dco-win: multipeer support

This is the main commit for dco-win multipeer
implementation.

This adds concept of "mode" to DCO implementation,
which is peer-to-peer or multipeer. Depending on mode,
some functions use MP-specific IOCTL commands, which
include peer-id as a part of input.

The driver initialization accomodates server mode,
in which tun device is created before transport.

Since on Windows the socket is visible to the kernel only,
control channel packets have to be prepended with remote
sockaddr of the peer - this allows userspace to distinguish
among peers. Sadly there is no reliable way to get peer local
address, such as on Linux/FreeBSD, so we have to do a bit of
guesswork to figure out IP address based on remote IP and local
routing table, which may backfire if there are multiple IPs
assigned to the same network adapter. However, as for now
peer-specific local IP is not used by the driver. We use
instead the result of bind() to the listening address.

Existing sockethandle_finalize() function has been refactored
to accomodate packets with possibly prepended sockaddr.

Change-Id: Ia267276d61fa1425ba205f54ba6eb89021f32dba
Signed-off-by: Lev Stipakov <[email protected]>
Acked-by: Gert Doering <[email protected]>
Message-Id: <[email protected]>
URL: https://www.mail-archive.com/[email protected]/msg30935.html
Signed-off-by: Gert Doering <[email protected]>

src/openvpn/dco.h

@@ -106,9 +106,10 @@ bool dco_check_pull_options(int msglevel, const struct options *o);
  *
  * @param mode      the instance operating mode (P2P or multi-peer)
  * @param dco       the context to initialize
+ * @param dev_node  device node, used on Windows to specify certain DCO adapter
  * @return          true on success, false otherwise
  */
-bool ovpn_dco_init(int mode, dco_context_t *dco);
+bool ovpn_dco_init(int mode, dco_context_t *dco, const char *dev_node);
 
 /**
  * Open/create a DCO interface
@@ -293,7 +294,7 @@ dco_check_pull_options(int msglevel, const struct options *o)
 }
 
 static inline bool
-ovpn_dco_init(int mode, dco_context_t *dco)
+ovpn_dco_init(int mode, dco_context_t *dco, const char *dev_node)
 {
     return true;
 }

src/openvpn/dco_freebsd.c

@@ -165,7 +165,7 @@ close_fd(dco_context_t *dco)
 }
 
 bool
-ovpn_dco_init(int mode, dco_context_t *dco)
+ovpn_dco_init(int mode, dco_context_t *dco, const char *dev_node)
 {
     if (open_fd(dco) < 0)
     {

src/openvpn/dco_linux.c

@@ -422,7 +422,7 @@ ovpn_dco_init_netlink(dco_context_t *dco)
 }
 
 bool
-ovpn_dco_init(int mode, dco_context_t *dco)
+ovpn_dco_init(int mode, dco_context_t *dco, const char *dev_node)
 {
     switch (mode)
     {