  When IP-packet processing is unconditionally carried out on behalf of an
operating system kernel thread, processing systems can experience overload in
high incoming traffic scenarios. This is especially worrying for embedded
real-time devices controlling their physical environment in industrial IoT
scenarios and automotive systems. We propose an embedded real-time aware IP
stack adaption with an early demultiplexing scheme for incoming packets and
subsequent per-flow aperiodic scheduling. By instrumenting existing embedded IP
stacks, rigid prioritization with minimal latency is deployed without the need
of further task resources. Simple mitigation techniques can be applied to
individual flows, causing hardly measurable overhead while at the same time
protecting the system from overload conditions. Our IP stack adaption is able
to reduce the low-priority packet processing time by over 86% compared to an
unmodified stack. The network subsystem can thereby remain active at a 7x
higher general traffic load before disabling the receive IRQ as a last resort
to assure deadlines.
