udp suggestions about erldns

[aeden]

Thanks for the suggestions.

Given {active, once} mode, the larger buffer is essentially unnecessary since there will only be one packet in the buffer at any given time, correct? The typical DNS packet size is 512 bytes, unless EDNS specifies a larger size. Even in that case the typical packet size will still be less than the default 8k size used in Erlang.

So in the current setup the default buffer size is fine.

Now, let's consider if I switched to {active, 100}. In this case the buffer size would need to be larger. My understanding of {active, N}, based on http://www.erlang.org/doc/man/inet.html#setopts-2 , I would need to also listen for the {udp_passive, Socket} message and set {active, N} again. I'm not sure how much of a gain we'd get by letting the socket buffer, but I may try some testing.

Finally, regarding inet_udp:send versus gen_udp:send, are there any drawbacks?

[SergejJurecko]

About buffers you are very wrong. This is kernel space reserved for
incomming packets. Nothing to do with active setting.

Once it is full (because they were not processed fast enough) every arrived
udp packet is dropped. I had this problem on every project I used udp in
erlang. It was always filling up.

The difference in inet_udp is that IPs must be in tuple form. That timer is
so that it tries to resolve address in list form. But if it is tuple it
just sets timer, noop then cancel. Unfortunate design.
On Jan 21, 2016 23:31, "Anthony Eden" [email protected] wrote:

Thanks for the suggestions.

Given {active, once} mode, the larger buffer is essentially unnecessary
since there will only be one packet in the buffer at any given time,
correct? The typical DNS packet size is 512 bytes, unless EDNS specifies a
larger size. Even in that case the typical packet size will still be less
than the default 8k size used in Erlang.

So in the current setup the default buffer size is fine.

Now, let's consider if I switched to {active, 100}. In this case the
buffer size would need to be larger. My understanding of {active, N},
based on http://www.erlang.org/doc/man/inet.html#setopts-2 , I would need
to also listen for the {udp_passive, Socket} message and set {active, N}
again. I'm not sure how much of a gain we'd get by letting the socket
buffer, but I may try some testing.

Finally, regarding inet_udp:send versus gen_udp:send, are there any
drawbacks?

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#37 (comment).

[aeden]

Implemented two of the three suggested changes with #61