ipv6: support IPV6_PMTU_INTERFACE on sockets

IPV6_PMTU_INTERFACE is the same as IPV6_PMTU_PROBE for ipv6. Add it
nontheless for symmetry with IPv4 sockets. Also drop incoming MTU
information if this mode is enabled.

The additional bit in ipv6_pinfo just eats in the padding behind the
bitfield. There are no changes to the layout of the struct at all.

Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 11 insertions, 2 deletions

diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index 3fde06645553..7e1ded0d8e45 100644
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -191,7 +191,7 @@ struct ipv6_pinfo {
         /* sockopt flags */
         __u16                   recverr:1,
                                 sndflow:1,
-                                pmtudisc:2,
+                                pmtudisc:3,
                                 ipv6only:1,
                                 srcprefs:3,     /* 001: prefer temporary address
                                                  * 010: prefer public address
diff --git a/include/net/ip6_route.h b/include/net/ip6_route.h
index 733747ce163c..c2626ce1f2ad 100644
--- a/include/net/ip6_route.h
+++ b/include/net/ip6_route.h
@@ -178,10 +178,15 @@ static inline int ip6_skb_dst_mtu(struct sk_buff *skb)
 {
         struct ipv6_pinfo *np = skb->sk ? inet6_sk(skb->sk) : NULL;
 
-        return (np && np->pmtudisc == IPV6_PMTUDISC_PROBE) ?
+        return (np && np->pmtudisc >= IPV6_PMTUDISC_PROBE) ?
                skb_dst(skb)->dev->mtu : dst_mtu(skb_dst(skb));
 }
 
+static inline bool ip6_sk_accept_pmtu(const struct sock *sk)
+{
+        return inet6_sk(sk)->pmtudisc != IPV6_PMTUDISC_INTERFACE;
+}
+
 static inline struct in6_addr *rt6_nexthop(struct rt6_info *rt)
 {
         return &rt->rt6i_gateway;
diff --git a/include/uapi/linux/in6.h b/include/uapi/linux/in6.h
index 440d5c479145..f94f1d013bf2 100644
--- a/include/uapi/linux/in6.h
+++ b/include/uapi/linux/in6.h
@@ -188,6 +188,10 @@ enum {
 #define IPV6_PMTUDISC_WANT              1
 #define IPV6_PMTUDISC_DO                2
 #define IPV6_PMTUDISC_PROBE             3
+/* same as IPV6_PMTUDISC_PROBE, provided for symetry with IPv4
+ * also see comments on IP_PMTUDISC_INTERFACE
+ */
+#define IPV6_PMTUDISC_INTERFACE         4
 
 /* Flowlabel */
 #define IPV6_FLOWLABEL_MGR      32