[PATCH v3 -mm 0/9] netconsole: Multiple targets and dynamic reconfigurability

[PATCH v3 -mm 0/9] netconsole: Multiple targets and dynamic reconfigurability

[Satyam Sharma]

[0/9] netconsole: Multiple targets and dynamic reconfigurability

This is v3 of the patchset, the previous versions are available at:
http://lkml.org/lkml/2007/7/4/107
http://lkml.org/lkml/2007/7/10/78

Diffed against 2.6.23-rc1-git6 (6c8dca5d as of writing), but applies
successfully to 2.6.23-rc1-mm1 as well.

Patches 1-5 are okay-to-apply to current mainline -git, I think.

Patches 6-9 introduce the new functionality and are requested for
inclusion in -mm.

[1/9] netconsole: Cleanups, codingstyle, prettyfication
[2/9] netconsole: Remove bogus check
[3/9] netconsole: Simplify boot/module option setup logic
[4/9] netconsole: Use netif_running() in write_msg()
[5/9] netconsole: Add some useful tips to documentation
[6/9] netconsole: Introduce netconsole_target
[7/9] netconsole: Introduce netconsole_netdev_notifier
[8/9] netconsole: Support multiple logging targets
[9/9] netconsole: Support dynamic reconfiguration using configfs

Changes since v2:
=================

* "enabled" must be defined outside #ifdef NETCONSOLE_DYNAMIC

* Some simple enhancements to documentation

* Drop the use of "unlikely" from a condition where I'd got the
  common case wrong

About this patchset:
====================

What?

Support multiple remote logging targets in netconsole. Also, ability to
dynamically add or remove targets or modify parameters (IP, port, remote
MAC address) of targets at runtime, from userspace, using configfs.

Why?

>From Keiichi Kii's original post:

[...] current netconsole is not flexible. For example, if you want to change
ip address for logging agent, in the case of built-in netconsole, you can't
change config except for changing boot parameter and rebooting your system,
or in the case of module netconsole, you need to remove it and reload
with different parameters. [...] and we have been losing serial console
port with PCs and Servers.

(... and especially laptops, I would add.)


Satyam

[PATCH v3 -mm 1/9] netconsole: Cleanups, codingstyle, prettyfication

[Satyam Sharma]

From: Satyam Sharma <satyam@infradead.org>

[1/9] netconsole: Cleanups, codingstyle, prettyfication

(1) Remove unwanted headers.
(2) Mark __init and __exit as appropriate.
(3) Various trivial codingstyle and prettification stuff.

Signed-off-by: Satyam Sharma <satyam@infradead.org>
Signed-off-by: Keiichi Kii <k-keiichi@bx.jp.nec.com>
Acked-by: Matt Mackall <mpm@selenic.com>

---

 drivers/net/netconsole.c |   55 ++++++++++++++++++++++-----------------------
 1 files changed, 27 insertions(+), 28 deletions(-)

diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index 69233f6..f1c2a2d 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -35,35 +35,32 @@
  ****************************************************************/
 
 #include <linux/mm.h>
-#include <linux/tty.h>
 #include <linux/init.h>
 #include <linux/module.h>
 #include <linux/console.h>
-#include <linux/tty_driver.h>
 #include <linux/moduleparam.h>
 #include <linux/string.h>
-#include <linux/sysrq.h>
-#include <linux/smp.h>
 #include <linux/netpoll.h>
 
 MODULE_AUTHOR("Maintainer: Matt Mackall <mpm@selenic.com>");
 MODULE_DESCRIPTION("Console driver for network interfaces");
 MODULE_LICENSE("GPL");
 
-static char config[256];
-module_param_string(netconsole, config, 256, 0);
+#define MAX_PARAM_LENGTH	256
+#define MAX_PRINT_CHUNK		1000
+
+static char config[MAX_PARAM_LENGTH];
+module_param_string(netconsole, config, MAX_PARAM_LENGTH, 0);
 MODULE_PARM_DESC(netconsole, " netconsole=[src-port]@[src-ip]/[dev],[tgt-port]@<tgt-ip>/[tgt-macaddr]\n");
 
 static struct netpoll np = {
-	.name = "netconsole",
-	.dev_name = "eth0",
-	.local_port = 6665,
-	.remote_port = 6666,
-	.remote_mac = {0xff, 0xff, 0xff, 0xff, 0xff, 0xff},
+	.name		= "netconsole",
+	.dev_name	= "eth0",
+	.local_port	= 6665,
+	.remote_port	= 6666,
+	.remote_mac	= {0xff, 0xff, 0xff, 0xff, 0xff, 0xff},
 };
-static int configured = 0;
-
-#define MAX_PRINT_CHUNK 1000
+static int configured;
 
 static void write_msg(struct console *con, const char *msg, unsigned int len)
 {
@@ -75,7 +72,7 @@ static void write_msg(struct console *con, const char *msg, unsigned int len)
 
 	local_irq_save(flags);
 
-	for(left = len; left; ) {
+	for (left = len; left;) {
 		frag = min(left, MAX_PRINT_CHUNK);
 		netpoll_send_udp(&np, msg, frag);
 		msg += frag;
@@ -86,12 +83,12 @@ static void write_msg(struct console *con, const char *msg, unsigned int len)
 }
 
 static struct console netconsole = {
-	.name = "netcon",
-	.flags = CON_ENABLED | CON_PRINTBUFFER,
-	.write = write_msg
+	.name	= "netcon",
+	.flags	= CON_ENABLED | CON_PRINTBUFFER,
+	.write	= write_msg,
 };
 
-static int option_setup(char *opt)
+static int __init option_setup(char *opt)
 {
 	configured = !netpoll_parse_options(&np, opt);
 	return 1;
@@ -99,28 +96,30 @@ static int option_setup(char *opt)
 
 __setup("netconsole=", option_setup);
 
-static int init_netconsole(void)
+static int __init init_netconsole(void)
 {
-	int err;
+	int err = 0;
 
-	if(strlen(config))
+	if (strnlen(config, MAX_PARAM_LENGTH))
 		option_setup(config);
 
-	if(!configured) {
-		printk("netconsole: not configured, aborting\n");
-		return 0;
+	if (!configured) {
+		printk(KERN_INFO "netconsole: not configured, aborting\n");
+		goto out;
 	}
 
 	err = netpoll_setup(&np);
 	if (err)
-		return err;
+		goto out;
 
 	register_console(&netconsole);
 	printk(KERN_INFO "netconsole: network logging started\n");
-	return 0;
+
+out:
+	return err;
 }
 
-static void cleanup_netconsole(void)
+static void __exit cleanup_netconsole(void)
 {
 	unregister_console(&netconsole);
 	netpoll_cleanup(&np);

[PATCH v3 -mm 2/9] netconsole: Remove bogus check

[Satyam Sharma]

From: Satyam Sharma <satyam@infradead.org>

[2/9] netconsole: Remove bogus check

The (!np.dev) check in write_msg() is bogus (always false), because:
np.dev is set by netpoll_setup(), which is called by init_netconsole()
before register_console(), so write_msg() cannot be triggered unless
netpoll_setup() successfully set np.dev. Also np.dev cannot go away
from under us, because netpoll_setup() grabs us reference on it. So
let's remove the bogus check.

Signed-off-by: Satyam Sharma <satyam@infradead.org>
Acked-by: Keiichi Kii <k-keiichi@bx.jp.nec.com>
Acked-by: Matt Mackall <mpm@selenic.com>

---

 drivers/net/netconsole.c |    3 ---
 1 files changed, 0 insertions(+), 3 deletions(-)

diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index f1c2a2d..2c2aef1 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -67,9 +67,6 @@ static void write_msg(struct console *con, const char *msg, unsigned int len)
 	int frag, left;
 	unsigned long flags;
 
-	if (!np.dev)
-		return;
-
 	local_irq_save(flags);
 
 	for (left = len; left;) {

[PATCH v3 -mm 3/9] netconsole: Simplify boot/module option setup logic

[Satyam Sharma]

From: Satyam Sharma <satyam@infradead.org>

[3/9] netconsole: Simplify boot/module option setup logic

Presently, boot/module parameters are set up quite differently for the
case of built-in netconsole (__setup() -> obsolete_checksetup() ->
netpoll_parse_options() -> strlen(config) == 0 in init_netconsole())
vs modular netconsole (module_param_string() -> string copied to the
config variable -> strlen(config) != 0 init_netconsole() ->
netpoll_parse_options()).

This patch makes both of them similar by doing exactly the equivalent
of a module_param_string() in option_setup() also -- just copying the
param string passed from the kernel command line into "config" variable.
So, strlen(config) != 0 in both cases, and netpoll_parse_options() is
always called from init_netconsole(), thus making the setup logic for
both cases similar.

Now, option_setup() is only ever called / used for the built-in case,
so we put it inside a #ifndef MODULE, otherwise gcc will complain about
option_setup() being "defined but not used". Also, the "configured"
variable is redundant with this patch and hence removed.

Signed-off-by: Satyam Sharma <satyam@infradead.org>
Signed-off-by: Keiichi Kii <k-keiichi@bx.jp.nec.com>
Acked-by: Matt Mackall <mpm@selenic.com>

---

 drivers/net/netconsole.c |   27 ++++++++++++++-------------
 1 files changed, 14 insertions(+), 13 deletions(-)

diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index 2c2aef1..e56aa6c 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -53,6 +53,15 @@ static char config[MAX_PARAM_LENGTH];
 module_param_string(netconsole, config, MAX_PARAM_LENGTH, 0);
 MODULE_PARM_DESC(netconsole, " netconsole=[src-port]@[src-ip]/[dev],[tgt-port]@<tgt-ip>/[tgt-macaddr]\n");
 
+#ifndef	MODULE
+static int __init option_setup(char *opt)
+{
+	strlcpy(config, opt, MAX_PARAM_LENGTH);
+	return 1;
+}
+__setup("netconsole=", option_setup);
+#endif	/* MODULE */
+
 static struct netpoll np = {
 	.name		= "netconsole",
 	.dev_name	= "eth0",
@@ -60,7 +69,6 @@ static struct netpoll np = {
 	.remote_port	= 6666,
 	.remote_mac	= {0xff, 0xff, 0xff, 0xff, 0xff, 0xff},
 };
-static int configured;
 
 static void write_msg(struct console *con, const char *msg, unsigned int len)
 {
@@ -85,26 +93,19 @@ static struct console netconsole = {
 	.write	= write_msg,
 };
 
-static int __init option_setup(char *opt)
-{
-	configured = !netpoll_parse_options(&np, opt);
-	return 1;
-}
-
-__setup("netconsole=", option_setup);
-
 static int __init init_netconsole(void)
 {
 	int err = 0;
 
-	if (strnlen(config, MAX_PARAM_LENGTH))
-		option_setup(config);
-
-	if (!configured) {
+	if (!strnlen(config, MAX_PARAM_LENGTH)) {
 		printk(KERN_INFO "netconsole: not configured, aborting\n");
 		goto out;
 	}
 
+	err = netpoll_parse_options(&np, config);
+	if (err)
+		goto out;
+
 	err = netpoll_setup(&np);
 	if (err)
 		goto out;

[PATCH v3 -mm 4/9] netconsole: Use netif_running() in write_msg()

[Satyam Sharma]

From: Satyam Sharma <satyam@infradead.org>

[4/9] netconsole: Use netif_running() in write_msg()

Avoid unnecessarily disabling interrupts and calling netpoll_send_udp()
if the corresponding local interface is not up.

Signed-off-by: Satyam Sharma <satyam@infradead.org>
Acked-by: Keiichi Kii <k-keiichi@bx.jp.nec.com>
Cc: Matt Mackall <mpm@selenic.com>

---

 drivers/net/netconsole.c |   18 +++++++++---------
 1 files changed, 9 insertions(+), 9 deletions(-)

diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index e56aa6c..75cb761 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -75,16 +75,16 @@ static void write_msg(struct console *con, const char *msg, unsigned int len)
 	int frag, left;
 	unsigned long flags;
 
-	local_irq_save(flags);
-
-	for (left = len; left;) {
-		frag = min(left, MAX_PRINT_CHUNK);
-		netpoll_send_udp(&np, msg, frag);
-		msg += frag;
-		left -= frag;
+	if (netif_running(np.dev)) {
+		local_irq_save(flags);
+		for (left = len; left;) {
+			frag = min(left, MAX_PRINT_CHUNK);
+			netpoll_send_udp(&np, msg, frag);
+			msg += frag;
+			left -= frag;
+		}
+		local_irq_restore(flags);
 	}
-
-	local_irq_restore(flags);
 }
 
 static struct console netconsole = {

[PATCH v3 -mm 5/9] netconsole: Add some useful tips to documentation

[Satyam Sharma]

From: Satyam Sharma <satyam@infradead.org>

[5/9] netconsole: Add some useful tips to documentation

Add some useful general-purpose tips. Also suggest solution for the frequent
problem of console loglevel set too low numerically (i.e. for high priority
messages only) on the sender.

Signed-off-by: Satyam Sharma <satyam@infradead.org>
Acked-by: Keiichi Kii <k-keiichi@bx.jp.nec.com>
Acked-by: Matt Mackall <mpm@selenic.com>

---

 Documentation/networking/netconsole.txt |   25 +++++++++++++++++++++++++
 1 files changed, 25 insertions(+), 0 deletions(-)

diff --git a/Documentation/networking/netconsole.txt b/Documentation/networking/netconsole.txt
index 1caa6c7..5962f45 100644
--- a/Documentation/networking/netconsole.txt
+++ b/Documentation/networking/netconsole.txt
@@ -44,11 +44,36 @@ WARNING: the default target ethernet setting uses the broadcast
 ethernet address to send packets, which can cause increased load on
 other systems on the same ethernet segment.
 
+TIP: some LAN switches may be configured to suppress ethernet broadcasts
+so it is advised to explicitly specify the remote agents' MAC addresses
+from the config parameters passed to netconsole.
+
+TIP: to find out the MAC address of, say, 10.0.0.2, you may try using:
+
+ ping -c 1 10.0.0.2 ; /sbin/arp -n | grep 10.0.0.2
+
+TIP: in case the remote logging agent is on a separate LAN subnet than
+the sender, it is suggested to try specifying the MAC address of the
+default gateway (you may use /sbin/route -n to find it out) as the
+remote MAC address instead.
+
 NOTE: the network device (eth1 in the above case) can run any kind
 of other network traffic, netconsole is not intrusive. Netconsole
 might cause slight delays in other traffic if the volume of kernel
 messages is high, but should have no other impact.
 
+NOTE: if you find that the remote logging agent is not receiving or
+printing all messages from the sender, it is likely that you have set
+the "console_loglevel" parameter (on the sender) to only send high
+priority messages to the console. You can change this at runtime using:
+
+ dmesg -n 8
+
+or by specifying "debug" on the kernel command line at boot, to send
+all kernel messages to the console. A specific value for this parameter
+can also be set using the "loglevel" kernel boot option. See the
+dmesg(8) man page and Documentation/kernel-parameters.txt for details.
+
 Netconsole was designed to be as instantaneous as possible, to
 enable the logging of even the most critical kernel bugs. It works
 from IRQ contexts as well, and does not enable interrupts while

[PATCH v3 -mm 6/9] netconsole: Introduce netconsole_target

[Satyam Sharma]

From: Satyam Sharma <satyam@infradead.org>

[6/9] netconsole: Introduce netconsole_target

Introduce a wrapper structure over netpoll to represent logging targets
configured in netconsole. This will get extended with other members in
further patches.

This is done independent of the (to-be-introduced) NETCONSOLE_DYNAMIC
config option so that we're able to drastically cut down on the #ifdef
complexity of final netconsole.c. Also, struct netconsole_target would be
required for multiple targets support also, and not just dynamic
reconfigurability.

Signed-off-by: Satyam Sharma <satyam@infradead.org>
Signed-off-by: Keiichi Kii <k-keiichi@bx.jp.nec.com>

---

 drivers/net/netconsole.c |   36 +++++++++++++++++++++++++-----------
 1 files changed, 25 insertions(+), 11 deletions(-)

diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index 75cb761..be15ca6 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -62,24 +62,35 @@ static int __init option_setup(char *opt)
 __setup("netconsole=", option_setup);
 #endif	/* MODULE */
 
-static struct netpoll np = {
-	.name		= "netconsole",
-	.dev_name	= "eth0",
-	.local_port	= 6665,
-	.remote_port	= 6666,
-	.remote_mac	= {0xff, 0xff, 0xff, 0xff, 0xff, 0xff},
+/**
+ * struct netconsole_target - Represents a configured netconsole target.
+ * @np:		The netpoll structure for this target.
+ */
+struct netconsole_target {
+	struct netpoll		np;
+};
+
+static struct netconsole_target default_target = {
+	.np		= {
+		.name		= "netconsole",
+		.dev_name	= "eth0",
+		.local_port	= 6665,
+		.remote_port	= 6666,
+		.remote_mac	= {0xff, 0xff, 0xff, 0xff, 0xff, 0xff},
+	},
 };
 
 static void write_msg(struct console *con, const char *msg, unsigned int len)
 {
 	int frag, left;
 	unsigned long flags;
+	struct netconsole_target *nt = &default_target;
 
-	if (netif_running(np.dev)) {
+	if (netif_running(nt->np.dev)) {
 		local_irq_save(flags);
 		for (left = len; left;) {
 			frag = min(left, MAX_PRINT_CHUNK);
-			netpoll_send_udp(&np, msg, frag);
+			netpoll_send_udp(&nt->np, msg, frag);
 			msg += frag;
 			left -= frag;
 		}
@@ -96,17 +107,18 @@ static struct console netconsole = {
 static int __init init_netconsole(void)
 {
 	int err = 0;
+	struct netconsole_target *nt = &default_target;
 
 	if (!strnlen(config, MAX_PARAM_LENGTH)) {
 		printk(KERN_INFO "netconsole: not configured, aborting\n");
 		goto out;
 	}
 
-	err = netpoll_parse_options(&np, config);
+	err = netpoll_parse_options(&nt->np, config);
 	if (err)
 		goto out;
 
-	err = netpoll_setup(&np);
+	err = netpoll_setup(&nt->np);
 	if (err)
 		goto out;
 
@@ -119,8 +131,10 @@ out:
 
 static void __exit cleanup_netconsole(void)
 {
+	struct netconsole_target *nt = &default_target;
+
 	unregister_console(&netconsole);
-	netpoll_cleanup(&np);
+	netpoll_cleanup(&nt->np);
 }
 
 module_init(init_netconsole);

[PATCH v3 -mm 7/9] netconsole: Introduce netconsole_netdev_notifier

[Satyam Sharma]

From: Satyam Sharma <satyam@infradead.org>

[7/9] netconsole: Introduce netconsole_netdev_notifier

To update fields of underlying netpoll structure at runtime on
corresponding NETDEV_CHANGEADDR or NETDEV_CHANGENAME notifications.

ioctl(SIOCSIFHWADDR or SIOCSIFNAME) could be used to change the
hardware/MAC address or name of the local interface that our netpoll
is attached to. Whenever this happens, netdev notifier chain is called
out with the NETDEV_CHANGEADDR or NETDEV_CHANGENAME event message. We
respond to that and update the local_mac or dev_name field of the struct
netpoll. This makes sense anyway, but is especially required for dynamic
netconsole because the netpoll structure's internal members become user
visible files when either sysfs or configfs are used. So this helps us
to keep up with the MAC address/name changes and keep values in struct
netpoll uptodate.

[ Note that ioctl(SIOCSIFADDR) to change IP address of interface at
  runtime is not handled (to update local_ip of netpoll) on purpose --
  some setups may set the local_ip to a private address, not necessary
  the actual IP address of the sender host, as presently allowed. ]

Signed-off-by: Satyam Sharma <satyam@infradead.org>
Signed-off-by: Keiichi Kii <k-keiichi@bx.jp.nec.com>

---

 drivers/net/netconsole.c |   32 ++++++++++++++++++++++++++++++++
 1 files changed, 32 insertions(+), 0 deletions(-)

diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index be15ca6..5557098 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -80,6 +80,33 @@ static struct netconsole_target default_target = {
 	},
 };
 
+/* Handle network interface device notifications */
+static int netconsole_netdev_event(struct notifier_block *this,
+				   unsigned long event,
+				   void *ptr)
+{
+	struct net_device *dev = ptr;
+	struct netconsole_target *nt = &default_target;
+
+	if (nt->np.dev == dev) {
+		switch (event) {
+		case NETDEV_CHANGEADDR:
+			memcpy(nt->np.local_mac, dev->dev_addr, ETH_ALEN);
+			break;
+
+		case NETDEV_CHANGENAME:
+			strlcpy(nt->np.dev_name, dev->name, IFNAMSIZ);
+			break;
+		}
+	}
+
+	return NOTIFY_DONE;
+}
+
+static struct notifier_block netconsole_netdev_notifier = {
+	.notifier_call  = netconsole_netdev_event,
+};
+
 static void write_msg(struct console *con, const char *msg, unsigned int len)
 {
 	int frag, left;
@@ -122,6 +149,10 @@ static int __init init_netconsole(void)
 	if (err)
 		goto out;
 
+	err = register_netdevice_notifier(&netconsole_netdev_notifier);
+	if (err)
+		goto out;
+
 	register_console(&netconsole);
 	printk(KERN_INFO "netconsole: network logging started\n");
 
@@ -134,6 +165,7 @@ static void __exit cleanup_netconsole(void)
 	struct netconsole_target *nt = &default_target;
 
 	unregister_console(&netconsole);
+	unregister_netdevice_notifier(&netconsole_netdev_notifier);
 	netpoll_cleanup(&nt->np);
 }
 

[PATCH v3 -mm 8/9] netconsole: Support multiple logging targets

[Satyam Sharma]

From: Satyam Sharma <satyam@infradead.org>

[8/9] netconsole: Support multiple logging targets

This patch introduces support for multiple targets, independent of
CONFIG_NETCONSOLE_DYNAMIC -- this is useful even in the default case and
(including the infrastructure introduced in previous patches) doesn't
really add too many bytes to module text. All the complexity (and size)
comes with the dynamic reconfigurability / userspace interface patch,
and so it's plausible users may want to keep this enabled but that
disabled (say to avoid a dependency on CONFIG_CONFIGFS_FS too).

Also update documentation to mention the use of ";" separator to specify
multiple logging targets in the boot/module option string.

Brief overview:

We maintain a target_list (and corresponding lock). Get rid of the static
"default_target" and introduce allocation and release functions for our
netconsole_target objects (but keeping sure to preserve previous behaviour
such as default values). During init_netconsole(), ";" is used as the
separator to identify multiple target specifications in the boot/module
option string. The target specifications are parsed and netpolls setup.
During exit, the target_list is torn down and all items released.

Signed-off-by: Satyam Sharma <satyam@infradead.org>
Signed-off-by: Keiichi Kii <k-keiichi@bx.jp.nec.com>

---

 Documentation/networking/netconsole.txt |    6 +
 drivers/net/netconsole.c                |  171 +++++++++++++++++++++++-------
 2 files changed, 137 insertions(+), 40 deletions(-)

diff --git a/Documentation/networking/netconsole.txt b/Documentation/networking/netconsole.txt
index 5962f45..1aaa738 100644
--- a/Documentation/networking/netconsole.txt
+++ b/Documentation/networking/netconsole.txt
@@ -34,6 +34,12 @@ Examples:
 
  insmod netconsole netconsole=@/,@10.0.0.2/
 
+It also supports logging to multiple remote agents by specifying
+parameters for the multiple agents separated by semicolons and the
+complete string enclosed in "quotes", thusly:
+
+ modprobe netconsole netconsole="@/,@10.0.0.2/;@/eth1,6892@10.0.0.3/"
+
 Built-in netconsole starts immediately after the TCP stack is
 initialized and attempts to bring up the supplied dev at the supplied
 address.
diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index 5557098..458c4d6 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -62,44 +62,93 @@ static int __init option_setup(char *opt)
 __setup("netconsole=", option_setup);
 #endif	/* MODULE */
 
+/* Linked list of all configured targets */
+static LIST_HEAD(target_list);
+
+/* This needs to be a spinlock because write_msg() cannot sleep */
+static DEFINE_SPINLOCK(target_list_lock);
+
 /**
  * struct netconsole_target - Represents a configured netconsole target.
+ * @list:	Links this target into the target_list.
  * @np:		The netpoll structure for this target.
  */
 struct netconsole_target {
+	struct list_head	list;
 	struct netpoll		np;
 };
 
-static struct netconsole_target default_target = {
-	.np		= {
-		.name		= "netconsole",
-		.dev_name	= "eth0",
-		.local_port	= 6665,
-		.remote_port	= 6666,
-		.remote_mac	= {0xff, 0xff, 0xff, 0xff, 0xff, 0xff},
-	},
-};
+/* Allocate new target and setup netpoll for it */
+static struct netconsole_target *alloc_target(char *target_config)
+{
+	int err = -ENOMEM;
+	struct netconsole_target *nt;
+
+	/* Allocate and initialize with defaults */
+	nt = kzalloc(sizeof(*nt), GFP_KERNEL);
+	if (!nt) {
+		printk(KERN_ERR "netconsole: failed to allocate memory\n");
+		goto fail;
+	}
+
+	nt->np.name = "netconsole";
+	strlcpy(nt->np.dev_name, "eth0", IFNAMSIZ);
+	nt->np.local_port = 6665;
+	nt->np.remote_port = 6666;
+	memset(nt->np.remote_mac, 0xff, ETH_ALEN);
+
+	/* Parse parameters and setup netpoll */
+	err = netpoll_parse_options(&nt->np, target_config);
+	if (err)
+		goto fail;
+
+	err = netpoll_setup(&nt->np);
+	if (err)
+		goto fail;
+
+	return nt;
+
+fail:
+	kfree(nt);
+	return ERR_PTR(err);
+}
+
+/* Cleanup netpoll for given target and free it */
+static void free_target(struct netconsole_target *nt)
+{
+	netpoll_cleanup(&nt->np);
+	kfree(nt);
+}
 
 /* Handle network interface device notifications */
 static int netconsole_netdev_event(struct notifier_block *this,
 				   unsigned long event,
 				   void *ptr)
 {
+	unsigned long flags;
+	struct netconsole_target *nt;
 	struct net_device *dev = ptr;
-	struct netconsole_target *nt = &default_target;
 
-	if (nt->np.dev == dev) {
-		switch (event) {
-		case NETDEV_CHANGEADDR:
-			memcpy(nt->np.local_mac, dev->dev_addr, ETH_ALEN);
-			break;
+	if (!(event == NETDEV_CHANGEADDR || event == NETDEV_CHANGENAME))
+		goto done;
+
+	spin_lock_irqsave(&target_list_lock, flags);
+	list_for_each_entry(nt, &target_list, list) {
+		if (nt->np.dev == dev) {
+			switch (event) {
+			case NETDEV_CHANGEADDR:
+				memcpy(nt->np.local_mac, dev->dev_addr, ETH_ALEN);
+				break;
 
-		case NETDEV_CHANGENAME:
-			strlcpy(nt->np.dev_name, dev->name, IFNAMSIZ);
-			break;
+			case NETDEV_CHANGENAME:
+				strlcpy(nt->np.dev_name, dev->name, IFNAMSIZ);
+				break;
+			}
 		}
 	}
+	spin_unlock_irqrestore(&target_list_lock, flags);
 
+done:
 	return NOTIFY_DONE;
 }
 
@@ -111,18 +160,32 @@ static void write_msg(struct console *con, const char *msg, unsigned int len)
 {
 	int frag, left;
 	unsigned long flags;
-	struct netconsole_target *nt = &default_target;
-
-	if (netif_running(nt->np.dev)) {
-		local_irq_save(flags);
-		for (left = len; left;) {
-			frag = min(left, MAX_PRINT_CHUNK);
-			netpoll_send_udp(&nt->np, msg, frag);
-			msg += frag;
-			left -= frag;
+	struct netconsole_target *nt;
+	const char *tmp;
+
+	/* Avoid taking lock and disabling interrupts unnecessarily */
+	if (list_empty(&target_list))
+		return;
+
+	spin_lock_irqsave(&target_list_lock, flags);
+	list_for_each_entry(nt, &target_list, list) {
+		if (netif_running(nt->np.dev)) {
+			/*
+			 * We nest this inside the for-each-target loop above
+			 * so that we're able to get as much logging out to
+			 * at least one target if we die inside here, instead
+			 * of unnecessarily keeping all targets in lock-step.
+			 */
+			tmp = msg;
+			for (left = len; left;) {
+				frag = min(left, MAX_PRINT_CHUNK);
+				netpoll_send_udp(&nt->np, tmp, frag);
+				tmp += frag;
+				left -= frag;
+			}
 		}
-		local_irq_restore(flags);
 	}
+	spin_unlock_irqrestore(&target_list_lock, flags);
 }
 
 static struct console netconsole = {
@@ -134,39 +197,67 @@ static struct console netconsole = {
 static int __init init_netconsole(void)
 {
 	int err = 0;
-	struct netconsole_target *nt = &default_target;
+	struct netconsole_target *nt, *tmp;
+	unsigned long flags;
+	char *target_config;
+	char *input = config;
 
-	if (!strnlen(config, MAX_PARAM_LENGTH)) {
+	if (!strnlen(input, MAX_PARAM_LENGTH)) {
 		printk(KERN_INFO "netconsole: not configured, aborting\n");
 		goto out;
 	}
 
-	err = netpoll_parse_options(&nt->np, config);
-	if (err)
-		goto out;
-
-	err = netpoll_setup(&nt->np);
-	if (err)
-		goto out;
+	while ((target_config = strsep(&input, ";"))) {
+		nt = alloc_target(target_config);
+		if (IS_ERR(nt)) {
+			err = PTR_ERR(nt);
+			goto fail;
+		}
+		spin_lock_irqsave(&target_list_lock, flags);
+		list_add(&nt->list, &target_list);
+		spin_unlock_irqrestore(&target_list_lock, flags);
+	}
 
 	err = register_netdevice_notifier(&netconsole_netdev_notifier);
 	if (err)
-		goto out;
+		goto fail;
 
 	register_console(&netconsole);
 	printk(KERN_INFO "netconsole: network logging started\n");
 
 out:
 	return err;
+
+fail:
+	printk(KERN_ERR "netconsole: cleaning up\n");
+
+	/*
+	 * Remove all targets and destroy them. Skipping the list
+	 * lock is safe here, and netpoll_cleanup() will sleep.
+	 */
+	list_for_each_entry_safe(nt, tmp, &target_list, list) {
+		list_del(&nt->list);
+		free_target(nt);
+	}
+
+	return err;
 }
 
 static void __exit cleanup_netconsole(void)
 {
-	struct netconsole_target *nt = &default_target;
+	struct netconsole_target *nt, *tmp;
 
 	unregister_console(&netconsole);
 	unregister_netdevice_notifier(&netconsole_netdev_notifier);
-	netpoll_cleanup(&nt->np);
+
+	/*
+	 * Remove all targets and destroy them. Skipping the list
+	 * lock is safe here, and netpoll_cleanup() will sleep.
+	 */
+	list_for_each_entry_safe(nt, tmp, &target_list, list) {
+		list_del(&nt->list);
+		free_target(nt);
+	}
 }
 
 module_init(init_netconsole);

[PATCH v3 -mm 9/9] netconsole: Support dynamic reconfiguration using configfs

[Satyam Sharma]

From: Satyam Sharma <satyam@infradead.org>

[9/9] netconsole: Support dynamic reconfiguration using configfs

This patch introduces support for dynamic reconfiguration (adding, removing
and/or modifying parameters of netconsole targets at runtime) using a
userspace interface exported via configfs. Documentation is also updated
accordingly.

Issues and brief design overview:

(1) Kernel-initiated creation / destruction of kernel objects is not
possible with configfs -- the lifetimes of the "config items" is managed
exclusively from userspace. But netconsole must support boot/module params
too, and these are parsed in kernel and hence netpolls must be setup from
the kernel. Joel Becker suggested to separately manage the lifetimes of
the two kinds of netconsole_target objects -- those created via configfs
mkdir(2) from userspace and those specified from the boot/module option
string. This adds complexity and some redundancy here and also means that
boot/module param-created targets are not exposed through the configfs
namespace (and hence cannot be updated / destroyed dynamically). However,
this saves us from locking / refcounting complexities that would need to
be introduced in configfs to support kernel-initiated item creation /
destroy there.

(2) In configfs, item creation takes place in the call chain of the mkdir(2)
syscall in the driver subsystem. If we used an ioctl(2) to create / destroy
objects from userspace, the special userspace program is able to fill out
the structure to be passed into the ioctl and hence specify attributes such
as local interface that are required at the time we set up the netpoll.
For configfs, this information is not available at the time of mkdir(2).
So, we keep all newly-created targets (via configfs) disabled by default.
The user is expected to set various attributes appropriately (including the
local network interface if required) and then write(2) "1" to the "enabled"
attribute. Thus, netpoll_setup() is then called on the set parameters in the
context of _this_ write(2) on the "enabled" attribute itself. This design
enables the user to reconfigure existing netconsole targets at runtime to
be attached to newly-come-up interfaces that may not have existed when
netconsole was loaded or when the targets were actually created. All this
effectively enables us to get rid of custom ioctls.

(3) Ultra-paranoid configfs attribute show() and store() operations, with
sanity and input range checking, using only safe string primitives, and
compliant with the recommendations in Documentation/filesystems/sysfs.txt.

(4) A new function netpoll_print_options() is created in the netpoll API,
that just prints out the configured parameters for a netpoll structure.
netpoll_parse_options() is modified to use that and it is also exported to
be used from netconsole.

Signed-off-by: Satyam Sharma <satyam@infradead.org>
Acked-by: Keiichi Kii <k-keiichi@bx.jp.nec.com>

---

 Documentation/networking/netconsole.txt |   68 ++++
 drivers/net/Kconfig                     |   10 +
 drivers/net/netconsole.c                |  605 +++++++++++++++++++++++++++++--
 include/linux/netpoll.h                 |    1 +
 net/core/netpoll.c                      |   44 ++-
 5 files changed, 683 insertions(+), 45 deletions(-)

diff --git a/Documentation/networking/netconsole.txt b/Documentation/networking/netconsole.txt
index 1aaa738..3c2f2b3 100644
--- a/Documentation/networking/netconsole.txt
+++ b/Documentation/networking/netconsole.txt
@@ -3,6 +3,10 @@ started by Ingo Molnar <mingo@redhat.com>, 2001.09.17
 2.6 port and netpoll api by Matt Mackall <mpm@selenic.com>, Sep 9 2003
 
 Please send bug reports to Matt Mackall <mpm@selenic.com>
+and Satyam Sharma <satyam.sharma@gmail.com>
+
+Introduction:
+=============
 
 This module logs kernel printk messages over UDP allowing debugging of
 problem where disk logging fails and serial consoles are impractical.
@@ -13,6 +17,9 @@ the specified interface as soon as possible. While this doesn't allow
 capture of early kernel panics, it does capture most of the boot
 process.
 
+Sender and receiver configuration:
+==================================
+
 It takes a string configuration parameter "netconsole" in the
 following format:
 
@@ -46,6 +53,67 @@ address.
 
 The remote host can run either 'netcat -u -l -p <port>' or syslogd.
 
+Dynamic reconfiguration:
+========================
+
+Dynamic reconfigurability is a useful addition to netconsole that enables
+remote logging targets to be dynamically added, removed, or have their
+parameters reconfigured at runtime from a configfs-based userspace interface.
+[ Note that the parameters of netconsole targets that were specified/created
+from the boot/module option are not exposed via this interface, and hence
+cannot be modified dynamically. ]
+
+To include this feature, select CONFIG_NETCONSOLE_DYNAMIC when building the
+netconsole module (or kernel, if netconsole is built-in).
+
+Some examples follow (where configfs is mounted at the /sys/kernel/config
+mountpoint).
+
+To add a remote logging target (target names can be arbitrary):
+
+ cd /sys/kernel/config/netconsole/
+ mkdir target1
+
+Note that newly created targets have default parameter values (as mentioned
+above) and are disabled by default -- they must first be enabled by writing
+"1" to the "enabled" attribute (usually after setting parameters accordingly)
+as described below.
+
+To remove a target:
+
+ rmdir /sys/kernel/config/netconsole/othertarget/
+
+The interface exposes these parameters of a netconsole target to userspace:
+
+	enabled		Is this target currently enabled?	(read-write)
+	dev_name	Local network interface name		(read-write)
+	local_port	Source UDP port to use			(read-write)
+	remote_port	Remote agent's UDP port			(read-write)
+	local_ip	Source IP address to use		(read-write)
+	remote_ip	Remote agent's IP address		(read-write)
+	local_mac	Local interface's MAC address		(read-only)
+	remote_mac	Remote agent's MAC address		(read-write)
+
+The "enabled" attribute is also used to control whether the parameters of
+a target can be updated or not -- you can modify the parameters of only
+disabled targets (i.e. if "enabled" is 0).
+
+To update a target's parameters:
+
+ cat enabled				# check if enabled is 1
+ echo 0 > enabled			# disable the target (if required)
+ echo eth2 > dev_name			# set local interface
+ echo 10.0.0.4 > remote_ip		# update some parameter
+ echo cb:a9:87:65:43:21 > remote_mac	# update more parameters
+ echo 1 > enabled			# enable target again
+
+You can also update the local interface dynamically. This is especially
+useful if you want to use interfaces that have newly come up (and may not
+have existed when netconsole was loaded / initialized).
+
+Miscellaneous notes:
+====================
+
 WARNING: the default target ethernet setting uses the broadcast
 ethernet address to send packets, which can cause increased load on
 other systems on the same ethernet segment.
diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
index f8a602c..89c21d7 100644
--- a/drivers/net/Kconfig
+++ b/drivers/net/Kconfig
@@ -2972,6 +2972,16 @@ config NETCONSOLE
 	If you want to log kernel messages over the network, enable this.
 	See <file:Documentation/networking/netconsole.txt> for details.
 
+config NETCONSOLE_DYNAMIC
+	bool "Dynamic reconfiguration of logging targets (EXPERIMENTAL)"
+	depends on NETCONSOLE && SYSFS && EXPERIMENTAL
+	select CONFIGFS_FS
+	help
+	  This option enables the ability to dynamically reconfigure target
+	  parameters (interface, IP addresses, port numbers, MAC addresses)
+	  at runtime through a userspace interface exported using configfs.
+	  See <file:Documentation/networking/netconsole.txt> for details.
+
 config NETPOLL
 	def_bool NETCONSOLE
 
diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index 458c4d6..0269323 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -41,6 +41,8 @@
 #include <linux/moduleparam.h>
 #include <linux/string.h>
 #include <linux/netpoll.h>
+#include <linux/inet.h>
+#include <linux/configfs.h>
 
 MODULE_AUTHOR("Maintainer: Matt Mackall <mpm@selenic.com>");
 MODULE_DESCRIPTION("Console driver for network interfaces");
@@ -71,20 +73,100 @@ static DEFINE_SPINLOCK(target_list_lock);
 /**
  * struct netconsole_target - Represents a configured netconsole target.
  * @list:	Links this target into the target_list.
+ * @item:	Links us into the configfs subsystem hierarchy.
+ * @enabled:	On / off knob to enable / disable target.
+ *		Visible from userspace (read-write).
+ *		We maintain a strict 1:1 correspondence between this and
+ *		whether the corresponding netpoll is active or inactive.
+ *		Also, other parameters of a target may be modified at
+ *		runtime only when it is disabled (enabled == 0).
  * @np:		The netpoll structure for this target.
+ *		Contains the other userspace visible parameters:
+ *		dev_name	(read-write)
+ *		local_port	(read-write)
+ *		remote_port	(read-write)
+ *		local_ip	(read-write)
+ *		remote_ip	(read-write)
+ *		local_mac	(read-only)
+ *		remote_mac	(read-write)
  */
 struct netconsole_target {
 	struct list_head	list;
+#ifdef	CONFIG_NETCONSOLE_DYNAMIC
+	struct config_item	item;
+#endif
+	int			enabled;
 	struct netpoll		np;
 };
 
-/* Allocate new target and setup netpoll for it */
-static struct netconsole_target *alloc_target(char *target_config)
+#ifdef	CONFIG_NETCONSOLE_DYNAMIC
+
+static struct configfs_subsystem netconsole_subsys;
+
+static int __init dynamic_netconsole_init(void)
+{
+	config_group_init(&netconsole_subsys.su_group);
+	mutex_init(&netconsole_subsys.su_mutex);
+	return configfs_register_subsystem(&netconsole_subsys);
+}
+
+static void __exit dynamic_netconsole_exit(void)
+{
+	configfs_unregister_subsystem(&netconsole_subsys);
+}
+
+/*
+ * Targets that were created by parsing the boot/module option string
+ * do not exist in the configfs hierarchy (and have NULL names) and will
+ * never go away, so make these a no-op for them.
+ */
+static void netconsole_target_get(struct netconsole_target *nt)
+{
+	if (config_item_name(&nt->item))
+		config_item_get(&nt->item);
+}
+
+static void netconsole_target_put(struct netconsole_target *nt)
+{
+	if (config_item_name(&nt->item))
+		config_item_put(&nt->item);
+}
+
+#else	/* !CONFIG_NETCONSOLE_DYNAMIC */
+
+static int __init dynamic_netconsole_init(void)
+{
+	return 0;
+}
+
+static void __exit dynamic_netconsole_exit(void)
+{
+}
+
+/*
+ * No danger of targets going away from under us when dynamic
+ * reconfigurability is off.
+ */
+static void netconsole_target_get(struct netconsole_target *nt)
+{
+}
+
+static void netconsole_target_put(struct netconsole_target *nt)
+{
+}
+
+#endif	/* CONFIG_NETCONSOLE_DYNAMIC */
+
+/* Allocate new target (from boot/module param) and setup netpoll for it */
+static struct netconsole_target *alloc_param_target(char *target_config)
 {
 	int err = -ENOMEM;
 	struct netconsole_target *nt;
 
-	/* Allocate and initialize with defaults */
+	/*
+	 * Allocate and initialize with defaults.
+	 * Note that these targets get their config_item fields zeroed-out.
+	 */
 	nt = kzalloc(sizeof(*nt), GFP_KERNEL);
 	if (!nt) {
 		printk(KERN_ERR "netconsole: failed to allocate memory\n");
@@ -106,6 +188,8 @@ static struct netconsole_target *alloc_target(char *target_config)
 	if (err)
 		goto fail;
 
+	nt->enabled = 1;
+
 	return nt;
 
 fail:
@@ -113,13 +197,469 @@ fail:
 	return ERR_PTR(err);
 }
 
-/* Cleanup netpoll for given target and free it */
-static void free_target(struct netconsole_target *nt)
+/* Cleanup netpoll for given target (from boot/module param) and free it */
+static void free_param_target(struct netconsole_target *nt)
 {
 	netpoll_cleanup(&nt->np);
 	kfree(nt);
 }
 
+#ifdef	CONFIG_NETCONSOLE_DYNAMIC
+
+/*
+ * Our subsystem hierarchy is:
+ *
+ * /sys/kernel/config/netconsole/
+ *				|
+ *				<target>/
+ *				|	enabled
+ *				|	dev_name
+ *				|	local_port
+ *				|	remote_port
+ *				|	local_ip
+ *				|	remote_ip
+ *				|	local_mac
+ *				|	remote_mac
+ *				|
+ *				<target>/...
+ */
+
+struct netconsole_target_attr {
+	struct configfs_attribute	attr;
+	ssize_t				(*show)(struct netconsole_target *nt,
+						char *buf);
+	ssize_t				(*store)(struct netconsole_target *nt,
+						 const char *buf,
+						 size_t count);
+};
+
+static struct netconsole_target *to_target(struct config_item *item)
+{
+	return item ?
+		container_of(item, struct netconsole_target, item) :
+		NULL;
+}
+
+/*
+ * Wrapper over simple_strtol (base 10) with sanity and range checking.
+ * We return (signed) long only because we may want to return errors.
+ * Do not use this to convert numbers that are allowed to be negative.
+ */
+static long strtol10_check_range(const char *cp, long min, long max)
+{
+	long ret;
+	char *p = (char *) cp;
+
+	WARN_ON(min < 0);
+	WARN_ON(max < min);
+
+	ret = simple_strtol(p, &p, 10);
+
+	if (*p && (*p != '\n')) {
+		printk(KERN_ERR "netconsole: invalid input\n");
+		return -EINVAL;
+	}
+	if ((ret < min) || (ret > max)) {
+		printk(KERN_ERR "netconsole: input %ld must be between "
+				"%ld and %ld\n", ret, min, max);
+		return -EINVAL;
+	}
+
+	return ret;
+}
+
+/*
+ * Attribute operations for netconsole_target.
+ */
+
+static ssize_t show_enabled(struct netconsole_target *nt, char *buf)
+{
+	return snprintf(buf, PAGE_SIZE, "%d\n", nt->enabled);
+}
+
+static ssize_t show_dev_name(struct netconsole_target *nt, char *buf)
+{
+	return snprintf(buf, PAGE_SIZE, "%s\n", nt->np.dev_name);
+}
+
+static ssize_t show_local_port(struct netconsole_target *nt, char *buf)
+{
+	return snprintf(buf, PAGE_SIZE, "%d\n", nt->np.local_port);
+}
+
+static ssize_t show_remote_port(struct netconsole_target *nt, char *buf)
+{
+	return snprintf(buf, PAGE_SIZE, "%d\n", nt->np.remote_port);
+}
+
+static ssize_t show_local_ip(struct netconsole_target *nt, char *buf)
+{
+	return snprintf(buf, PAGE_SIZE, "%d.%d.%d.%d\n",
+			HIPQUAD(nt->np.local_ip));
+}
+
+static ssize_t show_remote_ip(struct netconsole_target *nt, char *buf)
+{
+	return snprintf(buf, PAGE_SIZE, "%d.%d.%d.%d\n",
+			HIPQUAD(nt->np.remote_ip));
+}
+
+static ssize_t show_local_mac(struct netconsole_target *nt, char *buf)
+{
+	return snprintf(buf, PAGE_SIZE, "%02x:%02x:%02x:%02x:%02x:%02x\n",
+			nt->np.local_mac[0], nt->np.local_mac[1],
+			nt->np.local_mac[2], nt->np.local_mac[3],
+			nt->np.local_mac[4], nt->np.local_mac[5]);
+}
+
+static ssize_t show_remote_mac(struct netconsole_target *nt, char *buf)
+{
+	return snprintf(buf, PAGE_SIZE, "%02x:%02x:%02x:%02x:%02x:%02x\n",
+			nt->np.remote_mac[0], nt->np.remote_mac[1],
+			nt->np.remote_mac[2], nt->np.remote_mac[3],
+			nt->np.remote_mac[4], nt->np.remote_mac[5]);
+}
+
+/*
+ * This one is special -- targets created through the configfs interface
+ * are not enabled (and the corresponding netpoll activated) by default.
+ * The user is expected to set the desired parameters first (which
+ * would enable him to dynamically add new netpoll targets for new
+ * network interfaces as and when they come up).
+ */
+static ssize_t store_enabled(struct netconsole_target *nt,
+			     const char *buf,
+			     size_t count)
+{
+	int err;
+	long enabled;
+
+	enabled = strtol10_check_range(buf, 0, 1);
+	if (enabled < 0)
+		return enabled;
+
+	if (enabled) {	/* 1 */
+
+		/*
+		 * Skip netpoll_parse_options() -- all the attributes are
+		 * already configured via configfs. Just print them out.
+		 */
+		netpoll_print_options(&nt->np);
+
+		err = netpoll_setup(&nt->np);
+		if (err)
+			return err;
+
+		printk(KERN_INFO "netconsole: network logging started\n");
+
+	} else {	/* 0 */
+		netpoll_cleanup(&nt->np);
+	}
+
+	nt->enabled = enabled;
+
+	return strnlen(buf, count);
+}
+
+static ssize_t store_dev_name(struct netconsole_target *nt,
+			      const char *buf,
+			      size_t count)
+{
+	size_t len;
+
+	if (nt->enabled) {
+		printk(KERN_ERR "netconsole: target (%s) is enabled, "
+				"disable to update parameters\n",
+				config_item_name(&nt->item));
+		return -EINVAL;
+	}
+
+	strlcpy(nt->np.dev_name, buf, IFNAMSIZ);
+
+	/* Get rid of possible trailing newline from echo(1) */
+	len = strnlen(nt->np.dev_name, IFNAMSIZ);
+	if (nt->np.dev_name[len - 1] == '\n')
+		nt->np.dev_name[len - 1] = '\0';
+
+	return strnlen(buf, count);
+}
+
+static ssize_t store_local_port(struct netconsole_target *nt,
+				const char *buf,
+				size_t count)
+{
+	long local_port;
+#define __U16_MAX	((__u16) ~0U)
+
+	if (nt->enabled) {
+		printk(KERN_ERR "netconsole: target (%s) is enabled, "
+				"disable to update parameters\n",
+				config_item_name(&nt->item));
+		return -EINVAL;
+	}
+
+	local_port = strtol10_check_range(buf, 0, __U16_MAX);
+	if (local_port < 0)
+		return local_port;
+
+	nt->np.local_port = local_port;
+
+	return strnlen(buf, count);
+}
+
+static ssize_t store_remote_port(struct netconsole_target *nt,
+				 const char *buf,
+				 size_t count)
+{
+	long remote_port;
+#define __U16_MAX	((__u16) ~0U)
+
+	if (nt->enabled) {
+		printk(KERN_ERR "netconsole: target (%s) is enabled, "
+				"disable to update parameters\n",
+				config_item_name(&nt->item));
+		return -EINVAL;
+	}
+
+	remote_port = strtol10_check_range(buf, 0, __U16_MAX);
+	if (remote_port < 0)
+		return remote_port;
+
+	nt->np.remote_port = remote_port;
+
+	return strnlen(buf, count);
+}
+
+static ssize_t store_local_ip(struct netconsole_target *nt,
+			      const char *buf,
+			      size_t count)
+{
+	if (nt->enabled) {
+		printk(KERN_ERR "netconsole: target (%s) is enabled, "
+				"disable to update parameters\n",
+				config_item_name(&nt->item));
+		return -EINVAL;
+	}
+
+	nt->np.local_ip = ntohl(in_aton(buf));
+
+	return strnlen(buf, count);
+}
+
+static ssize_t store_remote_ip(struct netconsole_target *nt,
+			       const char *buf,
+			       size_t count)
+{
+	if (nt->enabled) {
+		printk(KERN_ERR "netconsole: target (%s) is enabled, "
+				"disable to update parameters\n",
+				config_item_name(&nt->item));
+		return -EINVAL;
+	}
+
+	nt->np.remote_ip = ntohl(in_aton(buf));
+
+	return strnlen(buf, count);
+}
+
+static ssize_t store_remote_mac(struct netconsole_target *nt,
+				const char *buf,
+				size_t count)
+{
+	u8 remote_mac[ETH_ALEN];
+	char *p = (char *) buf;
+	int i;
+
+	if (nt->enabled) {
+		printk(KERN_ERR "netconsole: target (%s) is enabled, "
+				"disable to update parameters\n",
+				config_item_name(&nt->item));
+		return -EINVAL;
+	}
+
+	for (i = 0; i < ETH_ALEN - 1; i++) {
+		remote_mac[i] = simple_strtoul(p, &p, 16);
+		if (*p != ':')
+			goto invalid;
+		p++;
+	}
+	remote_mac[ETH_ALEN - 1] = simple_strtoul(p, &p, 16);
+	if (*p && (*p != '\n'))
+		goto invalid;
+
+	memcpy(nt->np.remote_mac, remote_mac, ETH_ALEN);
+
+	return strnlen(buf, count);
+
+invalid:
+	printk(KERN_ERR "netconsole: invalid input\n");
+	return -EINVAL;
+}
+
+/*
+ * Attribute definitions for netconsole_target.
+ */
+
+#define NETCONSOLE_TARGET_ATTR_RO(_name)				\
+static struct netconsole_target_attr netconsole_target_##_name =	\
+	__CONFIGFS_ATTR(_name, S_IRUGO, show_##_name, NULL)
+
+#define NETCONSOLE_TARGET_ATTR_RW(_name)				\
+static struct netconsole_target_attr netconsole_target_##_name =	\
+	__CONFIGFS_ATTR(_name, S_IRUGO | S_IWUSR, show_##_name, store_##_name)
+
+NETCONSOLE_TARGET_ATTR_RW(enabled);
+NETCONSOLE_TARGET_ATTR_RW(dev_name);
+NETCONSOLE_TARGET_ATTR_RW(local_port);
+NETCONSOLE_TARGET_ATTR_RW(remote_port);
+NETCONSOLE_TARGET_ATTR_RW(local_ip);
+NETCONSOLE_TARGET_ATTR_RW(remote_ip);
+NETCONSOLE_TARGET_ATTR_RO(local_mac);
+NETCONSOLE_TARGET_ATTR_RW(remote_mac);
+
+static struct configfs_attribute *netconsole_target_attrs[] = {
+	&netconsole_target_enabled.attr,
+	&netconsole_target_dev_name.attr,
+	&netconsole_target_local_port.attr,
+	&netconsole_target_remote_port.attr,
+	&netconsole_target_local_ip.attr,
+	&netconsole_target_remote_ip.attr,
+	&netconsole_target_local_mac.attr,
+	&netconsole_target_remote_mac.attr,
+	NULL,
+};
+
+/*
+ * Item operations and type for netconsole_target.
+ */
+
+static void netconsole_target_release(struct config_item *item)
+{
+	kfree(to_target(item));
+}
+
+static ssize_t netconsole_target_attr_show(struct config_item *item,
+					   struct configfs_attribute *attr,
+					   char *buf)
+{
+	ssize_t ret = -EINVAL;
+	struct netconsole_target *nt = to_target(item);
+	struct netconsole_target_attr *na =
+		container_of(attr, struct netconsole_target_attr, attr);
+
+	if (na->show)
+		ret = na->show(nt, buf);
+
+	return ret;
+}
+
+static ssize_t netconsole_target_attr_store(struct config_item *item,
+					    struct configfs_attribute *attr,
+					    const char *buf,
+					    size_t count)
+{
+	ssize_t ret = -EINVAL;
+	struct netconsole_target *nt = to_target(item);
+	struct netconsole_target_attr *na =
+		container_of(attr, struct netconsole_target_attr, attr);
+
+	if (na->store)
+		ret = na->store(nt, buf, count);
+
+	return ret;
+}
+
+static struct configfs_item_operations netconsole_target_item_ops = {
+	.release		= netconsole_target_release,
+	.show_attribute		= netconsole_target_attr_show,
+	.store_attribute	= netconsole_target_attr_store,
+};
+
+static struct config_item_type netconsole_target_type = {
+	.ct_attrs		= netconsole_target_attrs,
+	.ct_item_ops		= &netconsole_target_item_ops,
+	.ct_owner		= THIS_MODULE,
+};
+
+/*
+ * Group operations and type for netconsole_subsys.
+ */
+
+static struct config_item *make_netconsole_target(struct config_group *group,
+						  const char *name)
+{
+	unsigned long flags;
+	struct netconsole_target *nt;
+
+	/*
+	 * Allocate and initialize with defaults.
+	 * Target is disabled at creation (enabled == 0).
+	 */
+	nt = kzalloc(sizeof(*nt), GFP_KERNEL);
+	if (!nt) {
+		printk(KERN_ERR "netconsole: failed to allocate memory\n");
+		return NULL;
+	}
+
+	nt->np.name = "netconsole";
+	strlcpy(nt->np.dev_name, "eth0", IFNAMSIZ);
+	nt->np.local_port = 6665;
+	nt->np.remote_port = 6666;
+	memset(nt->np.remote_mac, 0xff, ETH_ALEN);
+
+	/* Initialize the config_item member */
+	config_item_init_type_name(&nt->item, name, &netconsole_target_type);
+
+	/* Adding, but it is disabled */
+	spin_lock_irqsave(&target_list_lock, flags);
+	list_add(&nt->list, &target_list);
+	spin_unlock_irqrestore(&target_list_lock, flags);
+
+	return &nt->item;
+}
+
+static void drop_netconsole_target(struct config_group *group,
+				   struct config_item *item)
+{
+	unsigned long flags;
+	struct netconsole_target *nt = to_target(item);
+
+	spin_lock_irqsave(&target_list_lock, flags);
+	list_del(&nt->list);
+	spin_unlock_irqrestore(&target_list_lock, flags);
+
+	/*
+	 * The target may have never been enabled, or was manually disabled
+	 * before being removed so netpoll may have already been cleaned up.
+	 */
+	if (nt->enabled)
+		netpoll_cleanup(&nt->np);
+
+	config_item_put(&nt->item);
+}
+
+static struct configfs_group_operations netconsole_subsys_group_ops = {
+	.make_item	= make_netconsole_target,
+	.drop_item	= drop_netconsole_target,
+};
+
+static struct config_item_type netconsole_subsys_type = {
+	.ct_group_ops	= &netconsole_subsys_group_ops,
+	.ct_owner	= THIS_MODULE,
+};
+
+/* The netconsole configfs subsystem */
+static struct configfs_subsystem netconsole_subsys = {
+	.su_group	= {
+		.cg_item	= {
+			.ci_namebuf	= "netconsole",
+			.ci_type	= &netconsole_subsys_type,
+		},
+	},
+};
+
+#endif	/* CONFIG_NETCONSOLE_DYNAMIC */
+
 /* Handle network interface device notifications */
 static int netconsole_netdev_event(struct notifier_block *this,
 				   unsigned long event,
@@ -134,6 +674,7 @@ static int netconsole_netdev_event(struct notifier_block *this,
 
 	spin_lock_irqsave(&target_list_lock, flags);
 	list_for_each_entry(nt, &target_list, list) {
+		netconsole_target_get(nt);
 		if (nt->np.dev == dev) {
 			switch (event) {
 			case NETDEV_CHANGEADDR:
@@ -145,6 +686,7 @@ static int netconsole_netdev_event(struct notifier_block *this,
 				break;
 			}
 		}
+		netconsole_target_put(nt);
 	}
 	spin_unlock_irqrestore(&target_list_lock, flags);
 
@@ -169,7 +711,8 @@ static void write_msg(struct console *con, const char *msg, unsigned int len)
 
 	spin_lock_irqsave(&target_list_lock, flags);
 	list_for_each_entry(nt, &target_list, list) {
-		if (netif_running(nt->np.dev)) {
+		netconsole_target_get(nt);
+		if (nt->enabled && netif_running(nt->np.dev)) {
 			/*
 			 * We nest this inside the for-each-target loop above
 			 * so that we're able to get as much logging out to
@@ -184,6 +727,7 @@ static void write_msg(struct console *con, const char *msg, unsigned int len)
 				left -= frag;
 			}
 		}
+		netconsole_target_put(nt);
 	}
 	spin_unlock_irqrestore(&target_list_lock, flags);
 }
@@ -196,48 +740,52 @@ static struct console netconsole = {
 
 static int __init init_netconsole(void)
 {
-	int err = 0;
+	int err;
 	struct netconsole_target *nt, *tmp;
 	unsigned long flags;
 	char *target_config;
 	char *input = config;
 
-	if (!strnlen(input, MAX_PARAM_LENGTH)) {
-		printk(KERN_INFO "netconsole: not configured, aborting\n");
-		goto out;
-	}
-
-	while ((target_config = strsep(&input, ";"))) {
-		nt = alloc_target(target_config);
-		if (IS_ERR(nt)) {
-			err = PTR_ERR(nt);
-			goto fail;
+	if (strnlen(input, MAX_PARAM_LENGTH)) {
+		while ((target_config = strsep(&input, ";"))) {
+			nt = alloc_param_target(target_config);
+			if (IS_ERR(nt)) {
+				err = PTR_ERR(nt);
+				goto fail;
+			}
+			spin_lock_irqsave(&target_list_lock, flags);
+			list_add(&nt->list, &target_list);
+			spin_unlock_irqrestore(&target_list_lock, flags);
 		}
-		spin_lock_irqsave(&target_list_lock, flags);
-		list_add(&nt->list, &target_list);
-		spin_unlock_irqrestore(&target_list_lock, flags);
 	}
 
 	err = register_netdevice_notifier(&netconsole_netdev_notifier);
 	if (err)
 		goto fail;
 
+	err = dynamic_netconsole_init();
+	if (err)
+		goto undonotifier;
+
 	register_console(&netconsole);
 	printk(KERN_INFO "netconsole: network logging started\n");
 
-out:
 	return err;
 
+undonotifier:
+	unregister_netdevice_notifier(&netconsole_netdev_notifier);
+
 fail:
 	printk(KERN_ERR "netconsole: cleaning up\n");
 
 	/*
-	 * Remove all targets and destroy them. Skipping the list
+	 * Remove all targets and destroy them (only targets created
+	 * from the boot/module option exist here). Skipping the list
 	 * lock is safe here, and netpoll_cleanup() will sleep.
 	 */
 	list_for_each_entry_safe(nt, tmp, &target_list, list) {
 		list_del(&nt->list);
-		free_target(nt);
+		free_param_target(nt);
 	}
 
 	return err;
@@ -248,15 +796,20 @@ static void __exit cleanup_netconsole(void)
 	struct netconsole_target *nt, *tmp;
 
 	unregister_console(&netconsole);
+	dynamic_netconsole_exit();
 	unregister_netdevice_notifier(&netconsole_netdev_notifier);
 
 	/*
-	 * Remove all targets and destroy them. Skipping the list
-	 * lock is safe here, and netpoll_cleanup() will sleep.
+	 * Targets created via configfs pin references on our module
+	 * and would first be rmdir(2)'ed from userspace. We reach
+	 * here only when they are already destroyed, and only those
+	 * created from the boot/module option are left, so remove and
+	 * destroy them. Skipping the list lock is safe here, and
+	 * netpoll_cleanup() will sleep.
 	 */
 	list_for_each_entry_safe(nt, tmp, &target_list, list) {
 		list_del(&nt->list);
-		free_target(nt);
+		free_param_target(nt);
 	}
 }
 
diff --git a/include/linux/netpoll.h b/include/linux/netpoll.h
index 29930b7..e0e0a7b 100644
--- a/include/linux/netpoll.h
+++ b/include/linux/netpoll.h
@@ -37,6 +37,7 @@ struct netpoll_info {
 
 void netpoll_poll(struct netpoll *np);
 void netpoll_send_udp(struct netpoll *np, const char *msg, int len);
+void netpoll_print_options(struct netpoll *np);
 int netpoll_parse_options(struct netpoll *np, char *opt);
 int netpoll_setup(struct netpoll *np);
 int netpoll_trap(void);
diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index de1b26a..3f753c6 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -519,6 +519,29 @@ out:
 	return 0;
 }
 
+void netpoll_print_options(struct netpoll *np)
+{
+	printk(KERN_INFO "%s: local port %d\n",
+			 np->name, np->local_port);
+	printk(KERN_INFO "%s: local IP %d.%d.%d.%d\n",
+			 np->name, HIPQUAD(np->local_ip));
+	printk(KERN_INFO "%s: interface %s\n",
+			 np->name, np->dev_name);
+	printk(KERN_INFO "%s: remote port %d\n",
+			 np->name, np->remote_port);
+	printk(KERN_INFO "%s: remote IP %d.%d.%d.%d\n",
+			 np->name, HIPQUAD(np->remote_ip));
+	printk(KERN_INFO "%s: remote ethernet address "
+			 "%02x:%02x:%02x:%02x:%02x:%02x\n",
+			 np->name,
+			 np->remote_mac[0],
+			 np->remote_mac[1],
+			 np->remote_mac[2],
+			 np->remote_mac[3],
+			 np->remote_mac[4],
+			 np->remote_mac[5]);
+}
+
 int netpoll_parse_options(struct netpoll *np, char *opt)
 {
 	char *cur=opt, *delim;
@@ -531,7 +554,6 @@ int netpoll_parse_options(struct netpoll *np, char *opt)
 		cur = delim;
 	}
 	cur++;
-	printk(KERN_INFO "%s: local port %d\n", np->name, np->local_port);
 
 	if (*cur != '/') {
 		if ((delim = strchr(cur, '/')) == NULL)
@@ -539,9 +561,6 @@ int netpoll_parse_options(struct netpoll *np, char *opt)
 		*delim = 0;
 		np->local_ip = ntohl(in_aton(cur));
 		cur = delim;
-
-		printk(KERN_INFO "%s: local IP %d.%d.%d.%d\n",
-		       np->name, HIPQUAD(np->local_ip));
 	}
 	cur++;
 
@@ -555,8 +574,6 @@ int netpoll_parse_options(struct netpoll *np, char *opt)
 	}
 	cur++;
 
-	printk(KERN_INFO "%s: interface %s\n", np->name, np->dev_name);
-
 	if (*cur != '@') {
 		/* dst port */
 		if ((delim = strchr(cur, '@')) == NULL)
@@ -566,7 +583,6 @@ int netpoll_parse_options(struct netpoll *np, char *opt)
 		cur = delim;
 	}
 	cur++;
-	printk(KERN_INFO "%s: remote port %d\n", np->name, np->remote_port);
 
 	/* dst ip */
 	if ((delim = strchr(cur, '/')) == NULL)
@@ -575,9 +591,6 @@ int netpoll_parse_options(struct netpoll *np, char *opt)
 	np->remote_ip = ntohl(in_aton(cur));
 	cur = delim + 1;
 
-	printk(KERN_INFO "%s: remote IP %d.%d.%d.%d\n",
-	       np->name, HIPQUAD(np->remote_ip));
-
 	if (*cur != 0) {
 		/* MAC address */
 		if ((delim = strchr(cur, ':')) == NULL)
@@ -608,15 +621,7 @@ int netpoll_parse_options(struct netpoll *np, char *opt)
 		np->remote_mac[5] = simple_strtol(cur, NULL, 16);
 	}
 
-	printk(KERN_INFO "%s: remote ethernet address "
-	       "%02x:%02x:%02x:%02x:%02x:%02x\n",
-	       np->name,
-	       np->remote_mac[0],
-	       np->remote_mac[1],
-	       np->remote_mac[2],
-	       np->remote_mac[3],
-	       np->remote_mac[4],
-	       np->remote_mac[5]);
+	netpoll_print_options(np);
 
 	return 0;
 
@@ -820,6 +825,7 @@ void netpoll_set_trap(int trap)
 
 EXPORT_SYMBOL(netpoll_set_trap);
 EXPORT_SYMBOL(netpoll_trap);
+EXPORT_SYMBOL(netpoll_print_options);
 EXPORT_SYMBOL(netpoll_parse_options);
 EXPORT_SYMBOL(netpoll_setup);
 EXPORT_SYMBOL(netpoll_cleanup);

Re: [PATCH v3 -mm 9/9] netconsole: Support dynamic reconfiguration using configfs

[Andrew Morton]

On Mon, 30 Jul 2007 08:19:10 +0530
Satyam Sharma <satyam@infradead.org> wrote:

> +/*
> + * Wrapper over simple_strtol (base 10) with sanity and range checking.
> + * We return (signed) long only because we may want to return errors.
> + * Do not use this to convert numbers that are allowed to be negative.
> + */
> +static long strtol10_check_range(const char *cp, long min, long max)
> +{
> +	long ret;
> +	char *p = (char *) cp;
> +
> +	WARN_ON(min < 0);
> +	WARN_ON(max < min);
> +
> +	ret = simple_strtol(p, &p, 10);
> +
> +	if (*p && (*p != '\n')) {
> +		printk(KERN_ERR "netconsole: invalid input\n");
> +		return -EINVAL;
> +	}
> +	if ((ret < min) || (ret > max)) {
> +		printk(KERN_ERR "netconsole: input %ld must be between "
> +				"%ld and %ld\n", ret, min, max);
> +		return -EINVAL;
> +	}
> +
> +	return ret;
> +}

There's probably other code around the place which does this.  It might
be worth making this function a general-purpose thing.

Re: [PATCH v3 -mm 9/9] netconsole: Support dynamic reconfiguration using configfs

[Satyam Sharma]

On Mon, 30 Jul 2007, Andrew Morton wrote:

> On Mon, 30 Jul 2007 08:19:10 +0530
> Satyam Sharma <satyam@infradead.org> wrote:
> 
> > +/*
> > + * Wrapper over simple_strtol (base 10) with sanity and range checking.
> > + * We return (signed) long only because we may want to return errors.
> > + * Do not use this to convert numbers that are allowed to be negative.
> > + */
> > +static long strtol10_check_range(const char *cp, long min, long max)
> > +{
> > +	long ret;
> > +	char *p = (char *) cp;
> > +
> > +	WARN_ON(min < 0);
> > +	WARN_ON(max < min);
> > +
> > +	ret = simple_strtol(p, &p, 10);
> > +
> > +	if (*p && (*p != '\n')) {
> > +		printk(KERN_ERR "netconsole: invalid input\n");
> > +		return -EINVAL;
> > +	}
> > +	if ((ret < min) || (ret > max)) {
> > +		printk(KERN_ERR "netconsole: input %ld must be between "
> > +				"%ld and %ld\n", ret, min, max);
> > +		return -EINVAL;
> > +	}
> > +
> > +	return ret;
> > +}
> 
> There's probably other code around the place which does this.  It might
> be worth making this function a general-purpose thing.

Probably, yes, I thought along similar lines.

[ BTW somewhere in the 9/9 patch I remember having to define a
  __U16_MAX as well. That could be pushed out to some generic
  or appropriate header as well, possibly. ]


Satyam

Re: [PATCH v3 -mm 0/9] netconsole: Multiple targets and dynamic reconfigurability

[Andrew Morton]

On Mon, 30 Jul 2007 08:17:41 +0530
Satyam Sharma <satyam@infradead.org> wrote:

> [0/9] netconsole: Multiple targets and dynamic reconfigurability
> 
> This is v3 of the patchset

That all looks pretty reasonable, thanks.

Are we all comfortable with the attributions?  As I have it now, everything
will go in as having been authored by yourself.  There is no formal (ie:
understood-by-git) way of recording joint authorship, unfortunately.  But one
can make a record of such things in the changelog.

I'll queue this material up in the to-be-sent-to-davem queue.

Re: [PATCH v3 -mm 0/9] netconsole: Multiple targets and dynamic reconfigurability

[Satyam Sharma]

On Mon, 30 Jul 2007, Andrew Morton wrote:

> On Mon, 30 Jul 2007 08:17:41 +0530
> Satyam Sharma <satyam@infradead.org> wrote:
> 
> > [0/9] netconsole: Multiple targets and dynamic reconfigurability
> > 
> > This is v3 of the patchset
> 
> That all looks pretty reasonable, thanks.
> 
> Are we all comfortable with the attributions?  As I have it now, everything
> will go in as having been authored by yourself.  There is no formal (ie:
> understood-by-git) way of recording joint authorship, unfortunately.  But one
> can make a record of such things in the changelog.

Ok, making such a record would be good, if possible. I did see that the
"author" field for git commits can have only one entry, unfortunately,
and it turns out "Signed-off-by" and "Acked-by" have other meanings
attached that have to do with the patch-journey-from-author-to-you chain.
But I'd like these to be somehow marked as jointly authored, definitely.

> I'll queue this material up in the to-be-sent-to-davem queue.

Ok, thanks.


Satyam