Re: [PATCH 1/2] updates for [nf|ct]netlink and event API

[Patrick McHardy <kaber@trash.net>]

Harald Welte wrote:
> On Tue, Jun 28, 2005 at 12:40:46AM +0200, Patrick McHardy wrote:
> 
>>These should be changed not to use internal conntrack structures, it
>>will hurt us when we want to change them. Instead it should replicate
>>the fields interesting for the user. Also please use fixed-size types
>>instead of unions etc. All structures including u64 types should be
>>padded to multiples of 8 so they are equally sized on 32-bit and 64-bit
>>systems.
> 
> agreed.  However, we still don't have some kind of versioning in the
> protocol, too.  I think we've learned by now that we need versioned
> structures ;)

Netlink is easy to extend by adding new fields at the end if users
only check for msgsize >= sizeof(struct). Do you think we should
have versioning anyway?

>>+/* ctnetlink multicast groups: reports any change of ctinfo,
>>+ * ctstatus, or protocol state change.
>>+ */
>>+#define NFGRP_IPV4_CT_TCP      0x01
>>+#define NFGRP_IPV4_CT_UDP      0x02
>>+#define NFGRP_IPV4_CT_ICMP     0x04
>>+#define NFGRP_IPV4_CT_OTHER    0x08
>>
>>I'm not sure how useful these groups are. I think groups for different
>>event-types might be more useful to reduce the noise.
> 
> 
> that was my idea in the beginning (since I didn't think of events at
> that point).
> 
> Still, I think creating messages for any kind of event (even if noone
> listens) is too much overhead.  netlink needs to be extended to deal
> with that issue.
> 
> Maybe the 'which socket is subscribed to which group' accounting should
> be done by the core netlink layer, which would then only export a
> merged bitmask of all netlink sockets.  This way ctnetlink can easily
> check whether it makes sense to create a certain event message or not.
> 
> This should be useful for other netlink users, too.

Sounds like a good idea.

Regards
Patrick