FreeBSD -- IPv6 remote Denial-of-Service

Problem Description:
Due do a missing check in the code of m_pulldown(9) data
returned may not be contiguous as requested by the caller.
Impact:
Extra checks in the IPv6 code catch the error condition
and trigger a kernel panic leading to a remote DoS
(denial-of-service) attack with certain Ethernet interfaces.
At this point it is unknown if any other than the IPv6 code
paths can trigger a similar condition.