>I was looking through the code in netinet/udp_usrreq.c and noticed that
>the mbuf chain was copied both for unicast and broadcast/multicast
>packets in udp4_realinput() (the copy operation is invoked from
>udp4_sendup()).  It seems to me that in the unicast case there is no
>apparent reason for this.  Prior to rev. 1.53 the copying did only
>happen for the broadcast/multicast case.
>
>Does anyone know why the extra copying was introduced for the unicast
>case?

	due to the extra complexity in supporting RFC2553 IPv4 mapped address
	(IPv4 traffic to AF_INET6 socket) i simplified the codepath, hence
	the extra mbuf copy.  usually m_copym() will not require real
	duplication of packet, as they tend to be M_EXT cluster mbuf.

itojun