questions about iptables

gengyabc · 05-12-2015, 09:39 AM

Hi everyone
I have a question about iptables

This line

Code:

iptables -A INPUT -p tcp  -m tcp --dport 80 -j ACCEPT

why there is a "-m tcp"? what does this mean? I checked some book and man, I did not find what does this mean.

Thank you very much for your help.

Habitual · 05-12-2015, 10:26 AM

Welcome to LQ!
at http://ipset.netfilter.org/iptables.man.html shows

Code:

       -m, --match match
              Specifies a match to use, that is, an extension module that tests for a specific property. The set  of
              matches  make up the condition under which a target is invoked. Matches are evaluated first to last as
              specified on the command line and work in short-circuit fashion, i.e. if one extension  yields  false,
              evaluation will stop.

What that means exactly, I don't know, never had to use or implement it or if it involves a rule named tcp.

lazydog · 05-12-2015, 10:26 AM

'-m' = Match

Code:

-m, --match match
Specifies a match to use, that is, an extension module that tests for a specific property. The set of matches make up the 
condition under which a target is invoked. Matches are evaluated first to last as specified on the command line and work in 
short-circuit fashion, i.e. if one extension yields false, evaluation will stop.

gengyabc · 05-13-2015, 09:12 AM

Thank you very much.
then I will not use -m tcp.