Modified patch from Alpine Linux
https://git.alpinelinux.org/aports/plain/main/pptpd/fix_MSG_TRYHARD.patch

--- a/bcrelay.c
+++ b/bcrelay.c
@@ -103,6 +103,10 @@
 #include "our_syslog.h"
 #include "our_getopt.h"
 
+#ifndef MSG_TRYHARD
+	#define MSG_TRYHARD    MSG_DONTROUTE
+#endif
+
 //#define VERSION "1.0"
 
 /* uncomment if you compile this without poptop's configure script */