[PATCH] rmnet: Handle toolchains with old kernel headers

The RMNET_FLAGS_*GRESS_MAP_CKSUMV5 defines were added to the kernel in
5.14[1] and some toolchains use older headers, so add fallback defines
in case they are needed.

[1] linux b6e5d27e32ef6089d316ce7e1ecaf595584d4b84
---
 src/rmnet.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/src/rmnet.c b/src/rmnet.c
index 42b03249..9a7f52fb 100644
--- a/src/rmnet.c
+++ b/src/rmnet.c
@@ -27,6 +27,16 @@
 #define MAX_MUX_IDS 254U
 #define DEFAULT_MTU 1400U
 
+/*
+ * These were added in 5.14 so define them here if the toolchain's kernel headers are old.
+ */
+#ifndef RMNET_FLAGS_INGRESS_MAP_CKSUMV5
+#define RMNET_FLAGS_INGRESS_MAP_CKSUMV5 (1U << 4)
+#endif
+#ifndef RMNET_FLAGS_EGRESS_MAP_CKSUMV5
+#define RMNET_FLAGS_EGRESS_MAP_CKSUMV5 (1U << 5)
+#endif
+
 struct rmnet_request {
 	uint32_t parent_ifindex;
 	rmnet_new_interfaces_func_t new_cb;
-- 
2.43.0