[網路科普] Linux cooked-mode capture (SLL)

之前用GoPacket去抓device name 為 "any" device interface (Pseudo-device that captures on all interfaces)，"any"可以透過 tcpdump -D 查看到:

"any"這個device interface可以抓到經過所有interfaces的封包，部分程式碼如下:

[Golang] 用 Golang 使用 Raw Socket v.s. libpcap 兩者優劣比較

前陣子花了一些時間在找一種方式，可以透過寫程式的方式抓取進出於任何device interfaces on Linux主機上的封包，目前主要是有這兩大作法: Raw Socket v.s. libpcap

常用Linux Commands筆記

 Use rsync on my Windows 10 D:\SourceCode to sync folder from Linux's ~/SourceCode

rsync -r liudanny@<your IP address>:/home/liudanny/SourceCode /cygdrive/d/

List all users with their UID

awk -F: '{printf "%s:%s\n",$1,$3}' /etc/passwd

kubectl command completion in ~/.bashrc

# enable programmable completion features (you don't need to enable

# this, if it's already enabled in /etc/bash.bashrc and /etc/profile

# sources /etc/bash.bashrc).

if ! shopt -oq posix; then

if [ -f /usr/share/bash-completion/bash_completion ]; then

. /usr/share/bash-completion/bash_completion

elif [ -f /etc/bash_completion ]; then

. /etc/bash_completion

fi

fi

source <(kubectl completion bash)

[Shared Library] How to check the used shared libraries in your program

This post is only to show the command about checking the used shared libraries in your program.

[Linux] Why does Linux require moving IP from eth interface to bridge interface?

This could be a common problem if you have KVM ( or other hypervisor in Linux ) on your physical server and want to use bridge mode with your VMs. At the same time, you also want to let your physical server has the network that can be accessed from other hosts at the same network subnet. At this moment, when a network interface (e.g., eth0) is added to a Linux bridge (e.g., br0), the IP address must be removed from eth0 and added to br0 for the networking to function properly.

I find some answers as follows:
http://unix.stackexchange.com/questions/86056/why-does-linux-require-moving-ip-from-eth-interface-to-bridge-interface
http://unix.stackexchange.com/questions/52674/why-doesnt-eth0-get-an-ip-address-when-set-up-in-a-bridge

==>
The NIC represents the uplink cable. A cable is layer 1, not layer 3. Now the Bridge works as the device that is being addressed for network traffic (incoming) on the server - either on layer 2 (Ethernet/MAC) and/or layer 3 (IP). So the device that responds to ARP-requests is the bridge - which is good, since it needs to distribute the traffic to the other interfaces on that bridge. If the responding device were the NIC, traffic would not be passed further on to the bridge.

==>
Normally it does not make sense to put any L3 protocol address on port interfaces - because incoming packets are diverted to the bridge interface before the L3 protocol is examined. This means the L3 protocol running on the port interface will never see any incoming packets.

[Linux] “No such file or directory” on files that exist?

First, this kind of problem is almost related with dynamic loader. You can check out what it is:
To understand Linux Dynamic Loader
http://www.cs.virginia.edu/~dww4s/articles/ld_linux.html

After verifying it with several ways:
# file "your binary"
# readelf -l  "your binary"
# strings "your binary" | grep ld-

Then you can find out which dynamic loader your binary uses.
For my case, I just create a symbolic link to my loader, and then it works.

liudanny@Debian7 x64_lsb $ ll /lib64/
total 8
drwxr-xr-x  2 root root 4096 Aug  2 20:49 .
drwxr-xr-x 24 root root 4096 Jun 20 18:14 ..
lrwxrwxrwx  1 root root   32 Feb 22 06:41 ld-linux-x86-64.so.2 -> /lib/x86_64-linux-gnu/ld-2.13.so
lrwxrwxrwx  1 root root   20 Aug  2 20:49 ld-lsb-x86-64.so.3 -> ld-linux-x86-64.so.2

I also find some other issue about running a 32-bit binary on a 64-bit system. Here is a good answer in the following link:
Quote:
"But the program is a 32-bit program (as the file output indicates), looking for the 32-bit loader /lib/ld-linux.so.2, and you've presumably only installed the 64-bit loader /lib64/ld-linux-x86-64.so.2 in the chroot."
http://unix.stackexchange.com/questions/13391/getting-not-found-message-when-running-a-32-bit-binary-on-a-64-bit-system



To install ia32-libs on debian wheezy amd64:

dpkg --add-architecture i386 
apt-get update
apt-get install libc6:i386

or:

sudo dpkg --add-architecture i386
sudo apt-get update
sudo aptitude install ia32-libs

[Linux Command] Redirect stderr to stdout and output to terminal and log into file at the same time

If you want to redirect stderr to stdout, append this at your command: 2>&1 , and also for outputting to terminal and logging into file you should use tee.
Both together would look like this:
$ yourcommand 2>&1 | tee yourlogfile.log