Core OS Index

2.2. Network

Operation of the network can be handle with init scripts or with network manager;

/etc/rc.d/iptables
Configure iptables, "start" option loads set of rules from file /etc/iptables/(name).v4, "open" option allows everything to outside and blocks everything from outside, "stop" option will block and log everything.
/etc/rc.d/net
Configure Ethernet interface with static or dynamic (dhcp) IP, set default route and add default gateway.
/etc/rc.d/wlan
Configure Wireless interface, launch wpa_supplicant to handle wireless authenticationand dynamic (dhcp) connection to router and add as default gateway.
/etc/rc.d/networkmanager
Use network manager to handle connections.

Choose wireless (wlan), cable network (net) or network manager in /etc/rc.conf to handle configuration of the network at startup, example using network manager;

        #
        # /etc/rc.conf: system configuration
        #

        FONT=default
        KEYMAP=dvorak
        TIMEZONE="Europe/Lisbon"
        HOSTNAME=machine
        SYSLOG=sysklogd
        SERVICES=(lo iptables networkmanager crond)

        # End of file
        

If is first boot after install configure iptables and one of above described scripts then proceed to update system.

2.2.1. Resolver

This example will use Chaos Computer Club server, edit /etc/resolv.conf and make it immutable;

        # /etc/resolv.conf.head can replace this line
        nameserver 2.2.73.91.35
        # /etc/resolv.conf.tail can replace this line
        
        # chattr +i /etc/resolv.conf
        

2.2.2. Static IP

Current example of /etc/rc.d/net;

        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)
        

Other IP class that can used for private network;

        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)
        

Manual configuring like net script;

        # DEV=enp8s0
        # ADDR=192.168.1.9
        # MASK=24
        # GW=192.168.1.254
        
        # 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}
        

2.2.3. Iptables

For more information about firewall systems read arch wiki iptables and nftables.

Diagram of a package route throw iptables;


                                 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

        

Command line usage;

        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]
        

Targets, can be a user defined chain;

        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.
        

Target Extensions

        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.
        

Commands

         -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
        

Parameters

         -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
        

See current rules and packets counts;

        # iptables -L -n -v | less
        

2.2.3.1. Iptable scripts

Scripts help to setup iptables rules so they can be saved using iptables-save and later restored using iptables-restore utilities. Init script /etc/rc.d/iptables loads set of rules from /etc/iptables folder at boot time. Start option "open" option allows everything to outside and blocks new connections from outside, "stop" will block and log everything.

Setup init script and rules;

        # mkdir /etc/iptables
        # cp core/conf/iptables/*.sh /etc/iptables/
        # cp core/conf/rc.d/iptables /etc/rc.d/
        # chmod +x /etc/rc.d/iptables
        

Change /etc/rc.conf and add iptables;

        SERVICES=(iptables lo net crond)
        

Change /etc/rc.d/iptables and define type; server, bridge or open.

Adjust /etc/iptables/ipt-conf.sh with your network configuration, and adjust /etc/iptables/ipt-server.sh, /etc/iptables/ipt-bridge.sh, /etc/iptables/ipt-open.sh according with host necessities.

When is everything configured run script to load the rules and save them on /etc/iptables. Example for bridge setup;

        # cd /etc/iptables
        # bash ipt-bridge.sh
        

From now on use /etc/rc.d/iptables to start and stop.

2.2.4. Wpa and dhcpd

There is more information on Wiki Wifi Start Scripts and see /etc/rc.d/wlan. Manual or first time configuration;

        # ip link
        
        # iwlist wlp2s0 scan
        
        # iwconfig wlp2s0 essid NAME key s:ABCDE12345
        

2.2.4.1. Wpa Supplicant

Configure wpa supplicant edit;

        # vim /etc/wpa_supplicant.conf
        
        ctrl_interface=/var/run/wpa_supplicant
        update_config=1
        fast_reauth=1
        ap_scan=1
        
        # wpa_passphrase <ssid> <password> >> /etc/wpa_supplicant.conf
        

Now start wpa_supplicant with:

        # wpa_supplicant -B -i wlp2s0 -c /etc/wpa_supplicant.conf
        Successfully initialized wpa_supplicant
        

Use /etc/rc.d/wlan init script to auto load wpa configuration and dhcp client.

2.2.4.2. Wpa Cli

        # wpa_cli
        > status
        
        > add_network
        3
        
        > set_network 3 ssid "Crux-Network"
        OK
        
        > set_network 3 psk "uber-secret-pass"
        OK
        
        > enable_network 3
        OK
        
        > list_networks
        
        > select_network 3
        
        > save_config
        

2.2.5. Network Manager

Wifi status;

        $ nmcli radio wifi
        $ nmcli radio wifi on
        

List wifi networks;

        $ nmcli device wifi rescan
        $ nmcli device wifi list
        

Connect to a wifi network;

        $ nmcli device wifi connect "network name" password "network password"
        

Edit and save network configuration;

        $ nmcli connection edit "network name"
        nmcli> save persistent
        
Core OS Index

This is part of the Tribu System Documentation. Copyright (C) 2020 Tribu Team. See the file Gnu Free Documentation License for copying conditions.