refactor: 将 DTLS 本地依赖迁移到 libs 目录

libs/dtls/src/extension/extension_use_extended_master_secret.rs

@@ -0,0 +1,39 @@
+#[cfg(test)]
+mod extension_use_extended_master_secret_test;
+
+use super::*;
+
+const EXTENSION_USE_EXTENDED_MASTER_SECRET_HEADER_SIZE: usize = 4;
+
+/// ## Specifications
+///
+/// * [RFC 8422]
+///
+/// [RFC 8422]: https://tools.ietf.org/html/rfc8422
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct ExtensionUseExtendedMasterSecret {
+    pub(crate) supported: bool,
+}
+
+impl ExtensionUseExtendedMasterSecret {
+    pub fn extension_value(&self) -> ExtensionValue {
+        ExtensionValue::UseExtendedMasterSecret
+    }
+
+    pub fn size(&self) -> usize {
+        2
+    }
+
+    pub fn marshal<W: Write>(&self, writer: &mut W) -> Result<()> {
+        // length
+        writer.write_u16::<BigEndian>(0)?;
+
+        Ok(writer.flush()?)
+    }
+
+    pub fn unmarshal<R: Read>(reader: &mut R) -> Result<Self> {
+        let _ = reader.read_u16::<BigEndian>()?;
+
+        Ok(ExtensionUseExtendedMasterSecret { supported: true })
+    }
+}