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ipv6: Add sysctl for per namespace flow label reflection

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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: Jakub Sitnicki <jkbs@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Jakub Sitnicki 2017-08-23 09:55:41 +02:00 committed by David S. Miller
parent 39a7e58924
commit 22b6722bfa
4 changed files with 19 additions and 0 deletions
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9
Documentation/networking/ip-sysctl.txt
View File

@ -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

1
include/net/netns/ipv6.h
View File

@ -36,6 +36,7 @@ struct netns_sysctl_ipv6 {
int idgen_retries;
int idgen_delay;
int flowlabel_state_ranges;
int flowlabel_reflect;
};
struct netns_ipv6 {

1
net/ipv6/af_inet6.c
View File

@ -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

8
net/ipv6/sysctl_net_ipv6.c
View File

@ -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)