Re: [PATCH]: Add Network Sysrq Support

On Tue, 21 Jun 2011 22:37:20 +0200 Florian Westphal wrote:

Randy Dunlap [off-list ref] wrote:

quoted

quoted

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)

quoted

+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.

There is an xt_SYSREQ module in xtables-addons package (i.e., a
netfilter target), it supports hashed passwords and has some sequence
number scheme to avoid replays.

I think it would make more sense to merge that upstream, simply because
it seems to be a bit more advanced...

in which case I would prefer this patch instead of a netfilter patch.  :)

---
~Randy
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