From f10c800e629770bdb360080c15c451549d74cb20 Mon Sep 17 00:00:00 2001
From: Runo <alan_salinas@live.com>
Date: Thu, 15 Jan 2026 21:11:01 +0000
Subject: [PATCH] Push genesis block to new peers after handshake to help late
 joiners

When a node has the genesis block and a new peer connects via handshake,
the node will now broadcast the genesis block to help late-joining nodes
receive it. This fixes the issue where genesis block was only broadcast
once when created, causing late joiners to never receive it.

Includes rate limiting (30s per peer) to prevent flooding.
---
 src/mxd_p2p.c | 63 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 63 insertions(+)

diff --git a/src/mxd_p2p.c b/src/mxd_p2p.c
index 3c56360..ac008b7 100644
--- a/src/mxd_p2p.c
+++ b/src/mxd_p2p.c
@@ -35,6 +35,11 @@
 #include "base58.h"
 #include "utils/mxd_replay.h"
 #include "metrics/mxd_prometheus.h"
+#include "mxd_blockchain_db.h"
+
+// Track last genesis push time per peer to avoid flooding
+static time_t last_genesis_push_time[MXD_MAX_PEERS] = {0};
+static char last_genesis_push_addr[MXD_MAX_PEERS][256] = {{0}};
 
 static struct {
     char address[256];
@@ -1040,6 +1045,61 @@ static int create_signed_handshake(mxd_handshake_payload_t *handshake, const uin
     return 0;
 }
 
+// Push genesis block to a newly connected peer if we have it and they might not
+// This helps propagate the genesis block to late joiners
+static void push_genesis_to_peer(const char *address, uint16_t port) {
+    // Check if we have a genesis block (height >= 1 means we have at least genesis)
+    uint32_t local_height = 0;
+    if (mxd_get_blockchain_height(&local_height) != 0 || local_height == 0) {
+        return;  // We don't have any blocks yet
+    }
+    
+    // Rate limit: don't push to the same peer more than once every 30 seconds
+    time_t now = time(NULL);
+    int found_slot = 0;
+    for (int i = 0; i < MXD_MAX_PEERS; i++) {
+        if (strcmp(last_genesis_push_addr[i], address) == 0) {
+            if (now - last_genesis_push_time[i] < 30) {
+                MXD_LOG_DEBUG("p2p", "Skipping genesis push to %s:%d (rate limited)", address, port);
+                return;
+            }
+            // Update timestamp and proceed
+            last_genesis_push_time[i] = now;
+            found_slot = 1;
+            break;
+        }
+        if (!found_slot && last_genesis_push_addr[i][0] == '\0') {
+            // Found empty slot, use it
+            strncpy(last_genesis_push_addr[i], address, sizeof(last_genesis_push_addr[i]) - 1);
+            last_genesis_push_time[i] = now;
+            found_slot = 1;
+            break;
+        }
+    }
+    
+    // Retrieve the genesis block
+    mxd_block_t genesis_block;
+    memset(&genesis_block, 0, sizeof(genesis_block));
+    
+    if (mxd_retrieve_block_by_height(0, &genesis_block) != 0) {
+        MXD_LOG_DEBUG("p2p", "Failed to retrieve genesis block for push to %s:%d", address, port);
+        return;
+    }
+    
+    // Use mxd_broadcast_block to send the genesis block to all peers
+    // This will serialize and broadcast the block properly
+    MXD_LOG_INFO("p2p", "Pushing genesis block to network after new peer %s:%d connected", address, port);
+    
+    extern int mxd_broadcast_block(const mxd_block_t *block);
+    if (mxd_broadcast_block(&genesis_block) == 0) {
+        MXD_LOG_INFO("p2p", "Successfully broadcast genesis block after peer %s:%d connected", address, port);
+    } else {
+        MXD_LOG_DEBUG("p2p", "Failed to broadcast genesis block after peer %s:%d connected", address, port);
+    }
+    
+    mxd_free_block(&genesis_block);
+}
+
 static int handle_handshake_message(const char *address, uint16_t port, 
                                      const void *payload, size_t length,
                                      peer_connection_t *conn) {
@@ -1188,6 +1248,9 @@ static int handle_handshake_message(const char *address, uint16_t port,
     
     update_unified_peer_algo(address, handshake.listen_port, handshake.algo_id);
     
+    // Push genesis block to new peer if we have it (helps late joiners get the genesis block)
+    push_genesis_to_peer(address, handshake.listen_port);
+    
     return 0;
 }