Linux what is sport and sport

What is sport and dport in iptables?

–dport — Sets the destination port for the packet. –sport — Sets the source port of the packet using the same options as –dport. The –source-port match option is synonymous with –sport. –syn — Applies to all TCP packets designed to initiate communication, commonly called SYN packets.

What does dport mean?

Acronym	Definition
DPORT	Destination Port

What is sport all about?

‘Sport’ means all forms of physical activity which, through casual or organised participation, aim at expressing or improving physical fitness and mental wellbeing, forming social relationships or obtaining results in competition at all levels.

What is sport in simple words?

Sport (or sports) is all forms of usually competitive physical activity which, through casual or organised participation, aim to use, maintain or improve physical ability and skills while providing entertainment to participants, and in some cases, spectators.

What defines a sport?

The Council of Europe charter on sport uses the following definition: “Sport means all forms of physical activity, which through casual or organised participation, aim at expressing or improving physical fitness and mental well-being, forming social relationships or obtaining results in competition at all levels”.

What is sport in your own words?

Sport pertains to any form of competitive physical activity or game that aims to use, maintain or improve physical ability and skills while providing enjoyment to participants and, in some cases, entertainment to spectators. Sports can, through casual or organized participation, improve one’s physical health.

What are the benefits of having a sport?

Great Benefits of Playing Sport

• Better Sleep. Fast Company suggests that exercise and sport triggers chemicals in the brain that can make you feel happier and relaxed.
• A Strong Heart.
• New Connections.
• Improved Lung Function.
• Increased Confidence.
• Reduces Stress.
• Improve Mental Health.
• Sport Builds Leaders.

What is a sport that starts with E?

E-Sports — another name for Gaming. European (Team) Handball — another name for the sport of Handball. Eventing — riders compete in three types of races, dressage, cross-country and show jumping, in a single competition. Expedition racing — an endurance event combining two or more disciplines.

What is the difference between sport and Dport?

–sport is short for –source-port –dport is short for –destination-port also the internet is not simply the HTTP protocol which is what typically runs on port 80. I Suspect you’re asking how to block HTTP requests. to do this you need to block 80 on the outbound chain.

What is sport about?

In the area of Sport & Development, ‘sport’ is generally understood to include physical activities that go beyond competitive sports. “Incorporated into the definition of ‘sport’ are all forms of physical activity that contribute to physical fitness, mental well-being and social interaction.

How does sport and dport work in Linux?

This of course will cut any connections to or from “the internet” even the not HTTP based ones and will prevent the slight performance hit of using iptables and processing OSI/ISO layer 2 traffic. Thanks for contributing an answer to Unix & Linux Stack Exchange!

What do you mean by sport and development?

In the area of Sport & Development, ‘sport’ is generally understood to include physical activities that go beyond competitive sports.

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What is sport and dport?

I want to stop internet on my system using iptables so what should I do? iptables -A INPUT -p tcp —sport 80 -j DROP or iptables -A INPUT -p tcp —dport 80 -j DROP ?

2 Answers 2

Reality is you’re asking 2 different questions.

also the internet is not simply the HTTP protocol which is what typically runs on port 80. I Suspect you’re asking how to block HTTP requests. to do this you need to block 80 on the outbound chain.

iptables -A OUTPUT -p tcp —dport 80 -j DROP

will block all outbound HTTP requests, going to port 80, so this won’t block SSL, 8080 (alt http) or any other weird ports, to do those kinds of things you need L7 filtering with a much deeper packet inspection.

Just to extend the answer of @xenoterracide You can read more about iptables in the manpage iptables(8) (type man 8 iptables ) but there you will not find —dport or —sport . These options are listed in iptables-extensions(8) in the section multiport, tcp, udp and elsewhere. This might be interesting to you.

To «stop the internet on your system», you can probably just turn off the network interface with sudo ifdown or sudo ip link set down for instance sudo ip link set eth0 down . To make this permanent, you need to have a look in /etc/network/interfaces (Ubuntu, Debian. ) or /etc/sysconfig/network-scripts/ifcfg- (on RHEL, SLES, CentOS, Oracle Linux, Fedora. ) or your network-manager config or anything else you use. This of course will cut any connections to or from «the internet» even the not HTTP based ones and will prevent the slight performance hit of using iptables and processing OSI/ISO layer 2 traffic.

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iptables —sport vs —dport. INPUT vs OUTPUT

I am having some trouble understanding iptables. I know it acts as a filter but something isn’t clicking because it isn’t working the way I think it should. Let me start by saying that I’m creating a white list, so all policies (INPUT, FORWARD, OUTPUT) default to DROP. I have the following rules related to SMTP: -A INPUT -m state —state ESTABLISHED,RELATED -j ACCEPT -A INPUT -p tcp —dport 25 -j ACCEPT -A OUTPUT -p tcp —dport 25 -j ACCEPT //needed for receiving? -A OUTPUT -p tcp —sport 25 -j ACCEPT //needed for sending? *these 3 lines also exist verbatim for ports 587 & 465 If I remove the first OUTPUT line then my server won’t receive emails & if I remove the last line it won’t send emails. What I don’t understand is why. Shouldn’t: -A INPUT -p tcp —dport 25 -j ACCEPT -A OUTPUT -p tcp —sport 25 -j ACCEPT be enough to let everything through? AFAIK all SMTP communication should go over 25, 587 or 465. My current understanding says an SMTP packet should always match one of these two rules. All input packets should come to port 25, and all output packets be sent from 25? What am I missing?

2 Answers 2

For SMTP you don’t need any —sport rule. The source and destination don’t depend on direction — they’re match on the packet’s source and destination ports. Every connection will have a random source port, so there’s nothing to match on.

If I remove the first OUTPUT line then my server won’t receive emails & if I remove the last line it won’t send emails.

This is wrong. Only the INPUT line matters for receiving emails. Also, only the OUTPUT —dport 25 line matters for sending emails. So these rules should be enough:

-A INPUT -p tcp --dport 25 -j ACCEPT -A OUTPUT -p tcp --dport 25 -j ACCEPT 

The problem may be that you set OUTPUT to default to DROP, but allowed established connection on INPUT only. Usually people leave OUTPUT defaulting to ACCEPT. If you want to continue using a whitelist for OUTPUT, you’ll have to add:

-A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT -A OUTPUT -m state --state ESTABLISHED,RELATED -j ACCEPT 

Also, please read up on SMTP ports. Some of those you listed are only needed for email submissions and deprecated encryption, not for server-to-server communication. This may change how you plan your rules.

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