From cb65b8c89b0b86024322d9e47add855ade307c99 Mon Sep 17 00:00:00 2001
From: Sunil Purushottam Thakare <sunil@thakares.com>
Date: Sat, 24 May 2025 23:12:15 +0530
Subject: [PATCH] Delete Algorithm-Flowchart.md

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-
-# DNS Server Algorithm & Flowchart
-
-This document outlines the algorithm and flowchart for a DNS server implementation compliant with RFC 1035 (DNS) and RFC 4034 (DNSSEC).
-
----
-
-## ✅ Server Algorithm
-
-### 1. Server Initialization
-
-1. Load configuration from environment variables.
-2. Initialize the logging system.
-3. Create SQLite database connection and initialize schema.
-4. Initialize cache with NS records.
-5. Start periodic cache cleanup task (every 5 minutes).
-6. Bind and listen on UDP and TCP sockets.
-
-### 2. Query Handling Flow
-
-#### Upon Receiving a DNS Query:
-
-1. Validate DNS query packet.
-2. Parse header and extract domain name and query type.
-3. If query type is `DNSKEY` or `DS`, return signed records.
-4. Check DNS cache:
-    - If **hit**, build and return response.
-    - If **miss**, lookup in database:
-        - If found, respond and cache it.
-        - If not found:
-            - If authoritative, return `NXDOMAIN`.
-            - Else, forward to upstream resolvers.
-5. Add DNSSEC signatures if applicable.
-6. Send response to the client.
-
-### 3. DNSSEC Signing Process
-
-1. Load DNSSEC key from configured file.
-2. For each relevant record:
-    - Generate `RRSIG`.
-    - Encode signature (Base64).
-    - Calculate key tag and signature expiration.
-3. Add `RRSIG` to the answer section.
-4. Include `DNSKEY` in the authority section if needed.
-
-### 4. Response Generation Logic
-
-1. Construct response header:
-    - Set QR flag and response code.
-    - Include Authoritative Answer (AA) if authoritative.
-2. Attach original question section.
-3. Populate:
-    - **Answer** section: with resolved records.
-    - **Authority** section: with NS and DS records.
-    - **Additional** section: with glue records, DNSKEY if required.
-
----
-
-## 📊 Flowchart
-
-Below is the visual representation of the DNS query handling logic:
-
-```
-
-+---------------------+
-|   Start DNS Server  |
-+---------------------+
-           |
-           v
-+---------------------+
-|  Receive DNS Query  |
-+---------------------+
-           |
-           v
-+---------------------+
-| Parse Header and    |
-| Extract Domain &    |
-| Query Type          |
-+---------------------+
-           |
-           +---------------------+
-           |                     |
-           v                     v
-+---------------------+  +---------------------+
-| Is Query Type       |  | Use Cache           |
-| DNSKEY/DS?          |  |                     |
-+---------------------+  +---------------------+
-           |                     |
-    Yes    |                     |
-           v                     v
-+---------------------+  +---------------------+
-| Return              |  | Lookup in SQLite DB |
-| DNSSEC Record       |  |                     |
-+---------------------+  +---------------------+
-                                   |
-                                   v
-                        +---------------------+
-                        | Is Authoritative    |
-                        | Zone?               |
-                        +---------------------+
-                                   |
-                            No     |
-                                   v
-                        +---------------------+
-                        | Return NXDOMAIN     |
-                        +---------------------+
-                                   |
-                                   v
-                        +---------------------+
-                        | Add GSSEC           |
-                        +---------------------+
-                                   |
-                                   v
-                        +---------------------+
-                        | Send Response       |
-                        +---------------------+
-                                   |
-                                   v
-                        +---------------------+
-                        | End                |
-                        +---------------------+
-
-```
-
-
-## 🧩 Key Components
-
-| Component      | Purpose                    | Details                                  |
-|----------------|----------------------------|------------------------------------------|
-| `DnsCache`     | DNS Response Cache         | Thread-safe HashMap with TTL             |
-| `ServerConfig` | Server Configuration       | Loaded via environment variables         |
-| `rusqlite`     | Record Storage             | SQLite database backend                  |
-| `tokio`        | Async I/O Runtime          | UDP/TCP async handlers and tasks         |
-| `DNSSEC`       | Secure DNS Signing         | RSA-SHA256 with Base64-encoded keys      |
-
----
-
-## ⚠️ Error Handling Strategy
-
-- Custom `DnsError` enum via `thiserror`
-- Graceful shutdown via `SIGINT`
-- Cache cleanup every 5 minutes
-- Fallback to resolver forwarding
-- Detailed logging at every stage
-
----
-## API Reference
-
-#### Get all items
-
-```http
-  GET /api/items
-```
-
-| Parameter | Type     | Description                |
-| :-------- | :------- | :------------------------- |
-| `api_key` | `string` | **Required**. Your API key |
-
-#### Get item
-
-```http
-  GET /api/items/${id}
-```
-
-| Parameter | Type     | Description                       |
-| :-------- | :------- | :-------------------------------- |
-| `id`      | `string` | **Required**. Id of item to fetch |
-
-#### add(num1, num2)
-
-Takes two numbers and returns the sum.
-