Re: [RFC] make thread-safe iface resolution in libnfnetlink

[Patrick McHardy <kaber@trash.net>]

Pablo Neira Ayuso wrote:
> Eric Leblond wrote:
>> Hi,
>>
>> I've encountered some problems with libnfnetlink iface resolution on a
>> system where some interfaces are getting up and down: NuFW which uses
>> this feature has crashed during a down/up of an interfaces. One of
>> the reason seems that nufw uses one thread is used for iface related
>> event treatment and another thread is doing iface name resolution.
>>
>> As the hash can be modified or read without any lock, I think the
>> problem can be linked with this issue. I thus propose a patch that
>> modifies the iface resolution subsystem to make it thread-safe.
> 
> Better do the locking in your application. You can define the lock in
> NuFW and protect the calls to libnfnetlink's interface API. Adding this
> locking to a library does not seem to me like the right thing, see that
> other non-threaded clients will have to live with the overhead of this
> lock that is completely useless for them. Of course, we can document
> that the interface API is not thread-safe.

I agree, it should be a user decision whether to use this.
Of course they need the information which callbacks need
protection.