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net: netconsole: Add continuation line prefix to userdata messages 

Add a space (' ') prefix to every userdata line to match docs for
dev-kmsg. To account for this extra character in each userdata entry,
reduce userdata entry names (directory name) from 54 characters to 53.

According to the dev-kmsg docs, a space is used for subsequent lines to
mark them as continuation lines.

> A line starting with ' ', is a continuation line, adding
> key/value pairs to the log message, which provide the machine
> readable context of the message, for reliable processing in
> userspace.

Testing for this patch::

 cd /sys/kernel/config/netconsole && mkdir cmdline0
 cd cmdline0
 mkdir userdata/test && echo "hello" > userdata/test/value
 mkdir userdata/test2 && echo "hello2" > userdata/test2/value
 echo "message" > /dev/kmsg

Outputs::

 6.8.0-rc5-virtme,12,493,231373579,-;message
  test=hello
  test2=hello2

And I confirmed all testing works as expected from the original patchset

Fixes: df03f830d0 ("net: netconsole: cache userdata formatted string in netconsole_target")
Signed-off-by: Matthew Wood <thepacketgeek@gmail.com>
Reviewed-by: Breno Leitao <leitao@debian.org>
Link: https://lore.kernel.org/r/20240308002525.248672-1-thepacketgeek@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Matthew Wood 2024-03-07 16:25:24 -08:00 committed by Jakub Kicinski
parent 031a239c22
commit 2b39535859
2 changed files with 11 additions and 9 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
Documentation/networking/netconsole.rst
View File

@ -180,7 +180,7 @@ Custom user data can be appended to the end of messages with netconsole
dynamic configuration enabled. User data entries can be modified without
changing the "enabled" attribute of a target.
Directories (keys) under `userdata` are limited to 54 character length, and
Directories (keys) under `userdata` are limited to 53 character length, and
data in `userdata/<key>/value` are limited to 200 bytes::
cd /sys/kernel/config/netconsole && mkdir cmdline0
@ -197,8 +197,8 @@ Messages will now include this additional user data::
Sends::
12,607,22085407756,-;This is a message
foo=bar
qux=baz
foo=bar
qux=baz
Preview the userdata that will be appended with::
@ -218,7 +218,7 @@ The `qux` key is omitted since it has no value::
echo "This is a message" > /dev/kmsg
12,607,22085407756,-;This is a message
foo=bar
foo=bar
Delete `userdata` entries with `rmdir`::

12
drivers/net/netconsole.c
View File

@ -42,12 +42,14 @@ MODULE_AUTHOR("Maintainer: Matt Mackall <mpm@selenic.com>");
MODULE_DESCRIPTION("Console driver for network interfaces");
MODULE_LICENSE("GPL");
#define MAX_PARAM_LENGTH 256
#define MAX_USERDATA_NAME_LENGTH 54
#define MAX_USERDATA_VALUE_LENGTH 200
#define MAX_PARAM_LENGTH 256
#define MAX_USERDATA_ENTRY_LENGTH 256
#define MAX_USERDATA_VALUE_LENGTH 200
/* The number 3 comes from userdata entry format characters (' ', '=', '\n') */
#define MAX_USERDATA_NAME_LENGTH (MAX_USERDATA_ENTRY_LENGTH - \
MAX_USERDATA_VALUE_LENGTH - 3)
#define MAX_USERDATA_ITEMS 16
#define MAX_PRINT_CHUNK 1000
#define MAX_PRINT_CHUNK 1000
static char config[MAX_PARAM_LENGTH];
module_param_string(netconsole, config, MAX_PARAM_LENGTH, 0);
@ -671,7 +673,7 @@ static void update_userdata(struct netconsole_target *nt)
* checked to not exceed MAX items with child_count above
*/
complete_idx += scnprintf(&nt->userdata_complete[complete_idx],
MAX_USERDATA_ENTRY_LENGTH, "%s=%s\n",
MAX_USERDATA_ENTRY_LENGTH, " %s=%s\n",
item->ci_name, udm_item->value);
}
nt->userdata_length = strnlen(nt->userdata_complete,