[TCP]: Congestion control API RTT sampling fix

Commit 164891aadf1721fca4dce473bb0e0998181537c6 broke RTT
sampling of congestion control modules. Inaccurate timestamps
could be fed to them without providing any way for them to
identify such cases. Previously RTT sampler was called only if
FLAG_RETRANS_DATA_ACKED was not set filtering inaccurate
timestamps nicely. In addition, the new behavior could give an
invalid timestamp (zero) to RTT sampler if only skbs with
TCPCB_RETRANS were ACKed. This solves both problems.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 4 insertions, 0 deletions

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index e7367c74e1bb..6f0b2f7d0010 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1579,6 +1579,10 @@ static inline ktime_t net_timedelta(ktime_t t)
         return ktime_sub(ktime_get_real(), t);
 }
 
+static inline ktime_t net_invalid_timestamp(void)
+{
+        return ktime_set(0, 0);
+}
 
 extern __sum16 __skb_checksum_complete_head(struct sk_buff *skb, int len);
 extern __sum16 __skb_checksum_complete(struct sk_buff *skb);