Can you point me to an example of a timer in the kernel that is not settable/tunable that should be? My experience in looking at such things suggests that most

Can you point me to an example of a timer in the kernel that is not settable/tunable that should be? My experience in looking at such things suggests that most of the #defined bits are because RFCs define the protocol that way. As for network stack per application: you're more than welcome to so so a myriad of ways - linux provides many different ways to pull raw IP, or raw ethernet into userspace (e.g. xdp, tun/tap devices, dpdk, and so on). It's not like you're being forced to use the kernel stack from lack of supported alternatives.