Hi,

On Wed, Aug 23, 2017 at 3:42 PM, Xunlei Pang <xpang@redhat.com> wrote:
On 08/23/2017 at 03:18 PM, Xunlei Pang wrote:
> On 08/23/2017 at 01:50 PM, Ziyue Yang wrote:
>>
>> On Tue, Aug 22, 2017 at 4:29 PM, Xunlei Pang <xpang@redhat.com <mailto:xpang@redhat.com>> wrote:
>>
>>     On 08/22/2017 at 11:34 AM, Ziyue Yang wrote:
>>     > Hi,
>>     >
>>     > On Tue, Aug 22, 2017 at 9:30 AM, Xunlei Pang <xpang@redhat.com <mailto:xpang@redhat.com> <mailto:xpang@redhat.com <mailto:xpang@redhat.com>>> wrote:
>>     >
>>     >     On 08/22/2017 at 09:10 AM, Baoquan He wrote:
>>     >     > On 08/22/17 at 08:59am, Xunlei Pang wrote:
>>     >     >> On 08/21/2017 at 10:07 AM, Ziyue Yang wrote:
>>     >     >>>
>>     >     >>> On Fri, Aug 18, 2017 at 11:33 AM, Xunlei Pang <xpang@redhat.com <mailto:xpang@redhat.com> <mailto:xpang@redhat.com <mailto:xpang@redhat.com>> <mailto:xpang@redhat.com <mailto:xpang@redhat.com> <mailto:xpang@redhat.com <mailto:xpang@redhat.com>>>> wrote:
>>     >     >>>
>>     >     >>>     On 08/13/2017 at 05:41 PM, Ziyue Yang wrote:
>>     >     >>>     > When dumping to ssh via local ipv6 address, the ssh parameter
>>     >     >>>     > in kdump.conf is supposed to have the form like
>>     >     >>>     >
>>     >     >>>     > ssh user@fe80::cc1:8bff:fe90:b95f%eth0
>>     >     >>>     >
>>     >     >>>     > where "%eth0" is an existing network interface supporting ipv6.
>>     >     >>>     >
>>     >     >>>     > The get_remote_host function in kdump-lib.sh currently
>>     >     >>>     > doesn't remove the network interface in the link local ipv6
>>     >     >>>     > addresses, causing the ip command in kdump_install_net
>>     >     >>>     > function to fail, leading to a "Bad kdump location" message.
>>     >     >>>     >
>>     >     >>>     > This commit
>>     >     >>>     > 1) makes get_remote_host function remove network interface
>>     >     >>>     > in ipv6 addresses if there are any to support host finding;
>>     >     >>>     > 2) adds is_prefixed_ipv6_link_local function to detect link local
>>     >     >>>     > ipv6 address with 'kdump-' prefixed interface name.
>>     >     >>>     >
>>     >     >>>     > Signed-off-by: Ziyue Yang <ziyang@redhat.com <mailto:ziyang@redhat.com> <mailto:ziyang@redhat.com <mailto:ziyang@redhat.com>> <mailto:ziyang@redhat.com <mailto:ziyang@redhat.com> <mailto:ziyang@redhat.com <mailto:ziyang@redhat.com>>>>
>>     >     >>>     > ---
>>     >     >>>     >  kdump-lib.sh | 12 ++++++++++++
>>     >     >>>     >  1 file changed, 12 insertions(+)
>>     >     >>>     >
>>     >     >>>     > diff --git a/kdump-lib.sh b/kdump-lib.sh
>>     >     >>>     > index 3f0af91..e67b28f 100755
>>     >     >>>     > --- a/kdump-lib.sh
>>     >     >>>     > +++ b/kdump-lib.sh
>>     >     >>>     > @@ -312,6 +312,14 @@ is_ipv6_address()
>>     >     >>>     >      echo $1 | grep -q ":"
>>     >     >>>     >  }
>>     >     >>>     >
>>     >     >>>     > +is_prefixed_ipv6_link_local()
>>     >     >>>     > +{
>>     >     >>>     > +    is_ipv6_address $1 && {
>>     >     >>>     > +        local _host_postfix=${1##*\%}
>>     >     >>>     > +        echo $_host_postfix | grep -q "^kdump-eth"
>>     >     >>>     > +    }
>>     >     >>>     > +}
>>     >     >>>     > +
>>     >     >>>     >  # get ip address or hostname from nfs/ssh config value
>>     >     >>>     >  get_remote_host()
>>     >     >>>     >  {
>>     >     >>>     > @@ -323,6 +331,10 @@ get_remote_host()
>>     >     >>>     >      _config_val=${_config_val%:/*}
>>     >     >>>     >      _config_val=${_config_val#[}
>>     >     >>>     >      _config_val=${_config_val%]}
>>     >     >>>     > +    # factor out network inteface segment in local ipv6 address
>>     >     >>>     > +    if is_ipv6_address $_config_val; then
>>     >     >>>     > +        _config_val=${_config_val%\%*}
>>     >     >>>     > +    fi
>>     >     >>>
>>     >     >>>     There is something unclear to me, why does ipv6 address need an interface name followed?
>>     >     >>>     We can see in kdump_install_net(), it uses "ip -o route get to $_server" to acquire the
>>     >     >>>     interface name, is there any chance that the name got is different from that in "ssh"?
>>     >     >>>
>>     >     >>>
>>     >     >>> ssh related commands needs the interface name for routing, since for link local ipv6 addresses there might be multiple interfaces that could be used for routing.
>>     >     >> That's what I concerned about, e.g. there are multiple available routing, via eth0 or eth1.
>>     >     >> You specified eth1 for "ssh" in /etc/kdump.conf, unfortunately kdump_install_net() gets
>>     >     >> eth0 as kdump's netdev from $(get_ip_route_field "$_route" "dev"). Is this possible?
>>     >     > An available route entry must include destination ip and next hop
>>     >     > information, either next hop ip address, or interface to next hop.
>>     >     > Only a destination is not a complete route.
>>     >
>>     >     I just simplified.
>>     >
>>     >     To be specific, my question is that whether the netdev got from the route entry can be ensured
>>     >     to be the same as the one we specified in "ssh" directive, because from the code we clearly see
>>     >     there are two different sources.
>>     >
>>     > Yes I agree.
>>     > Since $1 in kdump_setup_ifname is promised to be an interface with valid route, maybe we can use the $1 in kdump_setup_ifname directly as the interface in the ssh_target related code?
>>
>>     I think we should use the one in "ssh". Please see another reply of me.
>>
>>
>> Seems we have to modify the logic in kdump_install_net and kdump_setup_netdev if we want to use the interface specified in kdump.conf, since the interface was automatically chose by ip command.
> This should be easily done by adding a special case in kdump_install_net() to fetch
> $_route and $_srcaddr in a different way, how about pseudo-code below:
>
>     # Currently this is for sshing to the link local ipv6 target
>     if "$_server is ipv6 link local with zone index"; then
>         _netdev="get zone index from $config_val"
>         # Here we should do some investigation about how ipv6
>         # link local addr is configured, and verify if it works.
>         _srcaddr="get link local ipv6 addr of $_netdev"
>
>         if "$_netdev is eth* pattern"; then
>             Prefix "kdump-" to the zone index of "ssh" in ${initdir}/tmp/$$-kdump.conf

BTW, currently we only discussed ssh, you need to consider nfs mount using "ipv6 link local address" cases as well.

Just sent a new patch series using the network interface specified in kdump.conf.
I think the nfs case can be easily added to kdump_setup_ifname later, if the nfs command usage is similar to ssh.
 

>         fi
>     else
>         _route=`/sbin/ip -o route get to $_server 2>&1`
>         [ $? != 0 ] && echo "Bad kdump location: $config_val" && exit 1
>
>         #the field in the ip output changes if we go to another subnet
>         _srcaddr=$(get_ip_route_field "$_route" "src")
>         _netdev=$(get_ip_route_field "$_route" "dev")
>     fi
>
>     kdump_setup_netdev "${_netdev}" "${_srcaddr}"
>     <snip>
>
> We don't need to touch kdump_setup_netdev().
>
>> Like what Xunlei mentioned, either interface is valid once it has ipv6 route for the ssh target. Maybe we can replace user's choice in this case? Or we may have to consider network quality difference between the interfaces, which is not supported by kdump yet...
> You may get a wrong local link(i.e. ssh target), we can't change the user's intention.
>
>>
>>
>>
>>     >
>>     >
>>     >
>>     >     >>>
>>     >     >>>
>>     >     >>>
>>     >     >>>     Regards,
>>     >     >>>     Xunlei
>>     >     >>>
>>     >     >>>     >      echo $_config_val
>>     >     >>>     >  }
>>     >     >>>     >
>>     >     >>>
>>     >     >>>
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