gistfile1.txt

ip link add dev aaa0 type veth peer name aaa1
ip link add dev bbb0 type veth peer name bbb1
for if in aaa0 aaa1 bbb0 bbb1; do ip link set up $if; done

ip link set mtu 1300 dev aaa0
ip link set mtu 1300 dev aaa1

ip link set mtu 1400 dev bbb0
ip link set mtu 1400 dev bbb1

batctl -m bat0 if add aaa0
batctl -m bat1 if add aaa1
batctl -m bat1 if add bbb0
batctl -m bat2 if add bbb1

#    bat0      bat1      bat2
#    ------------------------
#          MTU
#         1300 
#    aaa0 ---- aaa1  MTU
#                   1400
#              bbb0 ---- bbb1

ip netns add ns0
ip netns add ns1
ip netns add ns2

ip link set dev bat0 netns ns0
ip link set dev bat1 netns ns1
ip link set dev bat2 netns ns2

ip netns exec ns0 ip link set up bat0
ip netns exec ns1 ip link set up bat1
ip netns exec ns2 ip link set up bat2

ip netns exec ns0 ip address add 10.0.0.1/16 dev bat0
ip netns exec ns1 ip address add 10.0.1.1/16 dev bat1
ip netns exec ns2 ip address add 10.0.2.1/16 dev bat2

# wait a little until the mesh is ready
sleep 15

ip netns exec ns0 ping -c 2 10.0.2.1 -s 100  # works
ip netns exec ns0 ping -c 2 10.0.2.1 -s 1500 # does not work