[tuetuopay]

From first hand experience, swapping the endianness is a non-issue in network processing performance-wise (it is headache-wise though). When processing packets in software, the cost is dominated by the following:

- memory bandwidth limits: for each packet, you do pkt NIC -> RAM, headers RAM -> cache, process, cache -> RAM, pkt RAM -> NIC. Oh and that's assuming you're only looking at headers for e.g. routing; performing DPI will have the whole packet do RAM -> cache.

- processing limits: route lookup, ACL evaluation, checksumming, etc

- branch predictor limits: if you have enough mixed traffic, the branch predictor will be basically useless. Even performing RPS will not save you if you have enough streams

So yeah, endianness is a non-issue processing-wise. So more so that one of the most expensive operations (checksumming) can be done on a LE CPU without swapping the byte order.