if_vxlan(4): Plug a memory leak

[zlei]

Summary

On clone creating, either failure from vxlan_set_user_config() or
ifc_copyin() will result in leaking previous allocated counters.

Since counter_u64_alloc(M_WAITOK) never fails, make vxlan_stats_alloc()
void and move the allocation for counters below checking ifd->params to
avoid memory leak.

Fixes: b092fd6c973d if_vxlan(4): add support for hardware assisted checksumming, TSO, and RSS
MFC after: 1 week

[kp]

sys/net/if_vxlan.c

2955

counter_u64_free(NULL) is safe (now), so even without the other changes getting rid of the check would be fine.

[zlei]

sys/net/if_vxlan.c

2955

Indeed.