if_vxlan(4): Check the size of data available in mbuf before using them

[zlei]

Summary

PR: 261711

[zlei]

sys/net/if_vxlan.c

2852

Check it lazily may be better, i.e. after checking if running status.

[kp]

This looks sane to me. We really do have to make sure there's enough contiguous data before we access it.

sys/net/if_vxlan.c

2852

I'm not sure it's worth having this check. m_pullup() simply won't do anything if the mbuf already has sufficient contiguous space.

[zlei]

sys/net/if_vxlan.c

2852

VXLAN over wireguard or some other setups that have deeper tunnels should be rare.
The m_pullup() is not defined as a macro or an inline function, thus a pre-check should be valuable.