[lime-dev] magic icmp

Pau pau.escrich at guifi.net
Wed May 15 19:35:19 UTC 2013

I don't think depending on libpcap (which is a known standard) is
something bad, but ok, for me the UDP approach is fine.

However, speaking about performance, take into account that the
magic-icmp code applies a libpcap filter which currently is "icmp6"
and it can be extended to something to filter only icmp6 requests and
comming from a link-local. Since the filter is applied directly to the
libpcap call, the kernel does not copy the non-filtered packets to the
user space.


On Wed, May 15, 2013 at 8:59 PM, Gioacchino Mazzurco <gio at eigenlab.org> wrote:
> On Wednesday 15 May 2013 20:30:59 Pau wrote:
>> I don't see the problem of depending in libpcap. I like to have
>> tcpdump-mini in my nodes and it also depends on it.
> yes but i think we doesn't want to depend on things unless are necessary
>> I like that with the icmp approach the packet can be send using normal
>> ping6 command.
> yes i liked it too
>> Anyway, magic-icmp is more than what we need and I will keep the
>> development until we don't use it in libremesh. So if you want to
>> implement it using UDP, for my is completelly fine!
> I think that using libpcap just for exchanging some packet is an overkill,
> maybe i am wrong but i think it can have a performance hit on routers
> because pcap works coping the packets from kernel space to user applying the
> filter you provide, i think this more CPU intensive than an udp socket moreover
> with udp socket we can use a specific multicast group that i think is a good
> thing ;)

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