ipv6: yet another new IPV6_MTU_DISCOVER option IPV6_PMTUDISC_OMIT
This option has the same semantic as IP_PMTUDISC_OMIT for IPv4 which
got recently introduced. It doesn't honor the path mtu discovered by the
host but in contrary to IPV6_PMTUDISC_INTERFACE allows the generation of
fragments if the packet size exceeds the MTU of the outgoing interface
MTU.
Fixes: 93b36cf3425b9b ("ipv6: support IPV6_PMTU_INTERFACE on sockets")
Cc: Florian Weimer <fweimer@redhat.com>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/ip6_route.h b/include/net/ip6_route.h
index 017badb..00e3f12 100644
--- a/include/net/ip6_route.h
+++ b/include/net/ip6_route.h
@@ -171,7 +171,14 @@
static inline bool ip6_sk_accept_pmtu(const struct sock *sk)
{
- return inet6_sk(sk)->pmtudisc != IPV6_PMTUDISC_INTERFACE;
+ return inet6_sk(sk)->pmtudisc != IPV6_PMTUDISC_INTERFACE &&
+ inet6_sk(sk)->pmtudisc != IPV6_PMTUDISC_OMIT;
+}
+
+static inline bool ip6_sk_local_df(const struct sock *sk)
+{
+ return inet6_sk(sk)->pmtudisc < IPV6_PMTUDISC_DO ||
+ inet6_sk(sk)->pmtudisc == IPV6_PMTUDISC_OMIT;
}
static inline struct in6_addr *rt6_nexthop(struct rt6_info *rt)
diff --git a/include/uapi/linux/in6.h b/include/uapi/linux/in6.h
index e9a1d2d..0d8e0f0 100644
--- a/include/uapi/linux/in6.h
+++ b/include/uapi/linux/in6.h
@@ -185,6 +185,10 @@
* also see comments on IP_PMTUDISC_INTERFACE
*/
#define IPV6_PMTUDISC_INTERFACE 4
+/* weaker version of IPV6_PMTUDISC_INTERFACE, which allows packets to
+ * get fragmented if they exceed the interface mtu
+ */
+#define IPV6_PMTUDISC_OMIT 5
/* Flowlabel */
#define IPV6_FLOWLABEL_MGR 32
diff --git a/net/ipv6/ip6_output.c b/net/ipv6/ip6_output.c
index 070a2fa..be1b7f5 100644
--- a/net/ipv6/ip6_output.c
+++ b/net/ipv6/ip6_output.c
@@ -1234,8 +1234,10 @@
sizeof(struct frag_hdr) : 0) +
rt->rt6i_nfheader_len;
- maxnonfragsize = (np->pmtudisc >= IPV6_PMTUDISC_DO) ?
- mtu : sizeof(struct ipv6hdr) + IPV6_MAXPLEN;
+ if (ip6_sk_local_df(sk))
+ maxnonfragsize = sizeof(struct ipv6hdr) + IPV6_MAXPLEN;
+ else
+ maxnonfragsize = mtu;
/* dontfrag active */
if ((cork->length + length > mtu - headersize) && dontfrag &&
@@ -1543,8 +1545,7 @@
}
/* Allow local fragmentation. */
- if (np->pmtudisc < IPV6_PMTUDISC_DO)
- skb->local_df = 1;
+ skb->local_df = ip6_sk_local_df(sk);
*final_dst = fl6->daddr;
__skb_pull(skb, skb_network_header_len(skb));
diff --git a/net/ipv6/ipv6_sockglue.c b/net/ipv6/ipv6_sockglue.c
index 0a00f44..edb58af 100644
--- a/net/ipv6/ipv6_sockglue.c
+++ b/net/ipv6/ipv6_sockglue.c
@@ -722,7 +722,7 @@
case IPV6_MTU_DISCOVER:
if (optlen < sizeof(int))
goto e_inval;
- if (val < IPV6_PMTUDISC_DONT || val > IPV6_PMTUDISC_INTERFACE)
+ if (val < IPV6_PMTUDISC_DONT || val > IPV6_PMTUDISC_OMIT)
goto e_inval;
np->pmtudisc = val;
retv = 0;