CCP_HDRLEN
if (dp + CCP_HDRLEN > ep)
slen >= CCP_HDRLEN + CCP_OPT_MINLEN &&
slen >= CCP_OPT_LENGTH(dp + CCP_HDRLEN) + CCP_HDRLEN) {
dp + CCP_HDRLEN, slen - CCP_HDRLEN,
dp + CCP_HDRLEN, slen - CCP_HDRLEN,