util.privateBlocks contains loopback address range about memberlist

[slackpad]

Yep I'll pull this through Serf and Consul - /cc @dadgar for Nomad.

[slackpad]

@sean- any thoughts on this one?

[sean-]

This is the express reason why hashicorp/go-sockaddr sorts its addresses before making an address selection. Jiggling the sort order of utils.go's privateBlocks is suboptimal, but pragmatic in a pinch (

memberlist/util.go

Lines 25 to 34 in 9800c50

	/*
	* Contains an entry for each private block:
	* 10.0.0.0/8
	* 100.64.0.0/10
	* 127.0.0.0/8
	* 169.254.0.0/16
	* 172.16.0.0/12
	* 192.168.0.0/16
	*/
	var privateBlocks []*net.IPNet

).

From a correctness perspective, there are a few possible solutions, some more correct than others, but all solutions involve the use of hashicorp/go-sockaddr (mostly because that's the bestest hammer available, imnsho! 😁 ).

• Sort the addresses returned from the host by their mask length. Something like: https://github.com/hashicorp/go-sockaddr/blob/c403ce7245ed06f545550eb6b80e0f2b1bd7566f/ipaddrs_test.go#L163
• Expose a template that can be evaluated and use a sane default that filters out 127.0.0.1 or uses one of the template helper functions: https://github.com/hashicorp/go-sockaddr/blob/a99c57b5a5f48c51607e63089075fe7434fe219a/template/template.go#L29-L53
• Use sockaddr.GetPrivateIP() and remove most of the code in utils.go: https://github.com/hashicorp/go-sockaddr/blob/a99c57b5a5f48c51607e63089075fe7434fe219a/ifaddr.go#L11-L31 . @slackpad, now that we've just cut a release of both Serf and Consul, I think now would be a good time to do this so any breakage can marinate in master for a while.

@woodsaj , can you run the following few commands and see if they're correct for your environment:

$ go get -u github.com/hashicorp/go-sockaddr/cmd/sockaddr
$ sockaddr eval GetPrivateIP

[woodsaj]

$ sockaddr eval GetPrivateIP
192.168.0.102

looks to work correctly. :)

[sean-]

Ha!, excellent. Thank you for that point of validation.

@slackpad, your call now. :) I'm game for PRing this at some point unless you beat me to it. As far as impact, Consul already has a vendor dependency on go-sockaddr so that's a no op there. As far as other public projects, Serf and Nomad will need love because there will be a new library dependency. It's not that high on my list to tackle atm, but I can squeeze it in if needed.... or I'll do it on the train this morning (#108).

[slackpad]

Should be fixed at this level by #108.