ipv6: Flow label state ranges

This patch divides the IPv6 flow label space into two ranges:
0-7ffff is reserved for flow label manager, 80000-fffff will be
used for creating auto flow labels (per RFC6438). This only affects how
labels are set on transmit, it does not affect receive. This range split
can be disbaled by systcl.

Background:

IPv6 flow labels have been an unmitigated disappointment thus far
in the lifetime of IPv6. Support in HW devices to use them for ECMP
is lacking, and OSes don't turn them on by default. If we had these
we could get much better hashing in IPv6 networks without resorting
to DPI, possibly eliminating some of the motivations to to define new
encaps in UDP just for getting ECMP.

Unfortunately, the initial specfications of IPv6 did not clarify
how they are to be used. There has always been a vague concept that
these can be used for ECMP, flow hashing, etc. and we do now have a
good standard how to this in RFC6438. The problem is that flow labels
can be either stateful or stateless (as in RFC6438), and we are
presented with the possibility that a stateless label may collide
with a stateful one.  Attempts to split the flow label space were
rejected in IETF. When we added support in Linux for RFC6438, we
could not turn on flow labels by default due to this conflict.

This patch splits the flow label space and should give us
a path to enabling auto flow labels by default for all IPv6 packets.
This is an API change so we need to consider compatibility with
existing deployment. The stateful range is chosen to be the lower
values in hopes that most uses would have chosen small numbers.

Once we resolve the stateless/stateful issue, we can proceed to
look at enabling RFC6438 flow labels by default (starting with
scaled testing).

Signed-off-by: Tom Herbert <tom@herbertland.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt
index 071fb18dc57c868e99367f9d3872bc0e91401414..5095c63e50eda6783f847ddf36f2a47cd8d2cdd2 100644 (file)
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -1213,6 +1213,14 @@ auto_flowlabels - BOOLEAN
        FALSE: disabled
        Default: false
 
+flowlabel_state_ranges - BOOLEAN
+       Split the flow label number space into two ranges. 0-0x7FFFF is
+       reserved for the IPv6 flow manager facility, 0x80000-0xFFFFF
+       is reserved for stateless flow labels as described in RFC6437.
+       TRUE: enabled
+       FALSE: disabled
+       Default: true
+
 anycast_src_echo_reply - BOOLEAN
        Controls the use of anycast addresses as source addresses for ICMPv6
        echo reply

diff --git a/include/net/ipv6.h b/include/net/ipv6.h
index eec8ad3c98432af6250a7a0c659d443da90ce45a..53d25ef1699a49ebd29a49eb17ded222dc6c8f5c 100644 (file)
--- a/include/net/ipv6.h
+++ b/include/net/ipv6.h
@@ -239,8 +239,10 @@ struct ip6_flowlabel {
        struct net              *fl_net;
 };
 
-#define IPV6_FLOWINFO_MASK     cpu_to_be32(0x0FFFFFFF)
-#define IPV6_FLOWLABEL_MASK    cpu_to_be32(0x000FFFFF)
+#define IPV6_FLOWINFO_MASK             cpu_to_be32(0x0FFFFFFF)
+#define IPV6_FLOWLABEL_MASK            cpu_to_be32(0x000FFFFF)
+#define IPV6_FLOWLABEL_STATELESS_FLAG  cpu_to_be32(0x00080000)
+
 #define IPV6_TCLASS_MASK (IPV6_FLOWINFO_MASK & ~IPV6_FLOWLABEL_MASK)
 #define IPV6_TCLASS_SHIFT      20
 
@@ -719,6 +721,9 @@ static inline __be32 ip6_make_flowlabel(struct net *net, struct sk_buff *skb,
                hash ^= hash >> 12;
 
                flowlabel = (__force __be32)hash & IPV6_FLOWLABEL_MASK;
+
+               if (net->ipv6.sysctl.flowlabel_state_ranges)
+                       flowlabel |= IPV6_FLOWLABEL_STATELESS_FLAG;
        }
 
        return flowlabel;

diff --git a/include/net/netns/ipv6.h b/include/net/netns/ipv6.h
index d2527bf81142e28508e4d415353d8a4ecf8c609e..8d93544a2d2b5f21c7ed8b8137394df0758dbef3 100644 (file)
--- a/include/net/netns/ipv6.h
+++ b/include/net/netns/ipv6.h
@@ -34,6 +34,7 @@ struct netns_sysctl_ipv6 {
        int fwmark_reflect;
        int idgen_retries;
        int idgen_delay;
+       int flowlabel_state_ranges;
 };
 
 struct netns_ipv6 {

diff --git a/net/ipv6/af_inet6.c b/net/ipv6/af_inet6.c
index eef63b394c5ab9ae2e2b5c060a9960f62d671a3a..4632afa57e05c7f1d01b2f0c2991ae8b25548c86 100644 (file)
--- a/net/ipv6/af_inet6.c
+++ b/net/ipv6/af_inet6.c
@@ -768,6 +768,7 @@ static int __net_init inet6_net_init(struct net *net)
        net->ipv6.sysctl.auto_flowlabels = 0;
        net->ipv6.sysctl.idgen_retries = 3;
        net->ipv6.sysctl.idgen_delay = 1 * HZ;
+       net->ipv6.sysctl.flowlabel_state_ranges = 1;
        atomic_set(&net->ipv6.fib6_sernum, 1);
 
        err = ipv6_init_mibs(net);

diff --git a/net/ipv6/ip6_flowlabel.c b/net/ipv6/ip6_flowlabel.c
index d491125011c4d1c47fd92180efb1cf2e22a85e22..1f9ebe3cbb4ac042edd0b05754d1fc03cdfe73cd 100644 (file)
--- a/net/ipv6/ip6_flowlabel.c
+++ b/net/ipv6/ip6_flowlabel.c
@@ -595,6 +595,10 @@ int ipv6_flowlabel_opt(struct sock *sk, char __user *optval, int optlen)
                if (freq.flr_label & ~IPV6_FLOWLABEL_MASK)
                        return -EINVAL;
 
+               if (net->ipv6.sysctl.flowlabel_state_ranges &&
+                   (freq.flr_label & IPV6_FLOWLABEL_STATELESS_FLAG))
+                       return -ERANGE;
+
                fl = fl_create(net, sk, &freq, optval, optlen, &err);
                if (!fl)
                        return err;

diff --git a/net/ipv6/sysctl_net_ipv6.c b/net/ipv6/sysctl_net_ipv6.c
index abcc79f649b34750ee5f25051d5197dd64d91856..4e705add4f187c69b1b11202d47808308e87cf80 100644 (file)
--- a/net/ipv6/sysctl_net_ipv6.c
+++ b/net/ipv6/sysctl_net_ipv6.c
@@ -68,6 +68,13 @@ static struct ctl_table ipv6_table_template[] = {
                .mode           = 0644,
                .proc_handler   = proc_dointvec_jiffies,
        },
+       {
+               .procname       = "flowlabel_state_ranges",
+               .data           = &init_net.ipv6.sysctl.flowlabel_state_ranges,
+               .maxlen         = sizeof(int),
+               .mode           = 0644,
+               .proc_handler   = proc_dointvec
+       },
        { }
 };
 
@@ -109,6 +116,7 @@ static int __net_init ipv6_sysctl_net_init(struct net *net)
        ipv6_table[4].data = &net->ipv6.sysctl.fwmark_reflect;
        ipv6_table[5].data = &net->ipv6.sysctl.idgen_retries;
        ipv6_table[6].data = &net->ipv6.sysctl.idgen_delay;
+       ipv6_table[7].data = &net->ipv6.sysctl.flowlabel_state_ranges;
 
        ipv6_route_table = ipv6_route_sysctl_init(net);
        if (!ipv6_route_table)