2.6.12-rc5-mm2: "bic unavailable using TCP reno" messages

2.6.12-rc5-mm2: "bic unavailable using TCP reno" messages

[Adrian Bunk]

On Wed, Jun 01, 2005 at 02:28:24AM -0700, Andrew Morton wrote:
>...
> Changes since 2.6.12-rc5-mm1:
>...
> +tcp-tcp_infra.patch
>...
>  Steve Hemminger's TCP enhancements.
>...

I said "no" to CONFIG_TCP_CONG_BIC, and now my syslog is full of messages
   kernel: bic unavailable using TCP reno

I have no problem with such a message being shown once - but once should 
be enough.  

cu
Adrian

-- 

       "Is there not promise of rain?" Ling Tan asked suddenly out
        of the darkness. There had been need of rain for many days.
       "Only a promise," Lao Er said.
                                       Pearl S. Buck - Dragon Seed

Re: 2.6.12-rc5-mm2: "bic unavailable using TCP reno" messages

[Baruch Even]

Adrian Bunk wrote:
> On Wed, Jun 01, 2005 at 02:28:24AM -0700, Andrew Morton wrote:
> 
>>...
>>Changes since 2.6.12-rc5-mm1:
>>...
>>+tcp-tcp_infra.patch
>>...
>> Steve Hemminger's TCP enhancements.
>>...
> 
> 
> I said "no" to CONFIG_TCP_CONG_BIC, and now my syslog is full of messages
>    kernel: bic unavailable using TCP reno
> 
> I have no problem with such a message being shown once - but once should 
> be enough.  

The best solution for this would be to check the available protocols at
setup time and not at connection creation time. This would also provide
a better feedback to the user, since he will either see that what he set
was taken, or it wasn't.

In the current mechanism you can set the protocol to 'foo' and it will
show back as 'foo'. You'll get complaints only once a connection is
attempted with this protocol.

It does mean some extra work in the sysctl stage, but it's better IMO to
do it there rather than at connection setup time.

Baruch

Re: 2.6.12-rc5-mm2: "bic unavailable using TCP reno" messages

[Stephen Hemminger]

On Thu, 02 Jun 2005 14:58:17 +0100
Baruch Even <baruch@ev-en.org> wrote:

> Adrian Bunk wrote:
> > On Wed, Jun 01, 2005 at 02:28:24AM -0700, Andrew Morton wrote:
> > 
> >>...
> >>Changes since 2.6.12-rc5-mm1:
> >>...
> >>+tcp-tcp_infra.patch
> >>...
> >> Steve Hemminger's TCP enhancements.
> >>...
> > 
> > 
> > I said "no" to CONFIG_TCP_CONG_BIC, and now my syslog is full of messages
> >    kernel: bic unavailable using TCP reno
> > 
> > I have no problem with such a message being shown once - but once should 
> > be enough.  
> 
> The best solution for this would be to check the available protocols at
> setup time and not at connection creation time. This would also provide
> a better feedback to the user, since he will either see that what he set
> was taken, or it wasn't.
> 
> In the current mechanism you can set the protocol to 'foo' and it will
> show back as 'foo'. You'll get complaints only once a connection is
> attempted with this protocol.
> 
> It does mean some extra work in the sysctl stage, but it's better IMO to
> do it there rather than at connection setup time.
> 
> Baruch

Your right, the sysctl handler should be smarter, but that is not the problem here.
The problem is that the default value is set to be BIC to be compatible with earlier kernels.
Since 75% of the world isn't smart enough to figure out how to use sysctl, there is a
question of what the default should be, and what to do if that is missing.

One version had a messy ifdef chain to try and avoid the warning:

char sysctl_tcp_congestion_control[] = 
#if defined(CONFIG_TCP_BIC)
	"bic"
#elif defined(CONFIG_TCP_HTCP)
	"htcp"
#else
	"reno"
#endif
	;

but that was ugly.

Another possibility is putting it in as yet another config value at kernel build time.

To suppress the warning repeating, probably the best solution would be rewrite the string
if we have to revert to reno. But carefully to avoid SMP issues.  This also implies a smarter
sysctl string handler for this value as well.

P.s: saw your comparison paper, after a little more corroboration I would like to make
H-TCP the default.

Re: 2.6.12-rc5-mm2: "bic unavailable using TCP reno" messages

[Adrian Bunk]

On Thu, Jun 02, 2005 at 10:38:05AM -0700, Stephen Hemminger wrote:
> On Thu, 02 Jun 2005 14:58:17 +0100
> Baruch Even <baruch@ev-en.org> wrote:
> 
> >...
> 
> Your right, the sysctl handler should be smarter, but that is not the problem here.
> The problem is that the default value is set to be BIC to be compatible with earlier kernels.
> Since 75% of the world isn't smart enough to figure out how to use sysctl, there is a
> question of what the default should be, and what to do if that is missing.
> 
> One version had a messy ifdef chain to try and avoid the warning:
> 
> char sysctl_tcp_congestion_control[] = 
> #if defined(CONFIG_TCP_BIC)
> 	"bic"
> #elif defined(CONFIG_TCP_HTCP)
> 	"htcp"
> #else
> 	"reno"
> #endif
> 	;
> 
> but that was ugly.
> 
> Another possibility is putting it in as yet another config value at kernel build time.
>...


One thing that currently makes all solutions harder (and the #ifdef 
example above not ugly but simply wrong) is that you allow modular 
congestion control options for the always static net support.

Is this really required?


The IO schedulers have a similar problem, and they are using the #ifdef 
approach for selecting the default.


One approach is to actually choose the default using #ifdef's.

You could also do any kind of runtime selection, but please don't print 
the warning more than once.


cu
Adrian

-- 

       "Is there not promise of rain?" Ling Tan asked suddenly out
        of the darkness. There had been need of rain for many days.
       "Only a promise," Lao Er said.
                                       Pearl S. Buck - Dragon Seed

Re: 2.6.12-rc5-mm2: "bic unavailable using TCP reno" messages

[Stephen Hemminger]

Here is what I am working on as better way to make the sysctl selection.
I am not totally happy with the way the default congestion control value is determined
by the load order. But it does seem good that if you load "tcp_xxx" module and it
registers it becomes the default.

Index: 2.6.12-rc5-tcp3/include/net/tcp.h
===================================================================
--- 2.6.12-rc5-tcp3.orig/include/net/tcp.h
+++ 2.6.12-rc5-tcp3/include/net/tcp.h
@@ -1242,6 +1242,8 @@ extern int tcp_register_congestion_contr
 extern void tcp_unregister_congestion_control(struct tcp_congestion_ops *type);
 extern void tcp_init_congestion_control(struct tcp_sock *tp);
 extern void tcp_release_congestion_control(struct tcp_sock *tp);
+extern int tcp_set_congestion_control(const char *name);
+extern void tcp_get_congestion_control(char *name);
 
 extern struct tcp_congestion_ops tcp_reno;
 extern u32 tcp_reno_ssthresh(struct tcp_sock *tp);
Index: 2.6.12-rc5-tcp3/net/ipv4/tcp_cong.c
===================================================================
--- 2.6.12-rc5-tcp3.orig/net/ipv4/tcp_cong.c
+++ 2.6.12-rc5-tcp3/net/ipv4/tcp_cong.c
@@ -13,8 +13,6 @@
 #include <linux/list.h>
 #include <net/tcp.h>
 
-char sysctl_tcp_congestion_control[TCP_CA_NAME_MAX] = "bic";
-
 static DEFINE_SPINLOCK(tcp_cong_list_lock);
 static LIST_HEAD(tcp_cong_list);
 
@@ -23,7 +21,7 @@ static struct tcp_congestion_ops *tcp_ca
 {
 	struct tcp_congestion_ops *e;
 
-	list_for_each_entry_rcu(e, &tcp_cong_list, list) {
+	list_for_each_entry(e, &tcp_cong_list, list) {
 		if (strcmp(e->name, name) == 0) 
 			return e;
 	}
@@ -46,7 +44,7 @@ int tcp_register_congestion_control(stru
 		return -EINVAL;
 	}
 
-	spin_lock_irq(&tcp_cong_list_lock);
+	spin_lock(&tcp_cong_list_lock);
 	if (tcp_ca_find(ca->name)) {
 		printk(KERN_NOTICE "TCP %s already registered\n", ca->name);
 		ret = -EEXIST;
@@ -54,7 +52,7 @@ int tcp_register_congestion_control(stru
 		list_add_rcu(&ca->list, &tcp_cong_list);
 		printk(KERN_INFO "TCP %s registered\n", ca->name);
 	}
-	spin_unlock_irq(&tcp_cong_list_lock);
+	spin_unlock(&tcp_cong_list_lock);
 	
 	return ret;
 }
@@ -69,7 +67,6 @@ EXPORT_SYMBOL_GPL(tcp_register_congestio
 void tcp_unregister_congestion_control(struct tcp_congestion_ops *ca)
 {
 	spin_lock(&tcp_cong_list_lock);
-	BUG_ON(!tcp_ca_find(ca->name));
 	list_del_rcu(&ca->list);
 	spin_unlock(&tcp_cong_list_lock);
 }
@@ -78,34 +75,22 @@ EXPORT_SYMBOL_GPL(tcp_unregister_congest
 /* Assign choice of congestion control. */
 void tcp_init_congestion_control(struct tcp_sock *tp)
 {
-	const char *cong_proto = sysctl_tcp_congestion_control;
 	struct tcp_congestion_ops *ca;
 
 	rcu_read_lock();
-	ca = tcp_ca_find(cong_proto);
-#ifdef CONFIG_KMOD
-	if (!ca) {
-		/* autoload and try again */
-		rcu_read_unlock();
-		request_module("tcp_%s",  cong_proto);
-		rcu_read_lock();
-
-		ca = tcp_ca_find(cong_proto);
-	}
-#endif
-
-	/* If selection doesn't exist or is being removed use Reno */
-	if (!ca || !try_module_get(ca->owner)) {
-		if (net_ratelimit())
-			printk(KERN_WARNING "%s unavailable using TCP reno\n",
-			       cong_proto);
-		ca = &tcp_reno;
-	} 
-	tp->ca_ops = ca;
-	rcu_read_unlock();
+	tp->ca_ops = NULL;
+	list_for_each_entry_rcu(ca, &tcp_cong_list, list) {
+		if (try_module_get(ca->owner)) {
+			tp->ca_ops = ca;
+			break;
+		}
 
-	if (ca->init)
-		ca->init(tp);
+	}
+
+	/* We will always have reno to fallback on. */
+	if (tp->ca_ops->init)
+		tp->ca_ops->init(tp);
+	rcu_read_unlock();
 }
 EXPORT_SYMBOL(tcp_init_congestion_control);
 
@@ -122,6 +107,36 @@ void tcp_release_congestion_control(stru
 	}
 }
 
+/* Used by sysctl to change default congestion control */
+int tcp_set_congestion_control(const char *name)
+{
+	struct tcp_congestion_ops *ca;
+	int ret = -ENOENT;
+
+	spin_lock(&tcp_cong_list_lock);
+	ca = tcp_ca_find(name);
+	if (ca) {
+		list_move(&ca->list, &tcp_cong_list);
+		ret = 0;
+	}
+	spin_unlock(&tcp_cong_list_lock);
+
+	return ret;
+}
+
+/* Get current default congestion control */
+void tcp_get_congestion_control(char *name)
+{
+	struct tcp_congestion_ops *ca;
+	/* We will always have reno... */
+	BUG_ON(list_empty(&tcp_cong_list));
+
+	rcu_read_lock();
+	ca = list_entry(tcp_cong_list.next, struct tcp_congestion_ops, list);
+	strncpy(name, ca->name, TCP_CA_NAME_MAX);
+	rcu_read_lock();
+}
+
 /*
  * TCP Reno congestion control
  * This is special case used for fallback as well.
Index: 2.6.12-rc5-tcp3/net/ipv4/sysctl_net_ipv4.c
===================================================================
--- 2.6.12-rc5-tcp3.orig/net/ipv4/sysctl_net_ipv4.c
+++ 2.6.12-rc5-tcp3/net/ipv4/sysctl_net_ipv4.c
@@ -48,9 +48,6 @@ extern int inet_peer_maxttl;
 extern int inet_peer_gc_mintime;
 extern int inet_peer_gc_maxtime;
 
-/* From tcp_input.c */
-extern char sysctl_tcp_congestion_control[TCP_CA_NAME_MAX];
-
 #ifdef CONFIG_SYSCTL
 static int tcp_retr1_max = 255; 
 static int ip_local_port_range_min[] = { 1, 1 };
@@ -120,6 +117,52 @@ static int ipv4_sysctl_forward_strategy(
 	return 1;
 }
 
+static int proc_tcp_congestion_control(ctl_table *ctl, int write, struct file * filp,
+				       void __user *buffer, size_t *lenp, loff_t *ppos)
+{
+	char val[TCP_CA_NAME_MAX];
+	ctl_table tbl = {
+		.data = val,
+		.maxlen = TCP_CA_NAME_MAX,
+	};
+	int ret;
+
+	tcp_get_congestion_control(val);
+	
+	ret = proc_dostring(&tbl, write, filp, buffer, lenp, ppos);
+	if (write && ret == 0) {
+		ret = tcp_set_congestion_control(val);
+#ifdef CONFIG_KMOD
+		if (ret == -ENOENT) {
+			request_module("tcp_%s", val);
+			ret = tcp_set_congestion_control(val);
+		}
+#endif
+	}
+	return ret;
+}
+
+int sysctl_tcp_congestion_control(ctl_table *table, int __user *name, int nlen,
+				  void __user *oldval, size_t __user *oldlenp,
+				  void __user *newval, size_t newlen, 
+				  void **context)
+{
+	char val[TCP_CA_NAME_MAX];
+	ctl_table tbl = {
+		.data = val,
+		.maxlen = TCP_CA_NAME_MAX,
+	};
+	int ret;
+
+	tcp_get_congestion_control(val);
+	ret = sysctl_string(&tbl, name, nlen, oldval, oldlenp, newval, newlen,
+			    context);
+	if (ret == 0 && newval && newlen)
+		ret = tcp_set_congestion_control(val);
+	return ret;
+}
+
+
 ctl_table ipv4_table[] = {
         {
 		.ctl_name	= NET_IPV4_TCP_TIMESTAMPS,
@@ -624,11 +667,10 @@ ctl_table ipv4_table[] = {
 	{
 		.ctl_name	= NET_TCP_CONG_CONTROL,
 		.procname	= "tcp_congestion_control",
-		.data		= &sysctl_tcp_congestion_control,
-		.maxlen		= TCP_CA_NAME_MAX,
 		.mode		= 0644,
-		.proc_handler	= &proc_dostring,
-		.strategy	= &sysctl_string,
+		.maxlen		= TCP_CA_NAME_MAX,
+		.proc_handler	= &proc_tcp_congestion_control,
+		.strategy	= &sysctl_tcp_congestion_control,
 	},
 
 	{ .ctl_name = 0 }

Re: 2.6.12-rc5-mm2: "bic unavailable using TCP reno" messages

[Baruch Even]

Stephen Hemminger wrote:
> Here is what I am working on as better way to make the sysctl selection.
> I am not totally happy with the way the default congestion control value is determined
> by the load order. But it does seem good that if you load "tcp_xxx" module and it
> registers it becomes the default.

Looks good.

> @@ -120,6 +117,52 @@ static int ipv4_sysctl_forward_strategy(
>  	return 1;
>  }
>  
> +static int proc_tcp_congestion_control(ctl_table *ctl, int write, struct file * filp,
> +				       void __user *buffer, size_t *lenp, loff_t *ppos)
> +{
> +	char val[TCP_CA_NAME_MAX];
> +	ctl_table tbl = {
> +		.data = val,
> +		.maxlen = TCP_CA_NAME_MAX,
> +	};
> +	int ret;
> +
> +	tcp_get_congestion_control(val);

Maybe we should call this tcp_get_current_congestion_control(), the
current name implies (to me) that you give it a name and it returns the
the ca struct. get_current might also just return the current one and
the strcpy can be done here.

Otherwise you probably should document the tcp_get_congestion_control()
to say what size of string it accepts.

Baruch

[-mm patch] fix recursive IPW2200 dependencies

[Adrian Bunk]

On Wed, Jun 01, 2005 at 02:28:24AM -0700, Andrew Morton wrote:
>...
> Changes since 2.6.12-rc5-mm1:
>...
> +git-netdev-we18-ieee80211-wifi.patch
> 
>  Various things added and merged in netdev land.
>...

This results in recursive dependencies:
- IPW2200 depends on NET_RADIO
- IPW2200 selects IEEE80211
- IEEE80211 selects NET_RADIO


This patch fixes the IPW2200 dependencies in a way that they are similar 
to the IPW2100 dependencies.

Signed-off-by: Adrian Bunk <bunk@stusta.de>

--- linux-2.6.12-rc5-mm2-full/drivers/net/wireless/Kconfig.old	2005-06-02 22:04:02.000000000 +0200
+++ linux-2.6.12-rc5-mm2-full/drivers/net/wireless/Kconfig	2005-06-02 22:04:40.000000000 +0200
@@ -192,9 +192,8 @@
 
 config IPW2200
 	tristate "Intel PRO/Wireless 2200BG and 2915ABG Network Connection"
-	depends on NET_RADIO && PCI
+	depends on IEEE80211 && PCI
 	select FW_LOADER
-	select IEEE80211
 	---help---
           A driver for the Intel PRO/Wireless 2200BG and 2915ABG Network
 	  Connection adapters. 

RE: [-mm patch] fix recursive IPW2200 dependencies

[Alejandro Bonilla]

> On Wed, Jun 01, 2005 at 02:28:24AM -0700, Andrew Morton wrote:
> >...
> > Changes since 2.6.12-rc5-mm1:
> >...
> > +git-netdev-we18-ieee80211-wifi.patch
> >
> >  Various things added and merged in netdev land.
> >...
>
> This results in recursive dependencies:
> - IPW2200 depends on NET_RADIO
> - IPW2200 selects IEEE80211
> - IEEE80211 selects NET_RADIO
>
>
> This patch fixes the IPW2200 dependencies in a way that they
> are similar
> to the IPW2100 dependencies.
>
> Signed-off-by: Adrian Bunk <bunk@stusta.de>
>
> ---
> linux-2.6.12-rc5-mm2-full/drivers/net/wireless/Kconfig.old
> 2005-06-02 22:04:02.000000000 +0200
> +++ linux-2.6.12-rc5-mm2-full/drivers/net/wireless/Kconfig
> 2005-06-02 22:04:40.000000000 +0200
> @@ -192,9 +192,8 @@
>
>  config IPW2200
>  	tristate "Intel PRO/Wireless 2200BG and 2915ABG Network
> Connection"
> -	depends on NET_RADIO && PCI
> +	depends on IEEE80211 && PCI
>  	select FW_LOADER
> -	select IEEE80211
>  	---help---
>            A driver for the Intel PRO/Wireless 2200BG and
> 2915ABG Network
>  	  Connection adapters.

I think the normal usage of the name is Intel PRO/Wireless 2200BG/2915ABG
Network Connection. I'm just saying this in case that you care about Intel
Trademarking or about a more unified usage of the name of the Adapter.

maybe this is something silly.

.Alejandro