Set GnuTLS push/pull/errno functions on MinGW build

Based on a patch from Nikos Mavrogiannopoulos.

Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>

compat.c

@@ -238,4 +238,14 @@ int openconnect__win32_neterrno()
 	default:		return EIO;
 	}
 }
+
+ssize_t openconnect__win32_sock_read(gnutls_transport_ptr_t ptr, void *data, size_t size)
+{
+	return recv((long)ptr, data, size, 0);
+}
+
+ssize_t openconnect__win32_sock_write(gnutls_transport_ptr_t ptr, const void *data, size_t size)
+{
+	return send((long)ptr, data, size, 0);
+}
 #endif /* _WIN32 */

dtls.c

@@ -378,6 +378,12 @@ static int start_dtls_handshake(struct openconnect_info *vpninfo, int dtls_fd)
 
 	gnutls_transport_set_ptr(dtls_ssl,
 				 (gnutls_transport_ptr_t)(long) dtls_fd);
+#ifdef _WIN32
+	gnutls_transport_set_pull_function(dtls_ssl, openconnect__win32_sock_read);
+	gnutls_transport_set_push_function(dtls_ssl, openconnect__win32_sock_write);
+	gnutls_transport_set_errno_function(dtls_ssl, openconnect__win32_neterrno);
+#endif
+
 	gnutls_record_disable_padding(dtls_ssl);
 	master_secret.data = vpninfo->dtls_secret;
 	master_secret.size = sizeof(vpninfo->dtls_secret);

gnutls.c

@@ -1944,6 +1944,11 @@ int openconnect_open_https(struct openconnect_info *vpninfo)
 	gnutls_record_disable_padding(vpninfo->https_sess);
 	gnutls_credentials_set(vpninfo->https_sess, GNUTLS_CRD_CERTIFICATE, vpninfo->https_cred);
 	gnutls_transport_set_ptr(vpninfo->https_sess, /* really? */(gnutls_transport_ptr_t)(long) ssl_sock);
+#ifdef _WIN32
+	gnutls_transport_set_pull_function(vpninfo->https_sess, openconnect__win32_sock_read);
+	gnutls_transport_set_push_function(vpninfo->https_sess, openconnect__win32_sock_write);
+	gnutls_transport_set_errno_function(vpninfo->https_sess, openconnect__win32_neterrno);
+#endif
 
 	vpn_progress(vpninfo, PRG_INFO, _("SSL negotiation with %s\n"),
 		     vpninfo->hostname);

openconnect-internal.h

@@ -372,6 +372,8 @@ int openconnect__inet_aton(const char *cp, struct in_addr *addr);
 #ifdef _WIN32
 #define neterrno openconnect__win32_neterrno
 int openconnect__win32_neterrno();
+ssize_t openconnect__win32_sock_read(gnutls_transport_ptr_t ptr, void *data, size_t size);
+ssize_t openconnect__win32_sock_write(gnutls_transport_ptr_t ptr, const void *data, size_t size);
 #else
 #define neterrno() errno
 #define closesocket close