[Primipassi] Ubuntu e il masquerading della posta

[Simone Ballerini]

Ho finalmente installato Ubuntu 6.06 sul pc al posto della Slackware
10.2. Funziona tutto escluso il masquerading con iptables che ho copiato
pari pari da quello che usavo sulla slack.
Ovvero funziona con i protocolli web ma con la posta il client la vede
ma quando cerca di scaricarla non arriva niente.
Nella configurazione della rete non ho cambiato una virgola.
Io credo che sia un problema che riguarda il cambiamento del kernel,
cioè passando dal 2.4.x della slack al 2.6.x di ubuntu penso vada
modificato qualcosa nelle regole di iptables ma non so cosa.

Vi ringrazio per qualsiasi aiuto mi possiate dare.

Di seguito posto le impostazioni di iptables i moduli caricati, le
interfacce (su eth1 ho il modem eternet e su eth0 la lan):

simone@pandora:~$ cat /etc/ppp/ip-up.local
/sbin/modprobe ipt_MASQUERADE
iptables -F; iptables -t nat -F; iptables -t mangle -F
iptables -t nat -A POSTROUTING -o ppp0 -j MASQUERADE
iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
iptables -A INPUT -m state --state NEW -i ! ppp0 -j ACCEPT
iptables -P INPUT DROP
iptables -t filter -A INPUT --protocol tcp --dport 22 -j ACCEPT
iptables -t filter -A INPUT --protocol tcp --dport 4662 -j ACCEPT
iptables -t filter -A INPUT --protocol udp --dport 4672 -j ACCEPT
iptables -t filter -A INPUT --protocol tcp --dport 6881 -j ACCEPT
iptables -A FORWARD -i ppp0 -o ppp0 -j REJECT
echo 1 > /proc/sys/net/ipv4/ip_forward

simone@pandora:~$ lsmod | grep ^ip
ipt_REJECT              5632  1
ipt_state               2048  2
iptable_mangle          2944  0
iptable_nat             7812  1
iptable_filter          3072  1
ipt_MASQUERADE          3456  1
ip_nat                 19628  2 iptable_nat,ipt_MASQUERADE
ip_tables              22400  6
ipt_REJECT,ipt_state,iptable_mangle,iptable_nat,iptable_filter,ipt_MASQUERADE
ip_conntrack           51500  4
ipt_state,iptable_nat,ipt_MASQUERADE,ip_nat
ipv6                  265728  10

simone@pandora:~$ ifconfig
eth0      Link encap:Ethernet  HWaddr 52:54:00:DF:D9:FA
          inet addr:192.168.0.20  Bcast:192.168.0.255
Mask:255.255.255.0
          inet6 addr: fe80::5054:ff:fedf:d9fa/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:6 dropped:0 overruns:0 carrier:12
          collisions:102 txqueuelen:1000
          RX bytes:0 (0.0 b)  TX bytes:468 (468.0 b)
          Interrupt:9 Base address:0xd000

eth1      Link encap:Ethernet  HWaddr 00:08:A1:66:2E:76
          inet addr:192.168.1.16  Bcast:255.255.255.255
Mask:255.255.255.224
          inet6 addr: fe80::208:a1ff:fe66:2e76/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:472 errors:0 dropped:0 overruns:0 frame:0
          TX packets:269 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:203860 (199.0 KiB)  TX bytes:25197 (24.6 KiB)
          Interrupt:9 Base address:0xe000

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:5 errors:0 dropped:0 overruns:0 frame:0
          TX packets:5 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:272 (272.0 b)  TX bytes:272 (272.0 b)

ppp0      Link encap:Point-to-Point Protocol
          inet addr:82.57.127.144  P-t-P:192.168.100.1
Mask:255.255.255.255
          UP POINTOPOINT RUNNING NOARP MULTICAST  MTU:1492  Metric:1
          RX packets:393 errors:0 dropped:0 overruns:0 frame:0
          TX packets:185 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:3
          RX bytes:189202 (184.7 KiB)  TX bytes:15285 (14.9 KiB)