Links for 2014-05-23

  • BPF – the forgotten bytecode

    ‘In essence Tcpdump asks the kernel to execute a BPF program within the kernel context. This might sound risky, but actually isn’t. Before executing the BPF bytecode kernel ensures that it’s safe: * All the jumps are only forward, which guarantees that there aren’t any loops in the BPF program. Therefore it must terminate. * All instructions, especially memory reads are valid and within range. * The single BPF program has less than 4096 instructions. All this guarantees that the BPF programs executed within kernel context will run fast and will never infinitely loop. That means the BPF programs are not Turing complete, but in practice they are expressive enough for the job and deal with packet filtering very well.’ Good example of a carefully-designed DSL allowing safe “programs” to be written and executed in a privileged context without security risk, or risk of running out of control.

    (tags: coding dsl security via:oisin linux tcpdump bpf bsd kernel turing-complete configuration languages)

  • Handmade Kitchen Goods from Makers & Brothers – Cool Hunting

    lovely kitchen-gear design from local-boys-made-good Makers & Brothers

    (tags: makers-and-brothers design crafts kitchen nyc terrazo chopping-boards)

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