linux.git/Documentation/networking/netconsole.txt, branch master

docs: networking: convert netconsole.txt to ReST

2020-04-30T19:56:36+00:00

- add SPDX header;
- add a document title;
- mark code blocks and literals as such;
- mark tables as such;
- add notes markups;
- adjust identation, whitespaces and blank lines;
- add to networking/index.rst.

Signed-off-by: Mauro Carvalho Chehab 
Signed-off-by: David S. Miller

docs: fix locations of several documents that got moved

2016-10-24T10:12:35+00:00

The previous patch renamed several files that are cross-referenced
along the Kernel documentation. Adjust the links to point to
the right places.

Signed-off-by: Mauro Carvalho Chehab

netconsole: implement extended console support

2015-06-26T00:00:39+00:00

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 
Cc: David Miller 
Cc: Kay Sievers 
Cc: Petr Mladek 
Cc: Tetsuo Handa 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

netconsole: add IPv6 example in doc

2013-01-09T01:56:10+00:00

Update the netconsole document as well.

Cc: David S. Miller 
Signed-off-by: Cong Wang 
Signed-off-by: David S. Miller

netconsole.txt: revision of examples for the receiver of kernel messages

2012-08-14T21:33:33+00:00

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 
Signed-off-by: Cong Wang 
Signed-off-by: David S. Miller

networking: document "nc" in addition to "netcat" in netconsole.txt

2009-01-26T20:19:23+00:00

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 
Signed-off-by: Randy Dunlap 
Signed-off-by: Matt Mackall 
Signed-off-by: David S. Miller

[NET] netconsole: Support dynamic reconfiguration using configfs

2007-10-10T23:48:06+00:00

Based upon initial work by Keiichi Kii .

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 
Acked-by: Keiichi Kii 
Signed-off-by: Andrew Morton 
Signed-off-by: David S. Miller

[NET] netconsole: Support multiple logging targets

2007-10-10T23:48:06+00:00

Based upon initial work by Keiichi Kii .

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 
Signed-off-by: Keiichi Kii 
Signed-off-by: Andrew Morton 
Signed-off-by: David S. Miller

[NET] netconsole: Add some useful tips to documentation

2007-10-10T23:48:04+00:00

Based upon initial work by Keiichi Kii .

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 
Acked-by: Keiichi Kii 
Acked-by: Matt Mackall 
Signed-off-by: Andrew Morton 
Signed-off-by: David S. Miller

Fix "can not" in Documentation and Kconfig

2006-10-03T20:53:09+00:00

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 
Acked-by: Randy Dunlap 
Signed-off-by: Adrian Bunk