usbpcap_ctl_hdr
struct usbpcap_ctl_hdr uch;
uph->uph_hlen = htole16(sizeof(struct usbpcap_ctl_hdr));
struct usbpcap_ctl_hdr *ctl_hdr = (struct usbpcap_ctl_hdr *)p;
(p + sizeof(struct usbpcap_ctl_hdr));