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Date: Thu, 25 Jul 2013 14:43:44 +0200
From: Thomas Graf <tgraf@...g.ch>
To: davem@...emloft.net, jesse@...ira.com
Cc: netdev@...r.kernel.org, dev@...nvswitch.org, eric.dumazet@...il.com
Subject: [PATCH net-next 1/2] 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@...g.ch>
---
include/linux/skbuff.h | 3 ++
net/core/skbuff.c | 85 ++++++++++++++++++++++++++++++++++++
net/netfilter/nfnetlink_queue_core.c | 59 ++-----------------------
3 files changed, 92 insertions(+), 55 deletions(-)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 5afefa0..2f3c64f 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2381,6 +2381,9 @@ extern int skb_splice_bits(struct sk_buff *skb,
unsigned int len,
unsigned int flags);
extern void skb_copy_and_csum_dev(const struct sk_buff *skb, u8 *to);
+extern unsigned int skb_zerocopy_headlen(const struct sk_buff *from);
+extern void skb_zerocopy(struct sk_buff *to, const struct sk_buff *from,
+ int len, int hlen);
extern void skb_split(struct sk_buff *skb,
struct sk_buff *skb1, const u32 len);
extern int skb_shift(struct sk_buff *tgt, struct sk_buff *skb,
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 20e02d2..23736ad 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -2111,6 +2111,91 @@ void skb_copy_and_csum_dev(const struct sk_buff *skb, u8 *to)
EXPORT_SYMBOL(skb_copy_and_csum_dev);
/**
+ * 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);
+
+/**
* skb_dequeue - remove from the head of the queue
* @list: list to dequeue from
*
diff --git a/net/netfilter/nfnetlink_queue_core.c b/net/netfilter/nfnetlink_queue_core.c
index 971ea14..ba539a8 100644
--- 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 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 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;
@@ -501,7 +450,7 @@ nfqnl_build_packet_message(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;
--
1.8.3.1
--
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