Add ability to set multicast source address

include/Transmitter.h

@@ -381,9 +381,10 @@ namespace LibFlute {
           short port, uint64_t tsi, unsigned short mtu,
           uint32_t rate_limit,
           boost::asio::io_context& io_context,
-          const std::optional<boost::asio::ip::udp::endpoint> &tunnel_endpoint = std::nullopt,
+          const std::optional<boost::asio::ip::udp::endpoint>& tunnel_endpoint = std::nullopt,
           FdtNamespace fdt_namespace = FileDeliveryTable::FDT_NS_NONE,
-          bool active = true);
+          bool active = true,
+          const std::optional<std::string>& source_address = std::nullopt);
 
      /**
       *  Default destructor.
@@ -505,6 +506,29 @@ namespace LibFlute {
       Transmitter &endpoint(boost::asio::ip::udp::endpoint &&destination);
      /**@}*/
 
+     /**
+      * Get the optional source address for the FLUTE session
+      *
+      * @return The optional source address being used.
+      */
+      const std::optional<boost::asio::ip::address> &source_address() const { return _source_address; };
+
+     /**@{*/
+     /**
+      * Set the source address for FLUTE session
+      *
+      * Sets the optional source address to use for FLUTE session packets. If the UDP Tunnel Address is not set then the outgoing
+      * socket will be bound to this address, if set. When a UDP Tunnel Address is set then this provides the source address for
+      * encapsulated packets. If the source address is not set then a local address will be selected automatically.
+      *
+      * @param source The IP source address to use for FLUTE packets.
+      *
+      * @return This Transmitter object.
+      */
+      Transmitter &source_address(const std::optional<boost::asio::ip::address> &source);
+      Transmitter &source_address(std::optional<boost::asio::ip::address> &&source);
+     /**@}*/
+
      /**
       *  Enable IPSEC ESP encryption of FLUTE payloads.
       *
@@ -601,6 +625,7 @@ namespace LibFlute {
 
       void handle_send_to(const boost::system::error_code& error);
       boost::asio::ip::udp::endpoint _endpoint;
+      std::optional<boost::asio::ip::address> _source_address;
       boost::asio::ip::udp::socket _socket;
       boost::asio::io_context& _io_context;
       boost::asio::deadline_timer _send_timer;

src/Transmitter.cpp

@@ -460,8 +460,10 @@ Transmitter::Transmitter ( const std::string& address, short port,
                            uint64_t tsi, unsigned short mtu, uint32_t rate_limit,
                            boost::asio::io_context& io_context,
                            const std::optional<boost::asio::ip::udp::endpoint> &tunnel_endpoint,
-                           Transmitter::FdtNamespace fdt_namespace, bool active )
+                           Transmitter::FdtNamespace fdt_namespace, bool active,
+                           const std::optional<std::string> &source_address )
     : _endpoint(boost::asio::ip::make_address(address), port)
+    , _source_address()
     , _socket(io_context, _endpoint.protocol())
     , _io_context(io_context)
     , _send_timer(io_context)
@@ -476,6 +478,9 @@ Transmitter::Transmitter ( const std::string& address, short port,
     , _tunnel_local_address()
     , _active(active)
 {
+  if (source_address) {
+    _source_address = boost::asio::ip::make_address(source_address.value());
+  }
   _max_payload = mtu -
     20 - // IPv4 header
      8 - // UDP header
@@ -494,6 +499,10 @@ Transmitter::Transmitter ( const std::string& address, short port,
   _socket.set_option(boost::asio::ip::multicast::enable_loopback(true));
   _socket.set_option(boost::asio::ip::udp::socket::reuse_address(true));
 
+  if (_source_address && !_tunnel_endpoint) {
+    _socket.bind(boost::asio::ip::udp::endpoint(_source_address.value(),0));
+  }
+
   _fec_oti = FecOti{
     .encoding_id = FecScheme::CompactNoCode,
     .encoding_symbol_length = _max_payload,
@@ -570,6 +579,18 @@ auto Transmitter::endpoint(boost::asio::ip::udp::endpoint &&destination) -> Tran
   return *this;
 }
 
+auto Transmitter::source_address(const std::optional<boost::asio::ip::address> &source_address) -> Transmitter&
+{
+  _source_address = source_address;
+  return *this;
+}
+
+auto Transmitter::source_address(std::optional<boost::asio::ip::address> &&source_address) -> Transmitter&
+{
+  _source_address = std::move(source_address);
+  return *this;
+}
+
 auto Transmitter::enable_ipsec(uint32_t spi, const std::string& key) -> void
 {
   IpSec::enable_esp(spi, _mcast_address, IpSec::Direction::Out, key);
@@ -731,8 +752,8 @@ auto Transmitter::send_next_packet() -> void
         send_endpoint = _tunnel_endpoint.value();
         data_size = packet->size() + 20 /* IP header */ + 8 /* UDP header */;
         data = new char[data_size];
-        create_udp_pkt(data+20, _endpoint, packet->data(), packet->size(), _tunnel_local_address);
-        create_ip_hdr(data, _endpoint, data_size, _tunnel_local_address);
+        create_udp_pkt(data+20, _endpoint, packet->data(), packet->size(), _source_address?_source_address.value():_tunnel_local_address);
+        create_ip_hdr(data, _endpoint, data_size, _source_address?_source_address.value():_tunnel_local_address);
       } else {
         send_endpoint = _endpoint;
         data = packet->data();