datapath: Fix warning building datapath on pre-2.6.24 kernels.

The Linux 'min' macro checks that its arguments have the same type, and
if not the compiler reports a message about incompatible pointer types.
On pre-2.6.24 kernels skb_headroom() returns int, so this code was
firing a warning:
       unsigned headroom = max(min_headroom, skb_headroom(skb));

This commit makes skb_headroom() return an unsigned int regardless of
kernel version.

diff --git a/datapath/linux-2.6/compat-2.6/include/linux/skbuff.h b/datapath/linux-2.6/compat-2.6/include/linux/skbuff.h
index 2831721..dd9bfa3 100644 (file)
--- a/datapath/linux-2.6/compat-2.6/include/linux/skbuff.h
+++ b/datapath/linux-2.6/compat-2.6/include/linux/skbuff.h
@@ -5,6 +5,17 @@
 
 #include <linux/version.h>
 
+#if LINUX_VERSION_CODE < KERNEL_VERSION(2,6,24)
+/* In version 2.6.24 the return type of skb_headroom() changed from 'int' to
+ * 'unsigned int'.  We use skb_headroom() as one arm of a min(a,b) invocation
+ * in make_writable() in actions.c, so we need the correct type. */
+#define skb_headroom rpl_skb_headroom
+static inline unsigned int rpl_skb_headroom(const struct sk_buff *skb)
+{
+       return skb->data - skb->head;
+}
+#endif
+
 #ifndef HAVE_SKB_COPY_FROM_LINEAR_DATA_OFFSET
 static inline void skb_copy_from_linear_data_offset(const struct sk_buff *skb,
                                                     const int offset, void *to,