+/**
+ * skb_pull_rcsum - pull skb and update receive checksum
+ * @skb: buffer to update
+ * @start: start of data before pull
+ * @len: length of data pulled
+ *
+ * This function performs an skb_pull on the packet and updates
+ * update the CHECKSUM_COMPLETE checksum. It should be used on
+ * receive path processing instead of skb_pull unless you know
+ * that the checksum difference is zero (e.g., a valid IP header)
+ * or you are setting ip_summed to CHECKSUM_NONE.
+ */
+unsigned char *skb_pull_rcsum(struct sk_buff *skb, unsigned int len)
+{
+ BUG_ON(len > skb->len);
+ skb->len -= len;
+ BUG_ON(skb->len < skb->data_len);
+ skb_postpull_rcsum(skb, skb->data, len);
+ return skb->data += len;
+}
+
+EXPORT_SYMBOL_GPL(skb_pull_rcsum);
+
+/**
+ * skb_segment - Perform protocol segmentation on skb.
+ * @skb: buffer to segment
+ * @features: features for the output path (see dev->features)
+ *
+ * This function performs segmentation on the given skb. It returns
+ * the segment at the given position. It returns NULL if there are
+ * no more segments to generate, or when an error is encountered.
+ */
+struct sk_buff *skb_segment(struct sk_buff *skb, int features)
+{
+ struct sk_buff *segs = NULL;
+ struct sk_buff *tail = NULL;
+ unsigned int mss = skb_shinfo(skb)->gso_size;
+ unsigned int doffset = skb->data - skb->mac.raw;
+ unsigned int offset = doffset;
+ unsigned int headroom;
+ unsigned int len;
+ int sg = features & NETIF_F_SG;
+ int nfrags = skb_shinfo(skb)->nr_frags;
+ int err = -ENOMEM;
+ int i = 0;
+ int pos;
+
+ __skb_push(skb, doffset);
+ headroom = skb_headroom(skb);
+ pos = skb_headlen(skb);
+
+ do {
+ struct sk_buff *nskb;
+ skb_frag_t *frag;
+ int hsize;
+ int k;
+ int size;
+
+ len = skb->len - offset;
+ if (len > mss)
+ len = mss;
+
+ hsize = skb_headlen(skb) - offset;
+ if (hsize < 0)
+ hsize = 0;
+ if (hsize > len || !sg)
+ hsize = len;
+
+ nskb = alloc_skb(hsize + doffset + headroom, GFP_ATOMIC);
+ if (unlikely(!nskb))
+ goto err;
+
+ if (segs)
+ tail->next = nskb;
+ else
+ segs = nskb;
+ tail = nskb;
+
+ nskb->dev = skb->dev;
+ nskb->priority = skb->priority;
+ nskb->protocol = skb->protocol;
+ nskb->dst = dst_clone(skb->dst);
+ memcpy(nskb->cb, skb->cb, sizeof(skb->cb));
+ nskb->pkt_type = skb->pkt_type;
+ nskb->mac_len = skb->mac_len;
+
+ skb_reserve(nskb, headroom);
+ nskb->mac.raw = nskb->data;
+ nskb->nh.raw = nskb->data + skb->mac_len;
+ nskb->h.raw = nskb->nh.raw + (skb->h.raw - skb->nh.raw);
+ memcpy(skb_put(nskb, doffset), skb->data, doffset);
+
+ if (!sg) {
+ nskb->csum = skb_copy_and_csum_bits(skb, offset,
+ skb_put(nskb, len),
+ len, 0);
+ continue;
+ }
+
+ frag = skb_shinfo(nskb)->frags;
+ k = 0;
+
+ nskb->ip_summed = CHECKSUM_PARTIAL;
+ nskb->csum = skb->csum;
+ memcpy(skb_put(nskb, hsize), skb->data + offset, hsize);
+
+ while (pos < offset + len) {
+ BUG_ON(i >= nfrags);
+
+ *frag = skb_shinfo(skb)->frags[i];
+ get_page(frag->page);
+ size = frag->size;
+
+ if (pos < offset) {
+ frag->page_offset += offset - pos;
+ frag->size -= offset - pos;
+ }
+
+ k++;
+
+ if (pos + size <= offset + len) {
+ i++;
+ pos += size;
+ } else {
+ frag->size -= pos + size - (offset + len);
+ break;
+ }
+
+ frag++;
+ }
+
+ skb_shinfo(nskb)->nr_frags = k;
+ nskb->data_len = len - hsize;
+ nskb->len += nskb->data_len;
+ nskb->truesize += nskb->data_len;
+ } while ((offset += len) < skb->len);
+
+ return segs;
+
+err:
+ while ((skb = segs)) {
+ segs = skb->next;
+ kfree(skb);
+ }
+ return ERR_PTR(err);
+}
+
+EXPORT_SYMBOL_GPL(skb_segment);
+