On 10/14/15 3:34 AM, Hannes Frederic Sowa wrote:
Hello,
On Wed, Oct 14, 2015, at 03:45, David Miller wrote:
From: David Ahern <d...@cumulusnetworks.com>
Date: Mon, 12 Oct 2015 09:33:07 -0700
Currently, all ipv6 addresses are flushed when the interface is configured
down, including global, static addresses:
...
Add a new sysctl to make this behavior optional. The new setting defaults to
flush all addresses to maintain backwards compatibility. When the setting is
reset global addresses with no expire times are not flushed:
...
Signed-off-by: David Ahern <d...@cumulusnetworks.com>
Here is what I really don't like about these changes: the failure
semantics are terrible.
If I add an address or a route, and some memory allocation fails, I get
a notification and see that my operation did not succeed.
But here, my routes can fail to be added during an ifup and all I will
get, at best, is a kernel log message.
This places a serious disconnect between what the user asked for and
making sure he finds out directly that his operation did not really
fully succeed.
In fact, this failure handling here during ifup leaves the interface in
a partially configured state.
Agreed, it would be better.
There are really two ways to deal with this properly:
1) Propagate the failure back through the notifiers and fail the ifup
completely when the addrconf_dst_alloc() fails.
2) On ifdown, stash the objects away somewhere so that memory allocation
is not necessary on ifup.
In regard to error propagation I think 2) is the only viable option. I
don't think why you shouldn't be able to simply remove the ip6_rt_put
after the ip6_del_rt and keep the dst_entry hanging there and later
reinsert.
I don't agree with stashing it. IPv4 code does not do that and handling
the stashed routes makes the implementation more complex than needed.
This latest patch makes IPv6 static addresses on par with IPv4,
including error paths. On admin link down IPv4 code removes local and
connected routes. On admin link up they are reinserted. Error paths are
not handled. ie., any memory allocations or insertion failures are
silently ignored.
As for this IPv6 patch the only real failure scenario is ENOMEM in the
dst_alloc.
David
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