Merge branch 'ipv6-auto-flow-labels'

Tom Herbert says:

====================
ipv6: Turn on auto IPv6 flow labels by default

BSD (MacOS) has already turned on flow labels by default and this does
not seem to be causing any problems in the Internet. Let's go ahead
and turn them on by default. We'll continue to monitor for any devices
start choking on them.

Flow labels are important since they are the desired solution for
network devices to perform ECMP and RSS (RFC6437 and RFC6438).
Traditionally, devices perform a 5-tuple hash on packets that
includes port numbers. For the most part, these devices can only
compute 5-tuple hashes for TCP and UDP. This severely limits our ability
to get good network load balancing for other protocols (IPIP, GRE,ESP,
etc.), and hence we are limited in using other protocols. Unfortunately,
this method is accepted as the de facto standard to the extent that
there are several proposals to encapsulate protocols in UDP _just_ for
the purposes for getting ECMP to work. With hosts generating flow labels
and devices taking them as input into ECMP (several already do), we can
start to fix this fundamental problem.

This patch set:
 - Changes IPV6_FLOWINFO sockopt to be opt-out of flow labels for
   connections rather than opt-in
 - Disable flow label state ranges sysctl by default
 - Enable auto flow labels sysctl by default

v2:
  - Added functions to create an skb->hash based on flowi4 and flowi6.
    These are called in output path when creating a packet
  - Call skb_get_hash_flowi6 in ip6_make_flowlabel
  - Implement the auto_flowlabels sysctl as a mode for auto flowlabels.
    There are four modes which correspond to flow labels being enabled
    and whether socket option can be used to opt in or opt out of
    using them
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 13 insertions, 7 deletions

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 00d26d919459..56db1efd7189 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -1215,14 +1215,20 @@ flowlabel_consistency - BOOLEAN
 	FALSE: disabled
 	Default: TRUE
 
-auto_flowlabels - BOOLEAN
-	Automatically generate flow labels based based on a flow hash
-	of the packet. This allows intermediate devices, such as routers,
-	to idenfify packet flows for mechanisms like Equal Cost Multipath
+auto_flowlabels - INTEGER
+	Automatically generate flow labels based on a flow hash of the
+	packet. This allows intermediate devices, such as routers, to
+	identify packet flows for mechanisms like Equal Cost Multipath
 	Routing (see RFC 6438).
-	TRUE: enabled
-	FALSE: disabled
-	Default: false
+	0: automatic flow labels are completely disabled
+	1: automatic flow labels are enabled by default, they can be
+	   disabled on a per socket basis using the IPV6_AUTOFLOWLABEL
+	   socket option
+	2: automatic flow labels are allowed, they may be enabled on a
+	   per socket basis using the IPV6_AUTOFLOWLABEL socket option
+	3: automatic flow labels are enabled and enforced, they cannot
+	   be disabled by the socket option
+	Default: 1
 
 flowlabel_state_ranges - BOOLEAN
 	Split the flow label number space into two ranges. 0-0x7FFFF is