[INET]: Add IP(V6)_PMTUDISC_RPOBE

Add IP(V6)_PMTUDISC_PROBE value for IP(V6)_MTU_DISCOVER.  This option forces
us not to fragment, but does not make use of the kernel path MTU discovery.
That is, it allows for user-mode MTU probing (or, packetization-layer path
MTU discovery).  This is particularly useful for diagnostic utilities, like
traceroute/tracepath.

Signed-off-by: John Heffner <jheffner@psc.edu>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 2 insertions, 0 deletions

diff --git a/include/linux/in.h b/include/linux/in.h
index 1912e7c0bc26..3975cbf52f20 100644
--- a/include/linux/in.h
+++ b/include/linux/in.h
@@ -83,6 +83,7 @@ struct in_addr {
 #define IP_PMTUDISC_DONT                0       /* Never send DF frames */
 #define IP_PMTUDISC_WANT                1       /* Use per route hints  */
 #define IP_PMTUDISC_DO                  2       /* Always DF            */
+#define IP_PMTUDISC_PROBE               3       /* Ignore dst pmtu      */
 
 #define IP_MULTICAST_IF                 32
 #define IP_MULTICAST_TTL                33
diff --git a/include/linux/in6.h b/include/linux/in6.h
index 4e8350ae8869..d559fac4a26d 100644
--- a/include/linux/in6.h
+++ b/include/linux/in6.h
@@ -179,6 +179,7 @@ struct in6_flowlabel_req
 #define IPV6_PMTUDISC_DONT              0
 #define IPV6_PMTUDISC_WANT              1
 #define IPV6_PMTUDISC_DO                2
+#define IPV6_PMTUDISC_PROBE             3
 
 /* Flowlabel */
 #define IPV6_FLOWLABEL_MGR      32