> On Jun 9, 2018, at 7:50 PM, Jeremy Harris via Exim-dev <exim-dev@exim.org> > wrote: > >> OK, that's what I'd expect, from this you can conclude >> that "nomx.example" has no MX records. > > With a retry count of one, and the current coding, it failed > when it hit that case. It was far simpler to loop once than > try to rewrite all the code. My concern would be that if the code is unable to draw the right conclusion from just the initial response (i.e. it does not parse all the records to build a chain to the final target, and check for the presence or absence of the answer for that target), then one extra query could also be insufficient. CNAME chains can be multiple elements long (10 is a popular limit). A classic example is: $ dig +noall +ans +nocl +nottl -t a www.paypal.com www.paypal.com. CNAME geo.paypal.com.akadns.net. geo.paypal.com.akadns.net. CNAME hotspot-www.paypal.com.akadns.net. hotspot-www.paypal.com.akadns.net. CNAME wlb.paypal.com.akadns.net. wlb.paypal.com.akadns.net. CNAME www.paypal.com.edgekey.net. www.paypal.com.edgekey.net. CNAME e3694.a.akamaiedge.net. e3694.a.akamaiedge.net. A 104.123.10.240 which arrives as a single DNS response. -- Viktor. -- ## List details at https://lists.exim.org/mailman/listinfo/exim-dev Exim details at http://www.exim.org/ ##
Re: [exim-dev] [Bug 2264] DNS lookups should not chase CNAME chains
Viktor Dukhovni via Exim-dev Sat, 09 Jun 2018 17:03:00 -0700
- [exim-dev] [Bug 2264] New: DNS lookups should... admin--- via Exim-dev
- [exim-dev] [Bug 2264] DNS lookups should... admin--- via Exim-dev
- Re: [exim-dev] [Bug 2264] New: DNS looku... Viktor Dukhovni via Exim-dev
- [exim-dev] [Bug 2264] DNS lookups should... admin--- via Exim-dev
- [exim-dev] [Bug 2264] DNS lookups should... admin--- via Exim-dev
- [exim-dev] [Bug 2264] DNS lookups should... admin--- via Exim-dev
- Re: [exim-dev] [Bug 2264] DNS lookup... Viktor Dukhovni via Exim-dev
- Re: [exim-dev] [Bug 2264] DNS lo... Jeremy Harris via Exim-dev
- Re: [exim-dev] [Bug 2264] DN... Viktor Dukhovni via Exim-dev
- Re: [exim-dev] [Bug 226... Jeremy Harris via Exim-dev
- Re: [exim-dev] [Bug... Viktor Dukhovni via Exim-dev
- [exim-dev] [Bug 2264] DNS lookups should... admin--- via Exim-dev
- [exim-dev] [Bug 2264] DNS lookups should... admin--- via Exim-dev