Date: Mon, 2 Feb 2009 18:28:48 +0000 (GMT) From: Robert Watson <rwatson@FreeBSD.org> To: Derek Tattersall <dlt@mebtel.net> Cc: freebsd-net@freebsd.org Subject: Re: Multicast source address in recvfrom() Message-ID: <alpine.BSF.2.00.0902021827470.77103@fledge.watson.org> In-Reply-To: <20090201183057.GA47405@oriental.arm.org> References: <20090201183057.GA47405@oriental.arm.org>
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On Sun, 1 Feb 2009, Derek Tattersall wrote: > In order to become familiar with multicast implementation using FreeBSD, I > found via Google a pair of test programs which multicast sent a simple text > message and received the text message. I added some code to report the > source address, because none of the references that I looked at specified > the source IP address in the frame. > > I ran the sender on A -current system, AMD64 vintage last week. The > receiver was on a -current system I386 vintage last week. TCPDUMP shows the > source IP address in the frame as (correctly) 192.168.0.15. The receiver > reports the source IP address as 200.231.191.191. I have also run the same > test with an OpenBSD 4.4 Release I386 system as the receiver. The openBSD > system reports the sender as 192.168.0.15. A Fedora 10 system reported the > source IP address as 0.0.0.0. > > Googling the RFCs and other information and referring to Comer's and > Stevens' books on TCPIP I can't determine what should be reported. Does > anybody have clue for me? Hi Derek: It might depend on how you're querying the source address. Could you post a code excerpt? Robert N M Watson Computer Laboratory University of Cambridge
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