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|ID||Project||Category||View Status||Date Submitted||Last Update|
|0001515||Endian Firewall||Firewall (iptables)||public||2008-12-17 15:39||2009-04-14 20:56|
|Target Version||Fixed in Version||2.3|
|Summary||0001515: zonefw: --state NEW check blocks communication to clients behind a router due to triangle connection|
|Description||the following situation causes zonef firewall to block the connection:|
192.168.20.10 ---| .20.1 .0.2|-----| .0.1 |------| .0.10
since 192.168.0.10 in order to go to 20.10 passes through it's default gateway: .0.1, but 0.2 can communicate directly with .0.10 because they are in the same subnet, response packets from 20.10 to 0.10 pass directly, without going through .0.1
the zone firewall in .0.1 however blocks because the zone firewall accepts only packets which are NEW. ESTABLISHED packets will be accepted at the beginning of the firewall construct.
since response packets never pass the firewall, the connection never becomes ESTABLISHED and the next request packet is NEW but not SYN, which causes the firewall to block.
this can be solved by removing the stateful check --state NEW from the zone firewall, or, as it has been in 2.1, re-adding
net.ipv4.conf.all.send_redirects = 1
which would cause .0.1 to send redirect icmp's to .0.10 in order to allow .0.10 to directly send packets for .20.0/24 to .0.2
!we removed send_redirects because of routing problems in 2.1!
!!both solutions may cause other problems!!
it's to check what solution is better
|shorewall never checks --state NEW, accepts only ESTABLISHED and RELATED before all other rules|
only changing the stateful firewall behaviour causes to fill connection tracking table entries which each need to timeout in order to be removed.
icmp-redirect message would cause to completely circumvent the firewall which will not insert any conntrack entries when the sending host knows how to handle redirects.
probably the best solution would be a combination of both.
i think we had should toggle off only accept_redirects and shared_media, send_redirects maybe is not that disastruous (?)
need more research
this could be also resolved by adding 0.2 a bit more routing-input:
for the full network
route add -net 192.168.0.0 netmask 255.255.255.0 gw 192.168.0.1
just for the 0.10 host:
route add -host 192.168.0.10 gw 192.168.0.1
|and 192.168.0.2 should have a netmask of 255.255.255.255 (192.168.0.2/32) - if this is the only IP on that net|
it's not always possible to re-configure the router in order to make it send all to the default gateway
and you can't add the route on every single system in green
the diagram is maybe a little bit ambiguous.. here's a better one:
| EFW |
| + ...
| + 192.168.0.20
| router |
traffic from 192.168.0.2 will pass directly to 192.168.0.20 without going through 192.168.0.1
that will cause NEWnotSyn to block
thanx for the ascii
indeed - this makes auto-updating of routing tables a bit more complex
close this bug, since the described issue has been fixed in 2.3
discussion about reintroduction of NewNotSyn please in 0001768
|2008-12-17 15:39||peter-endian||New Issue|
|2008-12-17 15:39||peter-endian||Assigned To||=> peter-endian|
|2008-12-17 15:39||peter-endian||Tag Attached: needsfix|
|2008-12-17 15:39||peter-endian||Tag Attached: heavy|
|2008-12-17 16:37||peter-endian||Note Added: 0001886|
|2008-12-17 17:54||peter-endian||Note Added: 0001889|
|2008-12-23 22:06||peter-endian||Status||new => resolved|
|2008-12-23 22:06||peter-endian||Fixed in Version||=> 2.3|
|2008-12-23 22:06||peter-endian||Resolution||open => fixed|
|2009-04-14 12:52||mike-f||Note Added: 0002143|
|2009-04-14 12:52||mike-f||Status||resolved => feedback|
|2009-04-14 12:52||mike-f||Resolution||fixed => reopened|
|2009-04-14 13:21||mike-f||Note Added: 0002144|
|2009-04-14 19:25||peter-endian||Relationship added||related to 0001768|
|2009-04-14 19:28||peter-endian||Note Added: 0002147|
|2009-04-14 19:48||mike-f||Note Added: 0002150|
|2009-04-14 20:56||peter-endian||Note Added: 0002151|
|2009-04-14 20:56||peter-endian||Status||feedback => closed|
|2009-04-14 20:56||peter-endian||Resolution||reopened => fixed|
|2010-09-17 09:22||christian-endian||Relationship added||related to 0003081|
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