Commit 22b6722b authored by Jakub Sitnicki's avatar Jakub Sitnicki Committed by David S. Miller
Browse files

ipv6: Add sysctl for per namespace flow label reflection 

Reflecting IPv6 Flow Label at server nodes is useful in environments
that employ multipath routing to load balance the requests. As "IPv6
Flow Label Reflection" standard draft [1] points out - ICMPv6 PTB error
messages generated in response to a downstream packets from the server
can be routed by a load balancer back to the original server without
looking at transport headers, if the server applies the flow label
reflection. This enables the Path MTU Discovery past the ECMP router in
load-balance or anycast environments where each server node is reachable
by only one path.

Introduce a sysctl to enable flow label reflection per net namespace for
all newly created sockets. Same could be earlier achieved only per
socket by setting the IPV6_FL_F_REFLECT flag for the IPV6_FLOWLABEL_MGR
socket option.

[1] https://tools.ietf.org/html/draft-wang-6man-flow-label-reflection-01



Signed-off-by: default avatarJakub Sitnicki <jkbs@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 39a7e589

Documentation/networking/ip-sysctl.txt

+9 −0
Original line number Diff line number Diff line
@@ -1350,6 +1350,15 @@ flowlabel_state_ranges - BOOLEAN 
	FALSE: disabled

	Default: true



flowlabel_reflect - BOOLEAN

	Automatically reflect the flow label. Needed for Path MTU

	Discovery to work with Equal Cost Multipath Routing in anycast

	environments. See RFC 7690 and:

	https://tools.ietf.org/html/draft-wang-6man-flow-label-reflection-01

	TRUE: enabled

	FALSE: disabled

	Default: FALSE



anycast_src_echo_reply - BOOLEAN

	Controls the use of anycast addresses as source addresses for ICMPv6

	echo reply

include/net/netns/ipv6.h

+1 −0
Original line number Diff line number Diff line
@@ -36,6 +36,7 @@ struct netns_sysctl_ipv6 { 
	int idgen_retries;

	int idgen_delay;

	int flowlabel_state_ranges;

	int flowlabel_reflect;

};



struct netns_ipv6 {

net/ipv6/af_inet6.c

+1 −0
Original line number Diff line number Diff line
@@ -211,6 +211,7 @@ lookup_protocol: 
	np->mc_loop	= 1;

	np->pmtudisc	= IPV6_PMTUDISC_WANT;

	np->autoflowlabel = ip6_default_np_autolabel(net);

	np->repflow	= net->ipv6.sysctl.flowlabel_reflect;

	sk->sk_ipv6only	= net->ipv6.sysctl.bindv6only;



	/* Init the ipv4 part of the socket since we can have sockets

net/ipv6/sysctl_net_ipv6.c

+8 −0
Original line number Diff line number Diff line
@@ -90,6 +90,13 @@ static struct ctl_table ipv6_table_template[] = { 
		.mode		= 0644,

		.proc_handler	= proc_dointvec

	},

	{

		.procname	= "flowlabel_reflect",

		.data		= &init_net.ipv6.sysctl.flowlabel_reflect,

		.maxlen		= sizeof(int),

		.mode		= 0644,

		.proc_handler	= proc_dointvec,

	},

	{ }

};
@@ -149,6 +156,7 @@ static int __net_init ipv6_sysctl_net_init(struct net *net) 
	ipv6_table[6].data = &net->ipv6.sysctl.idgen_delay;

	ipv6_table[7].data = &net->ipv6.sysctl.flowlabel_state_ranges;

	ipv6_table[8].data = &net->ipv6.sysctl.ip_nonlocal_bind;

	ipv6_table[9].data = &net->ipv6.sysctl.flowlabel_reflect;



	ipv6_route_table = ipv6_route_sysctl_init(net);

	if (!ipv6_route_table)

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