How to find socket buffer size

Hi,

How can I find the default maximum socket buffer size in NetBSD?
For example, in Solaris it's 64KB and can be found using
 s = open ("/dev/udp", O_RDWR);
    if (s < 0) {
        return dflt;
    }
    strncpy (buf, "udp_max_buf", sizeof(buf));
    stri.ic_cmd = ND_GET;
    stri.ic_timout = 0;
    stri.ic_dp = buf;
    stri.ic_len = sizeof(buf);
    if (ioctl (s, I_STR, &stri) < 0) {
        value = dflt;
    } else {
        value = atoi(buf);

I could not find any /dev/udp as such. Any clue?

Regards
Prasanta