Hi all!
I cannot find kmod-ipv6 package in make menuconfig, do you know where I can find it? I want to deselect it.
According to researches, he should be there : Kernel modules ---> Network Support ---> kmod-ipv6
But nothing... I try many things without success.
Do you have ideas?
Thanks! 
press "/" without quotes to search while in make menuconfig
Thanks, seems not available!
There is no selectable kmod-ipv6 since September 2015.
https://git.openwrt.org/?p=openwrt/openwrt.git;a=commitdiff;h=0c8f0186d58468024db96a5ab0ca36a4d400d408
It is built-in and hidden. But I am not sure if it is still possible to somehow fully disable it.
From make menuconfig, I use "Global build settings" -> "Enable IPv6 support in packages" myself. According to the built-in help, this enables / disables the IPv6 support in kernel and packages.
In make kernel_menuconfig there's also "Networking support" -> "Networking options" -> "The IPv6 protocol".
My current understanding is that the first option configures IPv6 support as a "toggle once, configure everywhere" -option; it both enables IPv6 support in the kernel (probably as a loadable module) and causes other package configuration menus to make IPv6-related configs/options available.
The latter option is what actually configures the IPv6 support in the kernel, and can also either cause built-in support or loadable module support. Since the kernel-related configuration files are under source control, I can understand why the IPv6 option is found from the "normal" menuconfig instead: it allows toggling IPv6 on and off without causing changes to files under source control.
Thanks @hnyman and @Antek, do you know the size of the kmod-ipv6 package? It's to build LEDE firmware image with ROOter for 4 MB devices : LEDE Image Builder + ROOter packages?