Differences

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--- doc:appunti:net:source_routing [2013/06/25 11:48] – [Firewall dual homed e source routing con Shorewall] niccolo
+++ doc:appunti:net:source_routing [2025/10/07 10:56] (current) – [Firewall dual homed e source routing con Shorewall] niccolo
@@ Line 27: / Line 27: @@
 # Special table for source routing.
 # See /etc/network/interfaces.
      eth2_tbl
 </file>
@@ Line 42: / Line 42: @@
         broadcast 217.19.150.255
         # gateway 217.19.150.1
-        # Put a line "100 eth2_tbl" into /etc/iproute2/rt_tables
+        # Put a line "102 eth2_tbl" into /etc/iproute2/rt_tables
         up /sbin/ip rule add from 217.19.150.6 table eth2_tbl || true
         up /sbin/ip route add 217.19.150.0/24 dev eth2 table eth2_tbl || true
         up /sbin/ip route add default via 217.19.150.1 table eth2_tbl || true
-        down /sbin/ip rule del from 217.19.150.6 table eth2_tbl || true
-        down /sbin/ip route del 217.19.150.0/24 dev eth2 table eth2_tbl || true
         down /sbin/ip route del default via 217.19.150.1 table eth2_tbl || true
+        down /sbin/ip route del 217.19.150.0/24 dev eth2 table eth2_tbl || true
+        down /sbin/ip rule del from 217.19.150.6 table eth2_tbl || true
 </file>
@@ Line 64: / Line 64: @@
 :  from all lookup default
 </code>
+Attenzione alla **priorità delle regole** (rules)! Il numero più basso ha priorità maggiore, se non viene indicato il parametro **''priority''** nel comando **''ip rule add''** viene assegnato automaticamente un numero decrescente a partire da **32767** (unsigned int). Secondo questa priorità automatica quindi **la regola inserita per ultima ha priorità maggiore**.
 ====== Source IP con ip route ======
@@ Line 76: / Line 78: @@
 ip route add 78.47.114.234/32 via 62.48.51.1 src 62.48.51.127
 </code>
 ====== Routing in base al servizio ======
@@ Line 93: / Line 96: @@
 # Special table for source routing.
 # See /etc/network/interfaces.
      eth2_tbl
 </file>
@@ Line 144: / Line 147: @@
 ====== Firewall dual homed e source routing con Shorewall ======
-**Esempio**: collegamento a internet con due interfacce, **eth0** ADSL e **eth2** (94.94.64.138, HDSL). La rotta predefinita è su eth0, parte del traffico viene dirottato su eth2 tramite regole di ''iptables''.
+**Esempio**: collegamento a internet con due interfacce, **eth0** (217.58.174.226, ADSL) e **eth2** (94.94.64.138, HDSL). La rotta predefinita è su eth0, parte del traffico viene dirottato su eth2 tramite regole di ''iptables''. La **LAN** 10.22.20.0/24 è collegata su **eth1**.
 Queste le accortezze da utilizzare:
   * In **''/etc/shorewall/interfaces''** si indicano le due interfacce collegate alla zona **net**.
-  * In **''/etc/shorewall/shorewall.conf''** si imposta **''ROUTE_FILTER=No''**, altrimenti il traffico in uscita dalla eth2 viene filtrato come //martian source//.
+  * In **''/etc/shorewall/shorewall.conf''** si imposta **ROUTE_FILTER=No**, altrimenti il traffico in uscita dalla eth2 viene filtrato come //martian source//.
+  * In **''/etc/shorewall/interfaces''** **NON** ci deve essere l'opzione **routefilter=1** (misura anti-spoofing), per lo stesso motivo di cui sopra. **ATTENZIONE**: Se in ''shorewall.conf'' c'è l'opzione ''ROUTE_FILTER=Yes'', impostare qui ''routefilter=0'' non è sufficiente.
+  * In **''/etc/shorewall/interfaces''** è opportuno avere l'opzione **sourceroute=0** (parametro accept_source_route del kernel) sulle interfacce collegate a peer non fidati (connessioni ISP, ecc).
+**''/etc/shorewall/interfaces''**
+<file>
+# Dual-homed external interfaces require global ROUTE_FILTER=No in shorewall.conf.
+# The safe policy for connections with untrusted peers is to set accept_source_route to 0.
+# Notice: source route packets are nonsensical on a PPP link.
+accept_source_route = 0
+net    eth0    tcpflags,nosmurfs,sourceroute=0
+net    eth2    tcpflags,nosmurfs,sourceroute=0
+# Enable route filter (rp_filter kernel paramter) specifically on the local interface.
+loc    eth1    dhcp,routefilter=1
+</file>
 **''/etc/iproute2/rt_tables''**
@@ Line 156: / Line 174: @@
 # Special table for source routing.
 # See /etc/network/interfaces.
      eth2_tbl
 </file>
@@ Line 169: / Line 187: @@
         # gateway 94.94.64.137
         up /sbin/ip rule add from 94.94.64.138 table eth2_tbl || true
-        up /sbin/ip rule add fwmark 100 table eth2_tbl || true
+        up /sbin/ip rule add fwmark 102 table eth2_tbl || true
         up /sbin/ip route add 94.94.64.136/29 dev eth2 table eth2_tbl || true
         up /sbin/ip route add default via 94.94.64.137 table eth2_tbl || true
         down /sbin/ip route del default via 94.94.64.137 table eth2_tbl || true
         down /sbin/ip route del 94.94.64.136/29 dev eth2 table eth2_tbl || true
-        down /sbin/ip rule del fwmark 100 table eth2_tbl || true
+        down /sbin/ip rule del fwmark 102 table eth2_tbl || true
         down /sbin/ip rule del from 94.94.64.138 table eth2_tbl || true
 </file>
-**''/etc/shorewall/masq''**
+**''/etc/shorewall/snat''** (per il nuovo Shorewall v.5)
 <file>
-eth0                    10.22.20.0/24                                           # LAN to internet via HDSL
+SNAT(217.58.174.226)    192.168.1.0/24   eth0    # LAN to internet via HDSL
-eth2                    10.22.20.0/24   94.94.64.138                            # LAN to internet via ADSL
+SNAT(94.94.64.138)      192.168.1.0/24   eth2    # LAN to internet via ADSL
 </file>
+**''/etc/shorewall/masq''** (per il vecchio Shorewall v.4)
+<file>
+eth0    10.22.20.0/24       # LAN to internet via HDSL
+eth2    10.22.20.0/24       # LAN to internet via ADSL
+</file>
 **''/etc/shorewall/start''**
 <file>
-# Mark some traffic to be routed via eth2.
+# Packets source-routed via eth2 must use eth2 source address,
-iptables -A PREROUTING -t mangle ! -d 62.48.51.0/24 -i eth1 --proto tcp --dport 80  -j MARK --set-mark 100
+# otherwise source address for default gateway is used.
-iptables -A PREROUTING -t mangle ! -d 62.48.51.0/24 -i eth1 --proto tcp --dport 443 -j MARK --set-mark 100
+iptables -t nat -A POSTROUTING -o eth2 -j SNAT --to-source 94.94.64.138
+# For connections originating from eth1 LAN.
+iptables -A PREROUTING -t mangle -i eth1 --proto tcp --dport 22  -j MARK --set-mark 102
+iptables -A PREROUTING -t mangle -i eth1 --proto tcp --dport 80  -j MARK --set-mark 102
+# For locally geneated connections.
+iptables -A OUTPUT -t mangle --proto tcp --dport 22 -j MARK --set-mark 102
 </file>