On 12/03/2019 19:19, James Gritton wrote:
On 2019-03-10 13:40, Grzegorz Junka wrote:
Hi,
I am not sure if this question fits better to net or jail list so
please delete one crosspost when replying.
I have two routers in separate subnets (say 10.0.0.0/16 and
172.16.0.0/16). I have enabled multiple fibs on the host and I am
trying to setup a jail so that packets from one router are returned to
the same router. The second subnet is configured like this:
setfib 1 route add -net 172.16.0.0/16 -iface lagg0
setfib 1 route add default 172.16.0.1
When the jail configuration is (differences in red):
mta {
exec.fib=1;
ip4.addr = 172.16.0.2;
interface = lagg0;
}
router 172.16.0.1 is able to send to and receive packets from the jail
as expected.
When the jail configuration is:
mta {
ip4.addr = 10.0.0.2,172.16.0.2;
interface = lagg0;
}
then router 10.0.0.1 is also able to send and receive packets from the
jail as expected.
However, when the configuration is:
mta {
exec.fib=1;
ip4.addr = 10.0.0.2,172.16.0.2;
interface = lagg0;
}
then router 172.16.0.1 is no longer able to receive a response from
the jail. The router's event log shows entry similar to the following
two about 2 minutes apart:
IN: ACCEPT [54] Connection opened (Port Forwarding: TCP
[172.16.0.2]:80 <--> [212.159.95.213]:80 - - -
[111.202.101.2]:34172 CLOSED/SYN_SENT ppp3 NAPT)
IN: ACCEPT [57] Connection closed (Port Forwarding: TCP
[172.16.0.2]:80 <--> [212.159.95.213]:80 - - -
[111.202.101.2]:34172 CLOSED/SYN_SENT ppp3 NAPT)
My question is why the 10.0.0.1 router is able to communicate with the
jail in the second configuration but 172.16.0.1 is not able to
communicate with the jail in the third configuration. Is it because of
order of IPs in ip4.addr?
When the jail is started jls shows only the first IP from either of
the configuration list above (i.e. 10.0.0.2 even if exec.fib is set to
1). So my guess is that the first IP is somehow a default IP?
Then my additional question is if it's possible for a jail to be in
two subnets at the same time, i.e. so that when the jail responds to a
packet received from router 10.0.0.1 it sends it to the default route
from fib0 and when it responds to a packet received from 172.16.0.1 it
sends it to the default route from fib1. What exec.fib should be in
such a case?
Any help would be greatly appreciated. Thanks!
You're correct in your assumption that a jail's first IP address is
its default: in the absence of binding a particular address for an
outgoing connection, the first-listed address will be used. So then
the problem with the third jail is you have a packing being sent from
10.0.0.2 with only the routing table that doesn't include 10.0/16. I
can't say exactly why your second example *does* work, but at least
from the jail side it has a default address that's reachable in its
routing table. I'm thinking you're saying that the second jail works
not only with 10.0 but also with 172.16 (it's the 172.16 part I'm
unsure about).
To answer your last question: sure, a jail can be in two subnets - but
it will still use its first address by default for any outbound
packets. Note that the FIB associated with the jail isn't *really*
associated with the jail, but with the processes jail(8) starts for it
- the reason for the "exec" in "exec.fib". You're still free to call
setfib from inside the jail to access a different table.
I haven't tried using two different routing tables in one jail at the
same time; the closest I've come is one jail that routed on the
non-default network. Outside of the jail world, I believe multiple
routing tables implies multiple instances of servers, and that would
be the same for inside a jail. Your router log shows port 80, so that
would imply two different apache (or whatever) processes running the
jail, each pointing to its own address, and rung under its own routing
table.
Many thanks for your response. The second example works with 10.0.0.1
but not with 172.16.0.1, otherwise there would be no post. Following on
your response, lets assume that a process (e.g. nginx) listens on both
IPs, 10.0.0.2,172.16.0.2. Is it possible to configure fibs or default
routes or whatever so that when a packet arrives from 10.0.0.1 it is
send back to 10.0.0.1 and if it arrives from 172.16.0.1 it is send back
to 172.16.0.1 (thus using default routes from either fib0 or fib1
depending if the packet came from a router in one of those network)? If
not, would it be possible to do this with some iptables/pf rules (which
I understand in FreeBSD 12 should work in a jail with VNET)?
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