WIP DNS notes

[secnet.git] / NOTES.ip-over-dns

diff --git a/NOTES.ip-over-dns b/NOTES.ip-over-dns
index c706b555ea31896688f5dcc18d203258ab0c3ad5..ea4c0f43fdd882b29fec90ac3e2ea2a2342dd925 100644 (file)
--- a/NOTES.ip-over-dns
+++ b/NOTES.ip-over-dns
@@ -10,3 +10,73 @@ Encoding:
   - client splits packet into appropriate fragments
   - makes A queries for
      
+
+
+
+We use CNAME queries.  The request/response Q and R are bit-encoded
+into the labels of the query domain and answer section domains,
+respectively.
+
+The server maintains a local cache of questions we have been asked and
+answers we gave.  Neither side ever retries packets; so any responses
+from our server's cache are due to resolvers between the client and
+the server.
+
+
+Requests by client:
+
+ Create Association
+       Q       client-init-nonce
+               4 bits          Length of client-message-nonce in bits,
+                                0 meaning 16; default is 8
+               remaining       Unfragmented response message data bytes
+
+       R       5 bits          Length of associd in bits
+                                0 meaning 32; default is 8
+               associd
+               queue-len-info
+               remaining=payload
+
+ Request Down
+       Q       associd
+               client-message-nonce
+
+       R       queue-len-info
+               remaining=payload
+
+ Submit Up
+       Q       associd
+               client-message-nonce
+               payload
+
+       R       queue-len-info
+               remaining       Unfragmented response message data bytes
+
+queue-len-info :=
+               4 bits          Double-logarithmic server queue length
+       # ciel(log_2( Number of bytes of queued message data ))
+       #  except that if no queued message data, value is 0
+
+payload :=
+       [ If there is actually any data to send:
+               1 bit           Only fragment ?
+         [ If not only fragment:
+               1 bit           Final fragment ?
+               12 bits         Fragment offset
+           [ In packets from server:
+               8 bits          netlink-packet-sequence-number
+               # In payloads from client, the client-message-nonce
+               #  is used for reassembly.
+           ]
+         ]
+               remaining       Data Bytes
+       ]
+
+associd :=     n bits          as specified in Create Association response
+
+client-init-nonce :=   64 bits         Random number
+client-message-nonce := some bits      Sequence number, starts at random value
+       # Ie if we start having more than 255 queries outstanding, we're
+       # going to start losing things.  With our default TTL of 1s and
+       # a compliant DNS server, that might limit us to 255 packets/sec.
+       # With noncompliant DNS servers it might reduce available bandwidth.