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Questions tagged [packet]

81 questions
14
votes
4 answers

How to capture all incoming packets to NIC even those packets are not belonging to me

AFAIK, the NIC receives all packets from the wire in a Local Area Network but rejects those packets which their destination address is not equal to its ip. I want to develop an application that monitors the internet usage of users. Each user has a…
Rezaeimh7
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11
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2 answers

What does iptables -j REDIRECT *actually* do to packet headers?

Out of curiosity I'm reading some tutorials about transparent TOR proxies as it's quite interesting topic from a networking standpoint. As opposed to VPN gateways which just use tun/tap interfaces and are totally clear to me, TOR proxy uses a…
Lapsio
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1 answer

Create UDP to TCP bridge with socat/netcat to relay control commands for vlc media-player

The UDP - must listen on port. The TCP - must connect to a server. I tried netcat and socat. nc -v -u -l -p 3333 | nc -v 127.0.0.1 50000 socat -v UDP-LISTEN:3333,fork TCP:localhost:50000 Both work -- they delivered the message -- but the line is…
Mihai Popescu
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6
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1 answer

How to get metrics about dropped traffic via iptables?

We are using iptables firewall. It is logging and dropping various packages depending on its defined rules. Iptables log file entries look like: 2017-08-08T19:42:38.237311-07:00 compute-nodeXXXXX kernel: [1291564.163235] drop-message : IN=vlanXXXX…
Hakan Baba
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5
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1 answer

IPTABLES: process a packet locally and send a copy to another host

I have a trouble configuring iptables to do this: some clients send messages to a server. I want that the host server processes the messages locally (host A, as normal) but that additionally for each message (tcp packet) sends a copy of the packet…
Armando Contestabile
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5
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1 answer

Block outgoing connections to certain IP using PF

Can someone give me a hint on how to setup a basic deny rule whenever any TCP request is sent to a specific IP address? I am using the PF packet filter. Any help?
Joseph
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4
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1 answer

how to intercept IP packets on linux

I am trying to achieve this goal on Linux (not sure if it is possible and how if so): I need to write a program to intercept all IP packets on an interface, and deliver this packet to a specific set of user-space programs. By intercept I mean, an…
user2975098
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3
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1 answer

How do I check if I have packet socket support enabled in my distro's kernel?

How do I check that packet socket support has been compiled into my kernel? I'm running Crunchbang, a Debian-based distribution.
user34789
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3
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1 answer

Package pre-installation script subprocess returned error exit status 1

I have question similar to this one dpkg: new pre-installation script returned error exit status 1 I'm getting error same as above when trying to install PacketTracer 7.3.1. I think I declined EULA. I know nothing about bash and debconf. Does anyone…
user3565923
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3
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1 answer

Why linux drop packets in netif_receive_skb?

I have a linux box where we see a lot of (30%) TCP retransmission in tcpdump when receiving (downloading) files from outside. Using the dropwatch utility we see many packet drops in kernel function net_receive_skb(). That means data have been…
Zhaohui Yang
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3
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1 answer

How do packets traverse tc/netfilter physical, VLAN and bridge interfaces?

Given the following setup on a router that performs NAT between two networks A and B: eth0 - physical interface - no ip address eth0.1 - VLAN interface for network A - no ip address eth0.2 - VLAN interface for network B - ip address for network…
xnor
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3
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1 answer

Remote control alarm

I want one of machine have a remote control alarm running that can be triggered by any remote machine. More precisely Machine A is running the service in the background Any remote machine B can send a packet to machine A to trigger the alarm (a…
user123456
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1 answer

How can I limit Download bandwidth of an existing process? (iptables, tc, ?)

I am happily limiting upload speed by port - but really want to limit download by process. It seems iptables did have functionality for matching and marking packets by process in the form of --pid-owner or --cmd-owner - but both have now been…
Chozabu
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3
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1 answer

record contents of packets dropped in iptables

I'm trying to find a way to record the entire contents of packets (possibly with tcpdump) that have been dropped according to rules in iptables. At present, I have a rule to log these packets (with a log prefix), then follow this with a rule to drop…
OneCheapDrunk
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2
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2 answers

Tshark not running via gdb

I have successfully installed wireshark on centos 6.4 I can run the command tshark it works perfectly fine. I want to run gdb so that I want to learn how it decodes tcp and udp packet as I am writing an application where I need to dissect these two…
biz14
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