Subject: strange loopback / route issue
From: Konrad Korzeniowski <konrad@pandur.net>
Date: Wed, 26 Nov 2008 22:18:57 +0100

Hi,

I'm lost...

HOST
--------------------------------------------------------------------

cat /proc/virtnet/40003/info
ID:     40003
Info:   f7d4c240
Bcast:  255.255.255.255
Lback:  127.156.67.1
0:      [10.10.43.31-0.0.0.0/0.0.0.0:0010]

route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use
Iface
10.10.10.0      0.0.0.0         255.255.255.0   U     0      0        0 eth1
10.10.43.0      0.0.0.0         255.255.255.0   U     0      0        0 eth0
0.0.0.0         10.10.43.1      0.0.0.0         UG    0      0        0 eth0

ifconfig
eth0      Link encap:Ethernet  HWaddr 00:30:05:CF:75:4B
          inet addr:10.10.43.31  Bcast:10.10.43.255  Mask:255.255.255.0
          inet6 addr: fe80::230:5ff:fecf:754b/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:1243495 errors:0 dropped:0 overruns:0 frame:0
          TX packets:778041 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:1196385313 (1.1 GiB)  TX bytes:112573993 (107.3 MiB)
          Memory:d0400000-d0420000

eth1      Link encap:Ethernet  HWaddr 00:1B:21:1A:9D:33
          inet addr:10.10.10.90  Bcast:10.10.10.255  Mask:255.255.255.0
          inet6 addr: fe80::21b:21ff:fe1a:9d33/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:8215890 errors:0 dropped:0 overruns:0 frame:0
          TX packets:16630944 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:598653130 (570.9 MiB)  TX bytes:2368811256 (2.2 GiB)

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:2761 errors:0 dropped:0 overruns:0 frame:0
          TX packets:2761 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:205129 (200.3 KiB)  TX bytes:205129 (200.3 KiB)


/etc/vservers/mx1# ls -la interfaces/
total 12
drwxr-xr-x 3 root root 4096 2008-11-26 15:46 .
drwxr-xr-x 6 root root 4096 2008-11-10 05:45 ..
drwxr-xr-x 2 root root 4096 2008-11-10 05:51 1

/etc/vservers/mx1# ls -la interfaces/1/
total 12
drwxr-xr-x 2 root root 4096 2008-11-10 05:51 .
drwxr-xr-x 3 root root 4096 2008-11-26 15:46 ..
-rw-r--r-- 1 root root   12 2008-11-10 05:51 ip
-rw-r--r-- 1 root root    0 2008-11-10 05:51 nodev

/etc/vservers/mx1# cat interfaces/1/ip
10.10.43.31

cat /proc/virtual/info
VCIVersion:     0002:0303
VCISyscall:     273
VCIKernel:      13000ff1

vserver-info
Versions:
                   Kernel: 2.6.26-bpo.1-vserver-686
                   VS-API: 0x00020303
             util-vserver: 0.30.216-pre2772; Nov  8 2008, 21:20:22

Features:
                       CC: gcc, gcc (GCC) 4.1.2 20061115 (prerelease)
(Debian 4.1.1-21)
                      CXX: g++, g++ (GCC) 4.1.2 20061115 (prerelease)
(Debian 4.1.1-21)
                 CPPFLAGS: ''
                   CFLAGS: '-Wall -g  -O2 -std=c99 -Wall -pedantic -W
-funit-at-a-time'
                 CXXFLAGS: '-g -O2 -ansi -Wall -pedantic -W
-fmessage-length=0 -funit-at-a-time'
               build/host: i486-pc-linux-gnu/i486-pc-linux-gnu
             Use dietlibc: yes
       Build C++ programs: yes
       Build C99 programs: yes
           Available APIs: v13,net,v21,v22,v23,netv2
            ext2fs Source: e2fsprogs
    syscall(2) invocation: alternative
      vserver(2) syscall#: 273/glibc
               crypto api: beecrypt

Paths:
                   prefix: /usr
        sysconf-Directory: /etc
            cfg-Directory: /etc/vservers
         initrd-Directory: $(sysconfdir)/init.d
       pkgstate-Directory: /var/run/vservers
          vserver-Rootdir: /var/lib/vservers


GUEST
--------------------------------------------------------------------

route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags Metric Ref    Use
Iface
10.10.10.0      0.0.0.0         255.255.255.0   U     0      0        0 *
10.10.43.0      0.0.0.0         255.255.255.0   U     0      0        0 eth0
0.0.0.0         10.10.43.1      0.0.0.0         UG    0      0        0 eth0

ifconfig
eth0      Link encap:Ethernet  HWaddr 00:30:05:CF:75:4B
          inet addr:10.10.43.31  Bcast:10.10.43.255  Mask:255.255.255.0
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:1243471 errors:0 dropped:0 overruns:0 frame:0
          TX packets:778019 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:1196383233 (1.1 GiB)  TX bytes:112570633 (107.3 MiB)
          Memory:d0400000-d0420000

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:2761 errors:0 dropped:0 overruns:0 frame:0
          TX packets:2761 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:205129 (200.3 KiB)  TX bytes:205129 (200.3 KiB)

cat /etc/hosts
# /etc/hosts

127.0.0.1       localhost
10.10.43.31     mx1.xxx.pl mx1

# The following lines are desirable for IPv6 capable hosts
# (added automatically by netbase upgrade)

::1     ip6-localhost ip6-loopback
fe00::0 ip6-localnet
ff00::0 ip6-mcastprefix
ff02::1 ip6-allnodes
ff02::2 ip6-allrouters
ff02::3 ip6-allhosts

NOW (on client)

telnet localhost 25
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
220 mx1.xxx.pl ESMTP Postfix (Debian/GNU)
quit
221 2.0.0 Bye

and:
Nov 26 19:16:39 mx1 postfix/smtpd[30797]: connect from
mx1.xxx.pl[10.10.43.31]
Nov 26 19:16:42 mx1 postfix/smtpd[30797]: disconnect from
mx1.xxx.pl[10.10.43.31]

Why is it connecting using source address 10.10.43.31 and not 127.0.0.1 ?

rgrds.,
Konrad Korzeniowski