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Date: Wed, 27 May 1998 20:00:06 +0900 (JST)
Message-Id: <199805271100.UAA21568@mail.hitachi-cable.co.jp>
From: Ito Kazumitsu <ito@htk.hitachi-cable.co.jp>
To: FreeBSD-users-jp@jp.freebsd.org
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Subject: [FreeBSD-users-jp 28761] Is IP_DF flag always set to 1?
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$BF|N)EE@~$N0KF#$H?=$7$^$9!#(B

FreeBSD $B$N%^%7%s$+$iAw=P$5$l$k%Q%1%C%H$N(B IP $B%X%C%@$N(B IP_DF $B$,(B
$B>o$K(B 1 $B$K$J$C$F$7$^$&$H$$$&8=>]$KG:$s$G$$$^$9!#(B

     -----+------
          | A
       FreeBSD 2.2.1-RELEASE (GATEWAY=YES)
          | B
     -----+------

$B%$%s%?!<%U%'%$%9(B A $B$KFO$/%Q%1%C%H$N(B IP_DF $B$,(B 0, B $B$+$i=P$?(B
$B%Q%1%C%H$N(B IP_DF $B$,(B 1 $B$G$"$k$3$H$,(B Sniffer $B$G3NG'$5$l$^$7$?!#(B

$B$^$?!"<RFb$NJL$NIt=p$N(B FreeBSD $BMxMQ<T$KLd$$9g$o$;$?$H$3$m!"(B

| tcpdump 'ip[6:2] & 0x4000 = 0x4000' $B$G8+$k$H;d$N(BFreeBSD2.2.2$B$b(B
| DF$B$,$D$-$^$/$j$G$9(B.

$B$H$$$&2sEz$,$"$j$^$7$?!#(B

$B$I$&$b(B FreeBSD $B$+$i=P$k$H>o$K(B IP_DF $B$,(B 1 $B$H$J$k$H$$$&8=>]$,(B
$B8+$i$l$k$N$G$9$,!"$3$l$O!"$=$&$$$&$b$N$J$N$G$7$g$&$+(B
(/usr/src/sys/netinet/* $B$rD/$a$F$b(B IP_DF $B%S%C%H$r(B 1 $B$K$9$k(B
$B$h$&$J2U=j$O8+$"$?$i$J$$$h$&$J5$$,$9$k$N$G$9$,(B)$B!#(B

$BDL>o$O(B IP_DF $B$,(B 1 $B$G$b:$$i$J$$$N$G$9$,!":G6a<!$N$h$&$J(B
$BLdBj$,H/3P$7!"$H$F$b:$$C$F$$$^$9!#(B

Ethernet $B$N(B MTU 1500 $B$.$j$.$j$N%Q%1%C%H$,!"1s3VCO$N(B
$B%k!<%?$N(B MTU 1492 (IEEE 802.3) $B$N%$%s%?!<%U%'%$%9$K(B
$B9T$/$H!"$=$3$G(B fragment $B$,$J$5$l$:$KGK4~$5$l$F$7$^$&!#(B

$BBP>INEK!$H$7$F$O!"(BMTU $B$r@hJ}$K9g$o$;$F>.$5$/$9$k$H(B
$B$$$&$3$H$G2?$H$+$J$j$=$&$G$9$,!"3d$j$-$l$J$$$b$N$r(B
$B46$8$^$9!#(B

********************
Ito Kazumitsu <ito@htk.hitachi-cable.co.jp>

