[PATCH] uapi: Prevent redefinition of struct iphdr

["A. Wilcox" <AWilcox@Wilcox-Tech.com>]

As with struct ethhdr, the musl libc provides its own definition of the
iphdr struct.  This guard ensures software like net-tools builds correctly
on the musl libc.

The __UAPI_DEF_IPHDR definition is in ip.h itself to prevent the issue in
commit da360299b673 ("uapi/if_ether.h: move __UAPI_DEF_ETHHDR libc define")
from being seen here.

Signed-off-by: A. Wilcox <AWilcox@Wilcox-Tech.com>
---
 include/uapi/linux/ip.h | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/include/uapi/linux/ip.h b/include/uapi/linux/ip.h
index e42d13b55cf3..d34a0d295672 100644
--- a/include/uapi/linux/ip.h
+++ b/include/uapi/linux/ip.h
@@ -83,6 +83,13 @@
 
 #define IPV4_BEET_PHMAXLEN 8
 
+/* Allow libcs to deactivate this - musl has its own copy in <netinet/ip.h> */
+
+#ifndef __UAPI_DEF_IPHDR
+#define __UAPI_DEF_IPHDR	1
+#endif
+
+#if __UAPI_DEF_IPHDR
 struct iphdr {
 #if defined(__LITTLE_ENDIAN_BITFIELD)
 	__u8	ihl:4,
@@ -104,6 +111,7 @@ struct iphdr {
 	__be32	daddr;
 	/*The options start here. */
 };
+#endif
 
 
 struct ip_auth_hdr {
-- 
2.22.1