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tracing/ipv4/ipv6: Give size to name field in fib*_lookup_table event

Message ID 20220703102359.30f12e39@rorschach.local.home (mailing list archive)
State Changes Requested
Delegated to: Netdev Maintainers
Headers show
Series tracing/ipv4/ipv6: Give size to name field in fib*_lookup_table event | expand

Checks

Context Check Description
netdev/tree_selection success Not a local patch

Commit Message

Steven Rostedt July 3, 2022, 2:23 p.m. UTC 
From: "Steven Rostedt (Google)" <rostedt@goodmis.org>

The fib_lookup_table and fib6_lookup_table events declare name as a
dynamic_array, but also give it a fixed size, which defeats the purpose of
the dynamic array, especially since the dynamic array also includes meta
data in the event to specify its size.

Considering that the intent was to only reserve the size needed for the
name and not a fixed size, convert the size part of the __dynamic_array()
field to contain the necessary code to determine the size needed to save
the name.

Alternatively, if the intent was to use a fixed size, then it should be
converted into __array() of type char, which will remove the meta data in
the event that stores the size.

Cc: David Ahern <dsahern@gmail.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: netdev@vger.kernel.org
Signed-off-by: Steven Rostedt (Google) <rostedt@goodmis.org>
---
 include/trace/events/fib.h  | 2 +-
 include/trace/events/fib6.h | 3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

Comments

David Ahern July 3, 2022, 7:03 p.m. UTC | #1 
On 7/3/22 8:23 AM, Steven Rostedt wrote:
> From: "Steven Rostedt (Google)" <rostedt@goodmis.org>
> 
> The fib_lookup_table and fib6_lookup_table events declare name as a
> dynamic_array, but also give it a fixed size, which defeats the purpose of
> the dynamic array, especially since the dynamic array also includes meta
> data in the event to specify its size.
> 
> Considering that the intent was to only reserve the size needed for the
> name and not a fixed size, convert the size part of the __dynamic_array()
> field to contain the necessary code to determine the size needed to save
> the name.
> 
> Alternatively, if the intent was to use a fixed size, then it should be
> converted into __array() of type char, which will remove the meta data in
> the event that stores the size.

I would prefer this option over duplicating the all of the checks to
save 14B.
Steven Rostedt July 3, 2022, 11:16 p.m. UTC | #2 
On Sun, 3 Jul 2022 13:03:20 -0600
David Ahern <dsahern@gmail.com> wrote:


> > Alternatively, if the intent was to use a fixed size, then it should be
> > converted into __array() of type char, which will remove the meta data in
> > the event that stores the size.  
> 
> I would prefer this option over duplicating the all of the checks to
> save 14B.

That's why I mentioned the alternative. To give you that option.

I'll send a v2 later that uses the static array.

-- Steve
diff mbox series

Patch

diff --git a/include/trace/events/fib.h b/include/trace/events/fib.h
index 6f2a4dc35e37..76f925f5519a 100644
--- a/include/trace/events/fib.h
+++ b/include/trace/events/fib.h
@@ -32,7 +32,7 @@  TRACE_EVENT(fib_table_lookup,
 		__array(	__u8,	gw6,	16	)
 		__field(	u16,	sport		)
 		__field(	u16,	dport		)
-		__dynamic_array(char,  name,   IFNAMSIZ )
+		__dynamic_array(char,  name,   nhc && nhc->nhc_dev ? strlen(nhc->nhc_dev->name) + 1 : sizeof("-") )
 	),
 
 	TP_fast_assign(
diff --git a/include/trace/events/fib6.h b/include/trace/events/fib6.h
index c6abdcc77c12..d3aee58e58fd 100644
--- a/include/trace/events/fib6.h
+++ b/include/trace/events/fib6.h
@@ -31,7 +31,8 @@  TRACE_EVENT(fib6_table_lookup,
 		__field(        u16,	dport		)
 		__field(        u8,	proto		)
 		__field(        u8,	rt_type		)
-		__dynamic_array(	char,	name,	IFNAMSIZ )
+		__dynamic_array(	char,	name,	res->nh && res->nh->fib_nh_dev ?
+							strlen(res->nh->fib_nh_dev->name) + 1 : sizeof("-") )
 		__array(		__u8,	gw,	16	 )
 	),