From f9928a1a08c57fe853888119a996c3acc98ee09d Mon Sep 17 00:00:00 2001
From: Johannes Stoelp <johannes.stoelp@gmail.com>
Date: Fri, 14 Jan 2022 23:51:05 +0100
Subject: Initial version of nodemcuv2 dhcp server

Able to offer IP address + DNS/Gateway ...
Worked with devices at my hand.
---
 lib/dhcp/dhcp.cc | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)
 create mode 100644 lib/dhcp/dhcp.cc

(limited to 'lib/dhcp/dhcp.cc')

diff --git a/lib/dhcp/dhcp.cc b/lib/dhcp/dhcp.cc
new file mode 100644
index 0000000..1e5f785
--- /dev/null
+++ b/lib/dhcp/dhcp.cc
@@ -0,0 +1,36 @@
+// Copyright (c) 2022 Johannes Stoelp
+
+#include "dhcp.h"
+#include "utils.h"
+
+std::optional<struct option_view> get_option(const u8* opt, usize len, dhcp_option search_tag) {
+    const u8* end = opt + len;
+
+    while (opt < end) {
+        // Get tag of current option.
+        dhcp_option tag = from_raw<dhcp_option>(*opt++);
+
+        if (tag == dhcp_option::END) {
+            break;
+        }
+
+        // Extract length of current option.
+        usize len = *opt++;
+
+        if (tag == search_tag) {
+            if (static_cast<usize>(end - opt) < len) {
+                // If length is malformed.
+                return std::nullopt;
+            } else {
+                // Option found.
+                return {{opt, len}};
+            }
+        }
+
+        // Advance option iterator to beginning of next option.
+        opt = opt + len;
+    }
+
+    // Option not found.
+    return std::nullopt;
+}
-- 
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