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printk logbuf keeps various metadata and optional key=value dictionary for
structured messages, both of which are stripped when messages are handed
to regular console drivers.
It can be useful to have this metadata and dictionary available to
netconsole consumers. This obviously makes logging via netconsole more
complete and the sequence number in particular is useful in environments
where messages may be lost or reordered in transit - e.g. when netconsole
is used to collect messages in a large cluster where packets may have to
travel congested hops to reach the aggregator. The lost and reordered
messages can easily be identified and handled accordingly using the
sequence numbers.
printk recently added extended console support which can be selected by
setting CON_EXTENDED flag. From console driver side, not much changes.
The only difference is that the text passed to the write callback is
formatted the same way as /dev/kmsg.
This patch implements extended console support for netconsole which can be
enabled by either prepending "+" to a netconsole boot param entry or
echoing 1 to "extended" file in configfs. When enabled, netconsole
transmits extended log messages with headers identical to /dev/kmsg
output.
There's one complication due to message fragments. netconsole limits the
maximum message size to 1k and messages longer than that are split into
multiple fragments. As all extended console messages should carry
matching headers and be uniquely identifiable, each extended message
fragment carries full copy of the metadata and an extra header field to
identify the specific fragment. The optional header is of the form
"ncfrag=OFF/LEN" where OFF is the byte offset into the message body and
LEN is the total length.
To avoid unnecessarily making printk format extended messages, Extended
netconsole is registered with printk when the first extended netconsole is
configured.
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: David Miller <davem@davemloft.net>
Cc: Kay Sievers <kay@vrfy.org>
Cc: Petr Mladek <pmladek@suse.cz>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Update the netconsole document as well.
Cc: David S. Miller <davem@davemloft.net>
Signed-off-by: Cong Wang <amwang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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There are at least 4 implementations of netcat with the BSD-based
being the only one that has to be used without the -p switch to
specify the listening port.
Jan Engelhardt suggested to add an example for socat(1).
Signed-off-by: Dirk Gouders <gouders@et.bocholt.fh-gelsenkirchen.de>
Signed-off-by: Cong Wang <amwang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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It always annoyed me that the netconsole documentation didn't give me the
correct command for my distro. Update it with a command line that actually
works on my Fedora install.
Signed-off-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Matt Mackall <mpm@selenic.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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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: Satyam Sharma <satyam@infradead.org>
Acked-by: Keiichi Kii <k-keiichi@bx.jp.nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Based upon initial work by Keiichi Kii <k-keiichi@bx.jp.nec.com>.
This patch introduces support for multiple targets, independent of
CONFIG_NETCONSOLE_DYNAMIC -- this is useful even in the default case and
(including the infrastructure introduced in previous patches) doesn't really
add too many bytes to module text. All the complexity (and size) comes with
the dynamic reconfigurability / userspace interface patch, and so it's
plausible users may want to keep this enabled but that disabled (say to avoid
a dependency on CONFIG_CONFIGFS_FS too).
Also update documentation to mention the use of ";" separator to specify
multiple logging targets in the boot/module option string.
Brief overview:
We maintain a target_list (and corresponding lock). Get rid of the static
"default_target" and introduce allocation and release functions for our
netconsole_target objects (but keeping sure to preserve previous behaviour
such as default values). During init_netconsole(), ";" is used as the
separator to identify multiple target specifications in the boot/module option
string. The target specifications are parsed and netpolls setup. During
exit, the target_list is torn down and all items released.
Signed-off-by: Satyam Sharma <satyam@infradead.org>
Signed-off-by: Keiichi Kii <k-keiichi@bx.jp.nec.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Based upon initial work by Keiichi Kii <k-keiichi@bx.jp.nec.com>.
Add some useful general-purpose tips. Also suggest solution for the frequent
problem of console loglevel set too low numerically (i.e. for high priority
messages only) on the sender.
Signed-off-by: Satyam Sharma <satyam@infradead.org>
Acked-by: Keiichi Kii <k-keiichi@bx.jp.nec.com>
Acked-by: Matt Mackall <mpm@selenic.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
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Randy brought it to my attention that in proper english "can not" should always
be written "cannot". I donot see any reason to argue, even if I mightnot
understand why this rule exists. This patch fixes "can not" in several
Documentation files as well as three Kconfigs.
Signed-off-by: Matt LaPlante <kernel1@cyberdogtech.com>
Acked-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: Adrian Bunk <bunk@stusta.de>
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Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.
Let it rip!
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