Date: Sun, 21 Apr 2002 17:22:04 +0200 From: "Richie B." <richie@NO-SPAM-HERE.com> To: freebsd-net@freebsd.org Subject: Path MTU Discovery and missing DF bit Message-ID: <3CC2D91C.2010308@NO-SPAM-HERE.com>
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This is a multi-part message in MIME format. --------------090407090603000004000204 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit When using Path MTU Discovery, according to RFC 1191, all TCP datagrams must have the Don't Fragment (DF) bit set. It seems that FreeBSD does not obey this rule. On "SYN ACK" packets, the DF bit is not set. It is set on all other packets though (including SYN packets). See attached dumps (use ethereal to view them). The versions of the systems are: $ uname -a SunOS mort 5.9 s81_57 sun4u sparc SUNW,Sun-Blade-100 $ uname -a FreeBSD trantor.xs4all.nl 5.0-CURRENT FreeBSD 5.0-CURRENT #6: Mon Apr 15 20:16:39 MET DST 2002 paulz@trantor.xs4all.nl:/usr/obj/usr/source/src/sys/trantor i386 Can anyone explain this behaviour? Thanks to paulz for providing the dumps. Please respond to me directly (as well), since I am not a member of this list. Richie -- Yes that *is* my E-mail address --------------090407090603000004000204 Content-Type: application/gzip; name="snooplog-solaris-to-to-bsd.gz" Content-Transfer-Encoding: base64 Content-Disposition: inline; filename="snooplog-solaris-to-to-bsd.gz" H4sICG3QwjwAA3Nub29wbG9nLXNvbGFyaXMtdG8tdG8tYnNkACvOy88vYAADJiBmAWI7KI4A CdocupDDwKuszHBhO9/K0wzMu3jv+XEwuDIwGJhdcWBwYPs09cCKE1xAzNTPzMD76XjZDpCu AqaDL7a7A41kYd3CyMjCBDbfBoqRzFVZDzERYjrYXJ0d6xiA5m7YDzITZDYDbz/zvzqnMKDZ OxOE/v/3DYSYywADZlAcgGTuVQz3aphdBbt3Dpp7dwLNDg8QOPhisSrUvAAozkCYp/sKw51O O9aDzCtYgebOcJCZAZL//0cA3RRcmqfgWFCkYGSoYGhmZWJqZWCoYGRgYMTLhd3dekZY3H0N 7O7ZWNxdBHY3F+5wMLuIxbzrYPNmYTVPEGgeJ9Q8LPFlfgwjHDR2bACHw0G0cCgCmrkrQOD/ /5RPDEgAAOoG8WVwAgAA --------------090407090603000004000204 Content-Type: application/gzip; name="tcpdump-log-bsd-to-solaris.gz" Content-Transfer-Encoding: base64 Content-Disposition: inline; filename="tcpdump-log-bsd-to-solaris.gz" H4sICPzOwjwAA3RjcGR1bXAtbG9nLWJzZC10by1zb2xhcmlzALtyeNNCJgYWBhhIAGJGIP52 7pDN2q18DF5ANggzMO/ivefHcGE738rTHAyuAgw2U144MDiwTUk9sOIEExBznVzNwOumq1EK UryA6f//s6YMDEwsrFsYmZkZGRk5uBg/G6kyQE3evB3JZLCZEPOBJjMw2GhqOzDYsLEYg0wF mc7Ae3L1W6nsFUDTyxYIHQjQdQe6EWRicWs4yFSoLWCTPwNNdgIa6oTNzSZTXoLdnIPm5jKg 6SsbBJokpjtDTQaaCjIdZOLy3XwMMUDDYrC51U9TB+xWBTS3rgSZ2iBxIMBbC9WtwaV5Co4F RQpGhgqGZlbGFlYmZgpGBgZGXLwgux7vRnI9ul0mmrpguyzR7DoMtkvwQEDEB1S7QCby7sEb Hq/A4ZGNJTyOAMODe7opZngY7cNr4muwiVlYTRQEhrA6pokiB/D6Wg/saws0Xx8BmlreIAD0 9XtUXwMAJdHM4NICAAA= --------------090407090603000004000204-- To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
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