/*
 * VFS Operations.
 *
 * mount system call
 */
int
nfs_vfs_mount(mount_t mp, vnode_t vp, user_addr_t data, vfs_context_t ctx)
{
    // ...
    switch (argsversion) {
    // ...
    case 6:
        /* convert old-style args to xdr */
        error = nfs_convert_old_nfs_args(mp, data, ctx, argsversion, inkernel, &xdrbuf);
        break;
}


/*
 * Convert old style NFS mount args to XDR.
 */
static int
nfs_convert_old_nfs_args(mount_t mp, user_addr_t data, vfs_context_t ctx, int argsversion, int inkernel, char **xdrbufp)
{
    // ...
    struct sockaddr_storage ss;
    // ...
    /* copy socket address */
    if (inkernel)
        bcopy(CAST_DOWN(void *, args.addr), &ss, args.addrlen);
    else
        error = copyin(args.addr, &ss, args.addrlen);
    /* versus
    else {
        if ((size_t)args.addrlen > sizeof (struct sockaddr_storage))
            error = EINVAL;
        else
            error = copyin(args.addr, &ss, args.addrlen);
    }*/
    nfsmout_if(error);
    // ...
}