| Message ID | 1430346801-2297436-1-git-send-email-tom@herbertland.com |
|---|---|
| State | Accepted, archived |
| Delegated to: | David Miller |
| Headers | show |
From: Tom Herbert <tom@herbertland.com> Date: Wed, 29 Apr 2015 15:33:21 -0700 > 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> Ok, applied, let's see what happens. Thanks Tom. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/Documentation/networking/ip-sysctl.txt b/Documentation/networking/ip-sysctl.txt index 071fb18..5095c63 100644 --- 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 eec8ad3..53d25ef 100644 --- 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 d2527bf..8d93544 100644 --- 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 eef63b3..4632afa 100644 --- 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 d491125..1f9ebe3 100644 --- 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 abcc79f..4e705ad 100644 --- 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)
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> --- Documentation/networking/ip-sysctl.txt | 8 ++++++++ include/net/ipv6.h | 9 +++++++-- include/net/netns/ipv6.h | 1 + net/ipv6/af_inet6.c | 1 + net/ipv6/ip6_flowlabel.c | 4 ++++ net/ipv6/sysctl_net_ipv6.c | 8 ++++++++ 6 files changed, 29 insertions(+), 2 deletions(-)