[Xorp-cvs] Some problem in reading Kame code!

[Zhen Chen]

Dear Pavlin, 
I am reading the Kame code. I am very confused. I have not find how the
packet is sent out.
(1) in mip6.c (kame/sys/netinet6/)
mip6_sysctl(name, namelen, oldp, oldlenp, newp, newlen)
SYSCTL_SETUP(sysctl_net_inet6_mip6_setup, "sysctl.net.netinet6.mip6
subtree setup")

what is the purpose of SYSCTL_SETUP?

(2) in kame/sys/netinet6/ip6_output.c
It seems this file is used to send the packet out.  I always meet a
function called mtod(), Do you know what is this function functioning?
ip6 = mtod(m, struct ip6_hdr *); 


Best,

Zhen