Use EF instead of CS7 for DSCP

Some security guidelines recommend dropping CS7 tagged packets at the edge,
since CS7 is reserved for network control. EF seems to be the standard for
telephony applications and is fairly well preserved across the Internet per
https://www.sciencedirect.com/science/article/pii/S0166531619300203

unix.c

@@ -327,17 +327,17 @@ enet_socket_set_option (ENetSocket socket, ENetSocketOption option, int value)
 #else
 #ifdef IP_TOS
             // UNIX - IPv4
-            value = 0xE0; // DSCP: CS7
+            value = value ? 46 << 2 : 0; // DSCP: Expedited Forwarding
             result = setsockopt (socket, IPPROTO_IP, IP_TOS, (char *) & value, sizeof (int));
 #endif
 #ifdef IPV6_TCLASS
             // UNIX - IPv6
-            value = 0xE0; // DSCP: CS7
+            value = value ? 46 << 2: 0; // DSCP: Expedited Forwarding
             result = setsockopt (socket, IPPROTO_IPV6, IPV6_TCLASS, (char *) & value, sizeof (int));
 #endif
 #ifdef SO_PRIORITY
             // Linux
-            value = 6; // Max priority without NET_CAP_ADMIN
+            value = value ? 6 : 0; // Max priority without NET_CAP_ADMIN
             result = setsockopt (socket, SOL_SOCKET, SO_PRIORITY, (char *) & value, sizeof (int));
 #endif
 #endif /* SO_NET_SERVICE_TYPE */