jm + dsl   3

It's official, ADSL works over wet string
So, there you go, ADSL over 2m of literal "wet string". Well done all for testing this. It shows the importance of handling faults that seem to just be "low speed".
adsl  faults  hacks  funny  networking  dsl  telecoms 
december 2017 by jm
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.
coding  dsl  security  via:oisin  linux  tcpdump  bpf  bsd  kernel  turing-complete  configuration  languages 
may 2014 by jm
The things make got right (and how to make it better)
jgc provides a good demonstration of how a general-purpose programming language tends to make a crappy DSL -- specifically Rakefiles
dsl  build  make  coding  jgc  languages  configuration  makefiles  rake  ruby  from delicious
january 2011 by jm

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