[erlang-questions] Socket option FREEBIND

[Michael L Martin]

Raw socket options looks like it should be the answer, but I'm not 
getting good results:

iex(worker@REDACTED)28> {:ok, s} = :gen_tcp.connect('localhost', 80, 
[{:raw, 6, 15, <<1>>}, {:ip, {10, 138, 69, 63}}])

{:ok, #Port<0.12110>}

iex(worker@REDACTED)29> :inet.getopts(s, [{:raw, 6, 15, 32}])

{:ok, []}    <== option not set?

iex(worker@REDACTED)29> {:ok, s} = :gen_tcp.connect('localhost', 80, 
[{:raw, 6, 15, <<1>>}, {:ip, {10, 138, 69, 64}}])

** (MatchError) no match of right hand side value: {:error, :eaddrnotavail}


It appears that the IP_FREEBIND option is simply not set. If I use 
IP_TRANSPARENT instead:

iex(worker@REDACTED)35> {:ok, s} = :gen_tcp.connect('localhost', 80, 
[{:raw, 6, 19, <<1>>}, {:ip, {10, 138, 69, 63}}])

{:ok, #Port<0.12113>}

iex(worker@REDACTED)34> :inet.getopts(s, [{:raw, 6, 19, 32}])

{:ok, [{:raw, 6, 19, <<0, 0, 0, 0>>}]}


In this case, the raw option 19 (IP_TRANSPARENT) is set, but to false 
rather than true. I believe this is because the beam file needs root or 
CAP_NET_ADMIN.

Any thoughts?




On 2017-10-16 01:18 PM, Guilherme Andrade wrote:
> I believe you can use raw socket options[1] for that, but it won't be 
> portable.
>
> [1]: http://erlang.org/doc/man/inet.html#setopts-2 - {raw, Protocol, 
> OptionNum, ValueBin}
>
> On 16 October 2017 at 15:09, Michael L Martin <mmartin4242@REDACTED 
> <mailto:mmartin4242@REDACTED>> wrote:
>
>     Hi all,
>
>     Is there a way to specify the FREEBIND option when opening a
>     socket? I don't see any reference to it in the documentation.
>
>
>     Thanks,
>
>     _______________________________________________
>     erlang-questions mailing list
>     erlang-questions@REDACTED <mailto:erlang-questions@REDACTED>
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>
>
>
>
> -- 
> Guilherme

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