new rewrite function suggestion + patch, use case: DHCP assignment based on switch and port

[Josef Liška]

Hello,
I have chosen GNU radius as backend for my dhcp servers on mikrotik
routeros 3.x,
because it is probably most flexible implementation of radius server.

I need to do special rewriting of request in order to achieve IP address
assignment based on
switch and port and not mac address. For this i use dhcp option 82 on
switches, which sets
Agent-Remote-Id and Agent-Circuit-Id.

Agent-Remote-Id is basically mac address of the switch, and Circuit-Id
is basically port number and vlan.

Rewrite language is strong enough to do the transformation in case of
text fields. But Agent-Remote-Id
and Agent-Circuit-Id are binary. Rewrite includes function qprn, which I
simply modified to new function tohex.
tohex encodes all characters, so that field and gsub can be used to
separate useful bytes from
Agent-Remote-Id and Agent-Circuit-Id.

My rewrite configuration is:

string
decode_agent_remote_id()
{
        string agent;
        string newagent;

        agent = gsub("%"," ",tohex(%[Agent-Remote-Id]));

        newagent =
field(agent,3)+":"+field(agent,4)+":"+field(agent,5)+":"+field(agent,6)+":"+field(agent,7)+":"+field(agent,8);
        %[Orig-User-Name] = %[User-Name];
        %[User-Name] = newagent+"port:"+field(gsub("%","
",tohex(%[Agent-Circuit-Id])),6);
        return 0;
}

This return user names like "00:15:77:B1:D7:10port:03"

I would like to ask to include tohex function in next release, as this
might be useful.


--

Best regards
Josef Liška

CHL | system care

Phone: [phone]
Fax: [phone]
Cell: +420.776026526 denně 9:00 - 17:30 CEST

<https://www.chl.cz/>


--- radius-1.6.1/radiusd/rewrite.y 2008-12-15 09:03:24.000000000 +0100
+++ radius-1.6.1-phokz/radiusd/rewrite.y 2009-04-17 17:09:15.000000000 +0200
@@ -5519,6 +5519,34 @@
  *p = 0;
 }
 
+/* Phokz's hack */
+
+static void
+bi_tohex()
+{
+ grad_string_t arg;
+ char *p, *s, *end;
+ size_t count;
+ RWSTYPE *sp;
+
+ mem2string(&arg, (RWSTYPE*)getarg(1));
+ end = arg.data + arg.size;
+
+ /* Each encoded character takes 3 bytes. */
+ sp = heap_reserve(sizeof(RWSTYPE) + 3*arg.size + 1);
+ sp[0] = 3*arg.size;
+ pushn((RWSTYPE) sp);
+
+ for (p = (char*)(sp + 1), s = arg.data; s < end; s++) {
+ char buf[3];
+ snprintf(buf, sizeof buf, "%02X", *(unsigned char*)s);
+ *p++ = '%';
+ *p++ = buf[0];
+ *p++ = buf[1];
+ }
+ *p = 0;
+}
+
 static void
 bi_quote_string()
 {
@@ -5667,6 +5695,8 @@
  /* Time functions */
  { bi_time, "time", Integer, "" },
  { bi_strftime, "strftime", String, "si" },
+        /* Phokz's hack */
+ { bi_tohex, "tohex", String, "s" },
  { NULL }
 };
 

[jl.vcf]

---

begin:vcard
fn;quoted-printable:Josef Li=C5=A1ka
n;quoted-printable:Li=C5=A1ka;Josef
org;quoted-printable:CHL po=C4=8D=C3=ADta=C4=8De, s.r.o.
adr;quoted-printable:;;Karla Majera 93;V=C5=A1enory;;252 31;Czech Republic
email;internet:jl@...
title:root
tel;work:[phone]
tel;fax:[phone]
tel;cell:[phone]
note:jabber: jl@...
x-mozilla-html:FALSE
url:http://www.chl.cz
version:2.1
end:vcard

---

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[Sergey Poznyakoff-2]

Josef Li¡ka <jl@...> ha escrit:

> Rewrite includes function qprn, which
> I simply modified to new function tohex.
[...]
> I would like to ask to include tohex function in next release, as this
> might be useful.

Hi Josef,

Thanks for your contribution. Of course I will include it in the nearest
release.

Regards,
Sergey


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