C++ skb_shinfo函数代码示例

//.........这里部分代码省略.........
		vlan->vlanid = skb->vlan_tci & VLAN_VID_MASK;
		vlan->pri = (skb->vlan_tci & VLAN_PRIO_MASK) >>
				VLAN_PRIO_SHIFT;
	}

	if (skb_is_gso(skb)) {
		struct ndis_tcp_lso_info *lso_info;

		rndis_msg_size += NDIS_LSO_PPI_SIZE;
		ppi = init_ppi_data(rndis_msg, NDIS_LSO_PPI_SIZE,
				    TCP_LARGESEND_PKTINFO);

		lso_info = (struct ndis_tcp_lso_info *)((void *)ppi +
							ppi->ppi_offset);

		lso_info->lso_v2_transmit.type = NDIS_TCP_LARGE_SEND_OFFLOAD_V2_TYPE;
		if (skb->protocol == htons(ETH_P_IP)) {
			lso_info->lso_v2_transmit.ip_version =
				NDIS_TCP_LARGE_SEND_OFFLOAD_IPV4;
			ip_hdr(skb)->tot_len = 0;
			ip_hdr(skb)->check = 0;
			tcp_hdr(skb)->check =
				~csum_tcpudp_magic(ip_hdr(skb)->saddr,
						   ip_hdr(skb)->daddr, 0, IPPROTO_TCP, 0);
		} else {
			lso_info->lso_v2_transmit.ip_version =
				NDIS_TCP_LARGE_SEND_OFFLOAD_IPV6;
			ipv6_hdr(skb)->payload_len = 0;
			tcp_hdr(skb)->check =
				~csum_ipv6_magic(&ipv6_hdr(skb)->saddr,
						 &ipv6_hdr(skb)->daddr, 0, IPPROTO_TCP, 0);
		}
		lso_info->lso_v2_transmit.tcp_header_offset = skb_transport_offset(skb);
		lso_info->lso_v2_transmit.mss = skb_shinfo(skb)->gso_size;
	} else if (skb->ip_summed == CHECKSUM_PARTIAL) {
		if (net_checksum_info(skb) & net_device_ctx->tx_checksum_mask) {
			struct ndis_tcp_ip_checksum_info *csum_info;

			rndis_msg_size += NDIS_CSUM_PPI_SIZE;
			ppi = init_ppi_data(rndis_msg, NDIS_CSUM_PPI_SIZE,
					    TCPIP_CHKSUM_PKTINFO);

			csum_info = (struct ndis_tcp_ip_checksum_info *)((void *)ppi +
									 ppi->ppi_offset);

			csum_info->transmit.tcp_header_offset = skb_transport_offset(skb);

			if (skb->protocol == htons(ETH_P_IP)) {
				csum_info->transmit.is_ipv4 = 1;

				if (ip_hdr(skb)->protocol == IPPROTO_TCP)
					csum_info->transmit.tcp_checksum = 1;
				else
					csum_info->transmit.udp_checksum = 1;
			} else {
				csum_info->transmit.is_ipv6 = 1;

				if (ipv6_hdr(skb)->nexthdr == IPPROTO_TCP)
					csum_info->transmit.tcp_checksum = 1;
				else
					csum_info->transmit.udp_checksum = 1;
			}
		} else {
			/* Can't do offload of this type of checksum */
			if (skb_checksum_help(skb))
				goto drop;

static int start_xmit(struct sk_buff *skb, struct net_device *dev)
{
	struct virtnet_info *vi = netdev_priv(dev);
	int num, err;
	struct scatterlist sg[1+MAX_SKB_FRAGS];
	struct virtio_net_hdr *hdr;
	const unsigned char *dest = ((struct ethhdr *)skb->data)->h_dest;

	sg_init_table(sg, 1+MAX_SKB_FRAGS);

	pr_debug("%s: xmit %p " MAC_FMT "\n", dev->name, skb,
		 dest[0], dest[1], dest[2],
		 dest[3], dest[4], dest[5]);

	/* Encode metadata header at front. */
	hdr = skb_vnet_hdr(skb);
	if (skb->ip_summed == CHECKSUM_PARTIAL) {
		hdr->flags = VIRTIO_NET_HDR_F_NEEDS_CSUM;
		hdr->csum_start = skb->csum_start - skb_headroom(skb);
		hdr->csum_offset = skb->csum_offset;
	} else {
		hdr->flags = 0;
		hdr->csum_offset = hdr->csum_start = 0;
	}

	if (skb_is_gso(skb)) {
		hdr->hdr_len = skb_transport_header(skb) - skb->data;
		hdr->gso_size = skb_shinfo(skb)->gso_size;
		if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4)
			hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV4;
		else if (skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6)
			hdr->gso_type = VIRTIO_NET_HDR_GSO_TCPV6;
		else if (skb_shinfo(skb)->gso_type & SKB_GSO_UDP)
			hdr->gso_type = VIRTIO_NET_HDR_GSO_UDP;
		else
			BUG();
		if (skb_shinfo(skb)->gso_type & SKB_GSO_TCP_ECN)
			hdr->gso_type |= VIRTIO_NET_HDR_GSO_ECN;
	} else {
		hdr->gso_type = VIRTIO_NET_HDR_GSO_NONE;
		hdr->gso_size = hdr->hdr_len = 0;
	}

	vnet_hdr_to_sg(sg, skb);
	num = skb_to_sgvec(skb, sg+1, 0, skb->len) + 1;
	__skb_queue_head(&vi->send, skb);

again:
	/* Free up any pending old buffers before queueing new ones. */
	free_old_xmit_skbs(vi);
	err = vi->svq->vq_ops->add_buf(vi->svq, sg, num, 0, skb);
	if (err) {
		pr_debug("%s: virtio not prepared to send\n", dev->name);
		netif_stop_queue(dev);

		/* Activate callback for using skbs: if this returns false it
		 * means some were used in the meantime. */
		if (unlikely(!vi->svq->vq_ops->enable_cb(vi->svq))) {
			vi->svq->vq_ops->disable_cb(vi->svq);
			netif_start_queue(dev);
			goto again;
		}
		__skb_unlink(skb, &vi->send);

		return NETDEV_TX_BUSY;
	}
	vi->svq->vq_ops->kick(vi->svq);

	return 0;
}

//.........这里部分代码省略.........
                     crd1->crd_alg == CRYPTO_SHA1_HMAC ||
                     crd1->crd_alg == CRYPTO_MD5 ||
                     crd1->crd_alg == CRYPTO_SHA1) &&
		    (crd2->crd_alg == CRYPTO_DES_CBC ||
		     crd2->crd_alg == CRYPTO_3DES_CBC ||
		     crd2->crd_alg == CRYPTO_AES_CBC ||
		     crd2->crd_alg == CRYPTO_ARC4) &&
		    ((crd2->crd_flags & CRD_F_ENCRYPT) == 0)) {
			maccrd = crd1;
			enccrd = crd2;
		} else if ((crd1->crd_alg == CRYPTO_DES_CBC ||
		     crd1->crd_alg == CRYPTO_ARC4 ||
		     crd1->crd_alg == CRYPTO_3DES_CBC ||
		     crd1->crd_alg == CRYPTO_AES_CBC) &&
		    (crd2->crd_alg == CRYPTO_MD5_HMAC ||
                     crd2->crd_alg == CRYPTO_SHA1_HMAC ||
                     crd2->crd_alg == CRYPTO_MD5 ||
                     crd2->crd_alg == CRYPTO_SHA1) &&
		    (crd1->crd_flags & CRD_F_ENCRYPT)) {
			enccrd = crd1;
			maccrd = crd2;
		} else {
			/* We cannot order the SEC as requested */
			printk("%s: cannot do the order\n",
					device_get_nameunit(sc->sc_cdev));
			err = EINVAL;
			goto errout;
		}
	}
	/* assign in_fifo and out_fifo based on input/output struct type */
	if (crp->crp_flags & CRYPTO_F_SKBUF) {
		/* using SKB buffers */
		struct sk_buff *skb = (struct sk_buff *)crp->crp_buf;
		if (skb_shinfo(skb)->nr_frags) {
			printk("%s: skb frags unimplemented\n",
					device_get_nameunit(sc->sc_cdev));
			err = EINVAL;
			goto errout;
		}
		td->ptr[in_fifo].ptr = dma_map_single(NULL, skb->data, 
			skb->len, DMA_TO_DEVICE);
		td->ptr[in_fifo].len = skb->len;
		td->ptr[out_fifo].ptr = dma_map_single(NULL, skb->data, 
			skb->len, DMA_TO_DEVICE);
		td->ptr[out_fifo].len = skb->len;
		td->ptr[hmac_data].ptr = dma_map_single(NULL, skb->data,
			skb->len, DMA_TO_DEVICE);
	} else if (crp->crp_flags & CRYPTO_F_IOV) {
		/* using IOV buffers */
		struct uio *uiop = (struct uio *)crp->crp_buf;
		if (uiop->uio_iovcnt > 1) {
			printk("%s: iov frags unimplemented\n",
					device_get_nameunit(sc->sc_cdev));
			err = EINVAL;
			goto errout;
		}
		td->ptr[in_fifo].ptr = dma_map_single(NULL,
			uiop->uio_iov->iov_base, crp->crp_ilen, DMA_TO_DEVICE);
		td->ptr[in_fifo].len = crp->crp_ilen;
		/* crp_olen is never set; always use crp_ilen */
		td->ptr[out_fifo].ptr = dma_map_single(NULL,
			uiop->uio_iov->iov_base,
			crp->crp_ilen, DMA_TO_DEVICE);
		td->ptr[out_fifo].len = crp->crp_ilen;
	} else {
		/* using contig buffers */

//.........这里部分代码省略.........
	 *
	 * This padding exists because we manipulate event->u,
	 * and 'event' is not packed.
	 *
	 * An iw_point event is laid out like this instead:
	 *      |  0  |  1  |  2  |  3  |  4  |  5  |  6  |  7  |
	 *      | event.len | event.cmd |     p a d d i n g     |
	 *      | iwpnt.len | iwpnt.flg |     p a d d i n g     |
	 *      | extra data  ...
	 *
	 * The second padding exists because struct iw_point is extended,
	 * but this depends on the platform...
	 *
	 * On 32-bit, all the padding shouldn't be there.
	 */

	skb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_ATOMIC);
	if (!skb)
		return;

	/* Send via the RtNetlink event channel */
	nlh = rtnetlink_ifinfo_prep(dev, skb);
	if (WARN_ON(!nlh)) {
		kfree_skb(skb);
		return;
	}

	/* Add the wireless events in the netlink packet */
	nla = nla_reserve(skb, IFLA_WIRELESS, event_len);
	if (!nla) {
		kfree_skb(skb);
		return;
	}
	event = nla_data(nla);

	/* Fill event - first clear to avoid data leaking */
	memset(event, 0, hdr_len);
	event->len = event_len;
	event->cmd = cmd;
	memcpy(&event->u, ((char *) wrqu) + wrqu_off, hdr_len - IW_EV_LCP_LEN);
	if (extra_len)
		memcpy(((char *) event) + hdr_len, extra, extra_len);

	nlmsg_end(skb, nlh);
#ifdef CONFIG_COMPAT
	hdr_len = compat_event_type_size[descr->header_type];
	event_len = hdr_len + extra_len;

	compskb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_ATOMIC);
	if (!compskb) {
		kfree_skb(skb);
		return;
	}

	/* Send via the RtNetlink event channel */
	nlh = rtnetlink_ifinfo_prep(dev, compskb);
	if (WARN_ON(!nlh)) {
		kfree_skb(skb);
		kfree_skb(compskb);
		return;
	}

	/* Add the wireless events in the netlink packet */
	nla = nla_reserve(compskb, IFLA_WIRELESS, event_len);
	if (!nla) {
		kfree_skb(skb);
		kfree_skb(compskb);
		return;
	}
	compat_event = nla_data(nla);

	compat_event->len = event_len;
	compat_event->cmd = cmd;
	if (descr->header_type == IW_HEADER_TYPE_POINT) {
		compat_wrqu.length = wrqu->data.length;
		compat_wrqu.flags = wrqu->data.flags;
		memcpy(&compat_event->pointer,
			((char *) &compat_wrqu) + IW_EV_COMPAT_POINT_OFF,
			hdr_len - IW_EV_COMPAT_LCP_LEN);
		if (extra_len)
			memcpy(((char *) compat_event) + hdr_len,
				extra, extra_len);
	} else {
		/* extra_len must be zero, so no if (extra) needed */
		memcpy(&compat_event->pointer, wrqu,
			hdr_len - IW_EV_COMPAT_LCP_LEN);
	}

	nlmsg_end(compskb, nlh);

	skb_shinfo(skb)->frag_list = compskb;
#endif
#if (LINUX_VERSION_CODE >= KERNEL_VERSION(2,6,32))
	skb_queue_tail(&dev_net(dev)->wext_nlevents, skb);
	schedule_work(&wireless_nlevent_work);
#else
	skb_queue_tail(&wireless_nlevent_queue, skb);
	tasklet_schedule(&wireless_nlevent_tasklet);
#endif
}

struct sk_buff *skb_clone(struct sk_buff *skb, int gfp_mask)
{
    struct sk_buff *n;

    n = skb_head_from_pool();
    if (!n) {
        n = kmem_cache_alloc(skbuff_head_cache, gfp_mask);
        if (!n)
            return NULL;
    }

#define C(x) n->x = skb->x

    n->next = n->prev = NULL;
    n->list = NULL;
    n->sk = NULL;
    C(stamp);
    C(dev);
    C(h);
    C(nh);
    C(mac);
    C(dst);
    dst_clone(n->dst);
    memcpy(n->cb, skb->cb, sizeof(skb->cb));
    C(len);
    C(data_len);
    C(csum);
    n->cloned = 1;
    C(pkt_type);
    C(ip_summed);
    C(priority);
    atomic_set(&n->users, 1);
    C(protocol);
    C(security);
    C(truesize);
    C(head);
    C(data);
    C(tail);
    C(end);
    n->destructor = NULL;
#ifdef CONFIG_NETFILTER
    C(nfmark);
    C(nfcache);
    C(nfct);
#ifdef CONFIG_NETFILTER_DEBUG
    C(nf_debug);
#endif
#endif /*CONFIG_NETFILTER*/
#if defined(CONFIG_HIPPI)
    C(private);
#endif
#ifdef CONFIG_NET_SCHED
    C(tc_index);
#endif

    atomic_inc(&(skb_shinfo(skb)->dataref));
    skb->cloned = 1;
#ifdef CONFIG_NETFILTER
    nf_conntrack_get(skb->nfct);
#endif
    return n;
}

static int ip_frag_reasm(struct ipq *qp, struct sk_buff *prev,
			 struct net_device *dev)
{
	struct net *net = container_of(qp->q.net, struct net, ipv4.frags);
	struct iphdr *iph;
	struct sk_buff *fp, *head = qp->q.fragments;
	int len;
	int ihlen;
	int err;
	int sum_truesize;
	u8 ecn;

	ipq_kill(qp);

	ecn = ip_frag_ecn_table[qp->ecn];
	if (unlikely(ecn == 0xff)) {
		err = -EINVAL;
		goto out_fail;
	}
	/* Make the one we just received the head. */
	if (prev) {
		head = prev->next;
		fp = skb_clone(head, GFP_ATOMIC);
		if (!fp)
			goto out_nomem;

		fp->next = head->next;
		if (!fp->next)
			qp->q.fragments_tail = fp;
		prev->next = fp;

		skb_morph(head, qp->q.fragments);
		head->next = qp->q.fragments->next;

		consume_skb(qp->q.fragments);
		qp->q.fragments = head;
	}

	WARN_ON(head == NULL);
	WARN_ON(FRAG_CB(head)->offset != 0);

	/* Allocate a new buffer for the datagram. */
	ihlen = ip_hdrlen(head);
	len = ihlen + qp->q.len;

	err = -E2BIG;
	if (len > 65535)
		goto out_oversize;

	/* Head of list must not be cloned. */
	if (skb_unclone(head, GFP_ATOMIC))
		goto out_nomem;

	/* If the first fragment is fragmented itself, we split
	 * it to two chunks: the first with data and paged part
	 * and the second, holding only fragments. */
	if (skb_has_frag_list(head)) {
		struct sk_buff *clone;
		int i, plen = 0;

		if ((clone = alloc_skb(0, GFP_ATOMIC)) == NULL)
			goto out_nomem;
		clone->next = head->next;
		head->next = clone;
		skb_shinfo(clone)->frag_list = skb_shinfo(head)->frag_list;
		skb_frag_list_init(head);
		for (i = 0; i < skb_shinfo(head)->nr_frags; i++)
			plen += skb_frag_size(&skb_shinfo(head)->frags[i]);
		clone->len = clone->data_len = head->data_len - plen;
		head->data_len -= clone->len;
		head->len -= clone->len;
		clone->csum = 0;
		clone->ip_summed = head->ip_summed;
		add_frag_mem_limit(&qp->q, clone->truesize);
	}

	skb_push(head, head->data - skb_network_header(head));

	sum_truesize = head->truesize;
	for (fp = head->next; fp;) {
		bool headstolen;
		int delta;
		struct sk_buff *next = fp->next;

		sum_truesize += fp->truesize;
		if (head->ip_summed != fp->ip_summed)
			head->ip_summed = CHECKSUM_NONE;
		else if (head->ip_summed == CHECKSUM_COMPLETE)
			head->csum = csum_add(head->csum, fp->csum);

		if (skb_try_coalesce(head, fp, &headstolen, &delta)) {
			kfree_skb_partial(fp, headstolen);
		} else {
			if (!skb_shinfo(head)->frag_list)
				skb_shinfo(head)->frag_list = fp;
			head->data_len += fp->len;
			head->len += fp->len;
			head->truesize += fp->truesize;
		}
		fp = next;
//.........这里部分代码省略.........

static void xennet_make_frags(struct sk_buff *skb, struct net_device *dev,
			      struct xen_netif_tx_request *tx)
{
	struct netfront_info *np = netdev_priv(dev);
	char *data = skb->data;
	unsigned long mfn;
	RING_IDX prod = np->tx.req_prod_pvt;
	int frags = skb_shinfo(skb)->nr_frags;
	unsigned int offset = offset_in_page(data);
	unsigned int len = skb_headlen(skb);
	unsigned int id;
	grant_ref_t ref;
	int i;

	while (len > PAGE_SIZE - offset) {
		tx->size = PAGE_SIZE - offset;
		tx->flags |= XEN_NETTXF_more_data;
		len -= tx->size;
		data += tx->size;
		offset = 0;

		id = get_id_from_freelist(&np->tx_skb_freelist, np->tx_skbs);
		np->tx_skbs[id].skb = skb_get(skb);
		tx = RING_GET_REQUEST(&np->tx, prod++);
		tx->id = id;
		ref = gnttab_claim_grant_reference(&np->gref_tx_head);
		BUG_ON((signed short)ref < 0);

		mfn = virt_to_mfn(data);
		gnttab_grant_foreign_access_ref(ref, np->xbdev->otherend_id,
						mfn, GNTMAP_readonly);

		tx->gref = np->grant_tx_ref[id] = ref;
		tx->offset = offset;
		tx->size = len;
		tx->flags = 0;
	}

	
	for (i = 0; i < frags; i++) {
		skb_frag_t *frag = skb_shinfo(skb)->frags + i;

		tx->flags |= XEN_NETTXF_more_data;

		id = get_id_from_freelist(&np->tx_skb_freelist, np->tx_skbs);
		np->tx_skbs[id].skb = skb_get(skb);
		tx = RING_GET_REQUEST(&np->tx, prod++);
		tx->id = id;
		ref = gnttab_claim_grant_reference(&np->gref_tx_head);
		BUG_ON((signed short)ref < 0);

		mfn = pfn_to_mfn(page_to_pfn(skb_frag_page(frag)));
		gnttab_grant_foreign_access_ref(ref, np->xbdev->otherend_id,
						mfn, GNTMAP_readonly);

		tx->gref = np->grant_tx_ref[id] = ref;
		tx->offset = frag->page_offset;
		tx->size = skb_frag_size(frag);
		tx->flags = 0;
	}

	np->tx.req_prod_pvt = prod;
}

/**
 *	skb_copy_datagram_iovec - Copy a datagram to an iovec.
 *	@skb: buffer to copy
 *	@offset: offset in the buffer to start copying from
 *	@to: io vector to copy to
 *	@len: amount of data to copy from buffer to iovec
 *
 *	Note: the iovec is modified during the copy.
 */
int skb_copy_datagram_iovec(const struct sk_buff *skb, int offset,
			    struct iovec *to, int len)
{
	int start = skb_headlen(skb);
	int i, copy = start - offset;
	struct sk_buff *frag_iter;

	trace_skb_copy_datagram_iovec(skb, len);

	/* Copy header. */
	if (copy > 0) {
		if (copy > len)
			copy = len;
		if (memcpy_toiovec(to, skb->data + offset, copy))
			goto fault;
		if ((len -= copy) == 0)
			return 0;
		offset += copy;
	}

	/* Copy paged appendix. Hmm... why does this look so complicated? */
	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
		int end;

		WARN_ON(start > offset + len);

		end = start + skb_shinfo(skb)->frags[i].size;
		if ((copy = end - offset) > 0) {
			int err;
			u8  *vaddr;
			skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
			struct page *page = frag->page;

			if (copy > len)
				copy = len;
			vaddr = kmap(page);
			err = memcpy_toiovec(to, vaddr + frag->page_offset +
					     offset - start, copy);
			kunmap(page);
			if (err)
				goto fault;
			if (!(len -= copy))
				return 0;
			offset += copy;
		}
		start = end;
	}

	skb_walk_frags(skb, frag_iter) {
		int end;

		WARN_ON(start > offset + len);

		end = start + frag_iter->len;
		if ((copy = end - offset) > 0) {
			if (copy > len)
				copy = len;
			if (skb_copy_datagram_iovec(frag_iter,
						    offset - start,
						    to, copy))
				goto fault;
			if ((len -= copy) == 0)
				return 0;
			offset += copy;
		}
		start = end;
	}

/**
 *	__alloc_skb	-	allocate a network buffer
 *	@size: size to allocate
 *	@gfp_mask: allocation mask
 *	@fclone: allocate from fclone cache instead of head cache
 *		and allocate a cloned (child) skb
 *
 *	Allocate a new &sk_buff. The returned buffer has no headroom and a
 *	tail room of size bytes. The object has a reference count of one.
 *	The return is the buffer. On a failure the return is %NULL.
 *
 *	Buffers may only be allocated from interrupts using a @gfp_mask of
 *	%GFP_ATOMIC.
 */
struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
			    int fclone)
{
	kmem_cache_t *cache;
	struct skb_shared_info *shinfo;
	struct sk_buff *skb;
	u8 *data;

	cache = fclone ? skbuff_fclone_cache : skbuff_head_cache;

	/* Get the HEAD */
	skb = kmem_cache_alloc(cache, gfp_mask & ~__GFP_DMA);
	if (!skb)
		goto out;

	/* Get the DATA. Size must match skb_add_mtu(). */
	size = SKB_DATA_ALIGN(size);
	//data = kmalloc(size + sizeof(struct skb_shared_info), gfp_mask);
	//data = kmalloc(size + sizeof(struct skb_shared_info)+4, gfp_mask);//incifer support vlan id
    /* 20007/10/16 pppoe acc incifer    LAN2WAN */
    data = kmalloc(size + sizeof(struct skb_shared_info) + NK_EXTRA_OFFSET, gfp_mask);
	if (!data)
		goto nodata;

	memset(skb, 0, offsetof(struct sk_buff, truesize));
	skb->truesize = size + sizeof(struct sk_buff);
	atomic_set(&skb->users, 1);
	skb->head = data;
	//skb->data = data+4;//incifer
/* 20007/10/16 pppoe acc incifer    LAN2WAN */
    skb->data = data + NK_EXTRA_OFFSET;
	//skb->tail = data+4;//incifer
/* 20007/10/16 pppoe acc incifer    LAN2WAN */
    skb->tail = data + NK_EXTRA_OFFSET;
	//skb->end  = data + size+4;//incifer
    /* 20007/10/16 pppoe acc incifer    LAN2WAN */
    skb->end  = data + size + NK_EXTRA_OFFSET;
	/* make sure we initialize shinfo sequentially */
	shinfo = skb_shinfo(skb);
	atomic_set(&shinfo->dataref, 1);
	shinfo->nr_frags  = 0;
	shinfo->tso_size = 0;
	shinfo->tso_segs = 0;
	shinfo->ufo_size = 0;
	shinfo->ip6_frag_id = 0;
	shinfo->frag_list = NULL;

	if (fclone) {
		struct sk_buff *child = skb + 1;
		atomic_t *fclone_ref = (atomic_t *) (child + 1);

		skb->fclone = SKB_FCLONE_ORIG;
		atomic_set(fclone_ref, 1);

		child->fclone = SKB_FCLONE_UNAVAILABLE;
	}
out:
	return skb;
nodata:
	kmem_cache_free(cache, skb);
	skb = NULL;
	goto out;
}

static bool is_gre_gso(struct sk_buff *skb)
{
	return skb_shinfo(skb)->gso_type &
		(SKB_GSO_GRE | SKB_GSO_GRE_CSUM);
}

static int cp_start_xmit (struct sk_buff *skb, struct net_device *dev)
{
	struct cp_private *cp = netdev_priv(dev);
	unsigned entry;
	u32 eor;
#if CP_VLAN_TAG_USED
	u32 vlan_tag = 0;
#endif

	spin_lock_irq(&cp->lock);

	/* This is a hard error, log it. */
	if (TX_BUFFS_AVAIL(cp) <= (skb_shinfo(skb)->nr_frags + 1)) {
		netif_stop_queue(dev);
		spin_unlock_irq(&cp->lock);
		printk(KERN_ERR PFX "%s: BUG! Tx Ring full when queue awake!\n",
		       dev->name);
		return 1;
	}

#if CP_VLAN_TAG_USED
	if (cp->vlgrp && vlan_tx_tag_present(skb))
		vlan_tag = TxVlanTag | cpu_to_be16(vlan_tx_tag_get(skb));
#endif

	entry = cp->tx_head;
	eor = (entry == (CP_TX_RING_SIZE - 1)) ? RingEnd : 0;
	if (skb_shinfo(skb)->nr_frags == 0) {
		struct cp_desc *txd = &cp->tx_ring[entry];
		u32 len;
		dma_addr_t mapping;

		len = skb->len;
		mapping = pci_map_single(cp->pdev, skb->data, len, PCI_DMA_TODEVICE);
		CP_VLAN_TX_TAG(txd, vlan_tag);
		txd->addr = cpu_to_le64(mapping);
		wmb();

		if (skb->ip_summed == CHECKSUM_HW) {
			const struct iphdr *ip = skb->nh.iph;
			if (ip->protocol == IPPROTO_TCP)
				txd->opts1 = cpu_to_le32(eor | len | DescOwn |
							 FirstFrag | LastFrag |
							 IPCS | TCPCS);
			else if (ip->protocol == IPPROTO_UDP)
				txd->opts1 = cpu_to_le32(eor | len | DescOwn |
							 FirstFrag | LastFrag |
							 IPCS | UDPCS);
			else
				BUG();
		} else
			txd->opts1 = cpu_to_le32(eor | len | DescOwn |
						 FirstFrag | LastFrag);
		wmb();

		cp->tx_skb[entry].skb = skb;
		cp->tx_skb[entry].mapping = mapping;
		cp->tx_skb[entry].frag = 0;
		entry = NEXT_TX(entry);
	} else {
		struct cp_desc *txd;
		u32 first_len, first_eor;
		dma_addr_t first_mapping;
		int frag, first_entry = entry;
		const struct iphdr *ip = skb->nh.iph;

		/* We must give this initial chunk to the device last.
		 * Otherwise we could race with the device.
		 */
		first_eor = eor;
		first_len = skb_headlen(skb);
		first_mapping = pci_map_single(cp->pdev, skb->data,
					       first_len, PCI_DMA_TODEVICE);
		cp->tx_skb[entry].skb = skb;
		cp->tx_skb[entry].mapping = first_mapping;
		cp->tx_skb[entry].frag = 1;
		entry = NEXT_TX(entry);

		for (frag = 0; frag < skb_shinfo(skb)->nr_frags; frag++) {
			skb_frag_t *this_frag = &skb_shinfo(skb)->frags[frag];
			u32 len;
			u32 ctrl;
			dma_addr_t mapping;

			len = this_frag->size;
			mapping = pci_map_single(cp->pdev,
						 ((void *) page_address(this_frag->page) +
						  this_frag->page_offset),
						 len, PCI_DMA_TODEVICE);
			eor = (entry == (CP_TX_RING_SIZE - 1)) ? RingEnd : 0;

			if (skb->ip_summed == CHECKSUM_HW) {
				ctrl = eor | len | DescOwn | IPCS;
				if (ip->protocol == IPPROTO_TCP)
					ctrl |= TCPCS;
				else if (ip->protocol == IPPROTO_UDP)
					ctrl |= UDPCS;
				else
					BUG();
			} else
//.........这里部分代码省略.........

struct sk_buff *skb_clone(struct sk_buff *skb, gfp_t gfp_mask)
{
	struct sk_buff *n;

	n = skb + 1;
	if (skb->fclone == SKB_FCLONE_ORIG &&
	    n->fclone == SKB_FCLONE_UNAVAILABLE) {
		atomic_t *fclone_ref = (atomic_t *) (n + 1);
		n->fclone = SKB_FCLONE_CLONE;
		atomic_inc(fclone_ref);
	} else {
		n = kmem_cache_alloc(skbuff_head_cache, gfp_mask);
		if (!n)
			return NULL;
		n->fclone = SKB_FCLONE_UNAVAILABLE;
	}

#define C(x) n->x = skb->x

	n->next = n->prev = NULL;
	n->sk = NULL;
	C(tstamp);
	C(dev);
	C(h);
	C(nh);
	C(mac);
	C(dst);
	dst_clone(skb->dst);
	C(sp);
#ifdef CONFIG_INET
	secpath_get(skb->sp);
#endif
	memcpy(n->cb, skb->cb, sizeof(skb->cb));
	C(len);
	C(data_len);
	C(csum);
	C(local_df);
	n->cloned = 1;
	n->nohdr = 0;
	C(pkt_type);
	C(ip_summed);
	C(priority);
#if defined(CONFIG_IP_VS) || defined(CONFIG_IP_VS_MODULE)
	C(ipvs_property);
#endif
	C(protocol);
	n->destructor = NULL;
#ifdef CONFIG_NETFILTER
	C(nfmark);
	C(nfct);
	nf_conntrack_get(skb->nfct);
	C(nfctinfo);
#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
	C(nfct_reasm);
	nf_conntrack_get_reasm(skb->nfct_reasm);
#endif
#ifdef CONFIG_BRIDGE_NETFILTER
	C(nf_bridge);
	nf_bridge_get(skb->nf_bridge);
#endif
#endif /*CONFIG_NETFILTER*/
#ifdef CONFIG_NET_SCHED
	C(tc_index);
#ifdef CONFIG_NET_CLS_ACT
	n->tc_verd = SET_TC_VERD(skb->tc_verd,0);
	n->tc_verd = CLR_TC_OK2MUNGE(n->tc_verd);
	n->tc_verd = CLR_TC_MUNGED(n->tc_verd);
	C(input_dev);
#endif

#endif
	C(truesize);
	atomic_set(&n->users, 1);
	C(head);
	C(data);
	C(tail);
	C(end);

	atomic_inc(&(skb_shinfo(skb)->dataref));
	skb->cloned = 1;

	return n;
}

/** Copy some data bits from a kernel buffer to an skb.
 * Derived in the obvious way from skb_copy_bits().
 */
int skb_put_bits(const struct sk_buff *skb, int offset, void *src, int len)
{
    int i, copy;
    int start = skb->len - skb->data_len;

    if (offset > (int)skb->len-len)
        goto fault;

    /* Copy header. */
    if ((copy = start-offset) > 0) {
        if (copy > len)
            copy = len;
        memcpy(skb->data + offset, src, copy);
        if ((len -= copy) == 0)
            return 0;
        offset += copy;
        src += copy;
    }

#ifdef __KERNEL__
    for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
        int end;

        BUG_TRAP(start <= offset+len);

        end = start + skb_shinfo(skb)->frags[i].size;
        if ((copy = end-offset) > 0) {
            u8 *vaddr;

            if (copy > len)
                copy = len;

            vaddr = kmap_skb_frag(&skb_shinfo(skb)->frags[i]);
            memcpy(vaddr + skb_shinfo(skb)->frags[i].page_offset + offset - start,
                   src,
                   copy);
            kunmap_skb_frag(vaddr);

            if ((len -= copy) == 0)
                return 0;
            offset += copy;
            src += copy;
        }
        start = end;
    }

    if (skb_shinfo(skb)->frag_list) {
        struct sk_buff *list;
        
        for (list = skb_shinfo(skb)->frag_list; list; list=list->next) {
            int end;
            
            BUG_TRAP(start <= offset+len);
            
            end = start + list->len;
            if ((copy = end-offset) > 0) {
                if (copy > len)
                    copy = len;
                if (skb_put_bits(list, offset-start, src, copy))
                    goto fault;
                if ((len -= copy) == 0)
                    return 0;
                offset += copy;
                src += copy;
            }
            start = end;
        }
    }
#else
    i=0;
#endif

    if (len == 0)
        return 0;

 fault:
    return -EFAULT;
}

static void xennet_alloc_rx_buffers(struct net_device *dev)
{
	unsigned short id;
	struct netfront_info *np = netdev_priv(dev);
	struct sk_buff *skb;
	struct page *page;
	int i, batch_target, notify;
	RING_IDX req_prod = np->rx.req_prod_pvt;
	grant_ref_t ref;
	unsigned long pfn;
	void *vaddr;
	struct xen_netif_rx_request *req;

	if (unlikely(!netif_carrier_ok(dev)))
		return;

	batch_target = np->rx_target - (req_prod - np->rx.rsp_cons);
	for (i = skb_queue_len(&np->rx_batch); i < batch_target; i++) {
		skb = __netdev_alloc_skb(dev, RX_COPY_THRESHOLD + NET_IP_ALIGN,
					 GFP_ATOMIC | __GFP_NOWARN);
		if (unlikely(!skb))
			goto no_skb;

		
		skb_reserve(skb, NET_IP_ALIGN);

		page = alloc_page(GFP_ATOMIC | __GFP_NOWARN);
		if (!page) {
			kfree_skb(skb);
no_skb:
			
			if (i != 0)
				goto refill;
			
			mod_timer(&np->rx_refill_timer,
				  jiffies + (HZ/10));
			break;
		}

		__skb_fill_page_desc(skb, 0, page, 0, 0);
		skb_shinfo(skb)->nr_frags = 1;
		__skb_queue_tail(&np->rx_batch, skb);
	}

	
	if (i < (np->rx_target/2)) {
		if (req_prod > np->rx.sring->req_prod)
			goto push;
		return;
	}

	
	if (((req_prod - np->rx.sring->rsp_prod) < (np->rx_target / 4)) &&
	    ((np->rx_target *= 2) > np->rx_max_target))
		np->rx_target = np->rx_max_target;

 refill:
	for (i = 0; ; i++) {
		skb = __skb_dequeue(&np->rx_batch);
		if (skb == NULL)
			break;

		skb->dev = dev;

		id = xennet_rxidx(req_prod + i);

		BUG_ON(np->rx_skbs[id]);
		np->rx_skbs[id] = skb;

		ref = gnttab_claim_grant_reference(&np->gref_rx_head);
		BUG_ON((signed short)ref < 0);
		np->grant_rx_ref[id] = ref;

		pfn = page_to_pfn(skb_frag_page(&skb_shinfo(skb)->frags[0]));
		vaddr = page_address(skb_frag_page(&skb_shinfo(skb)->frags[0]));

		req = RING_GET_REQUEST(&np->rx, req_prod + i);
		gnttab_grant_foreign_access_ref(ref,
						np->xbdev->otherend_id,
						pfn_to_mfn(pfn),
						0);

		req->id = id;
		req->gref = ref;
	}

	wmb();		

	
	np->rx.req_prod_pvt = req_prod + i;
 push:
	RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&np->rx, notify);
	if (notify)
		notify_remote_via_irq(np->netdev->irq);
}

/** Convert a (possibly fragmented) skb into a scatter list.
 *
 * @param skb skb to convert
 * @param sg scatterlist to set up
 * @param sg_n size of sg on input, number of elements set on output
 * @param offset offset into data to start at
 * @param len number of bytes
 * @return 0 on success, error code otherwise
 */
int skb_scatterlist(struct sk_buff *skb, struct scatterlist *sg, int *sg_n,
                    int offset, int len){
    int err = 0;
    int start;		// No. of bytes copied so far (where next copy starts).
    int size;		// Size of the next chunk.
    int end;		// Where the next chunk ends (start + size).
    int copy;		// Number of bytes to copy in one operation.
    int sg_i = 0;	// Index into sg.
    int i;
    
    if(DEBUG_SCATTERLIST){
        dprintf("> offset=%d len=%d (end=%d), skb len=%d,\n",
                offset, len, offset+len, skb->len);
    }
    start = 0;
    size = skb_headlen(skb);
    end = start + size;
    copy = end - offset;
    if(copy > 0){
        char *p;
        if(copy > len) copy = len;
        if(sg_i >= *sg_n){
            err = -EINVAL;
            goto exit;
        }
        p = skb->data + offset;
        SET_SCATTER_ADDR(sg[sg_i], NULL);
        sg[sg_i].page = virt_to_page(p);
        sg[sg_i].offset = ((unsigned long)p & ~PAGE_MASK);
        sg[sg_i].length = copy;
        if(DEBUG_SCATTERLIST){
            dprintf("> sg_i=%d .page=%p .offset=%u .length=%d\n",
                    sg_i, sg[sg_i].page, sg[sg_i].offset, sg[sg_i].length);
        }
        sg_i++;
        if((len -= copy) == 0) goto exit;
        offset += copy;
    }
    start = end;
    for (i = 0; i < skb_shinfo(skb)->nr_frags; i++){
        BUG_TRAP(start <= offset + len);
        size = skb_shinfo(skb)->frags[i].size;
        end = start + size;
        copy = end - offset;
        if(copy > 0){
            skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
            if(copy > len) copy = len;
            if(sg_i >= *sg_n){
                err = -EINVAL;
                goto exit;
            }
            SET_SCATTER_ADDR(sg[sg_i], NULL);
            sg[sg_i].page = frag->page;
            sg[sg_i].offset = frag->page_offset + offset - start;
            sg[sg_i].length = copy;
            if(DEBUG_SCATTERLIST){
                dprintf("> sg_i=%d .page=%p .offset=%u .length=%d\n",
                        sg_i, sg[sg_i].page, sg[sg_i].offset, sg[sg_i].length);
            }
            sg_i++;
            if((len -= copy) == 0) goto exit;
            offset += copy;
        }
        start = end;
    }
  exit:
    if(!err) *sg_n = sg_i;
    if(len) wprintf("> len=%d\n", len);
    if(len) BUG();
    if(err) dprintf("< err=%d sg_n=%d\n", err, *sg_n);
    return err;
}