Understanding Linux Networking APIs

Key points:

• The whole network stack code and configuration are all located in the kernel space.
• User space tools may have their own configuration files which they read and apply to the kernel space by syscall. E.g. NetworkManager daemon automcatilly runs after system starts and applies its configuration to the kernel side.
• There are no standards for configuring network; netlink is Linux specific only.
• Most user space applications don't configure networking and don't care about it. 
• For containers, the container engine/runtime starts a new process, configure the networking such as IP addresses, routing,  then "exec" the image which doesn't need to worry about the networking config at all.