From 9b487dc46f897c57d453a113f069eac1b71a787e Mon Sep 17 00:00:00 2001
From: "iguerNL@Functori" <iguer@functori.com>
Date: Wed, 19 Mar 2025 13:51:29 +0100
Subject: [PATCH] P2P: temporarily allow network names DAL_* and dal-sandbox
 compatibility

---
 src/lib_p2p/p2p_connect_handler.ml | 55 ++++++++++++++++++++++++++++--
 1 file changed, 53 insertions(+), 2 deletions(-)

diff --git a/src/lib_p2p/p2p_connect_handler.ml b/src/lib_p2p/p2p_connect_handler.ml
index 3a167c5a83ec..25b01d360072 100644
--- a/src/lib_p2p/p2p_connect_handler.ml
+++ b/src/lib_p2p/p2p_connect_handler.ml
@@ -338,12 +338,63 @@ let may_select_version ~compare accepted_versions remote_version motive =
   then return remote_version
   else P2p_rejection.rejecting motive
 
+(* TODO: https://gitlab.com/tezos/tezos/-/issues/7851
+
+   The function [is_compatible_chain] below is temporary compatibility code to
+   support the migration of Tezos DAL nodes to the new network naming scheme
+   introduced in MR !17288 on master.
+
+   Before MR !17288, DAL nodes used the hardcoded "dal-sandbox" network name on
+   any Tezos network, which was incorrect. The fix in the MR above introduces a
+   proper naming scheme where the DAL network name is derived from the L1 chain
+   name and prefixed with "DAL_", e.g., "TEZOS_MAINNET" -> "DAL_TEZOS_MAINNET".
+
+   This breaking change would prevents old and new DAL nodes from connecting
+   during the handshake due to mismatched network names. Consequently, the new
+   naming scheme will only be activated starting with the V23 release, while
+   this temporary compatibility function [is_compatible_chain] will introduced
+   in V22.
+
+   More precisely, to handle this transition smoothly, we follow a phased
+   migration plan inspired by past L1 P2P migrations:
+
+   - Step 1 (V22 release): DAL nodes advertise the old "dal-sandbox" name but
+   accept both "dal-sandbox" and "DAL_*" network names.
+
+   - Step 2 (V23 release): Nodes advertise the new "DAL_*" name while still
+     accepting both "dal-sandbox" and "DAL_*" network names.
+
+   - Step 3 (V24 release): Nodes advertise and accept only the new "DAL_*"
+     network names.
+
+   Once all nodes have migrated and Step 3 is reached, this compatibility
+   function should be removed and replaced with a strict equality check
+   [local = remote].
+
+   Note: L1 nodes and existing L1 networks are not affected by this workaround,
+   as their names do not start with "dal-" or "DAL_".
+*)
+let is_compatible_chain =
+  let open Distributed_db_version in
+  let open String in
+  let is_legacy_dal_network_name = equal "dal-sandbox" in
+  fun ~(local : Name.t) ~(remote : Name.t) ->
+    let local = (local :> string) in
+    let remote = (remote :> string) in
+    equal local remote
+    || (is_legacy_dal_network_name local && starts_with ~prefix:"DAL_" remote)
+    || (is_legacy_dal_network_name remote && starts_with ~prefix:"DAL_" local)
+
 let select ~chain_name ~distributed_db_versions ~p2p_versions remote =
   let open Error_monad.Result_syntax in
   assert (distributed_db_versions <> []) ;
   assert (p2p_versions <> []) ;
-  if chain_name <> remote.Network_version.chain_name then
-    P2p_rejection.rejecting Unknown_chain_name
+  if
+    not
+      (is_compatible_chain
+         ~local:chain_name
+         ~remote:remote.Network_version.chain_name)
+  then P2p_rejection.rejecting Unknown_chain_name
   else
     let+ distributed_db_version =
       may_select_version
-- 
GitLab