prevent local delivery loop when target exchange resolves to a local hostname

[DoobleD]

Fixes #2809 also for host names (#2952 solved it for IPs only). Requires merge of haraka-net-utils#63 first.

Changes proposed in this pull request:

• new function net_utils.is_local_host is used instead of net_utils.is_local_ip to check if the exchange is localhost.

Checklist:

• docs updated
• tests updated
• Changes updated

[DoobleD]

The call to is_local_host seems to badly impact performance for some reason. Applying the change to production made CPU jump from ~15% to 99%.

[msimerson]

Yes, there's a bug in it somewhere that is calling done when done is undefined. I haven't had a chance to investigate further.

[DoobleD]

Yes, there's a bug in it somewhere that is calling done when done is undefined. I haven't had a chance to investigate further.

Thanks for the feedback @msimerson. Indeed the call to is_local_host in mx_lookup.js simply doesn't use the callback...I'll open fix PRs soon.

[DoobleD]

Here are the fix PRs:

• Fixes issue in the outbound local mx check introduced in #3002 #3010
• is_local_host refactoring to return a promise haraka-net-utils#65

Not sure if that works for you as it uses promises.

To be sure I tested this version on a production server and it seems to be working fine so far.