, BTM_UPLD_SIZE);
		return -EINVAL;
	}

	if (skb_headroom(skb) < BTM_HEADER_LEN) {
		struct sk_buff *tmp = skb;

		skb = skb_realloc_headroom(skb, BTM_HEADER_LEN);
		if (!skb) {
			BT_ERR("Tx Error: realloc_headroom failed %d",
				BTM_HEADER_LEN);
			skb = tmp;
			return -EINVAL;
		}

		kfree_skb(tmp);
	}

	skb_push(skb, BTM_HEADER_LEN);

	/* header type: byte[3]
	 * HCI_COMMAND = 1, ACL_DATA = 2, SCO_DATA = 3, 0xFE = Vendor
	 * header length: byte[2][1][0]
	 */

	skb->data[0] = (skb->len & 0x0000ff);
	skb->data[1] = (skb->len & 0x00ff00) >> 8;
	skb->data[2] = (skb->len & 0xff0000) >> 16;
	skb->data[3] = bt_cb(skb)->pkt_type;

	if (priv->hw_host_to_card)
		ret = priv->hw_host_to_card(priv, skb->data, skb->len);

	return ret;
}

/* Stolen from ip_finish_output2
 * PRE : skb->dev is set to the device we are leaving by
 *       skb->dst is not NULL
 * POST: the packet is sent with the link layer header pushed
 *       the packet is destroyed
 */
static void ip_direct_send(struct sk_buff *skb)
{
	struct dst_entry *dst = skb->dst;
	struct hh_cache *hh = dst->hh;
	struct net_device *dev = dst->dev;
	int hh_len = LL_RESERVED_SPACE(dev);
	unsigned seq;

	/* Be paranoid, rather than too clever. */
//	if (unlikely(skb_headroom(skb) < hh_len && dev->hard_header)) {
	if (unlikely(skb_headroom(skb) < hh_len &&   (dev->header_ops && dev->header_ops->create) )) {

		struct sk_buff *skb2;

		skb2 = skb_realloc_headroom(skb, LL_RESERVED_SPACE(dev));
		if (skb2 == NULL) {
			kfree_skb(skb);
			return;
		}
		if (skb->sk)
			skb_set_owner_w(skb2, skb->sk);
		kfree_skb(skb);
		skb = skb2;
	}

	if (hh) {
		do {
			int hh_alen;

			seq = read_seqbegin(&hh->hh_lock);
			hh_alen = HH_DATA_ALIGN(hh->hh_len);
			memcpy(skb->data - hh_alen, hh->hh_data, hh_alen);
		} while (read_seqretry(&hh->hh_lock, seq));
		skb_push(skb, hh->hh_len);
		hh->hh_output(skb);
	} else if (dst->neighbour)
		dst->neighbour->output(skb);
	else {
		if (net_ratelimit())
			DEBUGP(KERN_DEBUG "ipt_ROUTE: no hdr & no neighbour cache!\n");
		kfree_skb(skb);
	}
}

/** Make enough room in an skb for extra header and trailer.
 *
 * @param pskb return parameter for expanded skb
 * @param skb skb
 * @param head_n required headroom
 * @param tail_n required tailroom
 * @return 0 on success, error code otherwise
 */
int skb_make_room(struct sk_buff **pskb, struct sk_buff *skb, int head_n, int tail_n){
    int err = 0;
    int has_headroom = (head_n <= skb_headroom(skb));
    int has_tailroom = (tail_n <= skb_tailroom(skb));
    int writeable = !skb_cloned(skb) && !skb_shared(skb);

    dprintf("> skb=%p headroom=%d head_n=%d tailroom=%d tail_n=%d\n",
            skb,
            skb_headroom(skb), head_n,
            skb_tailroom(skb), tail_n);
    if(writeable && has_headroom && has_tailroom){
        // There's room! Reuse it.
        *pskb = skb;
    } else if(writeable && has_tailroom){
        // Tailroom, no headroom. Expand header the way GRE does.
        struct sk_buff *new_skb = skb_realloc_headroom(skb, head_n + 16);
        if(!new_skb){
            err = -ENOMEM;
            goto exit;
        }
        kfree_skb(skb);
        *pskb = new_skb;
    } else {
        // No room. Expand. There may be more efficient ways to do
        // this, but this is simple and correct.
        struct sk_buff *new_skb = skb_copy_expand(skb, head_n + 16, tail_n, GFP_ATOMIC);
        if(!new_skb){
            err = -ENOMEM;
            goto exit;
        }
        kfree_skb(skb);
        *pskb = new_skb;
    }
    dprintf("> skb=%p headroom=%d head_n=%d tailroom=%d tail_n=%d\n",
            *pskb,
            skb_headroom(*pskb), head_n,
            skb_tailroom(*pskb), tail_n);
  exit:
    dprintf("< err=%d\n", err);
    return err;
}