rpc: define xdr_restrict_buflen
With this xdr_reserve_space can help us enforce various limits.
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c
index 2b546e8..3992844 100644
--- a/net/sunrpc/xdr.c
+++ b/net/sunrpc/xdr.c
@@ -649,6 +649,35 @@
EXPORT_SYMBOL(xdr_truncate_encode);
/**
+ * xdr_restrict_buflen - decrease available buffer space
+ * @xdr: pointer to xdr_stream
+ * @newbuflen: new maximum number of bytes available
+ *
+ * Adjust our idea of how much space is available in the buffer.
+ * If we've already used too much space in the buffer, returns -1.
+ * If the available space is already smaller than newbuflen, returns 0
+ * and does nothing. Otherwise, adjusts xdr->buf->buflen to newbuflen
+ * and ensures xdr->end is set at most offset newbuflen from the start
+ * of the buffer.
+ */
+int xdr_restrict_buflen(struct xdr_stream *xdr, int newbuflen)
+{
+ struct xdr_buf *buf = xdr->buf;
+ int left_in_this_buf = (void *)xdr->end - (void *)xdr->p;
+ int end_offset = buf->len + left_in_this_buf;
+
+ if (newbuflen < 0 || newbuflen < buf->len)
+ return -1;
+ if (newbuflen > buf->buflen)
+ return 0;
+ if (newbuflen < end_offset)
+ xdr->end = (void *)xdr->end + newbuflen - end_offset;
+ buf->buflen = newbuflen;
+ return 0;
+}
+EXPORT_SYMBOL(xdr_restrict_buflen);
+
+/**
* xdr_write_pages - Insert a list of pages into an XDR buffer for sending
* @xdr: pointer to xdr_stream
* @pages: list of pages
