Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/jesse/openvswitch

[~andy/linux] / net / core / skbuff.c

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index eb96c2c22400dfb927e1cdfef847e629832d2f12..1d641e781f85c51d650e94aa800e546f34024aaa 100644 (file)
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2121,6 +2121,91 @@ __wsum skb_copy_and_csum_bits(const struct sk_buff *skb, int offset,
 }
 EXPORT_SYMBOL(skb_copy_and_csum_bits);
 
+ /**
+ *     skb_zerocopy_headlen - Calculate headroom needed for skb_zerocopy()
+ *     @from: source buffer
+ *
+ *     Calculates the amount of linear headroom needed in the 'to' skb passed
+ *     into skb_zerocopy().
+ */
+unsigned int
+skb_zerocopy_headlen(const struct sk_buff *from)
+{
+       unsigned int hlen = 0;
+
+       if (!from->head_frag ||
+           skb_headlen(from) < L1_CACHE_BYTES ||
+           skb_shinfo(from)->nr_frags >= MAX_SKB_FRAGS)
+               hlen = skb_headlen(from);
+
+       if (skb_has_frag_list(from))
+               hlen = from->len;
+
+       return hlen;
+}
+EXPORT_SYMBOL_GPL(skb_zerocopy_headlen);
+
+/**
+ *     skb_zerocopy - Zero copy skb to skb
+ *     @to: destination buffer
+ *     @source: source buffer
+ *     @len: number of bytes to copy from source buffer
+ *     @hlen: size of linear headroom in destination buffer
+ *
+ *     Copies up to `len` bytes from `from` to `to` by creating references
+ *     to the frags in the source buffer.
+ *
+ *     The `hlen` as calculated by skb_zerocopy_headlen() specifies the
+ *     headroom in the `to` buffer.
+ */
+void
+skb_zerocopy(struct sk_buff *to, const struct sk_buff *from, int len, int hlen)
+{
+       int i, j = 0;
+       int plen = 0; /* length of skb->head fragment */
+       struct page *page;
+       unsigned int offset;
+
+       BUG_ON(!from->head_frag && !hlen);
+
+       /* dont bother with small payloads */
+       if (len <= skb_tailroom(to)) {
+               skb_copy_bits(from, 0, skb_put(to, len), len);
+               return;
+       }
+
+       if (hlen) {
+               skb_copy_bits(from, 0, skb_put(to, hlen), hlen);
+               len -= hlen;
+       } else {
+               plen = min_t(int, skb_headlen(from), len);
+               if (plen) {
+                       page = virt_to_head_page(from->head);
+                       offset = from->data - (unsigned char *)page_address(page);
+                       __skb_fill_page_desc(to, 0, page, offset, plen);
+                       get_page(page);
+                       j = 1;
+                       len -= plen;
+               }
+       }
+
+       to->truesize += len + plen;
+       to->len += len + plen;
+       to->data_len += len + plen;
+
+       for (i = 0; i < skb_shinfo(from)->nr_frags; i++) {
+               if (!len)
+                       break;
+               skb_shinfo(to)->frags[j] = skb_shinfo(from)->frags[i];
+               skb_shinfo(to)->frags[j].size = min_t(int, skb_shinfo(to)->frags[j].size, len);
+               len -= skb_shinfo(to)->frags[j].size;
+               skb_frag_ref(to, j);
+               j++;
+       }
+       skb_shinfo(to)->nr_frags = j;
+}
+EXPORT_SYMBOL_GPL(skb_zerocopy);
+
 void skb_copy_and_csum_dev(const struct sk_buff *skb, u8 *to)
 {
        __wsum csum;