[NET] use the netpoll API to transmit kernel printks over UDP

Documentation/networking/netconsole.txt

+
+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>
+
+This module logs kernel printk messages over UDP allowing debugging of
+problem where disk logging fails and serial consoles are impractical.
+
+It can be used either built-in or as a module. As a built-in,
+netconsole initializes immediately after NIC cards and will bring up
+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.
+
+It takes a string configuration parameter "netconsole" in the
+following format:
+
+ netconsole=[src-port]@[src-ip]/[<dev>],[tgt-port]@<tgt-ip>/[tgt-macaddr]
+
+   where
+        src-port      source for UDP packets (defaults to 6665)
+        src-ip        source IP to use (interface address)
+        dev           network interface (eth0)
+        tgt-port      port for logging agent (6666)
+        tgt-ip        IP address for logging agent
+        tgt-macaddr   ethernet MAC address for logging agent (broadcast)
+
+Examples:
+
+ linux netconsole=4444@10.0.0.1/eth1,9353@10.0.0.2/12:34:56:78:9a:bc
+
+  or
+
+ insmod netconsole netconsole=@/,@10.0.0.2/
+
+Built-in netconsole starts immediately after the TCP stack is
+initialized and attempts to bring up the supplied dev at the supplied
+address.
+
+The remote host can run either 'netcat -u -l -p <port>' or syslogd.
+
+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.
+
+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.
+
+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
+sending packets. Due to these unique needs, configuration can not
+be more automatic, and some fundamental limitations will remain:
+only IP networks, UDP packets and ethernet devices are supported.

drivers/net/Kconfig

@@ -2441,6 +2441,13 @@ config SHAPER
 	  To compile this driver as a module, choose M here: the module
 	  will be called shaper.  If unsure, say N.
 
+config NETCONSOLE
+	tristate "Network console logging support (EXPERIMENTAL)"
+	depends on NETDEVICES && EXPERIMENTAL
+	---help---
+	If you want to log kernel messages over the network, enable this.
+	See Documentation/networking/netconsole.txt for details.
+
 source "drivers/net/wan/Kconfig"
 
 source "drivers/net/pcmcia/Kconfig"

drivers/net/Makefile

@@ -188,3 +188,4 @@ obj-$(CONFIG_NET_TULIP) += tulip/
 obj-$(CONFIG_HAMRADIO) += hamradio/
 obj-$(CONFIG_IRDA) += irda/
 
+obj-$(CONFIG_NETCONSOLE) += netconsole.o

drivers/net/netconsole.c

+/*
+ *  linux/drivers/net/netconsole.c
+ *
+ *  Copyright (C) 2001  Ingo Molnar <mingo@redhat.com>
+ *
+ *  This file contains the implementation of an IRQ-safe, crash-safe
+ *  kernel console implementation that outputs kernel messages to the
+ *  network.
+ *
+ * Modification history:
+ *
+ * 2001-09-17    started by Ingo Molnar.
+ * 2003-08-11    2.6 port by Matt Mackall
+ *               simplified options
+ *               generic card hooks
+ *               works non-modular
+ * 2003-09-07    rewritten with netpoll api
+ */
+
+/****************************************************************
+ *      This program is free software; you can redistribute it and/or modify
+ *      it under the terms of the GNU General Public License as published by
+ *      the Free Software Foundation; either version 2, or (at your option)
+ *      any later version.
+ *
+ *      This program is distributed in the hope that it will be useful,
+ *      but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *      GNU General Public License for more details.
+ *
+ *      You should have received a copy of the GNU General Public License
+ *      along with this program; if not, write to the Free Software
+ *      Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+ *
+ ****************************************************************/
+
+#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/module.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);
+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},
+};
+
+#define MAX_PRINT_CHUNK 1000
+
+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; ) {
+		frag = min(left, MAX_PRINT_CHUNK);
+		netpoll_send_udp(&np, msg, frag);
+		msg += frag;
+		left -= frag;
+	}
+
+	local_irq_restore(flags);
+}
+
+static struct console netconsole = {
+	.flags = CON_ENABLED | CON_PRINTBUFFER,
+	.write = write_msg
+};
+
+static int option_setup(char *opt)
+{
+	return netpoll_parse_options(&np, opt);
+}
+
+__setup("netconsole=", option_setup);
+
+static int init_netconsole(void)
+{
+	if(strlen(config) && option_setup(config))
+		return 1;
+
+	if(!np.remote_ip || netpoll_setup(&np))
+		return 1;
+
+	register_console(&netconsole);
+	printk(KERN_INFO "netconsole: network logging started\n");
+	return 0;
+}
+
+static void cleanup_netconsole(void)
+{
+	unregister_console(&netconsole);
+	netpoll_cleanup(&np);
+}
+
+module_init(init_netconsole);
+module_exit(cleanup_netconsole);

net/Kconfig

@@ -665,14 +665,16 @@ source "net/irda/Kconfig"
 source "net/bluetooth/Kconfig"
 
 config NETPOLL
-	bool "Netpoll API"
+	def_bool NETCONSOLE
 
 config NETPOLL_RX
-	bool "Netpoll receive hooks"
+	bool "Netpoll support for trapping incoming packets"
+	default n
 	depends on NETPOLL
 
 config NETPOLL_TRAP
 	bool "Netpoll traffic trapping"
+	default n
 	depends on NETPOLL
 
 config NET_POLL_CONTROLLER