mmds: added support for custom ipv4 address

Added a new API for configuring MMDS. At the moment,
this configuration applies only for the MMDS IPv4 address.

Besides the new API, this commits comprises changes to the
NetBuilder implementation and usages.

Signed-off-by: iulianbarbu <iul@amazon.com>
Signed-off-by: YUAN LYU <lyuyuan92@gmail.com>

src/connection.rs

@@ -131,6 +131,7 @@ impl<T: Read + Write> HttpConnection<T> {
                 Err(e) => return Err(ConnectionError::StreamError(e)),
             }
         }
+        Ok(bytes_read + self.read_cursor)
     }
 
     /// Parses bytes in `buffer` for a valid request line.

src/vmm/src/vmm_config/mmds.rs

@@ -0,0 +1,20 @@
+// Copyright 2020 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+use std::net::Ipv4Addr;
+
+/// Keeps the MMDS configuration.
+#[derive(Debug, Deserialize, PartialEq)]
+#[serde(deny_unknown_fields)]
+pub struct MmdsConfig {
+    /// MMDS IPv4 configured address.
+    ipv4_address: Option<Ipv4Addr>,
+}
+
+impl MmdsConfig {
+    /// Returns the MMDS IPv4 address if one was configured.
+    /// Otherwise returns None.
+    pub fn ipv4_addr(&self) -> Option<Ipv4Addr> {
+        self.ipv4_address
+    }
+}