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Date: Mon, 20 Apr 2009 14:25:46 +0300
From: "Michael S. Tsirkin" <mst@...hat.com>
To: "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
Herbert Xu <herbert@...dor.apana.org.au>,
Rusty Russell <rusty@...tcorp.com.au>
Subject: [PATCH 1/3] net: skb_copy_datagram_const_iovec()
There's an skb_copy_datagram_iovec() to copy out of a paged skb,
but it modifies the iovec, and does not support starting
at an offset in the destination. We want both in tun.c, so let's
add the function.
It's a carbon copy of skb_copy_datagram_iovec() with enough changes to
be annoying.
Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
---
include/linux/skbuff.h | 5 +++
include/linux/socket.h | 2 +
net/core/datagram.c | 92 ++++++++++++++++++++++++++++++++++++++++++++++++
net/core/iovec.c | 26 +++++++++++++
4 files changed, 125 insertions(+), 0 deletions(-)
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 5fd3891..af2b21b 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1717,6 +1717,11 @@ extern int skb_copy_datagram_from_iovec(struct sk_buff *skb,
int offset,
struct iovec *from,
int len);
+extern int skb_copy_datagram_const_iovec(const struct sk_buff *from,
+ int offset,
+ const struct iovec *to,
+ int to_offset,
+ int size);
extern void skb_free_datagram(struct sock *sk, struct sk_buff *skb);
extern int skb_kill_datagram(struct sock *sk, struct sk_buff *skb,
unsigned int flags);
diff --git a/include/linux/socket.h b/include/linux/socket.h
index 421afb4..171b08d 100644
--- a/include/linux/socket.h
+++ b/include/linux/socket.h
@@ -318,6 +318,8 @@ extern int csum_partial_copy_fromiovecend(unsigned char *kdata,
extern int verify_iovec(struct msghdr *m, struct iovec *iov, struct sockaddr *address, int mode);
extern int memcpy_toiovec(struct iovec *v, unsigned char *kdata, int len);
+extern int memcpy_toiovecend(const struct iovec *v, unsigned char *kdata,
+ int offset, int len);
extern int move_addr_to_user(struct sockaddr *kaddr, int klen, void __user *uaddr, int __user *ulen);
extern int move_addr_to_kernel(void __user *uaddr, int ulen, struct sockaddr *kaddr);
extern int put_cmsg(struct msghdr*, int level, int type, int len, void *data);
diff --git a/net/core/datagram.c b/net/core/datagram.c
index d0de644..4dbb05c 100644
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -339,6 +339,98 @@ fault:
}
/**
+ * skb_copy_datagram_const_iovec - Copy a datagram to an iovec.
+ * @skb: buffer to copy
+ * @offset: offset in the buffer to start copying from
+ * @to: io vector to copy to
+ * @to_offset: offset in the io vector to start copying to
+ * @len: amount of data to copy from buffer to iovec
+ *
+ * Returns 0 or -EFAULT.
+ * Note: the iovec is not modified during the copy.
+ */
+int skb_copy_datagram_const_iovec(const struct sk_buff *skb, int offset,
+ const struct iovec *to, int to_offset,
+ int len)
+{
+ int start = skb_headlen(skb);
+ int i, copy = start - offset;
+
+ /* Copy header. */
+ if (copy > 0) {
+ if (copy > len)
+ copy = len;
+ if (memcpy_toiovecend(to, skb->data + offset, to_offset, copy))
+ goto fault;
+ if ((len -= copy) == 0)
+ return 0;
+ offset += copy;
+ to_offset += copy;
+ }
+
+ /* Copy paged appendix. Hmm... why does this look so complicated? */
+ for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
+ int end;
+
+ WARN_ON(start > offset + len);
+
+ end = start + skb_shinfo(skb)->frags[i].size;
+ if ((copy = end - offset) > 0) {
+ int err;
+ u8 *vaddr;
+ skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
+ struct page *page = frag->page;
+
+ if (copy > len)
+ copy = len;
+ vaddr = kmap(page);
+ err = memcpy_toiovecend(to, vaddr + frag->page_offset +
+ offset - start, to_offset, copy);
+ kunmap(page);
+ if (err)
+ goto fault;
+ if (!(len -= copy))
+ return 0;
+ offset += copy;
+ to_offset += copy;
+ }
+ start = end;
+ }
+
+ if (skb_shinfo(skb)->frag_list) {
+ struct sk_buff *list = skb_shinfo(skb)->frag_list;
+
+ for (; list; list = list->next) {
+ int end;
+
+ WARN_ON(start > offset + len);
+
+ end = start + list->len;
+ if ((copy = end - offset) > 0) {
+ if (copy > len)
+ copy = len;
+ if (skb_copy_datagram_const_iovec(list,
+ offset - start,
+ to, to_offset,
+ copy))
+ goto fault;
+ if ((len -= copy) == 0)
+ return 0;
+ offset += copy;
+ to_offset += copy;
+ }
+ start = end;
+ }
+ }
+ if (!len)
+ return 0;
+
+fault:
+ return -EFAULT;
+}
+EXPORT_SYMBOL(skb_copy_datagram_const_iovec);
+
+/**
* skb_copy_datagram_from_iovec - Copy a datagram from an iovec.
* @skb: buffer to copy
* @offset: offset in the buffer to start copying to
diff --git a/net/core/iovec.c b/net/core/iovec.c
index 4c9c012..a215545 100644
--- a/net/core/iovec.c
+++ b/net/core/iovec.c
@@ -98,6 +98,31 @@ int memcpy_toiovec(struct iovec *iov, unsigned char *kdata, int len)
}
/*
+ * Copy kernel to iovec. Returns -EFAULT on error.
+ */
+
+int memcpy_toiovecend(const struct iovec *iov, unsigned char *kdata,
+ int offset, int len)
+{
+ int copy;
+ for (; len > 0; ++iov) {
+ /* Skip over the finished iovecs */
+ if (unlikely(offset >= iov->iov_len)) {
+ offset -= iov->iov_len;
+ continue;
+ }
+ copy = min_t(unsigned int, iov->iov_len - offset, len);
+ offset = 0;
+ if (copy_to_user(iov->iov_base, kdata, copy))
+ return -EFAULT;
+ kdata += copy;
+ len -= copy;
+ }
+
+ return 0;
+}
+
+/*
* Copy iovec to kernel. Returns -EFAULT on error.
*
* Note: this modifies the original iovec.
@@ -236,3 +261,4 @@ EXPORT_SYMBOL(csum_partial_copy_fromiovecend);
EXPORT_SYMBOL(memcpy_fromiovec);
EXPORT_SYMBOL(memcpy_fromiovecend);
EXPORT_SYMBOL(memcpy_toiovec);
+EXPORT_SYMBOL(memcpy_toiovecend);
--
1.6.0.6
--
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