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Questions tagged [packet]

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Why does tshark display "TLSv1" despite curl showing TLSv1.3 in the "Client Hello"?

The output from curl indicates TLSv1.3 (OUT), TLS handshake, Client hello (1). Use --tlsv1.3 to force it to use TLSv1.3: $ curl -6 --tlsv1.3 --tls13-ciphers TLS_AES_256_GCM_SHA384 -vL https://...
林果皞's user avatar
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1 vote
1 answer
603 views

How to mark packets by program

How to mark all packets (inbound and outbound) for specific program/ cmd in Linux using iptables or any other firewall/ tool Given that --cmd-owner option was deprecated ref:http://www.spinics.net/...
user216385's user avatar
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0 answers
618 views

understand different UDP packet loss results: iperf3 vs nuttcp

I try to measure UDP [%packet loss] between two machines. I'm getting different results while using two different tools: iperf3: machine 1: iperf3 -s machine 2: iperf3 -c <machine_1_ip> -u -...
hutcruchi's user avatar
  • 339
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1 answer
631 views

How to retrieve raw bytes of DNS response?

I want to retrieve raw bytes of DNS response for debugging reason, for example: dig -t https clickhouse.com ;; ANSWER SECTION: clickhouse.com. 242 IN HTTPS 1 . alpn="h3,h3-29,...
Kokizzu's user avatar
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1 answer
672 views

Dummy interface is not reachable from other system through ping

I connected two Debian 10 systems with a direct link. On one of them I defined a dummy interface and on the other I gave a static route to access it. I see the traffic from the sender on the interface,...
user8178737's user avatar
1 vote
1 answer
110 views

Why does adding a counter queue to my Netfilter chain break my VM?

I'm configuring Netfilter Tables to queue packets to and from the userspace, and the table configuration I have so far looks like: table inet filter { # protocols to allow set ...
wwillfred's user avatar
1 vote
0 answers
55 views

Why 802.1q protocal packet auto dropped by interface?

I transfer a series of test packet with IEC61850_SV protocal in my host as follows: 01 0C CD 04 00 03 00 0C CD 04 00 00 81 00 80 01 88 BA 40 03 01 24 00 00 00 00 60 82 01 18 80 01 01 A2 82 01 11 30 ...
Sun Caelus's user avatar
2 votes
1 answer
2k views

Error when trying to corrupt packets in linux terminal (netem)

The following rule corrupts 5% of the packets by introducing a single bit error at a random offset in the packet: sudo tc qdisc change dev ens8 root netem corrupt 5% But recently it gave me the ...
Arash's user avatar
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0 votes
1 answer
2k views

How to debug Linux TCP slows/packet loss

I'm trying to track down some particular network paths which are slowing down to about 200KByte/sec. I see this performance through various tests including with scp, rsync and iperf3: $ iperf3 -c 157....
bgp's user avatar
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0 answers
508 views

Why are packets being dropped (kfree_skb)?

I am currently sending ~9mpps, each packet is 72bytes large, and is a UDP DNS request. The packets are being sent to a Dell server I have using an intel i40e interface. The server is using all of its ...
Dave's user avatar
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1 vote
0 answers
107 views

How does libpcap read network packets, and why can it not operate in some VMs?

I'm interested to learn how libpcap reads network packets, as I am finding it is not possible when running on AWS Lambda From what I can understand, you need either or both of the CAP_NET_ADMIN and ...
Matty F's user avatar
  • 111
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0 answers
200 views

New install of Linux Mint 20.2 Cinnamon (5.0.4) has ~50% packet loss - Caused by router?

I have recently installed Linux Mint 20.2 Cinnamon (5.0.4) (Kernel 5.4.0-74-generic) on my desktop on a separate drive from a Windows 10 install. On Linux I noticed very inconsistent connections when ...
Mandias's user avatar
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0 votes
2 answers
19 views

extract application name from rawpacket

Sounds dumb, but can you extract application name from a packet/pcap. For eg: If a packet destination is to chrome process, can you extract that information from packet?
Fight Daily's user avatar
1 vote
0 answers
781 views

Can't find kutil after installation of krb5-usr

I need to merge keytab files and all tutorials mention kutil. But I can't find it: root@nfsserver:/etc# kutil bash: kutil: command not found But krb5-usr is already installed: krb5-user is already ...
Standard's user avatar
  • 161
1 vote
0 answers
86 views

Consistent missing packet only when flood pinging

I've been having one packet consistently dropping when initiating a flood ping in ubuntu I'll toss out that one with 2 dropped packets as randomness, is there something going on here within the ...
Edward's user avatar
  • 111
3 votes
1 answer
4k views

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 ...
user3565923's user avatar
1 vote
2 answers
589 views

Limit SSH to a range of IP

I work with OpenBSD and I want to limit the port 22 for all user who have an IP between 192.168.42.40 - 192.168.42.60. But I don't know how to do this. I need to modify the packet filter ? (SSH is on ...
rmarquet21's user avatar
1 vote
1 answer
454 views

Why is it that TCP packets can be modified to block invalid packets, but not UDP packets

On a random day I was googling iptables rules to harden my desktop, and came across this post[1]. At some point the guide mentions blocking invalid TCP packets using tcp-modules with these rules; ...
atheros's user avatar
  • 256
0 votes
2 answers
160 views

Counting bytes on all connections traversing a Linux router

I have a Linux box which works as a router. How can I measure which connections send and receive how much data? For each hour, I would like something like: src_addr src_port dst_addr ...
fadedbee's user avatar
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1 vote
1 answer
648 views

ncat stops listening after 100 UDP packets

I'm continuously sending packets to a UDP server after 1 second. To listen for UDP packets: ncat -klup 1234 --sh-exec "cat > /proc/$$/fd/1" However, after printing 100 packets, nothing else ...
epistemophiliac's user avatar
1 vote
1 answer
814 views

View packet data of ping

Is there a flag or other utility (perhaps tcpdump?) that can be used to see the outgoing packets that are sent via the ping utility? For example: $ ping -c 5 google.com PING google.com (172.217.14.78)...
David542's user avatar
  • 339
0 votes
1 answer
2k views

Why specify packet size during ping test?

Does it make a difference to specify packet size during ping tests (RedHat)? Engineers in my company asked for ping checks with packet size of 2000 bytes (-s 2000). On certain systems, this fails, ...
Dmitry Osinovsky's user avatar
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1 answer
231 views

possible packet loss

I have a program running on my local machine that prints data to port 50000. In a terminal on my local machine I run nc to connect to and print the data on the port. However, when using nc in terminal ...
Austin's user avatar
  • 101
1 vote
2 answers
4k views

How to check if a packet reached an interface in a multi-interface context?

Consider the following topology: I am sending ICMP (ping) packets from host B to 10.0.1.1. They reach the target and the target answers with a reply. The connectivity works fine. When running, on ...
WoJ's user avatar
  • 1,555
3 votes
1 answer
3k views

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 ...
Zhaohui Yang's user avatar
1 vote
1 answer
519 views

How to avoid forwarding ports?

I am doing UDP socket programming in C. In order to listen to a port, I need to forward ports in my router. My question is how to avoid doing that and still being able to communicate over the internet,...
Fuel's user avatar
  • 33
2 votes
1 answer
16k views

How does MTR (run with TCP protocol) calculate the loss rate?

I thought TCP protocol itself will guarantee not to loose any bytes while connecting. About this viewpoint, please refer to https://stackoverflow.com/questions/23841896/will-tcp-connection-lose-...
Daniel Mo's user avatar
1 vote
2 answers
585 views

Maintain destination port of TCP packets after leaving through another local port

problem: I have an application sitting on a host (let's call it host1) that sends TLS-encrypted TCP packets to another host's port 5015 (let's call it host2). Due to network restrictions, the host1 ...
thanos's user avatar
  • 123
2 votes
2 answers
284 views

Holding a Packet

I am trying to alter a stream of packets by temporarily holding a specific packet. For example, if the packet are numbered 1,2,3,4,5, and so on, I want to temporarily store packet 2 so that I can ...
scriptbaby's user avatar
1 vote
1 answer
3k views

iptables: transparent tcp traffic proxy

problem: I have a TCP server and client that each listen on port 9000. I have the server and client deployed on two different hosts where traffic can only pass through port 80 between them. I want the ...
thanos's user avatar
  • 123
12 votes
2 answers
10k views

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 ...
Lapsio's user avatar
  • 1,323
6 votes
1 answer
17k views

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 ...
Hakan Baba's user avatar
0 votes
1 answer
79 views

Network monitoring across my lan

I would like to monitor the network usage of all my deivces connected to same LAN network from raspberry pi 3. Since Pi3 is not a switch , it is also connected to the same network. Is it possible to ...
praveen's user avatar
  • 21
0 votes
2 answers
154 views

How does FreeBSD handle installing 2 packages which share a common dependency?

I'm working on FreeBSD 11 and already using programs with tcpdump as a dependency, which has libpcap and libsmi as dependencies. I want to also install tshark, the console version of wireshark. I'll ...
Stilez's user avatar
  • 1,261
1 vote
0 answers
484 views

RX and TX counts on various intermediate interfaces between two VMs

I am trying to figure out how the network stats are being reported when I send packets from within a VM to another VM on a different host. My network environment looks like the image below: Basically,...
Rahul's user avatar
  • 481
5 votes
1 answer
12k views

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 ...
Armando Contestabile's user avatar
1 vote
0 answers
1k views

Why my Raspberry pi receive no packets using Ethernet?

I use a Raspberry pi 3b. The OS is Raspbian jessie. I don't understand why I can't connect with any RJ45 cable, and only wireless connection works. The cable rj45 is straight. The step I did to ...
GameDevF7's user avatar
0 votes
2 answers
2k views

Packet sniffing with TL-WN722N

I've recently started to follow a lecture about wireless network, and I bought an external wifi card called TL-WN722N from TP-LINK to use it for packet sniffing. I tried to use it in a Kali Linux ...
user avatar
-1 votes
1 answer
8k views

Sending UDP packets to a destination

On my Linux machine, I am receiving UDP packets from another machine. When I receive the UDP packets, I get the message "Listening on UDP port : 8999" This is triggered by the following command ...
Ashish Kurian's user avatar
15 votes
4 answers
13k views

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 ...
Rezaeimh7's user avatar
  • 253
2 votes
2 answers
7k views

What can cause a large TX vs. RX average bytes/packet discrepancy?

According to a computation I did on the data from ifconfig, my ethernet connection between my router and computer averages 1298 bytes/packet for TX (close to the MTU of 1500) and only 131 bytes/packet ...
Geremia's user avatar
  • 1,183
1 vote
1 answer
2k views

How to capture traffic from an entire website (including external servers) using tcpdump

I was wondering if its possible to capture all network traffic coming from a single website using tcpdump. I am interested in capturing the sizes of all incoming and outgoing packets from and to a ...
QPTR's user avatar
  • 133
3 votes
1 answer
3k views

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 ...
xnor's user avatar
  • 151
3 votes
1 answer
106 views

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 ...
user123456's user avatar
  • 5,048
1 vote
3 answers
1k views

How does MTR work in detail? Shouldn't packet loss be observed to increase linearly?

If so, how come do we see packet loss be distributed unevenly among hops? That is, if there is 5 percent loss in the first hop, the following hops, should start out with 95 percent of the packets ...
user avatar
1 vote
0 answers
102 views

How to open a changing file with wireshark?

Given a pcap file that is being created in the background, e.g tshark -w out.pcap > /dev/null & How can I open the changing file with wireshark wireshark -r out.pcap Does nont work
wqh29974.dsiay.com's user avatar
3 votes
1 answer
5k views

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-...
Chozabu's user avatar
  • 141
1 vote
1 answer
3k views

how to get list of sites/domains linked to in wireshark

I have been trying to figure out how many sites does firefox connect wth and for that have been using wireshark. What I have done is made a new profile and whenever I run firefox in the browser it is ...
shirish's user avatar
  • 12.4k
2 votes
1 answer
231 views

Cannot ping OUT of a Mac OS X server

I have just inherited a Mac OS X server that is using pf. The problem I am trying to solve is why I can't ping OUT of the server. I can ping to the machine no worries, but just get timeouts on pinging ...
user avatar
7 votes
1 answer
27k views

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 ...
Mihai Popescu's user avatar