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Subject[RFC 5/6] Add skb_splice_bits to skbuff.c
Date

---
include/linux/skbuff.h | 2 +
net/core/skbuff.c | 137 ++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 139 insertions(+), 0 deletions(-)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 755e9cd..8f4b90e 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1338,6 +1338,8 @@ extern unsigned int skb_checksum(cons
int len, unsigned int csum);
extern int skb_copy_bits(const struct sk_buff *skb, int offset,
void *to, int len);
+extern int skb_splice_bits(const struct sk_buff *skb, int offset,
+ struct pipe_inode_info *pipe, int len, unsigned int flags);
extern int skb_store_bits(const struct sk_buff *skb, int offset,
void *from, int len);
extern unsigned int skb_copy_and_csum_bits(const struct sk_buff *skb,
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index c54f366..a92d165 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -53,6 +53,7 @@
#endif
#include <linux/string.h>
#include <linux/skbuff.h>
+#include <linux/pipe_fs_i.h>
#include <linux/cache.h>
#include <linux/rtnetlink.h>
#include <linux/init.h>
@@ -70,6 +71,17 @@
static kmem_cache_t *skbuff_head_cache __read_mostly;
static kmem_cache_t *skbuff_fclone_cache __read_mostly;

+/* Pipe buffer operations for a socket. */
+static struct pipe_buf_operations sock_buf_ops = {
+ .can_merge = 0,
+ .map = generic_pipe_buf_map,
+ .unmap = generic_pipe_buf_unmap,
+ .pin = generic_pipe_buf_pin,
+ .release = generic_sock_buf_release,
+ .steal = generic_pipe_buf_steal,
+ .get = generic_pipe_buf_get,
+};
+
/*
* Keep out-of-line to prevent kernel bloat.
* __builtin_return_address is not used because it is not always
@@ -1148,6 +1160,131 @@ fault:
return -EFAULT;
}

+/* Move specified number of bytes from the source skb to the
+ * destination pipe buffer. This function even handles all the
+ * bits of traversing fragment lists.
+ */
+int skb_splice_bits(const struct sk_buff *skb, int offset, struct pipe_inode_info *pipe, int len, unsigned int flags)
+{
+ struct page *page;
+ struct partial_page partial[PIPE_BUFFERS];
+ struct page *pages[PIPE_BUFFERS];
+ int buflen, available_len;
+ int pg_nr = 0;
+ int i, nfrags;
+ void *address;
+ size_t ret = 0;
+ struct splice_pipe_desc spd = {
+ .pages = pages,
+ .partial = partial,
+ .flags = flags,
+ .ops = &sock_buf_ops,
+ };
+
+ buflen = skb_headlen(skb);
+
+ if ((available_len = buflen - offset) >0) {
+ if (available_len > len)
+ available_len = len;
+
+ page = alloc_page(GFP_KERNEL);
+ if (!page)
+ return -ENOMEM;
+
+ address = kmap(page);
+ memcpy(address, skb->data + offset, available_len);
+ /* Push page into splice pipe desc. */
+ spd.pages[pg_nr] = page;
+ pg_nr++;
+ kunmap(page);
+
+ /* If entire length has been consumed or number of pages pushed into
+ * splice pipe desc(pipe buffer) equals 16, then call splice_to_pipe.
+ */
+ if (((len -= available_len) == 0) || pg_nr == PIPE_BUFFERS) {
+ spd.nr_pages = pg_nr;
+ offset += available_len;
+ ret = splice_to_pipe(pipe, &spd);
+ if (ret == -EPIPE)
+ return -EPIPE;
+ else if (ret == -EAGAIN)
+ return -EAGAIN;
+ else if (ret == -ERESTARTSYS)
+ return -ERESTARTSYS;
+ else goto frags;
+ }
+ }
+ frags:
+ if (skb_shinfo(skb)->nr_frags != 0) {
+ nfrags = skb_shinfo(skb)->nr_frags;
+
+ for (i = 0; i < nfrags; i++) {
+ int total;
+ skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
+ get_page(skb_shinfo(skb)->frags[i].page);
+
+ total = buflen + skb_shinfo(skb)->frags[i].size;
+
+ if ((available_len = total - offset) > 0) {
+
+ if (available_len > len)
+ available_len = len;
+
+ spd.pages[pg_nr] = frag->page;
+ spd.partial[pg_nr].offset = frag->page_offset;
+ spd.partial[pg_nr].len = frag->size;
+ pg_nr++;
+
+ if (((len -= available_len) == 0) || pg_nr == PIPE_BUFFERS) {
+ spd.nr_pages = pg_nr;
+ ret = splice_to_pipe(pipe, &spd);
+ goto out;
+ }
+
+ offset += available_len;
+ }
+ buflen = total;
+ }
+ spd.nr_pages = pg_nr;
+ ret = splice_to_pipe(pipe, &spd);
+ }
+ out:
+ if (ret == -EPIPE)
+ return -EPIPE;
+ if (ret == -EAGAIN)
+ return -EAGAIN;
+ if (ret == -ERESTARTSYS)
+ return -ERESTARTSYS;
+
+ if (skb_shinfo(skb)->frag_list) {
+ struct sk_buff *list = skb_shinfo(skb)->frag_list;
+
+ for(; list; list = list->next) {
+ int total, more;
+
+ total = buflen + list->len;
+ if ((available_len = total - offset) > 0) {
+
+ if (available_len > len)
+ available_len = len;
+
+ more = skb_splice_bits(list, offset - buflen, pipe, available_len, flags);
+ if (more >= 0)
+ ret += more;
+ else
+ return -EFAULT;
+
+ if ((len -= available_len) == 0)
+ return ret;
+
+ offset += available_len;
+ }
+ buflen = total;
+ }
+ }
+ return ret;
+}
+
/**
* skb_store_bits - store bits from kernel buffer to skb
* @skb: destination buffer
-
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