On Fri, 4 Aug 2006, Benjamin Lutz wrote:
Hello, I've noticed that FreeBSD does not by default comply to RFC 919, Chapter 7 (http://tools.ietf.org/html/rfc919). Specifically, it does not handle IP packets with a destination address of 255.255.255.255 properly. 255.255.255.255 is a "limited broadcast address" (the term is not mentioned in the RFC, but seems to be in use everywhere else). An IP packet send to that address should be broadcast to the whole IP subnet of the broadcasting device. However, in FreeBSD (4.11, 5.5, 6.1) this does not work, as is evident by this tcpdump output: 17:00:59.125132 00:12:17:5a:b3:b6 > 00:40:63:d9:a9:28, ethertype IPv4 (0x0800), length 98: 10.0.0.1 > 255.255.255.255: ICMP echo request, id 33319, seq 0, length 64 The destination MAC address is that of my gateway, but it should be ff:ff:ff:ff:ff:ff. You can reproduce this by running "tcpdump -en ip proto 1" and "ping 255.255.255.255". I found a discussion from 2003 about this, but it seems to have trailed off without coming to a conclusion: http://lists.freebsd.org/pipermail/freebsd-net/2003-July/000921.html I've noticed that the ip(7) manpage lists a SO_ONESBCAST option. The intention seems to be to enable packets to 255.255.255.255. However a test with a small program showed that this option seems to have no effect, outgoing packets still carried the gateway's MAC address as destination. Btw, Linux and NetBSD both handle packets to 255.255.255.255 as broadcasts. Now, is this behaviour intentional? Is there a way to turn on RFC 919 compliance? If not, would someone be willing to add this to the kernel? Should I submit a PR?
Does this feature really necessary? For waht purpose? I believe this feature is more harmful than useful.
Regards, Janos Mohacsi Network Engineer, Research Associate, Head of Network Planning NIIF/HUNGARNET, HUNGARY Key 00F9AF98: 8645 1312 D249 471B DBAE 21A2 9F52 0D1F 00F9 AF98
Cheers Benjamin _______________________________________________ freebsd-hackers@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/freebsd-hackers To unsubscribe, send any mail to "[EMAIL PROTECTED]"
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