[DCCP]: Introduces follows48 function

This adds a new function to see if two sequence numbers follow each
other.

Signed off by: Ian McDonald <ian.mcdonald@jandi.co.nz>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 8 insertions, 0 deletions

diff --git a/net/dccp/dccp.h b/net/dccp/dccp.h
index b8931d33bec3..a5c5475724c0 100644
--- a/net/dccp/dccp.h
+++ b/net/dccp/dccp.h
@@ -81,6 +81,14 @@ static inline u64 max48(const u64 seq1, const u64 seq2)
         return after48(seq1, seq2) ? seq1 : seq2;
 }
 
+/* is seq1 next seqno after seq2 */
+static inline int follows48(const u64 seq1, const u64 seq2)
+{
+        int diff = (seq1 & 0xFFFF) - (seq2 & 0xFFFF);
+
+        return diff==1;
+}
+
 enum {
         DCCP_MIB_NUM = 0,
         DCCP_MIB_ACTIVEOPENS,                   /* ActiveOpens */