Make your laptop into a working repeater/hotspot

dnsmasq.conf

bind-interfaces
no-resolv

dhcp-range=192.168.33.2,192.168.33.20,12h

dhcp-option=3,192.168.33.1 # Gateway (gw)
dhcp-option=6,192.168.33.1 # DNS

log-queries
log-dhcp
listen-address=192.168.33.1

hostapd.conf

interface=wlan1
ssid=file-sharing
channel=6
hw_mode=g

wpa=2
wpa_passphrase=password123
wpa_key_mgmt=WPA-PSK

Make your computer act as a router or repeater

to enable hotspot, start the following service as root:

dnsmasq -C dnsmasq.conf -q -d
hostapd -dd -t hostapd.conf
ifconfig wlan1 192.168.33.1 netmask 255.255.255.0 up

helpful post, but there's an exception, the step on the post is not entirely accurate: route command is unnecessary, and the listen address must be the same as gateaway to be able response to the client request.

Debugging

list routing table: route -n or ip route list
monitor network traffic: tcpdump -vv -i wlan1 'port 67 or port 68' (see man 7 pcap-filter for more information about the expression)
list used port netstat -tulpn
list reserved port: less /etc/services

Link and Reference

• DHCP Protocol
• IP Address
• Subnet
• DHCP with DNS
• Software access point - hotspot or repeater
• Hostapd
• Packet flow
• Internet Sharing
• Ad-Hoc Wikiepdia
• Ad-Hoc Arch Wiki

To enable internet access, use the following command:

sysctl net.ipv4.ip_forward=1
iptables -t nat -A POSTROUTING -o eth0 -s 192.168.33.0/24 ! -d 192.168.33.0/24 -j MASQUERADE

make sure it's applied:

iptables -t nat -S

flush or delete the rule:

iptables -t nat -F

Link and Reference

• askubuntu
• telegram

Related link

• airgeddon