Commit 0bcc1816 authored by Satyam Sharma's avatar Satyam Sharma Committed by David S. Miller

[NET] netconsole: Support dynamic reconfiguration using configfs

Based upon initial work by Keiichi Kii <k-keiichi@bx.jp.nec.com>.

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: default avatarSatyam Sharma <satyam@infradead.org>
Acked-by: default avatarKeiichi Kii <k-keiichi@bx.jp.nec.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent b5427c27
...@@ -3,6 +3,10 @@ started by Ingo Molnar <mingo@redhat.com>, 2001.09.17 ...@@ -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 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> 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 This module logs kernel printk messages over UDP allowing debugging of
problem where disk logging fails and serial consoles are impractical. 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 ...@@ -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 capture of early kernel panics, it does capture most of the boot
process. process.
Sender and receiver configuration:
==================================
It takes a string configuration parameter "netconsole" in the It takes a string configuration parameter "netconsole" in the
following format: following format:
...@@ -46,6 +53,67 @@ address. ...@@ -46,6 +53,67 @@ address.
The remote host can run either 'netcat -u -l -p <port>' or syslogd. 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 WARNING: the default target ethernet setting uses the broadcast
ethernet address to send packets, which can cause increased load on ethernet address to send packets, which can cause increased load on
other systems on the same ethernet segment. other systems on the same ethernet segment.
......
...@@ -3082,6 +3082,16 @@ config NETCONSOLE ...@@ -3082,6 +3082,16 @@ config NETCONSOLE
If you want to log kernel messages over the network, enable this. If you want to log kernel messages over the network, enable this.
See <file:Documentation/networking/netconsole.txt> for details. 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 config NETPOLL
def_bool NETCONSOLE def_bool NETCONSOLE
......
This diff is collapsed.
...@@ -35,6 +35,7 @@ struct netpoll_info { ...@@ -35,6 +35,7 @@ struct netpoll_info {
void netpoll_poll(struct netpoll *np); void netpoll_poll(struct netpoll *np);
void netpoll_send_udp(struct netpoll *np, const char *msg, int len); 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_parse_options(struct netpoll *np, char *opt);
int netpoll_setup(struct netpoll *np); int netpoll_setup(struct netpoll *np);
int netpoll_trap(void); int netpoll_trap(void);
......
...@@ -532,6 +532,29 @@ int __netpoll_rx(struct sk_buff *skb) ...@@ -532,6 +532,29 @@ int __netpoll_rx(struct sk_buff *skb)
return 0; 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) int netpoll_parse_options(struct netpoll *np, char *opt)
{ {
char *cur=opt, *delim; char *cur=opt, *delim;
...@@ -544,7 +567,6 @@ int netpoll_parse_options(struct netpoll *np, char *opt) ...@@ -544,7 +567,6 @@ int netpoll_parse_options(struct netpoll *np, char *opt)
cur = delim; cur = delim;
} }
cur++; cur++;
printk(KERN_INFO "%s: local port %d\n", np->name, np->local_port);
if (*cur != '/') { if (*cur != '/') {
if ((delim = strchr(cur, '/')) == NULL) if ((delim = strchr(cur, '/')) == NULL)
...@@ -552,9 +574,6 @@ int netpoll_parse_options(struct netpoll *np, char *opt) ...@@ -552,9 +574,6 @@ int netpoll_parse_options(struct netpoll *np, char *opt)
*delim = 0; *delim = 0;
np->local_ip = ntohl(in_aton(cur)); np->local_ip = ntohl(in_aton(cur));
cur = delim; cur = delim;
printk(KERN_INFO "%s: local IP %d.%d.%d.%d\n",
np->name, HIPQUAD(np->local_ip));
} }
cur++; cur++;
...@@ -568,8 +587,6 @@ int netpoll_parse_options(struct netpoll *np, char *opt) ...@@ -568,8 +587,6 @@ int netpoll_parse_options(struct netpoll *np, char *opt)
} }
cur++; cur++;
printk(KERN_INFO "%s: interface %s\n", np->name, np->dev_name);
if (*cur != '@') { if (*cur != '@') {
/* dst port */ /* dst port */
if ((delim = strchr(cur, '@')) == NULL) if ((delim = strchr(cur, '@')) == NULL)
...@@ -579,7 +596,6 @@ int netpoll_parse_options(struct netpoll *np, char *opt) ...@@ -579,7 +596,6 @@ int netpoll_parse_options(struct netpoll *np, char *opt)
cur = delim; cur = delim;
} }
cur++; cur++;
printk(KERN_INFO "%s: remote port %d\n", np->name, np->remote_port);
/* dst ip */ /* dst ip */
if ((delim = strchr(cur, '/')) == NULL) if ((delim = strchr(cur, '/')) == NULL)
...@@ -588,9 +604,6 @@ int netpoll_parse_options(struct netpoll *np, char *opt) ...@@ -588,9 +604,6 @@ int netpoll_parse_options(struct netpoll *np, char *opt)
np->remote_ip = ntohl(in_aton(cur)); np->remote_ip = ntohl(in_aton(cur));
cur = delim + 1; cur = delim + 1;
printk(KERN_INFO "%s: remote IP %d.%d.%d.%d\n",
np->name, HIPQUAD(np->remote_ip));
if (*cur != 0) { if (*cur != 0) {
/* MAC address */ /* MAC address */
if ((delim = strchr(cur, ':')) == NULL) if ((delim = strchr(cur, ':')) == NULL)
...@@ -621,15 +634,7 @@ int netpoll_parse_options(struct netpoll *np, char *opt) ...@@ -621,15 +634,7 @@ int netpoll_parse_options(struct netpoll *np, char *opt)
np->remote_mac[5] = simple_strtol(cur, NULL, 16); np->remote_mac[5] = simple_strtol(cur, NULL, 16);
} }
printk(KERN_INFO "%s: remote ethernet address " netpoll_print_options(np);
"%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]);
return 0; return 0;
...@@ -831,6 +836,7 @@ void netpoll_set_trap(int trap) ...@@ -831,6 +836,7 @@ void netpoll_set_trap(int trap)
EXPORT_SYMBOL(netpoll_set_trap); EXPORT_SYMBOL(netpoll_set_trap);
EXPORT_SYMBOL(netpoll_trap); EXPORT_SYMBOL(netpoll_trap);
EXPORT_SYMBOL(netpoll_print_options);
EXPORT_SYMBOL(netpoll_parse_options); EXPORT_SYMBOL(netpoll_parse_options);
EXPORT_SYMBOL(netpoll_setup); EXPORT_SYMBOL(netpoll_setup);
EXPORT_SYMBOL(netpoll_cleanup); EXPORT_SYMBOL(netpoll_cleanup);
......
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