MSG_CTRUNC
(msg.msg_flags & MSG_CTRUNC) != 0)
if (msg.msg_flags & MSG_CTRUNC)
{MSG_CTRUNC, LINUX_MSG_CTRUNC},
mp->msg_flags |= MSG_CTRUNC;
mp->msg_flags |= MSG_CTRUNC;
mp->msg_flags |= MSG_CTRUNC;
{RUMP_MSG_CTRUNC, MSG_CTRUNC},
(msg.msg_flags & MSG_CTRUNC))