Questions tagged [tcp-ip]
The tcp-ip tag has no usage guidance.
43
questions
0
votes
0answers
24 views
Why do my Send-Q keep getting loaded but nothing come out of it?
I'm currently diagnosing a issue related to packet forwarding. I forward link layer packets to B network namespace and I found that B network namespace didn't reply to them, but I could curl and view ...
0
votes
1answer
27 views
Dropping RSTs vs using NOTRACK
I'm in process building my own firewall. One can say I'm building user space TCP/IP stack.
However, When Kernel receive packet that it can't identify, Kernel would send out RST + ACK (Not sure whether ...
1
vote
1answer
188 views
Interface with apipa (i..e. 169.254.x.x)
I have a ubuntu machine with two interfaces (eth0 and eth1). Eth0 interface has a dhcp address and eth1 has apipa (169.254.x.x) address. eth1 is not connected and eth0 is connected to a local network. ...
2
votes
0answers
32 views
How many times is the data packet copied before finally reaching the NIC?
On a typical linux machine, how many times would packets be copied from the application layer to all the way in its journey to the network card. I am assuming the protocol being used here is TCP/IP ...
0
votes
1answer
41 views
Alternative to modifying /etc/hosts for dns lookup
I am a networking newb - ping cannot locate certain dns names, so I put them in /etc/hosts like this:
10.128.0.22 kafka.marathn.meso
10.128.0.31 elasticsearch.marathn.meso
and then ping can find ...
4
votes
2answers
1k views
Why does telnet on a non existent port not directly reject, but time out?
telnet 8.8.8.8 8888
displays
Trying...
I was expecting, that this directly is refused.
Background: When we have a NGINX reverse proxy server, it would be great, that it detects directly when the ...
0
votes
0answers
36 views
TCP/IP quits after 48 hours
I have a problem with a (remote) server running SCO UNIX. It's been working for years, but was recently moved, and I changed its IP address & gateway address. Since then it works perfectly until ...
0
votes
1answer
358 views
using PPP without TCP/IP
I'm using a PPP to communicate with a device. So far what I have been doing is instantiating PPP on my machine (Fedora 29) and on the device (Yocto Linux). Then I open a TCP/UDP socket and communicate ...
1
vote
2answers
631 views
Send TCP packet to the same source [closed]
I want to design a system which reduce travel time of packet what is happening in reality is I send a SYN bit from client side, this bit travel through router then to server and server reply SYN+ACK ...
0
votes
2answers
222 views
Routing multiple Virtual IP (192.168.11.X) to connect with test server (192.168.10.246)
We are trying to setup a test bed for our server testing, to simulate multiple connection / msg handling, I am trying to connect to our test server from a virtual IP.
on the client machine (Debian) ...
1
vote
2answers
11k views
How to map an IP address to localhost
So I have an IP Address 5x.2x.2xx.1xx I want to map to localhost. In my hosts file I have:
cat /etc/hosts
127.0.1.1 test test
127.0.0.1 localhost
# The following lines are desirable for IPv6 capable ...
3
votes
0answers
234 views
TCP Stack tuning,(TIME_WAIT) - python process ignores sysctl setting?
I'm playing around with tuning various tcp settings for high number of outgoing client connections. I've put following in my /etc/sysctl.conf on Ubuntu 16.04.
net.ipv4.ip_local_port_range = 18000 ...
2
votes
1answer
2k views
UDP or TCP hole punching to connect two peers (each one behind a router)
I'm trying to connect directly (without 3rd party server) my computer to a friend's computer. We are both behind a ISP router, and would like (as a challenge!) to connect without modifying the router ...
1
vote
0answers
55 views
linux failed to assign local port
Our nginx reported a error below:
2017/10/19 10:47:40 [crit] 41689#0: *23414459 connect() to 127.0.0.1:1234 failed (99: Cannot assign requested address) while connecting to upstream, client: 10.0.0.1,...
0
votes
1answer
235 views
Unordered ACK answer
is there any body knows ; how a server answers to client what if they send first packet as non-syn or the server finish the connection and wait for a new connection instead of getting an ACK or push ...
0
votes
1answer
68 views
why doesn't port 80 show up via firewall-cmd command?
Doesn't port 80/http need to be explicitly opened like other ports (such as 443/https or 8080/server), or is it a special case?
on my machine (CentOS Linux release 7.3.1611)
firewall-cmd --list-...
2
votes
0answers
62 views
syncookies and tcp options
enabling syncookies is helping against some attacks
but the official docs still say syncookies seriously violate TCP protocol, do not allow
to use TCP extensions
Today I discover that once upon ...
1
vote
0answers
169 views
Connect beaglebone black running Debian Image 2015-11-12 to PC through Ethernet.
I have the Beaglebone powered through 5V and the ethernet in a open port on my PC. I have added the lines to /etc/network/interfaces
auto eth0
iface eth0 inet static
address 192.168.1.80
...
1
vote
0answers
40 views
IS there a means of identifying the application path for the process which attempts to access the internet on a linux distributution?
Is there a means (kernel mode API) under Linux (any distro) that can identify the application path of a process that makes a connect() call and is attempting to access the internet ? Vice versa in the ...
3
votes
0answers
108 views
How to emulate LAN adresses locally?
I have this situation: a piece of software got hardcoded IP address (let assume it is being 196.10.10.100:20000) to which it binds a socket and sends TCP and UDP traffic to 196.10.10.9:20000 (...
1
vote
1answer
70 views
intercept traffic generated by pktgen
I'm generating traffic on a Linux host with pktgen. I thought I could intercept it with tc and apply certain actions, but apparently pktgen bypasses it and writes directly in driver. Is there a way to ...
4
votes
2answers
2k views
TCP keep-alive parameters not being honoured
I have a server running on my Linux box, also on which the following commands were run:
$ cat /proc/sys/net/ipv4/tcp_keepalive_time
7200
$ cat /proc/sys/net/ipv4/tcp_keepalive_intvl
75
$ cat /proc/sys/...
4
votes
1answer
1k views
How do I set a static IP address for a disconnected interface?
I am setting up an Arch/Manjaro-based machine that only occasionally will be connected to network. I.e. most of the time its Ethernet card is disconnected.
I run into this curious problem - when I ...
20
votes
4answers
69k views
Simple shell script to send socket message
For testing purposes I need to create a shell script that connects with a remote IP>Port and sends a simple text TCPIP Socket message.
1
vote
0answers
725 views
change TCP_TIMEWAIT_LEN at runtime
Linux kernel defines a timeout to destroy TIME-WAIT state of a connection in include/net/tcp.h:
#define TCP_TIMEWAIT_LEN (60*HZ)
Is there a way to change this parameter at runtime, via sysctl or /...
0
votes
1answer
797 views
How authentication is done between two nodes in tcp/ip or udp client server socket
I have a client socket program and server socket program in C TCP/IP . I execute the server program first on a port say 5000 and then executes client program on the same port and then server respond ...
2
votes
1answer
2k views
ICMP - Destination unreachable (Port unreachable)
I have two Ethernet-wired connected devices. I gave to both of them address from same sub-network. As result I can see second device in arp-table of the first.
$ arp -a
? (128.247.77.90) at 10:60:4b:...
5
votes
1answer
4k views
How do I configure Docker containers to have unique IP addresses that are not the default ones?
How do I configure Docker containers to have unique IP addresses that are not the default ones?
The Docker containers will run Apache or some web service. These Docker containers will share one host ...
1
vote
0answers
1k views
Why my server cannot serve more than 400 concurrent connections
I have an Ubuntu 14.04 LTS, kernel 3.13 in a Intel Xeon + 8Gb box. It has apache 2.4.7 configured in mpm worker with up to 4000 workers. The max bandwidth allowed by the ISP is 100Mbps.
If I test ...
3
votes
2answers
33k views
ICMP : Port unreachable error even if port is open
I am testing my Debian Server with some Nmap port Scanning. My Debian is a Virtual Machine running on a bridged connection.
Classic port scanning using TCP SYN request works fine and detects port 80 ...
1
vote
0answers
95 views
TCP/IP routes when using multiple DHCP servers
I have connected a computer (running Debian Wheezy) to two different DHCP servers (routers) through a cable and through a wifi device. If I look at the routes with route, I get the following result
...
1
vote
3answers
415 views
Unable to figure out how to route a packet through a multi-homed nic
The environment is FreeBSD for the most part and looks like this:
HOST_A <-> ROUTER <-> LOKI <-> HOST_B
Minimally, I would like to be able to ping ROUTER from HOST_B.
ROUTER is ...
0
votes
1answer
2k views
How can I edit /proc/net/tcp?
I need to edit 1 line in /proc/net/tcp while the file is also used by the linux kernel for updating other lines of it by the kernel.
Background: Each line in /proc/net/tcp represents a TCP socket. ...
0
votes
1answer
621 views
ip_conntrack and FreeBSD
We can figure out number of connections in GNU\Linux with ip_conntrack module, And I can print current connections and maximum of connections with:
root@debian:/home/mohsen/test/shell# sysctl net....
0
votes
1answer
39 views
How does tcp communicate back to the application? [closed]
Are there standard sytem calls to send data to TCP? And back? How does TCP tell the application to send more or less?
10
votes
1answer
3k views
How to investigate a random reset on TCP client port connected via loopback interface to a server
I have a test suite which initializes a server on the localhost and then runs thousands of stress tests which include starting and stopping clients connecting to this local server on same machine. I ...
2
votes
2answers
3k views
“tcpdump” to capture the last packets
I am monitoring a certain port, because my application uses that port, it seems that the connection drops at random times, I want to see what are the last packets passing through before the connection ...
1
vote
3answers
186 views
Is it bad to select remember me option in the browsers of a compromised machine?
I was reading an article on how to sniff network packets. (of course for knowledge purposes only). I came across these particular lines.
For instance, say I was sniffing traffic on the network, ...
8
votes
1answer
17k views
Comunicate with remote Serial over TCP/IP as /dev/ttyX device
I've one serial device on 192.168.x.x:yyyy (where "x" and "y" are real number) and it works correctly. But I want to communicate with this as /dev/ttyX device.
I've tested socat command but not ...
1
vote
1answer
3k views
Does an in-kernel firewall sit between the network access layer and Internet layer?
This question is a follow-up to my previous question.
Logic for me to says that an in-kernel firewall sits between the network access layer and the Internet layer, because it needs to have access to ...
9
votes
3answers
2k views
Disabling PHY auto-negotiation during Linux boot process on Xilinx
I'm trying to install Linux on an FPGA board. The linux flavour is petalinux for Xilinx FPGA chips.
The current Xilinx SoC has a Cortex A9 processor and a programmable hardware logic i.e FPGA. I ...
5
votes
1answer
9k views
What does net.ipv4.tcp_app_win do?
I can't figure out why do these variables coexist in Linux. The information from man tcp says (Ubuntu 12.04):
For tcp_adv_win_scale:
tcp_adv_win_scale (integer; default: 2; since Linux 2.4)
...
0
votes
1answer
1k views
How do I safely perform the below changes to network parameters on Solaris 10?
I need to change and test some TCP/IP network parameters on a Oracle Solaris 10 as a possible workaround for a bug in 'Oracle Hyperion EPM 11.2.1.0' in the development environment.
I am not a Solaris/...
