net: skb_copy_datagram_from_iovec()

There's an skb_copy_datagram_iovec() to copy out of a paged skb, but
nothing the other way around (because we don't do that).

We want to allocate big skbs 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: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 358661c..9099237 100644 (file)
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1452,6 +1452,10 @@ extern int              skb_copy_datagram_iovec(const struct sk_buff *from,
 extern int            skb_copy_and_csum_datagram_iovec(struct sk_buff *skb,
                                                        int hlen,
                                                        struct iovec *iov);
+extern int            skb_copy_datagram_from_iovec(struct sk_buff *skb,
+                                                   int offset,
+                                                   struct iovec *from,
+                                                   int len);
 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/net/core/datagram.c b/net/core/datagram.c
index dd61dca..52f577a 100644 (file)
--- a/net/core/datagram.c
+++ b/net/core/datagram.c
@@ -339,6 +339,93 @@ fault:
        return -EFAULT;
 }
 
+/**
+ *     skb_copy_datagram_from_iovec - Copy a datagram from an iovec.
+ *     @skb: buffer to copy
+ *     @offset: offset in the buffer to start copying to
+ *     @from: io vector to copy to
+ *     @len: amount of data to copy to buffer from iovec
+ *
+ *     Returns 0 or -EFAULT.
+ *     Note: the iovec is modified during the copy.
+ */
+int skb_copy_datagram_from_iovec(struct sk_buff *skb, int offset,
+                                struct iovec *from, int len)
+{
+       int start = skb_headlen(skb);
+       int i, copy = start - offset;
+
+       /* Copy header. */
+       if (copy > 0) {
+               if (copy > len)
+                       copy = len;
+               if (memcpy_fromiovec(skb->data + offset, from, copy))
+                       goto fault;
+               if ((len -= copy) == 0)
+                       return 0;
+               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_fromiovec(vaddr + frag->page_offset +
+                                              offset - start, from, copy);
+                       kunmap(page);
+                       if (err)
+                               goto fault;
+
+                       if (!(len -= copy))
+                               return 0;
+                       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_from_iovec(list,
+                                                                offset - start,
+                                                                from, copy))
+                                       goto fault;
+                               if ((len -= copy) == 0)
+                                       return 0;
+                               offset += copy;
+                       }
+                       start = end;
+               }
+       }
+       if (!len)
+               return 0;
+
+fault:
+       return -EFAULT;
+}
+EXPORT_SYMBOL(skb_copy_datagram_from_iovec);
+
 static int skb_copy_and_csum_datagram(const struct sk_buff *skb, int offset,
                                      u8 __user *to, int len,
                                      __wsum *csump)