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>

9 files changed, 28 insertions, 7 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
diff --git a/net/dccp/ipv6.c b/net/dccp/ipv6.c
index 2b90a786e475..629019e6f8e9 100644
--- a/net/dccp/ipv6.c
+++ b/net/dccp/ipv6.c
@@ -141,6 +141,9 @@ static void dccp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
         if (type == ICMPV6_PKT_TOOBIG) {
                 struct dst_entry *dst = NULL;
 
+                if (!ip6_sk_accept_pmtu(sk))
+                        goto out;
+
                 if (sock_owned_by_user(sk))
                         goto out;
                 if ((1 << sk->sk_state) & (DCCPF_LISTEN | DCCPF_CLOSED))
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 9a311cc79672..bc4e1bcdf4c0 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -1165,10 +1165,10 @@ int ip6_append_data(struct sock *sk, int getfrag(void *from, char *to,
                 np->cork.hop_limit = hlimit;
                 np->cork.tclass = tclass;
                 if (rt->dst.flags & DST_XFRM_TUNNEL)
-                        mtu = np->pmtudisc == IPV6_PMTUDISC_PROBE ?
+                        mtu = np->pmtudisc >= IPV6_PMTUDISC_PROBE ?
                               rt->dst.dev->mtu : dst_mtu(&rt->dst);
                 else
-                        mtu = np->pmtudisc == IPV6_PMTUDISC_PROBE ?
+                        mtu = np->pmtudisc >= IPV6_PMTUDISC_PROBE ?
                               rt->dst.dev->mtu : dst_mtu(rt->dst.path);
                 if (np->frag_size < mtu) {
                         if (np->frag_size)
@@ -1270,7 +1270,7 @@ alloc_new_skb:
                         if (skb == NULL || skb_prev == NULL)
                                 ip6_append_data_mtu(&mtu, &maxfraglen,
                                                     fragheaderlen, skb, rt,
-                                                    np->pmtudisc ==
+                                                    np->pmtudisc >=
                                                     IPV6_PMTUDISC_PROBE);
 
                         skb_prev = skb;
diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c
index 759fbf96515b..af0ecb94b3b4 100644
--- a/net/ipv6/ipv6_sockglue.c
+++ b/net/ipv6/ipv6_sockglue.c
@@ -722,7 +722,7 @@ done:
         case IPV6_MTU_DISCOVER:
                 if (optlen < sizeof(int))
                         goto e_inval;
-                if (val < IP_PMTUDISC_DONT || val > IP_PMTUDISC_PROBE)
+                if (val < IPV6_PMTUDISC_DONT || val > IPV6_PMTUDISC_INTERFACE)
                         goto e_inval;
                 np->pmtudisc = val;
                 retv = 0;
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index da046a5d7ffb..d955487f2c54 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -397,6 +397,9 @@ static void tcp_v6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
                 if (sk->sk_state == TCP_LISTEN)
                         goto out;
 
+                if (!ip6_sk_accept_pmtu(sk))
+                        goto out;
+
                 tp->mtu_info = ntohl(info);
                 if (!sock_owned_by_user(sk))
                         tcp_v6_mtu_reduced(sk);
diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 089c741a3992..65ed5cd79264 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -538,8 +538,11 @@ void __udp6_lib_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
         if (sk == NULL)
                 return;
 
-        if (type == ICMPV6_PKT_TOOBIG)
+        if (type == ICMPV6_PKT_TOOBIG) {
+                if (!ip6_sk_accept_pmtu(sk))
+                        goto out;
                 ip6_sk_update_pmtu(skb, sk, info);
+        }
         if (type == NDISC_REDIRECT) {
                 ip6_sk_redirect(skb, sk);
                 goto out;
diff --git a/net/sctp/input.c b/net/sctp/input.c
index 2a192a7c5d81..042ec6c9ae24 100644
--- a/net/sctp/input.c
+++ b/net/sctp/input.c
@@ -389,6 +389,9 @@ void sctp_icmp_frag_needed(struct sock *sk, struct sctp_association *asoc,
         if (!t || (t->pathmtu <= pmtu))
                 return;
 
+        if (!ip6_sk_accept_pmtu(sk))
+                return;
+
         if (sock_owned_by_user(sk)) {
                 asoc->pmtu_pending = 1;
                 t->pmtu_pending = 1;