On 30/12/2015 12:22 PM, Juan Herrera wrote:
Hello BSD folks,
I am developing a networking application in C and I have a question
regarding BPF (Berkeley Packet Filters),
I will give you an idea of the app first, I need to send a packet from
machine A to machine B (any kind of packet) so for this I wrote a packet
generator application which will send a packet to machine B, but before
sending the packet I need to append some metadata values at the end of the
packet, already done, so in machine B I have a raw socket listener app
ready to receive incoming packets from machine A, however I want to
implement filtering with BPF on machine B, but as my metadata was appended
at the end of the packet (have to be at the end), I need to read the packet
length with(using) Berkeley Packet Filter to match a specific field to
filter one of the bytes at the end of my packet (metadata appended), in
other words I need to know the incoming packet length to filtered against
one of the metadatas fields and be able to drop the packet before reaching
user space applications(drop it in kernel space).
So my question is, Can I use BPF to read the packet length to do what I
want?
you mean can you use a bpf filter to act upon a trailer?
yes you can
look at the man page for BPF_LD and BPF_LEN
Thank you in advance!
Happy Holidays!
_______________________________________________
freebsd-net@freebsd.org mailing list
https://lists.freebsd.org/mailman/listinfo/freebsd-net
To unsubscribe, send any mail to "freebsd-net-unsubscr...@freebsd.org"
_______________________________________________
freebsd-net@freebsd.org mailing list
https://lists.freebsd.org/mailman/listinfo/freebsd-net
To unsubscribe, send any mail to "freebsd-net-unsubscr...@freebsd.org"
