tipc: simplify packet sequence number handling

Although the sequence number in the TIPC protocol is 16 bits, we have
until now stored it internally as an unsigned 32 bits integer.
We got around this by always doing explicit modulo-65535 operations
whenever we need to access a sequence number.

We now make the incoming and outgoing sequence numbers to unsigned
16-bit integers, and remove the modulo operations where applicable.

We also move the arithmetic inline functions for 16 bit integers
to core.h, and the function buf_seqno() to msg.h, so they can easily
be accessed from anywhere in the code.

Reviewed-by: Erik Hugne <erik.hugne@ericsson.com>
Reviewed-by: Ying Xue <ying.xue@windriver.com>
Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 20 insertions, 0 deletions

diff --git a/net/tipc/core.h b/net/tipc/core.h
index 53e8146b14e0..0fcf133d5cb7 100644
--- a/net/tipc/core.h
+++ b/net/tipc/core.h
@@ -109,6 +109,26 @@ struct tipc_net {
 	atomic_t subscription_count;
 };
 
+static inline u16 mod(u16 x)
+{
+	return x & 0xffffu;
+}
+
+static inline int less_eq(u16 left, u16 right)
+{
+	return mod(right - left) < 32768u;
+}
+
+static inline int more(u16 left, u16 right)
+{
+	return !less_eq(left, right);
+}
+
+static inline int less(u16 left, u16 right)
+{
+	return less_eq(left, right) && (mod(right) != mod(left));
+}
+
 #ifdef CONFIG_SYSCTL
 int tipc_register_sysctl(void);
 void tipc_unregister_sysctl(void);