Multicast source address in recvfrom()
dlt at mebtel.net
Sun Feb 1 13:49:03 PST 2009
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 22.214.171.124. 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?
dlt at mebtel.net dlt666 at yahoo.com dtatters at gmail.com
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