ipcpd: Update DHT for unicast layer

This is a rewrite of the DHT for name-to-address resolution in the
unicast layer. It is now integrated as a proper directory policy. The
dir_wait_running function is removed, instead the a DHT peer is passed
on during IPCP enrolment.

Each DHT request/response gets a random 64-bit ID ('cookie'). DHT
messages to the same peer are deduped, except in the case when the DHT
is low on contacts. In that case, it will contact the per it received
at enrolment for more contacts. To combat packet loss, these messages
are not deduped by means of a 'magic cookie', chosen at random when
the DHT starts.

The DHT parameters (Kademlia) can be set using the configfile or the
IRM command line tools:

if DIRECTORY_POLICY == DHT
        [dht_alpha <search factor> (default: 3)]
        [dht_k <replication factor> (default: 8)]
        [dht_t_expire <expiration (s)> (default: 86400)]
        [dht_t_refresh <contact refresh (s)> (default: 900)]
        [dht_t_replicate <replication (s)> (default: 900)]

This commit also adds support for a protocol debug level (PP).
Protocol debugging for the DHT can be enabled using the
DEBUG_PROTO_DHT build flag.

The DHT has the following message types:

DHT_STORE, sent to k peers. Not acknowledged.

    DHT_STORE --> [2861814146dbf9b5|ed:d9:e2:c4].
      key: bcc236ab6ec69e65 [32 bytes]
      val: 00000000c4e2d9ed [8 bytes]
      exp: 2025-08-03 17:29:44 (UTC).

DHT_FIND_NODE_REQ, sent to 'alpha' peers, with a corresponding
response. This is used to update the peer routing table to iteratively
look for the nodes with IDs closest to the requested key.

    DHT_FIND_NODE_REQ --> [a62f92abffb451c4|ed:d9:e2:c4].
      cookie: 2d4b7acef8308210
      key:    a62f92abffb451c4 [32 bytes]

    DHT_FIND_NODE_RSP <-- [2861814146dbf9b5|ed:d9:e2:c4].
      cookie: 2d4b7acef8308210
      key:    a62f92abffb451c4 [32 bytes]
      contacts: [1]
        [a62f92abffb451c4|9f:0d:c1:fb]

DHT_FIND_VALUE_REQ, sent to 'k' peers, with a corresponding
response. Used to find a value for a key. Will also send its closest
known peers in the response.

    DHT_FIND_VALUE_REQ --> [2861814146dbf9b5|ed:d9:e2:c4].
      cookie: 80a1adcb09a2ff0a
      key:    42dee3b0415b4f69 [32 bytes]

    DHT_FIND_VALUE_RSP <-- [2861814146dbf9b5|ed:d9:e2:c4].
      cookie: 80a1adcb09a2ff0a
      key:    42dee3b0415b4f69 [32 bytes]
        values: [1]
          00000000c4e2d9ed [8 bytes]
        contacts: [1]
          [a62f92abffb451c4|9f:0d:c1:fb]

Also removes ubuntu 20 from appveyor config as it is not supported anymore.

Signed-off-by: Dimitri Staessens <dimitri@ouroboros.rocks>
Signed-off-by: Sander Vrijders <sander@ouroboros.rocks>

1 files changed, 27 insertions, 14 deletions

diff --git a/src/ipcpd/unicast/dir/dht.proto b/src/ipcpd/unicast/dir/dht.proto
index 4c5b06db..ea74805f 100644
--- a/src/ipcpd/unicast/dir/dht.proto
+++ b/src/ipcpd/unicast/dir/dht.proto
@@ -27,19 +27,32 @@ message dht_contact_msg {
         required uint64 addr = 2;
 }
 
+message dht_find_req_msg {
+        required uint64 cookie = 1;
+        required bytes key     = 2;
+}
+
+message dht_find_node_rsp_msg {
+        required uint64          cookie   = 1;
+        required bytes           key      = 2;
+        repeated dht_contact_msg contacts = 3;
+}
+
+message dht_find_value_rsp_msg {
+        repeated bytes values = 1;
+}
+
+message dht_store_msg {
+        required bytes  key = 1;
+        required bytes  val = 2;
+        required uint32 exp = 3;
+}
+
 message dht_msg {
-        required uint32 code              =  1;
-        required uint32 cookie            =  2;
-        required uint64 s_addr            =  3;
-        optional bytes  s_id              =  4;
-        optional bytes  key               =  5;
-        repeated uint64 addrs             =  6;
-        repeated dht_contact_msg contacts =  7;
-        // enrolment parameters
-        optional uint32 alpha             =  8;
-        optional uint32 b                 =  9;
-        optional uint32 k                 = 10;
-        optional uint32 t_expire          = 11;
-        optional uint32 t_refresh         = 12;
-        optional uint32 t_replicate       = 13;
+        required uint32                 code  = 1;
+        required dht_contact_msg        src   = 2;
+        optional dht_store_msg          store = 3;
+        optional dht_find_req_msg       find  = 4;
+        optional dht_find_node_rsp_msg  node  = 5;
+        optional dht_find_value_rsp_msg val   = 6;
 }