'no route to host" for cloned lo1 iface 12.0-CURRENT r334376+56a973815425(master) amd64

[Dave Cottlehuber]

On Wed, 30 May 2018, at 17:46, Rodney W. Grimes wrote:
> > > > > > ifconfig_lo1_aliases="inet 10.241.0.0-15/16"

> > > > > > lo1: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> metric 0 mtu 16384
> > > > > >         inet 10.241.0.0 netmask 0xffff0000
> > > > > >         inet 10.241.0.1 netmask 0xffffffff
> > > > > >         inet 10.241.0.2 netmask 0xffffffff

Thanks Rod, Andreas, Herbert for your help! Back at a proper computer now.

 I think there are 2 things; invalid IP (see end for some interesting notes), and also expansion of ifconfig_<if>_aliases.

# ifconfig_$(if)_aliases

This is my config:

> cloned_interfaces="lo1"
> ifconfig_lo1_aliases="inet 10.24 1.0.0-15/16"

But,  I *don't* have a line like this:

> ifconfig_lo1="inet 10.241.0.0/16" 

and if I add it and bump the range to 10.241.0.1/16,  then all is well again and ping $DODGY_IP works again, but I get 2 entries with /16 mask:

inet 10.241.0.0 netmask 0xffff0000
inet 10.241.0.1 netmask 0xffff0000
inet 10.241.0.2 netmask 0xffffffff

So the solution seems to be this, to keep the 0xfff0000 to just 1 IP:

> cloned_interfaces="lo1"
> ifconfig_lo1="inet 10.241.0.0/16" 
> ifconfig_lo1_aliases="inet 10.24 1.0.0-15/16"

Presumably I've copy-pasted this a long time ago and never questioned it. I checked several random websites, and there are quite a few skipping `ifconfig_lo1`, using just the aliases, and mainly with jail configs, so I guess this change will catch other people too.

I'm not sure what's changed, as nothing recent in /etc/rc.d or  /etc/network.subr commits seems related. What's the best option here? 

Just a doc patch saying you can't use aliases without a prior ifconfig_<if> ?

# invalid IP

TLDR 10.241.0.0/16  is technically not a valid host IP but it has obviously worked in the past.

I've been binding 10.241.0.1-15 to jail IPs, and abusing 10.241.0.0 as the "magic ip" that is bound to net/haproxy or spiped in the host system to broker exernal connections into the jail IP ranges from external internet.  I will rectify my configuration  but I will miss the symmetry :-)

https://tools.ietf.org/html/rfc1122#section-3.3.6 is the closest description I could find for this. Interestingly, they blame 4.2BSD for this and say it's addressed since 4.3:

## 3.3.6  Broadcasts

         Section 3.2.1.3 defined the four standard IP broadcast address
         forms:
           Limited Broadcast:  {-1, -1}
           Directed Broadcast:  {<Network-number>,-1}
           Subnet Directed Broadcast:
                              {<Network-number>,<Subnet-number>,-1}
           All-Subnets Directed Broadcast: {<Network-number>,-1,-1}
         A host MUST recognize any of these forms in the destination
         address of an incoming datagram.
         There is a class of hosts* that use non-standard broadcast
         address forms, substituting 0 for -1.  All hosts SHOULD
         recognize and accept any of these non-standard broadcast
         addresses as the destination address of an incoming datagram.
_________________________
*4.2BSD Unix and its derivatives, but not 4.3BSD.