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<a href="index.html">Core OS Index</a>
<h1>2.3. Network</h1>
<p>Operation of the network can be handle with init scripts;</p>
<dl>
<dt><a href="conf/rc.d/iptables">/etc/rc.d/iptables</a></dt>
<dd>Configure <a href="#iptables">iptables</a>, start option
loads set of rules from file /etc/iptables/net.v4, open option
allows everything to outside and blocks everything from outside,
stop will block and log everything.</dd>
<dt><a href="conf/rc.d/net">/etc/rc.d/net</a></dt>
<dd>Configure Ethernet interface with static or dynamic (dhcp)
IP, set default route and add default gateway.</dd>
<dt><a href="conf/rc.d/wlan">/etc/rc.d/wlan</a></dt>
<dd>Configure Wireless interface, launch wpa_supplicant to handle
wireless authenticationand dynamic (dhcp)
connection to router and add as default gateway.</dd>
</dl>
<p>Choose wireless or net as connection to outside world and configure
<a href="conf/rc.conf">/etc/rc.conf</a> to run at startup, example
connecting using wireless interface;</p>
<pre>
#
# /etc/rc.conf: system configuration
#
FONT=default
KEYMAP=dvorak
TIMEZONE="Europe/Lisbon"
HOSTNAME=c9
SYSLOG=sysklogd
SERVICES=(lo iptables wlan crond)
# End of file
</pre>
<p>If is first boot after install configure iptables and one of above
described scripts then proceed to
<a href="package.html#sysup">update system.</a></p>
<h2 id="resolv">2.3.1. Resolver</h2>
<p>This example will use
<a href="http://www.chaoscomputerclub.de/en/censorship/dns-howto">Chaos Computer Club</a>
server, edit /etc/resolv.conf and make it immutable;</p>
<pre>
# /etc/resolv.conf.head can replace this line
nameserver 213.73.91.35
# /etc/resolv.conf.tail can replace this line
</pre>
<pre>
# chattr +i /etc/resolv.conf
</pre>
<h2 id="static">2.3.2. Static IP</h2>
<p>Current example of <a href="conf/rc.d/net">/etc/rc.d/net</a>;</p>
<pre>
Address: 192.168.0.1 11000000.10101000.00000000 .00000001
Netmask: 255.255.255.0 = 24 11111111.11111111.11111111 .00000000
Wildcard: 0.0.0.255 00000000.00000000.00000000 .11111111
=>
Network: 192.168.0.0/24 11000000.10101000.00000000 .00000000 (Class C)
Broadcast: 192.168.0.255 11000000.10101000.00000000 .11111111
HostMin: 192.168.0.1 11000000.10101000.00000000 .00000001
HostMax: 192.168.0.254 11000000.10101000.00000000 .11111110
Hosts/Net: 254 (Private Internet)
</pre>
<p>Other IP class that can used for private network;</p>
<pre>
Address: 10.0.0.1 00001010.00000000.00000000 .00000001
Netmask: 255.255.255.0 = 24 11111111.11111111.11111111 .00000000
Wildcard: 0.0.0.255 00000000.00000000.00000000 .11111111
=>
Network: 10.0.0.0/24 00001010.00000000.00000000 .00000000 (Class A)
Broadcast: 10.0.0.255 00001010.00000000.00000000 .11111111
HostMin: 10.0.0.1 00001010.00000000.00000000 .00000001
HostMax: 10.0.0.254 00001010.00000000.00000000 .11111110
Hosts/Net: 254 (Private Internet)
</pre>
<p>Manual configuring like net script;</p>
<pre>
# DEV=enp8s0
# ADDR=192.168.1.9
# MASK=24
# GW=192.168.1.254
</pre>
<pre>
# ip addr flush dev ${DEV}
# ip route flush dev ${DEV}
# ip addr add ${ADDR}/${MASK} dev ${DEV} broadcast +
# ip link set ${DEV} up
# ip route add default via ${GW}
</pre>
<h2 id="iptables">2.3.3. Iptables</h2>
<p>For more information about firewall systems read arch wiki
<a href="https://wiki.archlinux.org/index.php/Iptables">iptables</a>
an <a href="https://wiki.archlinux.org/index.php/nftables">nftables</a>.</p>
<p>To setup iptables rules a set of scripts is used, init script
<a href="conf/rc.d/iptables">/etc/rc.d/iptables</a>
loads set of rules from file /etc/iptables/net.v4 at boot time.
Start option "open" option allows everything to outside
and blocks everything from outside, "stop" will block and log
everything. Setup init script and rules ;</p>
<pre>
# mkdir /etc/iptables
# cp core/conf/iptables/net.v4 /etc/iptables/
# cp core/conf/rc.d/iptables /etc/rc.d/
# chmod +x /etc/rc.d/iptables
</pre>
<p>Change /etc/rc.conf and add iptables;</p>
<pre>
SERVICES=(iptables lo net crond)
</pre>
<p>See current rules and packets counts;</p>
<pre>
# iptables -L -n -v | less
</pre>
<p>Diagram of a package route throw iptables;</p>
<pre>
XXXXXXXXXXXXXXXXX
XXXX Network XXXX
XXXXXXXXXXXXXXXXX
+
|
v
+-------------+ +------------------+
|table: filter| >---+ | table: nat |
|chain: INPUT | | | chain: PREROUTING|
+-----+-------+ | +--------+---------+
| | |
v | v
[local process] | **************** +--------------+
| +---------+ Routing decision +------< |table: filter |
v **************** |chain: FORWARD|
**************** +------+-------+
Routing decision |
**************** |
| |
v **************** |
+-------------+ +------< Routing decision >---------------+
|table: nat | | ****************
|chain: OUTPUT| | +
+-----+-------+ | |
| | v
v | +-------------------+
+--------------+ | | table: nat |
|table: filter | +----+ | chain: POSTROUTING|
|chain: OUTPUT | +--------+----------+
+--------------+ |
v
XXXXXXXXXXXXXXXXX
XXXX Network XXXX
XXXXXXXXXXXXXXXXX
</pre>
<p>Command line usage;</p>
<pre>
iptables [-t table] {-A|-C|-D} chain rule-specification
iptables [-t table] {-A|-C|-D} chain rule-specification
iptables [-t table] -I chain [rulenum] rule-specification
iptables [-t table] -R chain rulenum rule-specification
iptables [-t table] -D chain rulenum
iptables [-t table] -S [chain [rulenum]]
iptables [-t table] {-F|-L|-Z} [chain [rulenum]] [options...]
iptables [-t table] -N chain
iptables [-t table] -X [chain]
iptables [-t table] -P chain target
iptables [-t table] -E old-chain-name new-chain-name
rule-specification = [matches...] [target]
match = -m matchname [per-match-options]
</pre>
<p>Targets, can be a user defined chain;</p>
<pre>
ACCEPT - accepts the packet
DROP - drop the packet on the floor
QUEUE - packet will be stent to queue
RETURN - stop traversing this chain and
resume ate the next rule in the
previeus (calling) chain.
if packet reach the end of the chain or
a target RETURN, default policy for that
chain is applayed.
</pre>
<p>Target Extensions</p>
<pre>
AUDIT
CHECKSUM
CLASSIFY
DNAT
DSCP
LOG
Torn on kernel logging, will print some
some information on all matching packets.
Log data can be read with dmesg or syslogd.
This is a non-terminating target and a rule
should be created with matching criteria.
--log-level level
Level of logging (numeric or see sys-
log.conf(5)
--log-prefix prefix
Prefix log messages with specified prefix
up to 29 chars log
--log-uid
Log the userid of the process with gener-
ated the packet
NFLOG
This target pass the packet to loaded logging
backend to log the packet. One or more userspace
processes may subscribe to the group to receive
the packets.
ULOG
This target provides userspace logging of maching
packets. One or more userspace processes may then
then subscribe to various multicast groups and
then receive the packets.
</pre>
<p>Commands</p>
<pre>
-A, --append chain rule-specification
-C, --check chain rule-specification
-D, --delete chain rule-specification
-D, --delete chain rulenum
-I, --insert chain [rulenum] rule-specification
-R, --replace chain rulenum rule-specification
-L, --list [chain]
-P, --policy chain target
</pre>
<p>Parameters</p>
<pre>
-p, --protocol protocol
tcp, udp, udplite, icmp, esp, ah, sctp, all
-s, --source address[/mask][,...]
-d, --destination address[/mask][,...]
-j, --jump target
-g, --goto chain
-i, --in-interface name
-o, --out-interface name
-f, --fragment
-m, --match options module-name
iptables can use extended packet matching
modules.
-c, --set-counters packets bytes
</pre>
<h3 id="ipt_server">2.3.3.1. Server iptables</h3>
<p>Adjust <a href="scripts/iptables.sh">iptables.sh</a> with
your network configuration then run it;</p>
<p>Default configuration;</p>
<pre>
server)
echo "Setting server network..."
####### Input Chain ######
$IPT -A INPUT -j blocker
$IPT -A INPUT -i ${PUB_IF} -d ${PUB_IP} -s ${DNS} -j cli_dns_in
$IPT -A INPUT -i ${PUB_IF} -d ${PUB_IP} -s ${BR_NET} -j srv_https_in
$IPT -A INPUT -i ${PUB_IF} -d ${PUB_IP} -s ${BR_NET} -j srv_ssh_in
$IPT -A INPUT -i ${PUB_IF} -d ${PUB_IP} -s ${BR_NET} -j srv_git_in
$IPT -A INPUT -i ${PUB_IF} -d ${PUB_IP} -j cli_https_in
####### Output Chain ######
$IPT -A OUTPUT -j blocker
$IPT -A OUTPUT -o ${PUB_IF} -d ${DNS} -s ${PUB_IP} -j cli_dns_out
$IPT -A OUTPUT -o ${PUB_IF} -d ${BR_NET} -s ${PUB_IP} -j srv_https_out
$IPT -A OUTPUT -o ${PUB_IF} -d ${BR_NET} -s ${PUB_IP} -j srv_ssh_out
$IPT -A OUTPUT -o ${PUB_IF} -d ${BR_NET} -s ${PUB_IP} -j srv_git_out
$IPT -A OUTPUT -o ${PUB_IF} -s ${PUB_IP} -j cli_https_out
## log everything else and drop
iptables_log
iptables-save > /etc/iptables/net.v4
exit 0
;;
</pre>
<pre>
# bash core/scripts/iptables.sh
</pre>
<h3 id="ipt_client">2.3.3.2. Client iptables </h3>
<p></p>
<h3 id="ipt_client">2.3.3.3. Bridge iptables</h3>
<pre>
$IPT -A FORWARD -j blocker
$IPT -A FORWARD -i lo -s 127.0.0.0/8 -d 127.0.0.0/8 -j ACCEPT
$IPT -A FORWARD -o lo -s 127.0.0.0/8 -d 127.0.0.0/8 -j ACCEPT
$IPT -A FORWARD -i ${BR_IF} -o ${BR_IF} -m physdev --physdev-in ${PUB_IF} --physdev-out tap2 -d ${BR_NET} -j srv_ssh_in
$IPT -A FORWARD -i ${BR_IF} -o ${BR_IF} -m physdev --physdev-in tap2 --physdev-out ${PUB_IF} -j srv_ssh_out
$IPT -A FORWARD -i ${BR_IF} -o ${BR_IF} -m physdev --physdev-in ${PUB_IF} --physdev-out tap2 -j srv_https_in
$IPT -A FORWARD -i ${BR_IF} -o ${BR_IF} -m physdev --physdev-in tap2 --physdev-out ${PUB_IF} -j srv_https_out
$IPT -A FORWARD -i ${BR_IF} -o ${BR_IF} -m physdev --physdev-in ${PUB_IF} --physdev-out tap2 -j srv_rip
$IPT -A FORWARD -i ${BR_IF} -o ${BR_IF} -m physdev --physdev-in tap2 --physdev-out ${PUB_IF} -j srv_dhcp
$IPT -A FORWARD -i ${BR_IF} -o ${BR_IF} -m physdev --physdev-in ${PUB_IF} --physdev-out tap2 -j srv_dhcp
$IPT -A FORWARD -i ${BR_IF} -o ${BR_IF} -m physdev --physdev-in tap2 --physdev-out ${PUB_IF} -j cli_https_out
$IPT -A FORWARD -i ${BR_IF} -o ${BR_IF} -m physdev --physdev-in ${PUB_IF} --physdev-out tap2 -j cli_https_in
<pre>
<h2 id="wpa">2.3.4. Wpa and dhcpd</h2>
<p>There is more information on
<a href="http://crux.nu/Wiki/WifiStartScripts">Wiki Wifi Start Scripts</a> and
see <a href="conf/rc.d/wlan">/etc/rc.d/wlan</a>. Manual or first time configuration;</p>
<pre>
# ip link
</pre>
<pre>
# iwlist wlp2s0 scan
</pre>
<pre>
# iwconfig wlp2s0 essid NAME key s:ABCDE12345
</pre>
<h3>2.3.4.1. Wpa Supplicant</h3>
<p>Configure wpa supplicant edit;</p>
<pre>
# vim /etc/wpa_supplicant.conf
</pre>
<pre>
ctrl_interface=/var/run/wpa_supplicant
update_config=1
fast_reauth=1
ap_scan=1
</pre>
<pre>
# wpa_passphrase <ssid> <password> >> /etc/wpa_supplicant.conf
</pre>
<p>Now start wpa_supplicant with:</p>
<pre>
# wpa_supplicant -B -i wlp2s0 -c /etc/wpa_supplicant.conf
Successfully initialized wpa_supplicant
</pre>
<p>Use <a href="conf/rc.d/wlan">/etc/rc.d/wlan</a>
init script to auto load wpa configuration and dhcp
client.</p>
<h3>2.3.4.2. Wpa Cli</h3>
<pre>
# wpa_cli
> status
</pre>
<pre>
> add_network
3
</pre>
<pre>
> set_network 3 ssid "Crux-Network"
OK
</pre>
<pre>
> set_network 3 psk "uber-secret-pass"
OK
</pre>
<pre>
> enable_network 3
OK
</pre>
<pre>
> list_networks
</pre>
<pre>
> select_network 3
</pre>
<pre>
> save_config
</pre>
<a href="index.html">Core OS Index</a>
<p>
This is part of the c9-doc Manual.
Copyright (C) 2017
c9 team.
See the file <a href="../fdl-1.3-standalone.html">Gnu Free Documentation License</a>
for copying conditions.</p>
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