[SOLVED] (Was: Re: [FreeBSD 7.0-BETA1] strange behavior in hostname resolving order)

Byung-Hee HWANG bh at izb.knu.ac.kr
Fri Nov 2 16:46:57 UTC 2007


Dear Mr. UMEMOTO,

On Sat, 2007-11-03 at 00:58 +0900, Hajimu UMEMOTO wrote:
> Hi,
> 
> >>>>> On Sat, 03 Nov 2007 00:05:07 +0900
> >>>>> Byung-Hee HWANG <bh at izb.knu.ac.kr> said:
> 
> bh> To Whom It May Concern: (Cc'ed bind-users at isc.org)
> 
> bh> Usually i prefer 6to4(stf(4)) to 6over4(gif(4)) because some 
> bh> tunnel providers like to limit bandwidth too musch. So until my 
> bh> upstream ISP give me native ipv6 addresses (it's take long time maybe), 
> bh> i'm going to use 6to4 instead of 6over4 continuous.
> 
> bh> Here is my shot using 6to4:
> 
> bh> bh at viola:~> uname -a
> bh> FreeBSD viola.izb.knu.ac.kr 7.0-BETA1 FreeBSD 7.0-BETA1 #0: 
> bh> Fri Nov  2 12:13:10 KST 2007     
> bh> root at viola.izb.knu.ac.kr:/usr/obj/usr/src/sys/GENERIC  i386
> 
> bh> bh at viola:~> ifconfig rl0 | grep 2002
> bh> inet6 2002:9be6:9d5d:2:20b:6aff:fe56:969f prefixlen 64 autoconf 
> 
> bh> bh at viola:~> ping6 -c 5 mx.jp.freebsd.org.
> bh> PING6(56=40+8+8 bytes) 
> bh> 2002:9be6:9d5d:2:20b:6aff:fe56:969f --> 2001:218:422:1::15
> bh> 16 bytes from 2001:218:422:1::15, icmp_seq=0 hlim=49 time=225.297 ms
> bh> 16 bytes from 2001:218:422:1::15, icmp_seq=1 hlim=49 time=224.591 ms
> bh> 16 bytes from 2001:218:422:1::15, icmp_seq=2 hlim=49 time=237.175 ms
> bh> 16 bytes from 2001:218:422:1::15, icmp_seq=3 hlim=49 time=230.540 ms
> bh> 16 bytes from 2001:218:422:1::15, icmp_seq=4 hlim=49 time=224.681 ms
> 
> bh> --- mx.jp.freebsd.org ping6 statistics ---
> bh> 5 packets transmitted, 5 packets received, 0.0% packet loss
> bh> round-trip min/avg/max/std-dev = 224.591/228.457/237.175/4.889 ms
> 
> bh> bh at viola:~> traceroute6 mx.jp.freebsd.org.
> bh> traceroute6 to mx.jp.freebsd.org (2001:218:422:1::15) from 
> bh> 2002:9be6:9d5d:2:20b:6aff:fe56:969f, 64 hops max, 12 byte packets
> bh> 1  2002:9be6:9d5d:2:250:4dff:fe00:5df3  1.541 ms  0.949 ms  1.154 ms
> bh> [......]
> bh> 23  v6.imgsrc.co.jp  264.635 ms  226.812 ms  232.207 ms
> bh> 24  castle.jp.FreeBSD.org  427.683 ms  219.659 ms  222.862 ms
> bh> bh at viola:~> 
> 
> bh> And from now on, i would give you one question. Why is 7.0-BETA1 
> bh> different from another -RELEASE in hostname resolving order? AFAIK, at 
> bh> least on 6.2-RELEASE, the order is first IPv6 and then IPv4. However, 
> bh> 7.0-BETA1 try to lookup in first IPv4 than IPv6. Here is the evidence:
> 
> bh>         bh at setaria:~> uname -srm
> bh>         FreeBSD 6.2-RELEASE-p8 i386
> bh>         bh at setaria:~> telnet mx.jp.freebsd.org 25
> bh>         Trying 2001:218:422:1::15...
> bh>         Connected to mx.jp.freebsd.org.
> bh>         Escape character is '^]'.
> bh>         [......]
> bh>         bh at setaria:~> ssh -v mx.jp.freebsd.org.
> bh>         debug1: Connecting to mx.jp.freebsd.org. [2001:218:422:1::15]
> bh>         ^C
> bh>         
> bh> And
> 
> bh>         bh at viola:~> uname -srm
> bh>         FreeBSD 7.0-BETA1 i386
> bh>         bh at viola:~> telnet mx.jp.freebsd.org 25
> bh>         Trying 210.226.20.15...
> bh>         Connected to mx.jp.freebsd.org.
> bh>         Escape character is '^]'.
> bh>         [......]
> bh>         bh at viola:~> ssh -v mx.jp.freebsd.org.
> bh>         debug1: Connecting to mx.jp.freebsd.org. [210.226.20.15]
> bh>         ^C
> 
> bh> What happended? Is there anyone to dislike IPv6 in src committers?
> bh> Please let me know the correct answer to this puzzle ;;
> 
> The Default Address Selection is turned on by default after
> 6.2-RELEASE was out.  According to RFC 3484, the default policy is as
> follows:
> 
> Prefix                          Prec Label
> ::1/128                           50     0
> ::/0                              40     1
> 2002::/16                         30     2
> ::/96                             20     3
> ::ffff:0.0.0.0/96                 10     4
> 
> It means that communicating with native IP address is preferred over
> 6to4 address when source address and destination adddress are not 6to4
> address.
> 
> If you want not to treat 6to4 address as special, you can omit the
> line of 2002::/16 by putting the following lines into your
> /etc/ip6addrctl.conf:
> 
> ::1/128				  50	 0
> ::/0				  40	 1
> ::/96				  20	 3
> ::ffff:0.0.0.0/96		  10	 4
> 
> Then, run `/etc/rc.d/ip6addrctl restart'.
> 
> Please refer the ip6addrctl(8) manpage and RFC 3484 for detail.

Now i can understand the puzzle, thanks for the guidance.
Your answer has been useful and is greatly appreciated.

Byung-Hee

-- 
"He's a responsible man in his own way."
		-- Michael Corleone, "Chapter 25", page 363



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