[B.A.T.M.A.N.] Interface limit 127 in bat0?!

[B.A.T.M.A.N.] Interface limit 127 in bat0?!

[jens]

i observe a limit of 127 interfaces which can be hooked into bat0
where do i find this limit, or does somebody can tell me more about
this? Or, if it is a good idea to circumwent this at all? Or, if its
even possible in actual protocoll structure.

background:
Freifunk with tunneldigger and l2tp tunnel interfaces put a whole lot of
l2tp-eth interfaces in a bridge and hook the bridge into batman, which
make trouble and also doesnt feel like good practice. (i think to
circumvent this limit)

Freifunk with wireguard and gretap also have a lot of gretap tunnel
interfaces - but without bridging is limited to 127 interfaces
(we also experiment with vxlan which is limited to v4 in bridge
forwarding and by this not really an option - idea was to hook vxlan0 in
bat0 , which may be similar to bridging l2tp-eth)

you can find the test here (in german)
https://forum.freifunk.net/t/500-gretap-tunnel-interfaces-in-batman-einhaengen-fuer-wireguard/14245
or the wireguard in freifunk structures (batman network) here
https://forum.freifunk.net/t/wireguard-0-0-20161230-mit-linux-3-18-kernel-und-damit-gluon-v2016-2-2/14122/5

the error if you exceed the interface limit in dmesg :

|Error - can't write to file
'/sys/class/net/gre127/batman_adv/mesh_iface': Cannot allocate memory|


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Re: [B.A.T.M.A.N.] Interface limit 127 in bat0?!

[Andrew Lunn]

> |Error - can't write to file
> '/sys/class/net/gre127/batman_adv/mesh_iface': Cannot allocate memory|

As the message suggests, you are out of memory. This is not a BATMAN
limit, it is a limit from the amount of RAM you have in your device.

       Andrew

Re: [B.A.T.M.A.N.] Interface limit 127 in bat0?!

[Andrew Lunn]

Hi Jens

The script i just used is:

# add one if per 3 second and give output, also monitor dmesg
dmesg -w &
for i in `seq 1 255`; do
    # one interface
    ip link add gre$i type gretap local 192.168.99.1 remote 192.168.3.$i ttl 255 dev lan1
    ip link set up dev gre$i
    batctl if add gre$i
    # another inf
    ip link add grex$i type gretap local 192.168.99.1 remote 192.168.4.$i ttl 255 dev lan1
    ip link set up dev grex$i
    batctl if add grex$i
    echo -n $(uptime|cut -d"," -f4-) $(ifconfig lan1|grep TX\ p) $i
    sleep 3
done

So this adds two interfaces per 3 seconds to bat0.

root@wrt1900ac:~# batctl if
grex122: active
gre123: active
grex123: active
gre124: active
grex124: active
gre125: active
grex125: active
gre126: active
...
grex119: active
gre120: active
grex120: active
gre121: active
grex121: active
gre122: active


root@wrt1900ac:~# batctl if | wc
    344     688    5116

So i have 344 interfaces in the mesh. No memory problems reported.

   Andrew

Re: [B.A.T.M.A.N.] Interface limit 127 in bat0?!

[Sven Eckelmann]

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On Dienstag, 21. Februar 2017 17:24:35 CET Andrew Lunn wrote:
> > |Error - can't write to file
> > '/sys/class/net/gre127/batman_adv/mesh_iface': Cannot allocate memory|
> 
> As the message suggests, you are out of memory. This is not a BATMAN
> limit, it is a limit from the amount of RAM you have in your device.

contiguous kernel memory to store the per-interface originator data - to
be more precise. See batadv_iv_ogm_orig_add_if and all kmalloc*/kfree
references with bcast_own/bcast_own_sum

On Dienstag, 21. Februar 2017 17:19:42 CET jens wrote:
> i observe a limit of 127 interfaces which can be hooked into bat0
> where do i find this limit, or does somebody can tell me more about
> this? Or, if it is a good idea to circumwent this at all? Or, if its
> even possible in actual protocoll structure.

And we had this discussion before [1]. Not sure why you are now
pretending that this never happened.

Kind regards,
	Sven

[1] https://lists.open-mesh.org/pipermail/b.a.t.m.a.n/2017-January/016824.html

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Re: [B.A.T.M.A.N.] Interface limit 127 in bat0?!

[jens]

>> And we had this discussion before [1]. Not sure why you are now
>> pretending that this never happened.

sorry for that .

i had so much discussions and broad tests with wireguard, different
tunnel protocolls (l2tp,gretap,vxlan) the last weeks and simply forget
this, because last time this turned out unsatisfying , or i didnt see
where to go next - i saved this as "unaswered" and in between it was
gone  (for me)