This is getting rather technical, and probably some of CloudFlare’s secret 
sauce.
It sounds like the anycast DNS that cloudflare hosts isn’t really working, or 
at least I would assume that they are using anycast.

So you query current.cvd.clamav.net <http://current.cvd.clamav.net/> but are 
getting different results at IAD and BOS.  Now next is the inclusion of 
Comcast, which may and probably is caching DNS records beyond normal TTLs which 
could cause the difference.  I personally always run an Unbound cache server on 
my mailserver networks to cache dns for at least an hour for rbls that I’m not 
rsyncing, but that could cause an issue with Microsoft’s wonderful 10 second MX 
records.  So that’s where I’ve run into this issue, but not often enough since 
I’m just caching for an hour and probably MS expects it.

So my guess, is probably not anycast, but a caching DNS server that is still 
giving older records.

Sincerely,

Eric Tykwinski
TrueNet, Inc.
P: 610-429-8300

> On Dec 7, 2018, at 6:20 PM, Paul Kosinski <clamav-us...@iment.com> wrote:
> 
> As some of you may be aware, ever since ClamAV began using Cloudflare,
> we have seen many occasions when files like daily.cvd were not
> available to our LAN until well after the DNS TXT record implied they
> should be.
> 
> However, we discovered that these same files *are* available to our
> Web/email server right away. So what is the difference? The first
> difference is that our Web server (a VM) is offsite, and is served by
> the "IAD" Cloudflare complex, whereas our local setup is served by the
> "BOS" Cloudflare complex.
> 
> The second, and likely explanatory difference, is that our local setup
> is connected via Comcast (a dynamic IP and all that), while our Web
> server (with its static IP etc.) is almost certainly more directly
> connected to the Internet as a whole.
> 
> The workaround we have adopted is as follows: we installed a "tinyproxy"
> server on our offsite VM. To ensure it only proxys for us, it listens on
> the encrypted OpenVPN tunnel we already had in place for FTP uploads
> etc. Then, instead of directly accessing database.clamav.net, freshclam
> uses our remote VM as a proxy,so that the cvd files are downloaded
> indirectly from Cloudflare's IAD server complex (via tinyproxy) rather
> than directly from Cloudflare's BOS server complex.
> 
> Since switching to this workaround a few days ago, we haven't observed
> any delays: the cvd files are available right away when the DNS TXT
> query says they should be.
> 
> I strongly suspect that Comcast is the culprit in the delays that had
> plagued us. This is especially suggested by the fact that Cloudflare
> returns a "Cache-Control:" header similar to:
> 
>  Cache-Control: public, max-age=13672
> 
> where the max-age value varies, but is often several hours.
> 
> In my opinion, for data like ClamAV virus updates, the "Cache-Control:"
> should specify "no-cache". Can Cloudflare do this for ClamAV?
> 
> ---------------------------------------------------------------------
> 
> Below is a pair of recent (pre-workaround) log excerpts. They show a
> delay of over 2.5 hours experienced from BOS (via Comcast) vs no delay
> from IAD.
> 
> Note that the BOS "Date:" timestamp of 16:49:01 GMT *still* shows
> a "Last-Modified:" timestamp of 06:15:18 GMT, while IAD already shows
> the up-to-date "Last-Modified:" timestamp of 14:14:30 GMT at the much
> earlier "Date:" of 14:29:01 GMT!
> 
> 
>  IAD
> 
>    Date: Sun, 02 Dec 2018 14:09:01 GMT
>    Last-Modified: Sun, 02 Dec 2018 06:15:18 GMT
>    ClamAV-VDB:02 Dec 2018 01-14 
> -0500:25172:2167574:63:13c670e3a525c4fd17bf65524ff05fcd:nwPmlNwUbKmexgT
> 
>    Date: Sun, 02 Dec 2018 14:29:01 GMT
>    Last-Modified: Sun, 02 Dec 2018 14:14:30 GMT
>    ClamAV-VDB:02 Dec 2018 09-13 
> -0500:25173:2167842:63:ba557f61737b9d4b66acc96f7044b524:3nBAOxo97ssSNZb
> 
> 
>  BOS
> 
>    Date: Sun, 02 Dec 2018 14:09:01 GMT
>    Last-Modified: Sun, 02 Dec 2018 06:15:18 GMT
>    ClamAV-VDB:02 Dec 2018 01-14 
> -0500:25172:2167574:63:13c670e3a525c4fd17bf65524ff05fcd:nwPmlNwUbKmexgT
> 
>    Date: Sun, 02 Dec 2018 14:29:01 GMT
>    Last-Modified: Sun, 02 Dec 2018 06:15:18 GMT
>    ClamAV-VDB:02 Dec 2018 01-14 
> -0500:25172:2167574:63:13c670e3a525c4fd17bf65524ff05fcd:nwPmlNwUbKmexgT
> 
>    Date: Sun, 02 Dec 2018 14:49:01 GMT
>    Last-Modified: Sun, 02 Dec 2018 06:15:18 GMT
>    ClamAV-VDB:02 Dec 2018 01-14 
> -0500:25172:2167574:63:13c670e3a525c4fd17bf65524ff05fcd:nwPmlNwUbKmexgT
> 
>    Date: Sun, 02 Dec 2018 15:09:01 GMT
>    Last-Modified: Sun, 02 Dec 2018 06:15:18 GMT
>    ClamAV-VDB:02 Dec 2018 01-14 
> -0500:25172:2167574:63:13c670e3a525c4fd17bf65524ff05fcd:nwPmlNwUbKmexgT
> 
>    Date: Sun, 02 Dec 2018 15:29:02 GMT
>    Last-Modified: Sun, 02 Dec 2018 06:15:18 GMT
>    ClamAV-VDB:02 Dec 2018 01-14 
> -0500:25172:2167574:63:13c670e3a525c4fd17bf65524ff05fcd:nwPmlNwUbKmexgT
> 
>    Date: Sun, 02 Dec 2018 15:49:02 GMT
>    Last-Modified: Sun, 02 Dec 2018 06:15:18 GMT
>    ClamAV-VDB:02 Dec 2018 01-14 
> -0500:25172:2167574:63:13c670e3a525c4fd17bf65524ff05fcd:nwPmlNwUbKmexgT
> 
>    Date: Sun, 02 Dec 2018 16:09:01 GMT
>    Last-Modified: Sun, 02 Dec 2018 06:15:18 GMT
>    ClamAV-VDB:02 Dec 2018 01-14 
> -0500:25172:2167574:63:13c670e3a525c4fd17bf65524ff05fcd:nwPmlNwUbKmexgT
> 
>    Date: Sun, 02 Dec 2018 16:29:01 GMT
>    Last-Modified: Sun, 02 Dec 2018 06:15:18 GMT
>    ClamAV-VDB:02 Dec 2018 01-14 
> -0500:25172:2167574:63:13c670e3a525c4fd17bf65524ff05fcd:nwPmlNwUbKmexgT
> 
>    Date: Sun, 02 Dec 2018 16:49:01 GMT
>    Last-Modified: Sun, 02 Dec 2018 06:15:18 GMT
>    ClamAV-VDB:02 Dec 2018 01-14 
> -0500:25172:2167574:63:13c670e3a525c4fd17bf65524ff05fcd:nwPmlNwUbKmexgT
> 
>    Date: Sun, 02 Dec 2018 17:09:01 GMT
>    Last-Modified: Sun, 02 Dec 2018 14:14:30 GMT
>    ClamAV-VDB:02 Dec 2018 09-13 
> -0500:25173:2167842:63:ba557f61737b9d4b66acc96f7044b524:3nBAOxo97ssSNZb
> _______________________________________________
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> 
> 
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> 
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