<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<body dir="auto">
<div dir="ltr">
<div dir="ltr">
<div dir="ltr">“SHOULD” is not “SHALL”, and thus this doesn’t countermand RFC 768’s instruction “ If not used, a value of zero is inserted." So the key question is, when is the source port not used? When a reply is not requested, is my thinking. Is there an
application that implements this in UDP? (it’s nonsensical in TCP, which always requires a handshake, after all). I don’t recall one, but I can envision one: sending a one-way notification that requires no acknowledgement. </div>
<div dir="ltr"><br>
</div>
<div dir="ltr">Given that IP is designed to be extensible to support innovation, who’s to say that there won’t eventually be (if there isn’t already) an application that happens to follow the standard-declared mandate “If not used, a value of zero is inserted"?
Should this application be randomly crippled (by inconsistent filtering) for simply following the rules?</div>
<div dir="ltr"><br>
</div>
<div dir="ltr">I know some say there is a security risk to zero-sourced UDP, but it seems to me that risk is only due to incorrect IP stack code. Zero-sourced UDP should be in everyone’s regression tests to verify non-dangerous behavior, since it’s an edge
case specifically noticed by the standard.</div>
<div dir="ltr"><br>
</div>
<div dir="ltr">I think filtering zero-sourced UDP flies in the face of fundamental Internet interoperability.<br>
<br>
<div dir="ltr"> -mel </div>
<div dir="ltr"><br>
<blockquote type="cite">On Aug 25, 2020, at 8:06 AM, Douglas Fischer <fischerdouglas@gmail.com> wrote:<br>
<br>
</blockquote>
</div>
<blockquote type="cite">
<div dir="ltr">
<div dir="ltr">
<div class="gmail_default" style="font-family:courier new,monospace;font-size:small">
Sorry!<br>
<br>
sed 's/"I can think"/"I can't think"/g'</div>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">Em ter., 25 de ago. de 2020 às 09:16, Töma Gavrichenkov <<a href="mailto:ximaera@gmail.com">ximaera@gmail.com</a>> escreveu:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div dir="auto">Peace,<br>
<br>
<div class="gmail_quote" dir="auto">
<div dir="ltr" class="gmail_attr">On Tue, Aug 25, 2020, 2:14 PM Douglas Fischer <<a href="mailto:fischerdouglas@gmail.com" target="_blank">fischerdouglas@gmail.com</a>> </div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div dir="ltr">
<div class="gmail_default" dir="auto">I can think of a genuine use of it.<br>
</div>
</div>
</blockquote>
</div>
<div dir="auto"><br>
</div>
<div dir="auto">I'm curious which one.</div>
<div dir="auto">With Berkeley sockets there's technically no way to bind(2) to this port without some amount of kernel patching applied, and the system cannot allocate it by itself, either.</div>
<div dir="auto"><br>
</div>
<div dir="auto">--</div>
<div dir="auto">Töma</div>
<div class="gmail_quote" dir="auto">
<blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
<div dir="ltr">
<div dir="ltr">
<div style="padding:0px;margin-left:0px;margin-top:0px;overflow:hidden;color:black;text-align:left;line-height:130%;font-family:"courier new",monospace">
</div>
</div>
</div>
</blockquote>
</div>
</div>
</blockquote>
</div>
<br clear="all">
<div><br>
</div>
-- <br>
<div dir="ltr" class="gmail_signature"><font size="2"><span style="font-family:"courier new",monospace">Douglas Fernando Fischer</span><br style="font-family:"courier new",monospace">
<span style="font-family:"courier new",monospace">Engº de Controle e Automação</span></font>
<div style="padding:0px;margin-left:0px;margin-top:0px;overflow:hidden;color:black;text-align:left;line-height:130%;font-family:"courier new",monospace">
</div>
</div>
</div>
</blockquote>
</div>
</div>
</div>
</body>
</html>