how to translate these rules

RouterOS General
1

Hello,

I found on my OpenWrt router some default firewall rules.
These rules makes sense and are clear how to realize it on ROS.

DROP       all  --  anywhere             anywhere            state INVALID
ACCEPT     all  --  anywhere             anywhere            state RELATED,ESTABLISHED

But how can these rules be realized in ROS and which sense have these rules?

ACCEPT     gre  --  anywhere             anywhere
REJECT     all  --  anywhere             anywhere            reject-with icmp-port-unreachable
REJECT     tcp  --  anywhere             anywhere            reject-with tcp-reset
TCPMSS     tcp  --  anywhere             anywhere            tcp flags:SYN,RST/SYN TCPMSS clamp to PMTU
DROP       tcp  --  anywhere             anywhere            tcp option=!2 flags:SYN/SYN
2

noone? :frowning:

3

Such rules are in a MikroTik by default. Apparently you have modified it.
The match for connection state is in the add rule page, when you expand it you can tick those options you mention.

4

The first and second rule is a default rule but per default there were set 5 rules.

3 ACCEPT     gre  --  anywhere             anywhere
4 REJECT     all  --  anywhere             anywhere            reject-with icmp-port-unreachable
5 REJECT     tcp  --  anywhere             anywhere            reject-with tcp-reset
6 TCPMSS     tcp  --  anywhere             anywhere            tcp flags:SYN,RST/SYN TCPMSS clamp to PMTU
7 DROP       tcp  --  anywhere             anywhere            tcp option=!2 flags:SYN/SYN

What does the grep stand for in the rule #3?

How can I set the parameter icmp-port-unreachable in ROS?

What does reject with tcp-reset mean?

How can I configure the rule #6 and rule #7 in ROS?