Adding Recursion Available bit to name_query and node_status_query
rsharpe at ns.aus.com
Mon May 13 14:42:01 GMT 2002
On Mon, 13 May 2002, Christopher R. Hertel wrote:
> 1) It would be nice to see the flags on the outgoing packet as well
> as the repl[y|ies].
> 2) It might make sense produce this output on debug level 1, rather
> than by default. Or perhaps incoming flags at -d1 and both sets
> at -d2.
> 3) It would also be nice to see the RCode value in any error message
> received (we may already provide the diagnostics).
> For those just tuning in from home, here's a rundown of the flag
> values we are talking about:
> R - Reply bit.
> This should always be set on packets received by nmblookup. It
> would be an error if it wasn't.
> OpCode - Operation Code.
> Always 0x00 for queries (which is what nmblookup sends).
> AA - Authoritative Answer.
> Likewise. I *think* that the AA flag is a hold-over from the
> DNS system (the basis for the NBT Name Service).
> I would love to see this reported, however, because I am
> wondering whether WINS Proxies (does anyone still use those?)
> leave this bit clear.
> TC - Truncation flag.
> No one has, to my knowledge, ever implemented truncated Name
> Service packets. According to the RFCs, if you get a packet
> with the TC bit set, the you can negotiate the use of TCP.
> (Yes, that would be TCP on port 137. No one ever implemented
> that, as far as I know.) I believe that all implementations
> ignore this bit (though I've not tested to see what Windows
> does if this is set). I would be very surprised to see this
> bit set.
> RD - Recursion Desired.
> Only has meaning in request messages. Used to indicate that
> the NBNS (WINS) server should be consulted.
> There is a lengthy discussion of all of this in section 126.96.36.199
> of my docs. The RD bit is used heavily to distinguish between
> requests, queries, and demands. In reply messages, however, its
> state is (probably) not significant at all. My guess is that it
> will typically match the state of the RD bit in the request.
> RA - Recursion Available.
> Should only be set in messages which come from the NBNS (WINS)
> server itself. Note that a machine that is running WINS will
> also have a local name table. If the reply comes from the
> local name table, then RA should be clear even if the same node
> is running the NBNS (WINS) server.
> B - Broadcast bit.
> Set when the packet is being sent as a broadcast. Interesting
> to play with this bit, particularly in conjunction with the RD
> RCode - Result code.
> 0 for success, else an error code.
These would be nice, except that I have found that these bits are all
separate BOOLs in the decoded structure, instead of being a bit-field.
I will have to re-assemble them :-(
Richard Sharpe, rsharpe at ns.aus.com, rsharpe at samba.org,
sharpe at ethereal.com
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