[v3] net: netconsole: Add continuation line prefix to userdata messages

[PATCH net-next v3] net: netconsole: Add continuation line prefix to userdata messages

Posted by Matthew Wood 1 year, 11 months ago

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: df03f830d099 ("net: netconsole: cache userdata formatted string in netconsole_target")
Reviewed-by: Breno Leitao <leitao@debian.org>
Signed-off-by: Matthew Wood <thepacketgeek@gmail.com>
---

v1 -> v2:
- Calculate 53 byte user data name from: entry length - formatting chars - value length
- Update docs to reflect 53 byte limit for user data name (director)
v2 -> v3:
- Added #define for userdata formatting character length (3)
- Matched all #defines indent level

 Documentation/networking/netconsole.rst |  8 ++++----
 drivers/net/netconsole.c                | 14 +++++++++-----
 2 files changed, 13 insertions(+), 9 deletions(-)

diff --git a/Documentation/networking/netconsole.rst b/Documentation/networking/netconsole.rst
index b28c525e5d1e..d55c2a22ec7a 100644
--- a/Documentation/networking/netconsole.rst
+++ b/Documentation/networking/netconsole.rst
@@ -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`::
 
diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
index 0de108a1c0c8..8cc28aec59c8 100644
--- a/drivers/net/netconsole.c
+++ b/drivers/net/netconsole.c
@@ -42,12 +42,16 @@ 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
+/* characters used for formatting each userdata entry line (' ', '=', '\n') */
+#define USERDATA_FORMAT_CHARS		3
 #define MAX_USERDATA_ENTRY_LENGTH	256
+#define MAX_USERDATA_VALUE_LENGTH	200
+#define MAX_USERDATA_NAME_LENGTH	MAX_USERDATA_ENTRY_LENGTH - \
+					MAX_USERDATA_VALUE_LENGTH - \
+					USERDATA_FORMAT_CHARS
 #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 +675,7 @@ 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,
-- 
2.44.0

Re: [PATCH net-next v3] net: netconsole: Add continuation line prefix to userdata messages

Posted by Paolo Abeni 1 year, 11 months ago

On Fri, 2024-03-01 at 10:58 -0800, Matthew Wood wrote:
> 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: df03f830d099 ("net: netconsole: cache userdata formatted string in netconsole_target")
> Reviewed-by: Breno Leitao <leitao@debian.org>

I guess the tag arrived off-list, because I can't see any sign of it on
the ML?!?

> Signed-off-by: Matthew Wood <thepacketgeek@gmail.com>
> ---
> 
> v1 -> v2:
> - Calculate 53 byte user data name from: entry length - formatting chars - value length
> - Update docs to reflect 53 byte limit for user data name (director)
> v2 -> v3:
> - Added #define for userdata formatting character length (3)
> - Matched all #defines indent level
> 
>  Documentation/networking/netconsole.rst |  8 ++++----
>  drivers/net/netconsole.c                | 14 +++++++++-----
>  2 files changed, 13 insertions(+), 9 deletions(-)
> 
> diff --git a/Documentation/networking/netconsole.rst b/Documentation/networking/netconsole.rst
> index b28c525e5d1e..d55c2a22ec7a 100644
> --- a/Documentation/networking/netconsole.rst
> +++ b/Documentation/networking/netconsole.rst
> @@ -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`::
>  
> diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
> index 0de108a1c0c8..8cc28aec59c8 100644
> --- a/drivers/net/netconsole.c
> +++ b/drivers/net/netconsole.c
> @@ -42,12 +42,16 @@ 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
> +/* characters used for formatting each userdata entry line (' ', '=', '\n') */
> +#define USERDATA_FORMAT_CHARS		3
>  #define MAX_USERDATA_ENTRY_LENGTH	256
> +#define MAX_USERDATA_VALUE_LENGTH	200
> +#define MAX_USERDATA_NAME_LENGTH	MAX_USERDATA_ENTRY_LENGTH - \
> +					MAX_USERDATA_VALUE_LENGTH - \
> +					USERDATA_FORMAT_CHARS

AFAICS this is not what Breno asked, and checkpatch complains
rightfully. More importantly it's fragile: what will be the result of

	MAX_USERDATA_NAME_LENGTH * 2

?

At least some brackets are required:

#define MAX_USERDATA_NAME_LENGTH	(MAX_USERDATA_ENTRY_LENGTH -
					 MAX_USERDATA_VALUE_LENGTH - \
					 USERDATA_FORMAT_CHARS)

Thanks,

Paolo

Re: [PATCH net-next v3] net: netconsole: Add continuation line prefix to userdata messages

Posted by Matthew Wood 1 year, 11 months ago

On Tue, Mar 5, 2024 at 4:14 AM Paolo Abeni <pabeni@redhat.com> wrote:
>
> On Fri, 2024-03-01 at 10:58 -0800, Matthew Wood wrote:
> > 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: df03f830d099 ("net: netconsole: cache userdata formatted string in netconsole_target")
> > Reviewed-by: Breno Leitao <leitao@debian.org>
>
> I guess the tag arrived off-list, because I can't see any sign of it on
> the ML?!?
>
> > Signed-off-by: Matthew Wood <thepacketgeek@gmail.com>
> > ---
> >
> > v1 -> v2:
> > - Calculate 53 byte user data name from: entry length - formatting chars - value length
> > - Update docs to reflect 53 byte limit for user data name (director)
> > v2 -> v3:
> > - Added #define for userdata formatting character length (3)
> > - Matched all #defines indent level
> >
> >  Documentation/networking/netconsole.rst |  8 ++++----
> >  drivers/net/netconsole.c                | 14 +++++++++-----
> >  2 files changed, 13 insertions(+), 9 deletions(-)
> >
> > diff --git a/Documentation/networking/netconsole.rst b/Documentation/networking/netconsole.rst
> > index b28c525e5d1e..d55c2a22ec7a 100644
> > --- a/Documentation/networking/netconsole.rst
> > +++ b/Documentation/networking/netconsole.rst
> > @@ -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`::
> >
> > diff --git a/drivers/net/netconsole.c b/drivers/net/netconsole.c
> > index 0de108a1c0c8..8cc28aec59c8 100644
> > --- a/drivers/net/netconsole.c
> > +++ b/drivers/net/netconsole.c
> > @@ -42,12 +42,16 @@ 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
> > +/* characters used for formatting each userdata entry line (' ', '=', '\n') */
> > +#define USERDATA_FORMAT_CHARS                3
> >  #define MAX_USERDATA_ENTRY_LENGTH    256
> > +#define MAX_USERDATA_VALUE_LENGTH    200
> > +#define MAX_USERDATA_NAME_LENGTH     MAX_USERDATA_ENTRY_LENGTH - \
> > +                                     MAX_USERDATA_VALUE_LENGTH - \
> > +                                     USERDATA_FORMAT_CHARS
>
> AFAICS this is not what Breno asked, and checkpatch complains
> rightfully. More importantly it's fragile: what will be the result of
>
>         MAX_USERDATA_NAME_LENGTH * 2
>
> ?
>
> At least some brackets are required:
>
> #define MAX_USERDATA_NAME_LENGTH        (MAX_USERDATA_ENTRY_LENGTH -
>                                          MAX_USERDATA_VALUE_LENGTH - \
>                                          USERDATA_FORMAT_CHARS)
>
> Thanks,
>
> Paolo
>

Thank you Paolo, great points. I will fix the macro and remove the
Reviewed-by tag so Breno can reply on the ML