From 1f6e304ff4b095ee71f3406ccc3c80b46ac9c9f4 Mon Sep 17 00:00:00 2001
From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Thu, 21 Jul 2011 16:31:32 +0100
Subject: [PATCH] WIP NEW COMM

---
 dns-transp-server.c | 108 ++++++++++++++++++++++++++++++++++++++++++++
 secnet.h            |   1 +
 2 files changed, 109 insertions(+)
 create mode 100644 dns-transp-server.c

diff --git a/dns-transp-server.c b/dns-transp-server.c
new file mode 100644
index 0000000..154c907
--- /dev/null
+++ b/dns-transp-server.c
@@ -0,0 +1,108 @@
+/* Module for (ab)using DNS as a transport */
+
+/* This provides two new kinds of closure, both of type comm.
+ *  dns-transport-server
+ *    which takes an underlying udp comm
+ *    and which never supports lookup by address
+ *  dns-transport-client
+ */
+
+
+/*
+ * Query format: create assoc:
+ *    1 bit set    this a create assoc query
+ *   32 bits       clientnonce
+ *   10 bits       offset of this data fragment in packet
+ *    1 bit        is this the last fragment ?
+ *    remainder    data packet fragment
+ * data packet sequence number is always implicitly zero
+ *
+ * Query format: submit:
+ *    1 bit clear  this is not a create assoc query
+ *   32 bits       associd
+ *   16 bits       data packet sequence number
+ *   10 bits       offset of this data fragment in packet
+ *    1 bit        is this the last fragment
+ *    remainder    data packet fragment
+ *
+ * Query format: fetch:
+ *    1 bit clear  this is not a create assoc query
+ *   32 bits       associd
+ *   16 bits       client query distinguishper (for defeating dns cache)
+ *
+ * Response format:
+ * [ 32 bits       associd  - only for responses to create assoc ]
+ *    4 bits       log_2( number of bytes of outstanding data on server)
+ *   10 bits       offset of this data fragment in packet
+ *    1 bit        is this the last fragment ?
+ *    remainder    data packet fragment
+ */
+
+/*
+ * Query bitstring, from above, is encoded as follows:
+ *   1. 
+ *    . append our server's domain
+
+struct expires {
+    struct expires *next;
+    struct timeval expires;
+};
+
+struct dedupe {
+    uint8_t *qsubdomhash; /* of length dns_server->hash->len */
+    struct expires expires;
+    int responselen;   /* -1 if we are holding this query */
+    uint8_t *response; /*  0 if we are holding this query */
+};
+
+struct holding {
+    struct holding *next, *back;
+    struct expires expires;
+    int qsubdomlen; /* in octets */
+    uint8_t *qsubdom; /* in dns format ready for packet */
+    struct dedupe *dedupe;
+};
+
+struct assoc {
+    uint32_t associd;
+    struct expires expires; /* clock is running once the clientinit expires */
+    /* table of incoming partial messages */
+    int incoming_used, incoming_allocd;
+    uint32_t incoming_firstseq;
+    struct incomingmsg *incoming;
+    /* table of outgoing messages */
+    int outgoing_used, outgoing_allocd;
+    uint32_t outgoingmsg *outgoing;
+    /* dedupe table */
+    HASHTABLE(struct dedupe) dedupe;
+    /* holding responses */
+    SLIST(struct holding) holding;
+};
+
+struct clientinit {
+    struct sockaddr_in clientaddr;
+    uint32_t clientnonce;
+    struct expires expires;
+    struct assoc *assoc;
+};
+
+struct dns_server {
+    closure_t cl;
+    struct comm_if ops;
+    struct comm_if *port;
+    struct hash_if *hash; /* used for dedupe */
+    HASHTABLE(struct clientinit) clientinits;
+    HASHTABLE(struct assoc) assocs;
+};
+
+/*
+ * Incoming packet
+ *
+ * 1. decode dns packet, check it is for us, etc.
+ * 2. hash qsubdom
+ * 3. check qsubdomhash in dedupe
+ *    if found, send response (or discard, if we are holding), done.
+ * 4a. create assoc packet
+ *    look up {clientaddr,clientnonce} in clientinit
+ *    if not then create an assoc
+ *    
diff --git a/secnet.h b/secnet.h
index 9d0b09e..a206d05 100644
--- a/secnet.h
+++ b/secnet.h
@@ -312,6 +312,7 @@ struct comm_addr {
     struct comm_if *comm;
     union {
 	struct sockaddr_in sin;
+	uint32_t associd;
     } priv;
 };
 
-- 
2.30.2