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| /openbmc/linux/net/ipv6/ |
| H A D | addrconf.c | c9d55d5b Wed Sep 25 17:12:55 CDT 2013 Paul Marks <pmarks@google.com> ipv6: Fix preferred_lft not updating in some cases
Consider the scenario where an IPv6 router is advertising a fixed
preferred_lft of 1800 seconds, while the valid_lft begins at 3600
seconds and counts down in realtime.
A client should reset its preferred_lft to 1800 every time the RA is
received, but a bug is causing Linux to ignore the update.
The core problem is here:
if (prefered_lft != ifp->prefered_lft) {
Note that ifp->prefered_lft is an offset, so it doesn't decrease over
time. Thus, the comparison is always (1800 != 1800), which fails to
trigger an update.
The most direct solution would be to compute a "stored_prefered_lft",
and use that value in the comparison. But I think that trying to filter
out unnecessary updates here is a premature optimization. In order for
the filter to apply, both of these would need to hold:
- The advertised valid_lft and preferred_lft are both declining in
real time.
- No clock skew exists between the router & client.
So in this patch, I've set "update_lft = 1" unconditionally, which
allows the surrounding code to be greatly simplified.
Signed-off-by: Paul Marks <pmarks@google.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
c9d55d5b Wed Sep 25 17:12:55 CDT 2013 Paul Marks <pmarks@google.com> ipv6: Fix preferred_lft not updating in some cases
Consider the scenario where an IPv6 router is advertising a fixed
preferred_lft of 1800 seconds, while the valid_lft begins at 3600
seconds and counts down in realtime.
A client should reset its preferred_lft to 1800 every time the RA is
received, but a bug is causing Linux to ignore the update.
The core problem is here:
if (prefered_lft != ifp->prefered_lft) {
Note that ifp->prefered_lft is an offset, so it doesn't decrease over
time. Thus, the comparison is always (1800 != 1800), which fails to
trigger an update.
The most direct solution would be to compute a "stored_prefered_lft",
and use that value in the comparison. But I think that trying to filter
out unnecessary updates here is a premature optimization. In order for
the filter to apply, both of these would need to hold:
- The advertised valid_lft and preferred_lft are both declining in
real time.
- No clock skew exists between the router & client.
So in this patch, I've set "update_lft = 1" unconditionally, which
allows the surrounding code to be greatly simplified.
Signed-off-by: Paul Marks <pmarks@google.com>
Acked-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
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