Hi, Stephen.

Thank you for your comments.  I will fix them and re-send the
patch for 2.6.22.

From: Stephen Hemminger <redacted>
Subject: Re: [PATCH 2.6.22-rc5] TCP: Make TCP_RTO_MAX a variable
Date: Mon, 25 Jun 2007 09:07:48 -0700

quoted

diff -uprN -X a/Documentation/dontdiff linux-2.6.22-rc5-orig/include/linux/sysctl.h b/include/linux/sysctl.h

--- a/include/linux/sysctl.h	2007-06-22 21:34:33.000000000 +0900
+++ b/include/linux/sysctl.h	2007-06-25 16:27:29.000000000 +0900

@@ -441,6 +441,7 @@ enum
 	NET_TCP_ALLOWED_CONG_CONTROL=123,
 	NET_TCP_MAX_SSTHRESH=124,
 	NET_TCP_FRTO_RESPONSE=125,
+	NET_TCP_RTO_MAX=126,
 };
 

Rather than assigning another numeric sysctl value, you can use
CTL_UNNUMBERED.  The use of numeric sysctl's is being phased down, at one
point they were even going to be deprecated.

Understood.

quoted

diff -uprN -X a/Documentation/dontdiff linux-2.6.22-rc5-orig/include/net/tcp.h b/include/net/tcp.h

--- a/include/net/tcp.h	2007-06-22 21:34:33.000000000 +0900
+++ b/include/net/tcp.h	2007-06-22 21:40:05.000000000 +0900

@@ -121,7 +121,9 @@ extern void tcp_time_wait(struct sock *s
 #define TCP_DELACK_MIN	4U
 #define TCP_ATO_MIN	4U
 #endif
-#define TCP_RTO_MAX	((unsigned)(120*HZ))
+extern int sysctl_tcp_rto_max;
+#define TCP_RTO_MAX	((unsigned)(sysctl_tcp_rto_max))
+#define TCP_RTO_MAX_DEFAULT	((unsigned)(120*HZ))
 #define TCP_RTO_MIN	((unsigned)(HZ/5))
 #define TCP_TIMEOUT_INIT ((unsigned)(3*HZ))	/* RFC 1122 initial RTO value	*/

Rather than causing macro TCP_RTO_MAX to reference sysctl_rto_max directly.

Okay.  I will replace all occurrence of TCP_RTO_MAX to
sysctl_tcp_rto_max.

quoted

@@ -203,6 +205,7 @@ extern int sysctl_tcp_synack_retries;
 extern int sysctl_tcp_retries1;
 extern int sysctl_tcp_retries2;
 extern int sysctl_tcp_orphan_retries;
+extern int sysctl_tcp_rto_max;
 extern int sysctl_tcp_syncookies;
 extern int sysctl_tcp_retrans_collapse;
 extern int sysctl_tcp_stdurg;

Could sysctl_rto_max be unsigned instead of int to avoid possible sign wrap issues and
having to cast it on each use?

Yes.  As sysctl_tcp_rto_max is going to replace TCP_RTO_MAX,
which is unsigned, making sysctl_tcp_rto_max unsigned seems
reasonable.

quoted

 ctl_table ipv4_table[] = {
 	{
 		.ctl_name	= NET_IPV4_TCP_TIMESTAMPS,

@@ -363,6 +431,15 @@ ctl_table ipv4_table[] = {
 		.proc_handler	= &proc_dointvec
 	},
 	{
+		.ctl_name	= NET_TCP_RTO_MAX,
+		.procname	= "tcp_rto_max",
+		.data		= &sysctl_tcp_rto_max,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= &proc_tcp_rto_max,
+		.strategy	= &strategy_tcp_rto_max
+	},
+	{

I will remove .strategy and strategy_tcp_rto_max from my patch
because I'm not going to support the numeric sysctl.

Regards,

-- 
OBATA Noboru (noboru.obata.ar@hitachi.com)