y supplying any value one would supply as the <code>int flags</code> arg of Linux's <code>recvmsg()</code> (see <code>man recvmsg</code>). As one can see in the <code>man</code> page, this is a bit mask or ORed values. Formally, however, the only value supported (does not lead to undefined behavior) is <code>MSG_CMSG_CLOEXEC</code> (please read its docs elsewhere, but in summary it sets the close-on-<code>exec</code> bit of any non-null received <code>*target_payload_blob</code>). Informally: that flag may 