Para redirecionar os pacotes para a interface de loopback, você precisa usar o REDIRECT
target.
iptables -A PREROUTING -t nat -p udp --dport 8088 -i eth0 -j REDIRECT --to-ports 4569
Caso contrário, você alterará o endereço de destino antes que a decisão de roteamento seja tomada para 127.0.0.1
. Isso significa que ele será considerado um pacote marciano pelo kernel e descartado pela política de filtragem de caminho reverso.
Os dois parâmetros do kernel responsáveis por este comportamento são:
-
net.ipv4.conf.eth0.route_localnet
route_localnet - BOOLEAN
Do not consider loopback addresses as martian source or destination while routing. This enables the use of 127/8 for local routing purposes.
default FALSE
-
net.ipv4.conf.eth0.rp_filter
rp_filter - INTEGER
0 - No source validation.
1 - Strict mode as defined in RFC3704 Strict Reverse Path Each incoming packet is tested against the FIB and if the interface is not the best reverse path the packet check will fail. By default failed packets are discarded.
2 - Loose mode as defined in RFC3704 Loose Reverse Path Each incoming packet's source address is also tested against the FIB and if the source address is not reachable via any interface the packet check will fail.Current recommended practice in RFC3704 is to enable strict mode to prevent IP spoofing from DDos attacks. If using asymmetric routing or other complicated routing, then loose mode is recommended.
The max value from conf/{all,interface}/rp_filter is used when doing source validation on the {interface}.
Default value is 0. Note that some distributions enable it in startup scripts.
Como você quer manter esse comportamento legítimo, a corrente REDIRECT
deve ser usada para ignorar essa condição para uma determinada regra.