1 files changed, 36 insertions, 0 deletions
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;
+}