IPv6 addresses in tables not always working

[Fabian Wenk]

Hello

To test tables with IPv6 for use with fail2ban (see thread "IPv6 
Support" [1]), I tried it out on a FreeBSD 9.1-RELEASE (r244668) 
system. Not all possible rules with tables which include IPv6 
addresses seem to work.

   [1] http://sourceforge.net/mailarchive/message.php?msg_id=29387087

For fail2ban it will both be possible, using mixed tables with 
IPv4 and IPv6 addresses and separate tables with only IPv4 or 
IPv6 addresses. So I tried a few variants.

First I created 3 different tables (IPv4 only, IPv6 only, IPv4 
and IPv6 mixed), this worked so far:

root at freebsd9:~ # ipfw table 4 add 62.12.173.3
root at freebsd9:~ # ipfw table 4 add 62.2.85.180
root at freebsd9:~ # ipfw table 4 add 62.2.85.186
root at freebsd9:~ # ipfw table 4 list
62.2.85.180/32 0
62.2.85.186/32 0
62.12.173.3/32 0
root at freebsd9:~ #

root at freebsd9:~ # ipfw table 6 add 2001:8a8:1005:1::3
root at freebsd9:~ # ipfw table 6 add 2001:8a8:1005:2::180
root at freebsd9:~ # ipfw table 6 add 2001:8a8:1005:2::186
root at freebsd9:~ # ipfw table 6 list
2001:8a8:1005:1::3/128 0
2001:8a8:1005:2::180/128 0
2001:8a8:1005:2::186/128 0
root at freebsd9:~ #

root at freebsd9:~ # ipfw table 46 add 62.12.173.3
root at freebsd9:~ # ipfw table 46 add 62.2.85.180
root at freebsd9:~ # ipfw table 46 add 62.2.85.186
root at freebsd9:~ # ipfw table 46 add 2001:8a8:1005:1::3
root at freebsd9:~ # ipfw table 46 add 2001:8a8:1005:2::180
root at freebsd9:~ # ipfw table 46 add 2001:8a8:1005:2::186
root at freebsd9:~ # ipfw table 46 list
62.2.85.180/32 0
62.2.85.186/32 0
62.12.173.3/32 0
2001:8a8:1005:1::3/128 0
2001:8a8:1005:2::180/128 0
2001:8a8:1005:2::186/128 0
root at freebsd9:~ #

Then I created a few basic rules for testing, which also worked 
(I did shorten the hostname prompt to avoid line wrap):

f9:~ # ipfw add 1 unreach port tcp from table\(4\) to me 22 in
00001 unreach port tcp from table(4) to me dst-port 22 in
f9:~ # ipfw add 2 unreach6 port tcp from table\(6\) to me6 22 in
00002 unreach6 port tcp from table(6) to me6 dst-port 22 in
f9:~ # ipfw add 3 unreach port tcp from table\(46\) to me 22 in
00003 unreach port tcp from table(46) to me dst-port 22 in
root at freebsd9:~ #

root at freebsd9:~ # ipfw show | head -3
00001  0  0 unreach port tcp from table(4) to me dst-port 22 in
00002  0  0 unreach6 port tcp from table(6) to me6 dst-port 22 in
00003  0  0 unreach port tcp from table(46) to me dst-port 22 in
root at freebsd9:~ #

Then I did some testing from the remote system (the IP addresses 
in the tables). With IPv4 it is blocked right away with a 
connection refused, with IPv6 it takes 25 seconds and it tried to 
send much more packets. The destination systems (freebsd9) has 2 
IP addresses each. When I also test with telnet, it tries and 
shows to connect to both address, but with similar timeouts then 
with ssh below:

fabian at superman:~ $ time ssh -4 freebsd9
ssh: connect to host freebsd9.wenks.ch port 22: Connection refused

real    0m0.015s
user    0m0.002s
sys     0m0.008s
fabian at superman:~ $

fabian at superman:~ $ time ssh -6 freebsd9
ssh: connect to host freebsd9.wenks.ch port 22: Connection refused

real    0m25.212s
user    0m0.005s
sys     0m0.006s
fabian at superman:~ $

root at freebsd9:~ # ipfw show | head -3
00001  2 120 unreach port tcp from table(4) to me dst-port 22 in
00002 10 752 unreach6 port tcp from table(6) to me6 dst-port 22 in
00003  0   0 unreach port tcp from table(46) to me dst-port 22 in
root at freebsd9:~ #

Then I deleted the IPv4 and IPv6 only rules to only test with the 
mixed IPv4 and IPv6 table(46):

root at freebsd9:~ # ipfw delete 1 2
root at freebsd9:~ # ipfw show | head -1
00003  0   0 unreach port tcp from table(46) to me dst-port 22 in
root at freebsd9:~ #

And again testing from the remote system, the timeouts are still 
with the same difference for IPv4 and IPv6, but the message for 
IPv6 is now different:

fabian at superman:~ $ time ssh -4 freebsd9
ssh: connect to host freebsd9.wenks.ch port 22: Connection refused

real    0m0.012s
user    0m0.008s
sys     0m0.000s
fabian at superman:~ $

root at freebsd9:~ # ipfw show | head -1
00003  2 120 unreach port tcp from table(46) to me dst-port 22 in
root at freebsd9:~ #

fabian at superman:~ $ time ssh -6 freebsd9
ssh: connect to host freebsd9.wenks.ch port 22: Host is down

real    0m25.212s
user    0m0.009s
sys     0m0.001s
fabian at superman:~ $

root at freebsd9:~ # ipfw show | head -1
00003 12 872 unreach port tcp from table(46) to me dst-port 22 in
root at freebsd9:~ #


I also tried some other rules, which would be use cases for my 
setup with fail2ban, but not all of them work:

freebsd9:~ # ipfw add 4 deny ip6 from table\(6\) to me6 22 in
ipfw: bad address "table(6)"
root at freebsd9:~ #

root at freebsd9:~ # ipfw add 5 deny ip4 from table\(4\) to me 22 in
00005 deny ip4 from table(4) to me dst-port 22 in
root at freebsd9:~ #

Ok, the next one probably does not have a real use case, I was 
just testing:

freebsd9:~ # ipfw add 6 deny ip4 from table\(46\) to me 22 in
00006 deny ip4 from table(46) to me dst-port 22 in
root at freebsd9:~ #


To help collect the information regarding IPv6 support in ipfw 
tables, what other rules should I test? Or is this already enough 
information for any FreeBSD IPFW developer to be able to locate 
and probably fix this issues?

I guess it is probably better to first collect some more 
information regarding IPv6 and tables here on the list and then 
create a corresponding PR later on for it.


bye
Fabian