In user space, I encapsulated a L3 packet using sock_raw (including IP header) and send to kernel space using sock_sendmsg() using msghdr structure I cannot understand clearly the roles of msg_name. I already specified the source IP and dest IP in L3 header. Why do I need msg_name? Answer The msg_name and msg…
Tag: linux
epoll: must I use multi-threading
I’ve got a basic knowledge from here about epoll. I know that epoll can monitor multiple FDs and handle them. My question is: can a heavy event block the server so I must use multithreading? For example, the epoll of a server is monitoring 2 sockets A and B. Now A starts to send lot of messages to the s…
Why would this image threshold work in windows but not mono / linux?
I have a relatively simple threshold function that’s using unsafe code. This works a treat in Windows, however, in Mono on linux, no thresholding takes place. It’s difficult to debug as it’s on Linux only, I’ve checked the bitsPerPixel is correct along with the height h, width w and st…
Linux layer on macOS [closed]
Closed. This question does not meet Stack Overflow guidelines. It is not currently accepting answers. This question does not appear to be about a specific programming problem, a software algorithm, or software tools primarily used by programmers. If you believe the question would be on-topic on another Stack …
How to find a postion of the lowest value in the file?
How to output position of a line with the lowest value inside? I have a file with data like below: I need to find a lowest value from the last column and return its position Answer You can use this command in order to get only the line number where the value is shown(if the value appears more than one
ROS-Indigo Collada DOM installation dependency on libpcrecpp package cannot detect installed libpcrecpp package
I am trying to build ROS (Robot Operating System) Indigo on Debian 8. I’m running Debian 8 on Oracle VirtualBox (the 64-bit PC netinst ISO, found at https://www.debian.org/distrib/). I am following this set of instructions: http://wiki.ros.org/indigo/Installation/Debian Performing each instruction step-…
Why multiprocessing.Pool and multiprocessing.Process perform so differently in Linux
I ran some test code as below to check the performance of using Pool and Process in Linux. I’m using Python 2.7. The source code of multiprocessing.Pool seems showing it’s using multiprocessing.Process. However, multiprocessing.Pool cost much time and mem than equal # of multiprocessing.Process, a…
Bash parse output in route command
I am writing a bash script to register the remote hosts in a wireless network. I am getting the remote IPs, but I need help to parse the output. Here’s my output: I need to get these IPs and insert into a command like … <remote_ip_1> … How can it be done? I couldn’t find this cas…
How can we check if our mongodb is running on EC2 linux server?
I have installed and started the MongoDB on EC2 Linux instance. How can I verify whether it is running or not? 1 way I got to know how to verify whether it is started or not is: By checking the contents of the file at /var/log/mongodb/mongod.log for a line reading: [initandlisten] waiting for connections on p…
Receiving socket information from netfilter NF_INET_PRE_ROUTING hook function in linux kernel
I wrote a netfilter hook function for incoming packets in linux kernel. Is there a way to get the receiving socket information from the hook function. The code is Lets assume I have a udp socket open at port 15000 and a udp packet arrives at port 15000. In the above written hook function how can I access the …