SME 9.2 in server-only mode, fully patched, no contribs. The server is hosted in a IPv4 environment, I don't recall if I had to disable IPv6 specifically somewhere.
Today I've been starting to get a ton of freshclam-related connection errors, due possibly to the fact that database.clamav.net is IPv6-connected as well:
2018-05-17 09:45:02.855962500 ClamAV update process started at Thu May 17 09:45:02 2018
2018-05-17 09:45:02.856149500 WARNING: Your ClamAV installation is OUTDATED!
2018-05-17 09:45:02.856150500 WARNING: Local version: 0.99.3 Recommended version: 0.100.0
2018-05-17 09:45:02.856163500 DON'T PANIC! Read http://www.clamav.net/documents/upgrading-clamav
2018-05-17 09:45:02.856276500 main.cvd is up to date (version: 58, sigs: 4566249, f-level: 60, builder: sigmgr)
2018-05-17 09:45:03.309847500 WARNING: getpatch: Can't download daily-24576.cdiff from database.clamav.net
2018-05-17 09:45:03.310284500 WARNING: getpatch: Can't download daily-24576.cdiff from database.clamav.net
2018-05-17 09:45:03.310686500 WARNING: getpatch: Can't download daily-24576.cdiff from database.clamav.net
2018-05-17 09:45:03.311112500 WARNING: getpatch: Can't download daily-24576.cdiff from database.clamav.net
2018-05-17 09:45:03.311537500 WARNING: getpatch: Can't download daily-24576.cdiff from database.clamav.net
2018-05-17 09:45:03.311966500 ERROR: getpatch: Can't download daily-24576.cdiff from database.clamav.net
2018-05-17 09:45:03.346048500 WARNING: Incremental update failed, trying to download daily.cvd
2018-05-17 09:45:03.346795500 Trying host database.clamav.net (2400:cb00:2048:1::6810:ba8a)...
2018-05-17 09:45:03.346839500 nonblock_connect: connect(): fd=3 errno=101: Network is unreachable
2018-05-17 09:45:03.346851500 Can't connect to port 80 of host database.clamav.net (IP: 2400:cb00:2048:1::6810:ba8a)
2018-05-17 09:45:03.346861500 Trying host database.clamav.net (2400:cb00:2048:1::6810:bb8a)...
2018-05-17 09:45:03.346871500 nonblock_connect: connect(): fd=3 errno=101: Network is unreachable
2018-05-17 09:45:03.346881500 Can't connect to port 80 of host database.clamav.net (IP: 2400:cb00:2048:1::6810:bb8a)
2018-05-17 09:45:03.346891500 Trying host database.clamav.net (2400:cb00:2048:1::6810:bc8a)...
2018-05-17 09:45:03.346901500 nonblock_connect: connect(): fd=3 errno=101: Network is unreachable
2018-05-17 09:45:03.346911500 Can't connect to port 80 of host database.clamav.net (IP: 2400:cb00:2048:1::6810:bc8a)
2018-05-17 09:45:03.346920500 Trying host database.clamav.net (2400:cb00:2048:1::6810:bd8a)...
2018-05-17 09:45:03.346930500 nonblock_connect: connect(): fd=3 errno=101: Network is unreachable
2018-05-17 09:45:03.346931500 Can't connect to port 80 of host database.clamav.net (IP: 2400:cb00:2048:1::6810:bd8a)
2018-05-17 09:45:03.346941500 Trying host database.clamav.net (2400:cb00:2048:1::6810:b98a)...
2018-05-17 09:45:03.346962500 nonblock_connect: connect(): fd=3 errno=101: Network is unreachable
2018-05-17 09:45:03.346973500 Can't connect to port 80 of host database.clamav.net (IP: 2400:cb00:2048:1::6810:b98a)
2018-05-17 09:45:03.346983500 ERROR: Can't download daily.cvd from database.clamav.net
2018-05-17 09:45:03.347162500 Giving up on database.clamav.net...
2018-05-17 09:45:03.347162500 Update failed. Your network may be down or none of the mirrors listed in /etc/freshclam.conf is working. Check http://www.clamav.net/doc/mirrors-faq.html for possible reasons.
Dig'ing for database.clamav.net:
# dig database.clamav.net
; <<>> DiG 9.8.2rc1-RedHat-9.8.2-0.62.rc1.el6_9.5 <<>> database.clamav.net
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 39520
;; flags: qr rd ra; QUERY: 1, ANSWER: 9, AUTHORITY: 0, ADDITIONAL: 0
;; QUESTION SECTION:
;database.clamav.net. IN A
;; ANSWER SECTION:
database.clamav.net. 60 IN CNAME db.local.clamav.net.
db.local.clamav.net. 2158 IN CNAME db.southeu.clamav.net.
db.southeu.clamav.net. 60 IN CNAME db.eu.big.clamav.net.
db.eu.big.clamav.net. 60 IN CNAME db.eu.big.clamav.net.cdn.cloudflare.net.
db.eu.big.clamav.net.cdn.cloudflare.net. 7 IN A 104.16.185.138
db.eu.big.clamav.net.cdn.cloudflare.net. 7 IN A 104.16.186.138
db.eu.big.clamav.net.cdn.cloudflare.net. 7 IN A 104.16.187.138
db.eu.big.clamav.net.cdn.cloudflare.net. 7 IN A 104.16.188.138
db.eu.big.clamav.net.cdn.cloudflare.net. 7 IN A 104.16.189.138
;; Query time: 367 msec
;; SERVER: 192.168.1.2#53(192.168.1.2)
;; WHEN: Thu May 17 11:25:35 2018
;; MSG SIZE rcvd: 239
# freshclam --list-mirrors
Mirror #1
IP: 104.16.188.138
Successes: 0
Failures: 2
Last access: Thu May 17 03:37:04 2018
Ignore: Yes
-------------------------------------
Mirror #2
IP: 104.16.189.138
Successes: 0
Failures: 2
Last access: Thu May 17 03:37:10 2018
Ignore: Yes
-------------------------------------
Mirror #3
IP: 104.16.185.138
Successes: 0
Failures: 2
Last access: Thu May 17 03:37:04 2018
Ignore: Yes
-------------------------------------
Mirror #4
IP: 104.16.186.138
Successes: 0
Failures: 2
Last access: Thu May 17 03:37:10 2018
Ignore: Yes
-------------------------------------
Mirror #5
IP: 104.16.187.138
Successes: 0
Failures: 2
Last access: Thu May 17 03:37:10 2018
Ignore: Yes
-------------------------------------
Mirror #6
IP: 2400:cb00:2048:1::6810:bd8a
Successes: 0
Failures: 49
Last access: Thu May 17 10:45:31 2018
Ignore: Yes
-------------------------------------
Mirror #7
IP: 2400:cb00:2048:1::6810:b98a
Successes: 0
Failures: 49
Last access: Thu May 17 10:45:31 2018
Ignore: Yes
-------------------------------------
Mirror #8
IP: 2400:cb00:2048:1::6810:ba8a
Successes: 0
Failures: 49
Last access: Thu May 17 10:45:31 2018
Ignore: Yes
-------------------------------------
Mirror #9
IP: 2400:cb00:2048:1::6810:bb8a
Successes: 0
Failures: 49
Last access: Thu May 17 10:45:31 2018
Ignore: Yes
-------------------------------------
Mirror #10
IP: 2400:cb00:2048:1::6810:bc8a
Successes: 0
Failures: 49
Last access: Thu May 17 10:45:31 2018
Ignore: Yes
Can I somehow suppress ipv6 altogether?
EDIT: from the output of freshclam --list-mirrors above, all ipv4 became blacklisted too, will have to reset them.