findifcould be rewritten in shell

[b-a-t]

Referring to the #52 I got the idea that shell script for finding interface by IP address could be better solution than parsing routing table in C.

For (most) Linux distributions 'ip' command is a part of the standard installation and:

# ip route get 10.0.0.220
10.0.0.220 dev eth1  src 10.0.0.106

gives better and more portable results.

For FreeBSD(and Solaris I guess):

$ route -n get 192.168.0.30
   route to: 192.168.0.30
destination: 192.168.0.0
       mask: 255.255.255.192
  interface: xl0
      flags: 
 recvpipe  sendpipe  ssthresh  rtt,msec    rttvar  hopcount      mtu     expire
       0         0         0         0         0         0      1500  -2151423

Also gives meaningful results(and currently used in 'findif').

Even parsing of '/proc/net/route' is easier in shell, so I see no good reason for quite complex and not flexible C binary for these purpose(except the speed, possibly).

If this idea gets support I can try to write such a replacement.

With regards,
Timur.

[lge]

Taking this to the mailing list as well, to give it a wider audience ...

On Tue, Jan 31, 2012 at 07:56:56AM -0800, b-a-t wrote:

Referring to the #52 I got the idea that shell script for finding
interface by IP address could be better solution than parsing routing
table in C.

For (most) Linux distributions 'ip' command is a part of the standard installation and:

# ip route get 10.0.0.220
10.0.0.220 dev eth1  src 10.0.0.106

gives better and more portable results.

For FreeBSD(and Solaris I guess):

We can ignore non-Linux for IPaddr2, that is already linux specific.

Even parsing of '/proc/net/route' is easier in shell, so I see no good
reason for quite complex and not flexible C binary for these
purpose(except the speed, possibly).

If this idea gets support I can try to write such a replacement.

"once upon a time" I started something like that already,
just for fun. But then left it alone for quite some time,
because, well, if it ain't broken, don't fix it...

I'm not sure why we would care to specify an explicit broadcast address,
so we probably should not try to guess it (the kernel knows better, anyways)
and only put it into the command line if it really was passed in via
configuration parameters, in case there actually is a use case for that.

findif seems to have a few heuristics, which seem to override the input?
Not sure here.

There is also the hack-ish "LVS support" stuff in the script,
we need to make sure that does not break.
Nor any other aspect of "unusual" usage.

Anyways, it may be a starting point:

findif()
{
local match

# FIXME: if all is specified, why would we try to second guess?
# just use the input, and if it fails, it fails?

# non-local, "return" values
NIC= NETMASK=
BRDCAST="$OCF_RESKEY_broadcast"

# FIXME just make sure you drop the "brd $BRDCAST"
# from the ip addr add command if $BRDCAST is empty,
# and the kernel will do the right thing. Or so me thinks...
# Also see below, where we try to second guess BRDCAST.

match="$OCF_RESKEY_ip"

# ip actually does not care if the mask is cidr or dotted quad,
# as long as it is a mask.
# No mask implies "/32" (for the match, only).
# The "match" in "ip route list match ..." will find the best (longest prefix) route.
[ -n "$OCF_RESKEY_cidr_netmask" ] && match=$match/$OCF_RESKEY_cidr_netmask

# FIXME: what if the guessed nic,
# and the requested nic, do not match?
# Would tools/findif.c have ignored the input in that case?
# Should the RA return $OCF_ERR_CONFIGURED in that case?
### FIXME ### [ -n "$OCF_RESKEY_nic" ] && match="$match dev $OCF_RESKEY_nic"

# Only routes with scope link.
set -- `ip -o -f inet route list match $match scope link`
if [ $# = 0 ] ; then
    # possibly need to add special case for 127.x.y.z
    # at least tools/findif.c has one
    case $OCF_RESKEY_ip in
    127.*)
        set -- `ip -o -f inet route list match $match table local scope host`
        # prints "local" as first word
        shift
    esac
fi
# Still nothing? Too bad.
[ $# = 0 ] && return 1

# paranoia
case $1 in
*/*)    : OK ;;

*)
    # No slash should only happen for table local, no mask
    # (or /32), and address already present, and even then
    # it should not show up as first line of output...
    # If we cannot guess the netmask, you need to specify it.
    return 1 ;;
esac

NIC=$3
NETMASK=${1#*/}
: == DEBUG == $NIC / $NETMASK ==

# Do we really need to guess the broadcast? Why?
# We could try to guess it from the primary address on the nic
# but actually that seems pointless?
set -- `ip -o -f inet addr show dev $NIC primary`
# this really should have worked, always!?

# for 127.x.y.z, there usually won't be a broadcast address
[ "$5" = brd ] && BRDCAST=$6

: == DEBUG == brd $BRDCAST ==

return 0

}

try it:

set -vx
OCF_RESKEY_ip=10.9.9.99 findif
OCF_RESKEY_ip=127.1.2.3/27 findif

: Lars Ellenberg
: LINBIT | Your Way to High Availability
: DRBD/HA support and consulting http://www.linbit.com

[b-a-t]

Thanks, Lars, for participation and inspiration! Where I can join (what?) mailing list to take a part in the discussion?
I'm not regular user of pacemaker/corosync/ra, so not really familiar with the surrounding community.

Thanks,
Timur.

[lge]

On Thu, Feb 02, 2012 at 02:48:14AM -0800, Timur Bakeyev wrote:

Thanks, Lars, for participation and inspiration! Where I can join
(what?) mailing list to take a part in the discussion?
I'm not regular user of pacemaker/corosync/ra, so not really familiar
with the surrounding community.

Discussion of patches,
resource agents, "cluster glue", heartbeat etc:
http://lists.linux-ha.org/mailman/listinfo/linux-ha-dev

User list, slightly skewed to pacemaker on heartbeat stack
http://lists.linux-ha.org/mailman/listinfo/linux-ha

Pacemaker list, all issues pacemaker:
http://oss.clusterlabs.org/mailman/listinfo/pacemaker

There are more
(e.g. corosync specific, drbd specific,
or specific for certain use cases).

Most people on linux-ha-dev are also subscribed on both other lists.
I guess most people on linux-ha are also on pacemaker,
not sure if that is true the other way around.

We also hang out on freenode,
#linux-ha (started as heartbeat/pacemaker channel)
#linux-cluster (started as cman/rhcs channel),

Today, I guess regulars are on both.

We probably should update the README...

Lars

[kskmori]

I'm closing this as pull request #152 and #156 have been merged.