ipv6: add support of equal cost multipath (ECMP)

Each nexthop is added like a single route in the routing table. All routes
that have the same metric/weight and destination but not the same gateway
are considering as ECMP routes. They are linked together, through a list called
rt6i_siblings.

ECMP routes can be added in one shot, with RTA_MULTIPATH attribute or one after
the other (in both case, the flag NLM_F_EXCL should not be set).

The patch is based on a previous work from
Luc Saillard <luc.saillard@6wind.com>.

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Nicolas Dichtel 2012-10-22 03:42:09 +00:00 committed by David S. Miller
parent d94ce9b283
commit 51ebd31815
3 changed files with 200 additions and 3 deletions

View File

@ -47,6 +47,8 @@ struct fib6_config {
unsigned long fc_expires;
struct nlattr *fc_mx;
int fc_mx_len;
int fc_mp_len;
struct nlattr *fc_mp;
struct nl_info fc_nlinfo;
};
@ -99,6 +101,14 @@ struct rt6_info {
struct in6_addr rt6i_gateway;
/* Multipath routes:
* siblings is a list of rt6_info that have the the same metric/weight,
* destination, but not the same gateway. nsiblings is just a cache
* to speed up lookup.
*/
struct list_head rt6i_siblings;
unsigned int rt6i_nsiblings;
atomic_t rt6i_ref;
/* These are in a separate cache line. */

View File

@ -672,6 +672,8 @@ static int fib6_add_rt2node(struct fib6_node *fn, struct rt6_info *rt,
iter->rt6i_idev == rt->rt6i_idev &&
ipv6_addr_equal(&iter->rt6i_gateway,
&rt->rt6i_gateway)) {
if (rt->rt6i_nsiblings)
rt->rt6i_nsiblings = 0;
if (!(iter->rt6i_flags & RTF_EXPIRES))
return -EEXIST;
if (!(rt->rt6i_flags & RTF_EXPIRES))
@ -680,6 +682,21 @@ static int fib6_add_rt2node(struct fib6_node *fn, struct rt6_info *rt,
rt6_set_expires(iter, rt->dst.expires);
return -EEXIST;
}
/* If we have the same destination and the same metric,
* but not the same gateway, then the route we try to
* add is sibling to this route, increment our counter
* of siblings, and later we will add our route to the
* list.
* Only static routes (which don't have flag
* RTF_EXPIRES) are used for ECMPv6.
*
* To avoid long list, we only had siblings if the
* route have a gateway.
*/
if (rt->rt6i_flags & RTF_GATEWAY &&
!(rt->rt6i_flags & RTF_EXPIRES) &&
!(iter->rt6i_flags & RTF_EXPIRES))
rt->rt6i_nsiblings++;
}
if (iter->rt6i_metric > rt->rt6i_metric)
@ -692,6 +709,35 @@ static int fib6_add_rt2node(struct fib6_node *fn, struct rt6_info *rt,
if (ins == &fn->leaf)
fn->rr_ptr = NULL;
/* Link this route to others same route. */
if (rt->rt6i_nsiblings) {
unsigned int rt6i_nsiblings;
struct rt6_info *sibling, *temp_sibling;
/* Find the first route that have the same metric */
sibling = fn->leaf;
while (sibling) {
if (sibling->rt6i_metric == rt->rt6i_metric) {
list_add_tail(&rt->rt6i_siblings,
&sibling->rt6i_siblings);
break;
}
sibling = sibling->dst.rt6_next;
}
/* For each sibling in the list, increment the counter of
* siblings. BUG() if counters does not match, list of siblings
* is broken!
*/
rt6i_nsiblings = 0;
list_for_each_entry_safe(sibling, temp_sibling,
&rt->rt6i_siblings, rt6i_siblings) {
sibling->rt6i_nsiblings++;
BUG_ON(sibling->rt6i_nsiblings != rt->rt6i_nsiblings);
rt6i_nsiblings++;
}
BUG_ON(rt6i_nsiblings != rt->rt6i_nsiblings);
}
/*
* insert node
*/
@ -1193,6 +1239,17 @@ static void fib6_del_route(struct fib6_node *fn, struct rt6_info **rtp,
if (fn->rr_ptr == rt)
fn->rr_ptr = NULL;
/* Remove this entry from other siblings */
if (rt->rt6i_nsiblings) {
struct rt6_info *sibling, *next_sibling;
list_for_each_entry_safe(sibling, next_sibling,
&rt->rt6i_siblings, rt6i_siblings)
sibling->rt6i_nsiblings--;
rt->rt6i_nsiblings = 0;
list_del_init(&rt->rt6i_siblings);
}
/* Adjust walkers */
read_lock(&fib6_walker_lock);
FOR_WALKERS(w) {

View File

@ -57,6 +57,7 @@
#include <net/xfrm.h>
#include <net/netevent.h>
#include <net/netlink.h>
#include <net/nexthop.h>
#include <asm/uaccess.h>
@ -289,6 +290,8 @@ static inline struct rt6_info *ip6_dst_alloc(struct net *net,
memset(dst + 1, 0, sizeof(*rt) - sizeof(*dst));
rt6_init_peer(rt, table ? &table->tb6_peers : net->ipv6.peers);
rt->rt6i_genid = rt_genid(net);
INIT_LIST_HEAD(&rt->rt6i_siblings);
rt->rt6i_nsiblings = 0;
}
return rt;
}
@ -385,6 +388,69 @@ static bool rt6_need_strict(const struct in6_addr *daddr)
(IPV6_ADDR_MULTICAST | IPV6_ADDR_LINKLOCAL | IPV6_ADDR_LOOPBACK);
}
/* Multipath route selection:
* Hash based function using packet header and flowlabel.
* Adapted from fib_info_hashfn()
*/
static int rt6_info_hash_nhsfn(unsigned int candidate_count,
const struct flowi6 *fl6)
{
unsigned int val = fl6->flowi6_proto;
val ^= fl6->daddr.s6_addr32[0];
val ^= fl6->daddr.s6_addr32[1];
val ^= fl6->daddr.s6_addr32[2];
val ^= fl6->daddr.s6_addr32[3];
val ^= fl6->saddr.s6_addr32[0];
val ^= fl6->saddr.s6_addr32[1];
val ^= fl6->saddr.s6_addr32[2];
val ^= fl6->saddr.s6_addr32[3];
/* Work only if this not encapsulated */
switch (fl6->flowi6_proto) {
case IPPROTO_UDP:
case IPPROTO_TCP:
case IPPROTO_SCTP:
val ^= fl6->fl6_sport;
val ^= fl6->fl6_dport;
break;
case IPPROTO_ICMPV6:
val ^= fl6->fl6_icmp_type;
val ^= fl6->fl6_icmp_code;
break;
}
/* RFC6438 recommands to use flowlabel */
val ^= fl6->flowlabel;
/* Perhaps, we need to tune, this function? */
val = val ^ (val >> 7) ^ (val >> 12);
return val % candidate_count;
}
static struct rt6_info *rt6_multipath_select(struct rt6_info *match,
struct flowi6 *fl6)
{
struct rt6_info *sibling, *next_sibling;
int route_choosen;
route_choosen = rt6_info_hash_nhsfn(match->rt6i_nsiblings + 1, fl6);
/* Don't change the route, if route_choosen == 0
* (siblings does not include ourself)
*/
if (route_choosen)
list_for_each_entry_safe(sibling, next_sibling,
&match->rt6i_siblings, rt6i_siblings) {
route_choosen--;
if (route_choosen == 0) {
match = sibling;
break;
}
}
return match;
}
/*
* Route lookup. Any table->tb6_lock is implied.
*/
@ -702,6 +768,8 @@ static struct rt6_info *ip6_pol_route_lookup(struct net *net,
restart:
rt = fn->leaf;
rt = rt6_device_match(net, rt, &fl6->saddr, fl6->flowi6_oif, flags);
if (rt->rt6i_nsiblings && fl6->flowi6_oif == 0)
rt = rt6_multipath_select(rt, fl6);
BACKTRACK(net, &fl6->saddr);
out:
dst_use(&rt->dst, jiffies);
@ -863,7 +931,8 @@ static struct rt6_info *ip6_pol_route(struct net *net, struct fib6_table *table,
restart:
rt = rt6_select(fn, oif, strict | reachable);
if (rt->rt6i_nsiblings && oif == 0)
rt = rt6_multipath_select(rt, fl6);
BACKTRACK(net, &fl6->saddr);
if (rt == net->ipv6.ip6_null_entry ||
rt->rt6i_flags & RTF_CACHE)
@ -2249,6 +2318,7 @@ static const struct nla_policy rtm_ipv6_policy[RTA_MAX+1] = {
[RTA_IIF] = { .type = NLA_U32 },
[RTA_PRIORITY] = { .type = NLA_U32 },
[RTA_METRICS] = { .type = NLA_NESTED },
[RTA_MULTIPATH] = { .len = sizeof(struct rtnexthop) },
};
static int rtm_to_fib6_config(struct sk_buff *skb, struct nlmsghdr *nlh,
@ -2326,11 +2396,65 @@ static int rtm_to_fib6_config(struct sk_buff *skb, struct nlmsghdr *nlh,
if (tb[RTA_TABLE])
cfg->fc_table = nla_get_u32(tb[RTA_TABLE]);
if (tb[RTA_MULTIPATH]) {
cfg->fc_mp = nla_data(tb[RTA_MULTIPATH]);
cfg->fc_mp_len = nla_len(tb[RTA_MULTIPATH]);
}
err = 0;
errout:
return err;
}
static int ip6_route_multipath(struct fib6_config *cfg, int add)
{
struct fib6_config r_cfg;
struct rtnexthop *rtnh;
int remaining;
int attrlen;
int err = 0, last_err = 0;
beginning:
rtnh = (struct rtnexthop *)cfg->fc_mp;
remaining = cfg->fc_mp_len;
/* Parse a Multipath Entry */
while (rtnh_ok(rtnh, remaining)) {
memcpy(&r_cfg, cfg, sizeof(*cfg));
if (rtnh->rtnh_ifindex)
r_cfg.fc_ifindex = rtnh->rtnh_ifindex;
attrlen = rtnh_attrlen(rtnh);
if (attrlen > 0) {
struct nlattr *nla, *attrs = rtnh_attrs(rtnh);
nla = nla_find(attrs, attrlen, RTA_GATEWAY);
if (nla) {
nla_memcpy(&r_cfg.fc_gateway, nla, 16);
r_cfg.fc_flags |= RTF_GATEWAY;
}
}
err = add ? ip6_route_add(&r_cfg) : ip6_route_del(&r_cfg);
if (err) {
last_err = err;
/* If we are trying to remove a route, do not stop the
* loop when ip6_route_del() fails (because next hop is
* already gone), we should try to remove all next hops.
*/
if (add) {
/* If add fails, we should try to delete all
* next hops that have been already added.
*/
add = 0;
goto beginning;
}
}
rtnh = rtnh_next(rtnh, &remaining);
}
return last_err;
}
static int inet6_rtm_delroute(struct sk_buff *skb, struct nlmsghdr* nlh, void *arg)
{
struct fib6_config cfg;
@ -2340,7 +2464,10 @@ static int inet6_rtm_delroute(struct sk_buff *skb, struct nlmsghdr* nlh, void *a
if (err < 0)
return err;
return ip6_route_del(&cfg);
if (cfg.fc_mp)
return ip6_route_multipath(&cfg, 0);
else
return ip6_route_del(&cfg);
}
static int inet6_rtm_newroute(struct sk_buff *skb, struct nlmsghdr* nlh, void *arg)
@ -2352,7 +2479,10 @@ static int inet6_rtm_newroute(struct sk_buff *skb, struct nlmsghdr* nlh, void *a
if (err < 0)
return err;
return ip6_route_add(&cfg);
if (cfg.fc_mp)
return ip6_route_multipath(&cfg, 1);
else
return ip6_route_add(&cfg);
}
static inline size_t rt6_nlmsg_size(void)