ipv6: add IPV6_RECVFRAGSIZE cmsg
When reading a datagram or raw packet that arrived fragmented, expose
the maximum fragment size if recorded to allow applications to
estimate receive path MTU.
At this point, the field is only recorded when ipv6 connection
tracking is enabled. A follow-up patch will record this field also
in the ipv6 input path.
Tested using the test for IP_RECVFRAGSIZE plus
ip netns exec to ip addr add dev veth1 fc07::1/64
ip netns exec from ip addr add dev veth0 fc07::2/64
ip netns exec to ./recv_cmsg_recvfragsize -6 -u -p 6000 &
ip netns exec from nc -q 1 -u fc07::1 6000 < payload
Both with and without enabling connection tracking
ip6tables -A INPUT -m state --state NEW -p udp -j LOG
Signed-off-by: Willem de Bruijn <willemb@google.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/ipv6.h b/include/linux/ipv6.h
index ca1ad9e..1afb6e8 100644
--- a/include/linux/ipv6.h
+++ b/include/linux/ipv6.h
@@ -229,8 +229,9 @@
rxflow:1,
rxtclass:1,
rxpmtu:1,
- rxorigdstaddr:1;
- /* 2 bits hole */
+ rxorigdstaddr:1,
+ recvfragsize:1;
+ /* 1 bits hole */
} bits;
__u16 all;
} rxopt;