Hi.

A kernel compiled with sys/netinet6/icmp6.c 1.120 causes panic
when receiving an ICMP6_ECHO_REQUEST packet.

The panic message is
panic: m_copydata: m == NULL, len "VERY LARGE NUMBER"

According to mbuf(9) man page and sys/kern/uipc_mbuf.c, m_copydata
does not handling M_COPYALL, so you must specify correct "len".

Replacing M_COPYALL with n0->m_len seems to fix the problem,
but I don't know this is the correct fix or not. 

Would you please confirm the problem and fix it ?

TIA

Tacha