[TCP]: Update comment about highest_sack validity

This stale info came from the original idea, which proved to be
unnecessarily complex, sacked_out > 0 is easy to do and that when
it's going to be needed anyway (it _can_ be valid also when
sacked_out == 0 but there's not going to be a guarantee about it
for now).

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

1 files changed, 2 insertions, 1 deletions

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 1f12fa0b67d7..f8cf090e8f49 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -332,7 +332,8 @@ struct tcp_sock {
 
         struct tcp_sack_block_wire recv_sack_cache[4];
 
-        u32     highest_sack;   /* Start seq of globally highest revd SACK (valid only in slowpath) */
+        u32     highest_sack;   /* Start seq of globally highest revd SACK
+                                 * (validity guaranteed only if sacked_out > 0) */
 
         /* from STCP, retrans queue hinting */
         struct sk_buff* lost_skb_hint;