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@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 7 insertions, 0 deletions

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 5fd389162f01..af2b21bdda83 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 421afb4d29b0..171b08db9c4f 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);