From fc4214e34dc90689b5efd4657bfdce63ca9add24 Mon Sep 17 00:00:00 2001
From: geeksville <kevinh@geeksville.com>
Date: Thu, 16 Apr 2020 17:31:45 -0700
Subject: [PATCH] changes as prelude for turning mesh back on

---
 mesh.proto | 47 ++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 42 insertions(+), 5 deletions(-)

diff --git a/mesh.proto b/mesh.proto
index 1d909c2..0ee63ba 100644
--- a/mesh.proto
+++ b/mesh.proto
@@ -145,12 +145,14 @@ message User {
 // The payload portion fo a packet, this is the actual bytes that are sent
 // inside a radio packet (because from/to are broken out by the comms library)
 message SubPacket {
-  oneof variant {
-    Position position = 1;
 
-    Data data = 3;
-    User user = 4;
-  }
+  // Typically only one of the following fields are populated, but there is no
+  // restriction wrt that
+  Position position = 1;
+  Data data = 3;
+  User user = 4;
+
+  // FIXME, add mesh routing payloads
 
   /// Not normally used, but for testing a sender can request that recipient
   /// responds in kind (i.e. if it received a position, it should unicast back
@@ -184,6 +186,41 @@ message MeshPacket {
   /// (chain of SubPacket) sent to the phone (so the phone can know exact time
   /// of reception)
   uint32 rx_time = 4;
+
+  /// Never sent over the radio links.  Set during reception to indicate the SNR
+  /// of this packet.  Used to collect statistics on current link waulity.
+  sint32 rx_snr = 5;
+
+  /**
+  A unique ID for this packet.  Always 0 for no-ack packets or non broadcast
+  packets (and therefore take zero bytes of space).  Otherwise a unique ID for
+  this packet.  Useful for flooding algorithms.
+
+  ID only needs to be unique on a _per sender_ basis.   And it only
+  needs to be unique for a few minutes (long enough to last for the length of
+  any ACK or the completion of a mesh broadcast flood).
+
+  Rules for broadcasting (listing here for now, will move elsewhere eventually):
+
+  If to==BROADCAST and id==0, this is a simple broadcast (0 hops).  It will be
+  sent only by the current node and other nodes will not attempt to rebroadcast
+  it.
+
+  If to==BROADCAST and id!=0, this is a "naive flooding" broadcast.  The initial
+  node will send it on all local interfaces.
+
+  When other nodes receive this message, they will
+  first check if their recentBroadcasts table contains the (from, id) pair that
+  indicates this message.  If so, we've already seen it - so we discard it.  If
+  not, we add it to the table and then resend this message on all interfaces.
+  When resending we are careful to use the "from" ID of the original sender. Not
+  our own ID.  When resending we pick a random delay between 0 and 10 seconds to
+  decrease the chance of collisions with transmitters we can not even hear.
+
+  Any entries in recentBroadcasts that are older than X seconds (longer than the
+  max time a flood can take) will be discarded.
+  */
+  uint32 id = 6;
 }
 
 /// Shared constants between device and phone