On 06/08/2015 02:43 PM, Laine Stump wrote:
>> However, if I changed the destination address from "anywhere" to the
>> IP of the host machine, the problem resolved. So I change the script
>> to as follows. (Changes are highlighted. For some reason the original
>> script didn't work using /bin/sh, but it did with /bin/bash, so I
>> changed that too).
>
> I don't know for sure, but my guess is that this line:
>
>   length=$(( ${#Host_port[@]} - 1 ))

Correct - that line is a bashism, and is not portable when /bin/sh is dash.

>
> which was added by vgerris in order to support forwarding of multiple
> ports, could be what's causing the incompatibility (that wasn't in the
> original, simpler version of the script, written by me.)
>
>>
>> *#!/bin/bash*
>> # used some from advanced script to have multiple ports: use an equal
>> number of guest and host ports
>>
>> Guest_name=xxxxxxx
>> Guest_ipaddr=xxx.xxx.xxx.xx
>> *Host_ipaddr=xxx.xxx.xxx.xx*
>> Host_port=( '80' '443' )
>> Guest_port=( '80' '443' )

In fact, these two lines are also bashisms.  All the more reason to
require bash.

>> length=$(( ${#Host_port[@]} - 1 ))
>> if [ "${1}" = "${Guest_name}" ]; then
>>    if [ "${2}" = "stopped" -o "${2}" = "reconnect" ]; then

test ... -o ... (also spelled [ ... -o ... ]) is not portable, even on
bash.  There are some expressions that are completely ambiguous on how
to be parsed, when -o is in the mix.  It is better to spell it: [ ... ]
|| [ ... ] (that is, use the shell's || instead of test's -o to do the
conjunction).

>>        for i in `seq 0 $length`; do

seq is not portable outside of GNU/Linux systems.

>> Lastly, I should note that I am using Ubuntu 14.04, both for the host
>> and guest.

Yep, that's a system that uses dash for /bin/sh.

>>
>> I'm also curious as to why this is considered a hack method. It states
>> in the wiki that "This method is a hack", but it doesn't express why.
>
> I consider it a hack because:
>
> 1) It requires the IP address of the guest to be known before the guest
> is started, so either you need to guess the guest's IP (if the guest is
> getting its IP address via dhcp) or configured the guest IP address in
> multiple places.

Although recent work has been made to get libvirt to add an API that
queries the guest for its IP address, once the guest is running.

--
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org