On Jul 4, 2012, at 6:08 PM, Budnev Vladimir wrote:
> Good day to all.
>
> What is the correct way to distinguish udp packets that obtained by
> application and were send on 255.255.255.255 ip addr from those that were
> send to unicast ip?
>
> Seems it is impossible with read/recvfrom so we'v made that with libpcap. It
> coul be done with directly bpf api without pcap wrapper but i'm not sure
> about how big pcap overhead is.
>
> The questions is if we have about 1Gb incoming traffic and using pcap filter
> for specific port how big is impact of using pcap in such situation? Is it
> possbile to estimate? Target traffic is about 1Mbit and while testing CPU is
> about 1-2% but i'm not sure about all the conditions.
>
> recfrom recieves all the data without loss in such condition, is it possible
> that pcap because of its filtering nature(i dont know in details how bpf is
> realized deep in kernel:( ) will add big overhead while listening?
>
>
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If I'm understanding your question correctly you can lookup the ip(4) manual
page :
If the IP_RECVDSTADDR option is enabled on a SOCK_DGRAM socket, the
recvmsg call will return the destination IP address for a UDP datagram. The
msg_control field in the msghdr structure points to a buffer
that contains a cmsghdr structure followed by the IP address. The cmsghdr
fields have the following values:
You can use this in you application and get the destination address of the
packets be it unicast IP or the broadcast
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