dhcpcd-discuss

Hi Paul

On 2015-08-15 00:52, Walrath, Paul wrote:
> I'm seeing another unexplainable behavior that may be tied in with
> this.  If I change my DHCP servers from the DHCPv6 server providing
> DHCPv6 Option 39 Client FQDN to having the DHCPv4 server providing
> DHCPv4 Option 12 Hostname and DHCPv4 Option 15 Domain Name to my
> device then do an ifdown followed by an ifup on my device's network
> interface, the domain name changes (/etc/resolv.conf) to the DHCPv4
> provided name but the host name remains the same.  If I power-cycle my
> device, the host name gets updated.

This won't work, dhcpcd won't magically unset the hostname, thus 
probably won't change over.
I don't see a good way of doing this, but not thought about it too much 
either.

> I can make the host name get updated with just the ifdown/ifup
> sequence by making the following change in 30-hostname in the
> set_hostname function:
>
> Existing code:
>
> set_hostname()
> {
> 	local hfqdn=false hshort=false
>
> 	need_hostname || return
>
> New code:
>
> set_hostname()
> {
> 	local hfqdn=false hshort=false
>
> 	if [ need_hostname ]; then
> 		# Walrath: Debug
> 		printf "NEEDED\n" >> /var/log/rpw
> 	else
> 		# Walrath: Debug
> 		printf "NOT NEEDED\n" >> /var/log/rpw
> 		return
> 	fi
>
> I'm using the shell from Busybox (which is called ash).
>
> It appears as though the "if [ need_hostname] " method is more
> reliable.  Don't ask me why.  I did some printf tracing and here's
> what it showed:

It's wrong, as this snippet shows

$ cat x
#!/bin/sh

foo1()
{
        return 1
}

foo1 && echo bar1
[ foo1 ] && echo bar2


foo2()
{
        return 0
}

foo2 && echo bar21
[ foo2 ] && echo bar22

foo3 && echo bar31
[ foo3 ] && echo bar32

$ sh ./x
bar2
bar21
bar22
foo3: not found
bar32
$

Roy