svn commit: r343401 - head/sys/netinet

[Michael Tuexen]

Author: tuexen
Date: Thu Jan 24 16:40:14 2019
New Revision: 343401
URL: https://svnweb.freebsd.org/changeset/base/343401

Log:
  Update a comment to reflect the current reality.
  
  SYN-cache entries live for abaut 12 seconds, not 45, when default
  setting are used.
  
  MFC after:		1 week
  Sponsored by:		Netflix, Inc.

Modified:
  head/sys/netinet/tcp_syncache.c

Modified: head/sys/netinet/tcp_syncache.c
==============================================================================
--- head/sys/netinet/tcp_syncache.c	Thu Jan 24 14:33:15 2019	(r343400)
+++ head/sys/netinet/tcp_syncache.c	Thu Jan 24 16:40:14 2019	(r343401)
@@ -154,7 +154,12 @@ static int	 syncookie_cmp(struct in_conninfo *inc, str
 
 /*
  * Transmit the SYN,ACK fewer times than TCP_MAXRXTSHIFT specifies.
- * 3 retransmits corresponds to a timeout of 3 * (1 + 2 + 4 + 8) == 45 seconds,
+ * 3 retransmits corresponds to a timeout with default values of
+ * TCPTV_RTOBASE * (                 1 +
+ *                  tcp_syn_backoff[1] + 
+ *                  tcp_syn_backoff[2] +
+ *                  tcp_syn_backoff[3]) + 3 * tcp_rexmit_slop,
+ * 3000 ms * (1 + 1 + 1 + 1) +  3 * 200 ms = 12300 ms,
  * the odds are that the user has given up attempting to connect by then.
  */
 #define SYNCACHE_MAXREXMTS		3