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Message-Id: <20110621130929.ddd107f7.rdunlap@xenotime.net>
Date: Tue, 21 Jun 2011 13:09:29 -0700
From: Randy Dunlap <rdunlap@...otime.net>
To: Prarit Bhargava <prarit@...hat.com>
Cc: netdev@...r.kernel.org, davem@...emloft.net, agospoda@...hat.com,
nhorman@...hat.com, lwoodman@...hat.com
Subject: Re: [PATCH]: Add Network Sysrq Support
On Tue, 21 Jun 2011 09:00:40 -0400 Prarit Bhargava wrote:
> Add Network Sysrq Support
> Signed-off-by: Prarit Bhargava <prarit@...hat.com>
>
> diff --git a/Documentation/networking/sysrq-ping.txt b/Documentation/networking/sysrq-ping.txt
> new file mode 100644
> index 0000000..efa8be3
> --- /dev/null
> +++ b/Documentation/networking/sysrq-ping.txt
> @@ -0,0 +1,26 @@
> +In some circumstances, a system can hang/lockup in such a way that the system
> +is completely unresponsive to keyboard or console input but is still
> +responsive to ping. The config option, CONFIG_SYSRQ_PING, builds
> +net/ipv4/sysrq-ping.ko which allows a root user to configure the system for a
or it can be built-in the kernel image... (i.e., not a loadable module)
> +remote sysrq.
> +
> +To use this do:
> +
> +mount -t debugfs none /sys/kernel/debug/
> +echo 1 > /proc/sys/kernel/sysrq
> +echo <hex digit val> > /sys/kernel/debug/network_sysrq_magic
> +echo 1 > /sys/kernel/debug/network_sysrq_enable
so all of this (insecure) stuff has to be done before you suspect that
you need it .. in case the local keyboard/console is dead.
> +
> +Then on another system you can do:
> +
> +ping -c 1 -p <hex digit val><hex val of sysrq> <target_system_name>
What are the <up to 30 hex digits> for?
> +
> +ex) sysrq-m, m is ascii 0x6d
e.g., sysrq-m (m is ASCII 0x6d)
> +
> + ping -c 1 p 1623a06f554d46d676d <target_system_name>
> +
> +Note that the network sysrq automatically disables after the receipt of
> +the ping, ie) it is single-shot mode. If you want to use this again, you
i.e., it is single-shot mode.
> +must complete the above four steps again.
> +
> +Hint: 'man ascii' ;)
> diff --git a/net/ipv4/Kconfig b/net/ipv4/Kconfig
> index cbb505b..03bb7b1 100644
> --- a/net/ipv4/Kconfig
> +++ b/net/ipv4/Kconfig
> @@ -624,3 +624,11 @@ config TCP_MD5SIG
> on the Internet.
>
> If unsure, say N.
> +
> +config SYSRQ_PING
> + tristate
Needs a prompt?
> + default m
Please do not enable random code to be built.
> + help
> + Allows execution of sysrq-X commands via ping over ipv4. This is a
No ipv6 support? future?
> + known security hazard and should not be used in unsecure
insecure
> + environments.
---
~Randy
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