VMNET - problem with epair in jail, cannot ping itself?

[Nikos Vassiliadis]

On 3/19/2012 12:47 AM, Palle Girgensohn wrote:
> Hi!
>
> When I create an epair and pu one end inside a jail, and give that
> interface an IP address, the jail still seems to want to use the lo0
> interface to route traffic to that interface on the inside.
>
> Everything else works, I can set up bridges just like it would be an
> ethernet switch, add services on the inside, it is all fine, except this
> little annoying bug(?).
>
> See here:
>
> [root at hostname /home/girgen]# ifconfig epair create
> epair0a
> [root at hostname /home/girgen]# jail -c vnet name=bar host.hostname=bar
> path=/ persist
> [root at hostname /home/girgen]# jls
>     JID  IP Address      Hostname                      Path
>       1  -               bar                           /
> [root at hostname /home/girgen]# ifconfig epair0b vnet bar
> [root at hostname /home/girgen]# ifconfig -a
> bce0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST>  metric 0 mtu 1500
> 	options=c01bb<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU,VLAN_HWCSUM,TSO4,VLAN_HWTSO,LINKSTATE>
> 	ether 00:23:7d:23:9d:44
> 	inet 1.2.3.144 netmask 0xffffffc0 broadcast 1.2.3.191
> 	inet6 fe80::223:7dff:fe23:9d44%bce0 prefixlen 64 scopeid 0x1
> 	nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
> 	media: Ethernet autoselect (1000baseT<full-duplex>)
> 	status: active
> bce1: flags=8802<BROADCAST,SIMPLEX,MULTICAST>  metric 0 mtu 1500
> 	options=c01bb<RXCSUM,TXCSUM,VLAN_MTU,VLAN_HWTAGGING,JUMBO_MTU,VLAN_HWCSUM,TSO4,VLAN_HWTSO,LINKSTATE>
> 	ether 00:23:7d:23:9d:42
> 	nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
> 	media: Ethernet autoselect
> lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST>  metric 0 mtu 16384
> 	options=3<RXCSUM,TXCSUM>
> 	inet6 ::1 prefixlen 128
> 	inet6 fe80::1%lo0 prefixlen 64 scopeid 0x9
> 	inet 127.0.0.1 netmask 0xff000000
> 	nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>
> epair0a: flags=8842<BROADCAST,RUNNING,SIMPLEX,MULTICAST>  metric 0 mtu 1500
> 	options=8<VLAN_MTU>
> 	ether 02:f9:05:00:0a:0a
> 	nd6 options=29<PERFORMNUD,IFDISABLED,AUTO_LINKLOCAL>
> 	media: Ethernet 10Gbase-T (10Gbase-T<full-duplex>)
> 	status: active
> [root at hostname /home/girgen]# jexec bar ifconfig -a
> lo0: flags=8008<LOOPBACK,MULTICAST>  metric 0 mtu 16384
> 	options=3<RXCSUM,TXCSUM>
> 	nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>
> epair0b: flags=8842<BROADCAST,RUNNING,SIMPLEX,MULTICAST>  metric 0 mtu 1500
> 	options=8<VLAN_MTU>
> 	ether 02:f9:05:00:0b:0b
> 	nd6 options=21<PERFORMNUD,AUTO_LINKLOCAL>
> 	media: Ethernet 10Gbase-T (10Gbase-T<full-duplex>)
> 	status: active
> [root at hostname /home/girgen]# jexec bar ifconfig epair0b 10.1.1.2
> netmask 0xffffff00 up
> [root at hostname /home/girgen]# jexec bar ping 10.1.1.2
> PING 10.1.1.2 (10.1.1.2): 56 data bytes
> ^C
> --- 10.1.1.2 ping statistics ---
> 3 packets transmitted, 0 packets received, 100.0% packet loss
> [root at hostname /home/girgen]# jexec bar route -n get  10.1.1.2
>     route to: 10.1.1.2
> destination: 10.1.1.2
>    interface: lo0
>        flags:<UP,HOST,DONE,STATIC>
>   recvpipe  sendpipe  ssthresh  rtt,msec    mtu        weight    expire
>         0         0         0         0     16384         1         0
> [root at hostname /home/girgen]#
>
>
>
> Now why would the jail think that lo0 is the way to go to find 10.1.1.2?

That's because 10.1.1.2 is a local address for jail bar and all local
addresses are reachable via lo0. Keep in mind that this is the vnet's
lo0 and has nothing to do with the host's lo0. Just "up" your vnet's lo0
interface and everything will be ok. The lo0 loopback interface is
prerequisite for networking.

HTH, Nikos