Now to allow source IP do specific port

Question

I want to allow IP 1.2.3.4 on port 3306 with nftables, but I was not able to find how to actually insert port?

I was trying something like nft insert saddr 1.2.3.4.5 ip daddr server_ip accept

Answer 1

Since I assume it's the MySQL port, using the TCP protocol:

sudo nft add rule filter input ip saddr 1.2.3.4 tcp dport 3306 accept

The saddr and daddr options are part of ip setting, while the sport and dport options should be used with the layer 4 protocol such as tcp or udp.