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>

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 5fd3891..af2b21b 100644 (file)
--- 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 (file)
--- 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 (file)
--- 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 (file)
--- 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);