Add support to control DF bit behavior in VXLAN and GENEVE interfaces.
From iproute2 manual:
df DF - specifies the usage of the Don't Fragment flag (DF) bit in outgoing packets with IPv4 headers. The value inherit causes the bit to be copied from the original IP header. The values unset and set cause the bit to be always unset or always set, respectively. By default, the bit is not set.