INP_IPV6
isipv6 = (dp->inp_vflag & INP_IPV6) != 0;
dp->inp_vflag |= INP_IPV6;
#ifndef INP_IPV6
answer = inp->inp_vflag & INP_IPV6;
inp->inp_vflag |= INP_IPV6;
inp->inp_vflag |= INP_IPV6;
#ifndef INP_IPV6
intodccpcb(inp)->inp_vflag |= INP_IPV6;
dp->inp_vflag |= INP_IPV6;
inp->inp_vflag |= INP_IPV6;
inp->inp_vflag |= INP_IPV6;
inp->inp_vflag &= ~INP_IPV6;
inp->inp_vflag &= ~INP_IPV6;