tcpdump mailing list archives
Re: libpcap picks up sent packets on freebsd (plus link state query)
From: Guy Harris <guy () alum mit edu>
Date: Thu, 7 Jan 2016 02:51:17 -0800
On Jan 7, 2016, at 2:20 AM, mate csaba <matecs () niif hu> wrote:
i'm developing a router (rtros.nop.hu) which uses libpcap to capture and send packets to interfaces. the interface handler can be found here: http://sources.nop.hu/src/zzz/nat-pcapInt.c it's an interface<---->udp socket converter tool: when a packet captured, it'll be sent to the udp, when a packet received from the udp, it'll be sent to the interface. it works fine on linux for years. now i've noticed that on debian/sid/kfreebsd, when i send a packet to the interface, it's get captured. could you give me hints how to avoid it in a platform independent manner?
If you limit yourself to platforms on which libpcap has the pcap_setdirection() function, try calling pcap_setdirection(ifacePcap, PCAP_D_IN); before the printf("serving others\n"); call. (I'm a bit surprised that you're not seeing outgoing packets on Linux, though.)
and a bonus feature request (?): could you please provide an api for interface up/down states?
An API to query the interface state? Or a mechanism to get notified of interface state changes? The first could probably be done fairly straightforwardly (but you obviously will only be able to use it if you have a newer version of libpcap). The latter would involve more work, and might not be possible if the OS doesn't have a mechanism to deliver those events. (Linux and OS X can, I think - Wireshark uses mechanism on those OSes to be notified when interfaces appear and disappear - but it'd take a bit of work to find out what mechanisms, if any, exist on various *BSDs, Solaris, Windows, etc..) _______________________________________________ tcpdump-workers mailing list tcpdump-workers () lists tcpdump org https://lists.sandelman.ca/mailman/listinfo/tcpdump-workers
Current thread:
- libpcap picks up sent packets on freebsd (plus link state query) mate csaba (Jan 07)
- Re: libpcap picks up sent packets on freebsd (plus link state query) Guy Harris (Jan 07)
- Re: libpcap picks up sent packets on freebsd (plus link state query) mate csaba (Jan 07)
- Re: libpcap picks up sent packets on freebsd (plus link state query) mate csaba (Jan 18)
- Re: libpcap picks up sent packets on freebsd (plus link state query) mate csaba (Jan 07)
- Re: libpcap picks up sent packets on freebsd (plus link state query) Guy Harris (Jan 07)