Date: Fri, 25 Jun 2004 15:01:53 +0300 From: Ruslan Ermilov <ru@freebsd.org> To: kamal kc <rosey_kc@yahoo.com> Cc: freebsd-net@freebsd.org Subject: Re: newbie: ethernet, ip header proble Message-ID: <20040625120153.GA37003@ip.net.ua> In-Reply-To: <20040625104911.69479.qmail@web13004.mail.yahoo.com> References: <20040625104911.69479.qmail@web13004.mail.yahoo.com>
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On Fri, Jun 25, 2004 at 03:49:11AM -0700, kamal kc wrote:
> Hi i am new to this mailing list.
> =20
> I have written a program to capture packets using pcap library routines. =
I have a FreeBSD 5.1. The problem I faced was I successfully captured packe=
ts and parsed to ethernet header and ip header.
> =20
> i present a section of code how i did it.
> =20
> --
> char *ptr;
> ptr=3Dpcap_next(.....);
> =20
> struct ether_header *eth;
> struct ip *ip;
> =20
> eth=3D(struct ether_header *)ptr; // datalink type DLT_EN10MB
> ptr+=3D14; // the size of the ether_header being 14 bytes;=20
> =20
> ip=3D(struct ip *)ptr;
> =20
> printf("\n %s %s", ether_ntoa(eth->ether_dhost), ether_ntoa(eth->ether_sh=
ost));
> printf("\n %s %s", inet_ntoa(ip->ip_src), inet_ntoa(ip->ip_dst));
> =20
> ----------------
> =20
> Now the problem is that the ethernet destination and sender host is print=
ed the same.
> it is equal to that of the sender MAC address(linux) when ICMP packets (b=
y ping utility)
> is sent to the host(FreeBSD) running the program.
> =20
> Also that the ip adresses printed is the same as the sender ip address(ie=
linux).
> =20
> The program is run on host with FreeBSD.
> =20
> The ip address of the computers are:=20
> 192.168.1.10 has Linux
> 192.168.1.11 has FreeBSD
> =20
> I couldn't think of a solution as i guess the coding was alright.
> =20
> Anybody could help
> =20
Sure, carefully read the BUGS sections of both ether_ntoa(3) and inet_ntoa(=
3)
manpages.
Cheers,
--=20
Ruslan Ermilov
ru@FreeBSD.org
FreeBSD committer
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