On Sun, Nov 23, 2014 at 02:17:23PM -0500, Wietse Venema wrote:
> I have a preference for the design that addresses the problem at a
> lower level in the stack, so that the solution is not limited to
> the SMTP client and not limited to inet protocol selection.
>
> That code can then also be used to address other forms of trouble
> that manifest themselves via DNS (for example the next time someone
> changes the meaning of some corner case, like nullmx).
>
> I have a draft implementation that is being tested.
Feel free to compare notes. The code changes in inet_proto.c are
for example policy neutral, this just supports on-the-fly protocol
settings for whatever code happens to want such data. I forgot to
include one last change for that module, that avoids too large a
mask array should we ever support more than 2 protocols. (2^2^n
happens to equal 2*2^n for n=1,2).
diff --git a/src/util/inet_proto.c b/src/util/inet_proto.c
index 31b1ac1..d572c47 100644
--- a/src/util/inet_proto.c
+++ b/src/util/inet_proto.c
@@ -131,7 +131,7 @@ static const NAME_MASK proto_table[] = {
/*
* Cache by mask value.
*/
-static INET_PROTO_INFO *info_by_mask[1<<INET_PROTO_MASK_LAST];
+static INET_PROTO_INFO *info_by_mask[INET_PROTO_MASK_LAST<<1];
/* make_uchar_vector - create and initialize uchar vector */
I hope the low level mechanism in question will apply with some
specificity, e.g. for particular MX hosts among many for the same
nexthop domain. Some domains mix Google and non-google MX hosts.
If some day their non-Google MX hosts only support IPv6, we might
inadverantly disable these entirely:
kortingisleuk.nl. IN MX 10 kortingisleuk.nl.
kortingisleuk.nl. IN A 85.17.142.4
kortingisleuk.nl. IN MX 10 ASPMX.L.GOOGLE.COM.
kortingisleuk.nl. IN MX 20 ALT1.ASPMX.L.GOOGLE.COM.
kortingisleuk.nl. IN MX 20 ALT2.ASPMX.L.GOOGLE.COM.
kortingisleuk.nl. IN MX 30 ASPMX2.GOOGLEMAIL.COM.
kortingisleuk.nl. IN MX 30 ASPMX3.GOOGLEMAIL.COM.
kortingisleuk.nl. IN MX 30 ASPMX4.GOOGLEMAIL.COM.
kortingisleuk.nl. IN MX 30 ASPMX5.GOOGLEMAIL.COM.
Likewise, were someone to chose to only use IPv6 with Google some
day.
--
Viktor.
