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authorCarsten Emde <C.Emde@osadl.org>2011-07-19 13:51:17 +0100
committerClark Williams <williams@redhat.com>2012-04-10 16:37:31 -0500
commit7e4226a78990e1498ea7f19842f01aa34503c5a2 (patch)
tree97969345f424d0c0687d2896a2b831e37be2034f
parent066fc89f602eca226ef21561c2b93a08c658e136 (diff)
ping-sysrq.patch
There are (probably rare) situations when a system crashed and the system console becomes unresponsive but the network icmp layer still is alive. Wouldn't it be wonderful, if we then could submit a sysreq command via ping? This patch provides this facility. Please consult the updated documentation Documentation/sysrq.txt for details. Signed-off-by: Carsten Emde <C.Emde@osadl.org>
-rw-r--r--Documentation/sysrq.txt11
-rw-r--r--include/net/netns/ipv4.h1
-rw-r--r--net/ipv4/icmp.c30
-rw-r--r--net/ipv4/sysctl_net_ipv4.c7
4 files changed, 47 insertions, 2 deletions
diff --git a/Documentation/sysrq.txt b/Documentation/sysrq.txt
index 312e3754e8c5..9981f307ef0e 100644
--- a/Documentation/sysrq.txt
+++ b/Documentation/sysrq.txt
@@ -57,10 +57,17 @@ On PowerPC - Press 'ALT - Print Screen (or F13) - <command key>,
On other - If you know of the key combos for other architectures, please
let me know so I can add them to this section.
-On all - write a character to /proc/sysrq-trigger. e.g.:
-
+On all - write a character to /proc/sysrq-trigger, e.g.:
echo t > /proc/sysrq-trigger
+On all - Enable network SysRq by writing a cookie to icmp_echo_sysrq, e.g.
+ echo 0x01020304 >/proc/sys/net/ipv4/icmp_echo_sysrq
+ Send an ICMP echo request with this pattern plus the particular
+ SysRq command key. Example:
+ # ping -c1 -s57 -p0102030468
+ will trigger the SysRq-H (help) command.
+
+
* What are the 'command' keys?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
'b' - Will immediately reboot the system without syncing or unmounting
diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h
index d786b4fc02a4..8cef1d197dd2 100644
--- a/include/net/netns/ipv4.h
+++ b/include/net/netns/ipv4.h
@@ -47,6 +47,7 @@ struct netns_ipv4 {
int sysctl_icmp_echo_ignore_all;
int sysctl_icmp_echo_ignore_broadcasts;
+ int sysctl_icmp_echo_sysrq;
int sysctl_icmp_ignore_bogus_error_responses;
int sysctl_icmp_ratelimit;
int sysctl_icmp_ratemask;
diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
index ab188ae12fd9..028eb47226e8 100644
--- a/net/ipv4/icmp.c
+++ b/net/ipv4/icmp.c
@@ -67,6 +67,7 @@
#include <linux/jiffies.h>
#include <linux/kernel.h>
#include <linux/fcntl.h>
+#include <linux/sysrq.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/inet.h>
@@ -801,6 +802,30 @@ out_err:
}
/*
+ * 32bit and 64bit have different timestamp length, so we check for
+ * the cookie at offset 20 and verify it is repeated at offset 50
+ */
+#define CO_POS0 20
+#define CO_POS1 50
+#define CO_SIZE sizeof(int)
+#define ICMP_SYSRQ_SIZE 57
+
+/*
+ * We got a ICMP_SYSRQ_SIZE sized ping request. Check for the cookie
+ * pattern and if it matches send the next byte as a trigger to sysrq.
+ */
+static void icmp_check_sysrq(struct net *net, struct sk_buff *skb)
+{
+ int cookie = htonl(net->ipv4.sysctl_icmp_echo_sysrq);
+ char *p = skb->data;
+
+ if (!memcmp(&cookie, p + CO_POS0, CO_SIZE) &&
+ !memcmp(&cookie, p + CO_POS1, CO_SIZE) &&
+ p[CO_POS0 + CO_SIZE] == p[CO_POS1 + CO_SIZE])
+ handle_sysrq(p[CO_POS0 + CO_SIZE]);
+}
+
+/*
* Handle ICMP_ECHO ("ping") requests.
*
* RFC 1122: 3.2.2.6 MUST have an echo server that answers ICMP echo
@@ -827,6 +852,11 @@ static void icmp_echo(struct sk_buff *skb)
icmp_param.data_len = skb->len;
icmp_param.head_len = sizeof(struct icmphdr);
icmp_reply(&icmp_param, skb);
+
+ if (skb->len == ICMP_SYSRQ_SIZE &&
+ net->ipv4.sysctl_icmp_echo_sysrq) {
+ icmp_check_sysrq(net, skb);
+ }
}
}
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 69fd7201129a..0ecdb72e032a 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -680,6 +680,13 @@ static struct ctl_table ipv4_net_table[] = {
.proc_handler = proc_dointvec
},
{
+ .procname = "icmp_echo_sysrq",
+ .data = &init_net.ipv4.sysctl_icmp_echo_sysrq,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = proc_dointvec
+ },
+ {
.procname = "icmp_ignore_bogus_error_responses",
.data = &init_net.ipv4.sysctl_icmp_ignore_bogus_error_responses,
.maxlen = sizeof(int),