Re: [PATCH] net: compare_ether_addr[_64bits]() has no ordering

From: Johannes Berg <johannes@sipsolutions.net>
Date: Mon, 07 May 2012 16:12:41 +0200

On Mon, 2012-05-07 at 15:53 +0200, Eric Dumazet wrote:

quoted

On Mon, 2012-05-07 at 15:39 +0200, Johannes Berg wrote:

quoted

From: Johannes Berg <redacted>

Neither compare_ether_addr() nor compare_ether_addr_64bits()
(as it can fall back to the former) have comparison semantics
like memcmp() where the sign of the return value indicates sort
order. We had a bug in the wireless code due to a blind memcmp
replacement because of this.

A cursory look suggests that the wireless bug was the only one
due to this semantic difference.

Signed-off-by: Johannes Berg <redacted>
---
 include/linux/etherdevice.h |   11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

The right way to avoid this kind of problems is to change these
functions to return a bool

Well, I guess so, but that'd be a weird thing for a compare_ function...
should probably be named equal_... then, but I'm not really able to do
such a huge change on the first day after my vacation :-)

It's true the name could be improved, but changing the name is quite
a large undertaking even with automated scripts.

Even the bool change is slightly painful, since all of the explicit
tests against integers (%99.999 of these are in wireless BTW :-) would
need to be adjusted.

For now, I'll just apply Johannes's comment fix.