net: Export skb_zerocopy() to zerocopy from one skb to another

Make the skb zerocopy logic written for nfnetlink queue available for
use by other modules.

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Reviewed-by: Daniel Borkmann <dborkman@redhat.com>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jesse Gross <jesse@nicira.com>

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index bec1cc7..7c48e2d 100644 (file)
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2345,6 +2345,9 @@ int skb_splice_bits(struct sk_buff *skb, unsigned int offset,
                    struct pipe_inode_info *pipe, unsigned int len,
                    unsigned int flags);
 void skb_copy_and_csum_dev(const struct sk_buff *skb, u8 *to);
+unsigned int skb_zerocopy_headlen(const struct sk_buff *from);
+void skb_zerocopy(struct sk_buff *to, const struct sk_buff *from,
+                 int len, int hlen);
 void skb_split(struct sk_buff *skb, struct sk_buff *skb1, const u32 len);
 int skb_shift(struct sk_buff *tgt, struct sk_buff *skb, int shiftlen);
 void skb_scrub_packet(struct sk_buff *skb, bool xnet);

diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 2718fed..55859cb 100644 (file)
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2122,6 +2122,91 @@ __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;

diff --git a/net/netfilter/nfnetlink_queue_core.c b/net/netfilter/nfnetlink_queue_core.c
index 21258cf..615ee12 100644 (file)
--- a/net/netfilter/nfnetlink_queue_core.c
+++ b/net/netfilter/nfnetlink_queue_core.c
@@ -235,51 +235,6 @@ nfqnl_flush(struct nfqnl_instance *queue, nfqnl_cmpfn cmpfn, unsigned long data)
        spin_unlock_bh(&queue->lock);
 }
 
-static void
-nfqnl_zcopy(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;
-
-       /* 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;
-}
-
 static int
 nfqnl_put_packet_info(struct sk_buff *nlskb, struct sk_buff *packet,
                      bool csum_verify)
@@ -304,7 +259,7 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
 {
        size_t size;
        size_t data_len = 0, cap_len = 0;
-       int hlen = 0;
+       unsigned int hlen = 0;
        struct sk_buff *skb;
        struct nlattr *nla;
        struct nfqnl_msg_packet_hdr *pmsg;
@@ -356,14 +311,8 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
                if (data_len > entskb->len)
                        data_len = entskb->len;
 
-               if (!entskb->head_frag ||
-                   skb_headlen(entskb) < L1_CACHE_BYTES ||
-                   skb_shinfo(entskb)->nr_frags >= MAX_SKB_FRAGS)
-                       hlen = skb_headlen(entskb);
-
-               if (skb_has_frag_list(entskb))
-                       hlen = entskb->len;
-               hlen = min_t(int, data_len, hlen);
+               hlen = skb_zerocopy_headlen(entskb);
+               hlen = min_t(unsigned int, hlen, data_len);
                size += sizeof(struct nlattr) + hlen;
                cap_len = entskb->len;
                break;
@@ -504,7 +453,7 @@ nfqnl_build_packet_message(struct net *net, struct nfqnl_instance *queue,
                nla->nla_type = NFQA_PAYLOAD;
                nla->nla_len = nla_attr_size(data_len);
 
-               nfqnl_zcopy(skb, entskb, data_len, hlen);
+               skb_zerocopy(skb, entskb, data_len, hlen);
        }
 
        nlh->nlmsg_len = skb->len;