in.h: new IP_MTU_DISCOVER mode IP_PMTUDISC_INTERFACE
introduced in linux v3.13, 482fc6094afad572a4ea1fd722e7b11ca72022a0
to mitigate dns cache poisoning via fragmentation
diff --git a/include/netinet/in.h b/include/netinet/in.h
index 2e25afe..ee6e19f 100644
--- a/include/netinet/in.h
+++ b/include/netinet/in.h
@@ -217,6 +217,7 @@
#define IP_PMTUDISC_WANT 1
#define IP_PMTUDISC_DO 2
#define IP_PMTUDISC_PROBE 3
+#define IP_PMTUDISC_INTERFACE 4
#define IP_DEFAULT_MULTICAST_TTL 1
#define IP_DEFAULT_MULTICAST_LOOP 1