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ipv4: L3 hash-based multipath 

Replaces the per-packet multipath with a hash-based multipath using
source and destination address.

Signed-off-by: Peter Nørlund <pch@ordbogen.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Peter Nørlund 2015-09-30 10:12:21 +02:00 committed by David S. Miller
parent 2472186f58
commit 0e884c78ee
3 changed files with 98 additions and 72 deletions
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14
include/net/ip_fib.h
View File

@ -79,7 +79,7 @@ struct fib_nh {
unsigned char nh_scope;
#ifdef CONFIG_IP_ROUTE_MULTIPATH
int nh_weight;
int nh_power;
atomic_t nh_upper_bound;
#endif
#ifdef CONFIG_IP_ROUTE_CLASSID
__u32 nh_tclassid;
@ -118,7 +118,7 @@ struct fib_info {
#define fib_advmss fib_metrics[RTAX_ADVMSS-1]
int fib_nhs;
#ifdef CONFIG_IP_ROUTE_MULTIPATH
int fib_power;
int fib_weight;
#endif
struct rcu_head rcu;
struct fib_nh fib_nh[0];
@ -320,7 +320,15 @@ int ip_fib_check_default(__be32 gw, struct net_device *dev);
int fib_sync_down_dev(struct net_device *dev, unsigned long event);
int fib_sync_down_addr(struct net *net, __be32 local);
int fib_sync_up(struct net_device *dev, unsigned int nh_flags);
void fib_select_multipath(struct fib_result *res);
extern u32 fib_multipath_secret __read_mostly;
static inline int fib_multipath_hash(__be32 saddr, __be32 daddr)
{
return jhash_2words(saddr, daddr, fib_multipath_secret) >> 1;
}
void fib_select_multipath(struct fib_result *res, int hash);
/* Exported by fib_trie.c */
void fib_trie_init(void);

140
net/ipv4/fib_semantics.c
View File

@ -57,8 +57,7 @@ static unsigned int fib_info_cnt;
static struct hlist_head fib_info_devhash[DEVINDEX_HASHSIZE];
#ifdef CONFIG_IP_ROUTE_MULTIPATH
static DEFINE_SPINLOCK(fib_multipath_lock);
u32 fib_multipath_secret __read_mostly;
#define for_nexthops(fi) { \
int nhsel; const struct fib_nh *nh; \
@ -532,7 +531,67 @@ errout:
return ret;
}
#endif
static void fib_rebalance(struct fib_info *fi)
{
int total;
int w;
struct in_device *in_dev;
if (fi->fib_nhs < 2)
return;
total = 0;
for_nexthops(fi) {
if (nh->nh_flags & RTNH_F_DEAD)
continue;
in_dev = __in_dev_get_rcu(nh->nh_dev);
if (in_dev &&
IN_DEV_IGNORE_ROUTES_WITH_LINKDOWN(in_dev) &&
nh->nh_flags & RTNH_F_LINKDOWN)
continue;
total += nh->nh_weight;
} endfor_nexthops(fi);
w = 0;
change_nexthops(fi) {
int upper_bound;
in_dev = __in_dev_get_rcu(nexthop_nh->nh_dev);
if (nexthop_nh->nh_flags & RTNH_F_DEAD) {
upper_bound = -1;
} else if (in_dev &&
IN_DEV_IGNORE_ROUTES_WITH_LINKDOWN(in_dev) &&
nexthop_nh->nh_flags & RTNH_F_LINKDOWN) {
upper_bound = -1;
} else {
w += nexthop_nh->nh_weight;
upper_bound = DIV_ROUND_CLOSEST(2147483648LL * w,
total) - 1;
}
atomic_set(&nexthop_nh->nh_upper_bound, upper_bound);
} endfor_nexthops(fi);
net_get_random_once(&fib_multipath_secret,
sizeof(fib_multipath_secret));
}
static inline void fib_add_weight(struct fib_info *fi,
const struct fib_nh *nh)
{
fi->fib_weight += nh->nh_weight;
}
#else /* CONFIG_IP_ROUTE_MULTIPATH */
#define fib_rebalance(fi) do { } while (0)
#define fib_add_weight(fi, nh) do { } while (0)
#endif /* CONFIG_IP_ROUTE_MULTIPATH */
static int fib_encap_match(struct net *net, u16 encap_type,
struct nlattr *encap,
@ -1094,8 +1153,11 @@ struct fib_info *fib_create_info(struct fib_config *cfg)
change_nexthops(fi) {
fib_info_update_nh_saddr(net, nexthop_nh);
fib_add_weight(fi, nexthop_nh);
} endfor_nexthops(fi)
fib_rebalance(fi);
link_it:
ofi = fib_find_info(fi);
if (ofi) {
@ -1317,12 +1379,6 @@ int fib_sync_down_dev(struct net_device *dev, unsigned long event)
nexthop_nh->nh_flags |= RTNH_F_LINKDOWN;
break;
}
#ifdef CONFIG_IP_ROUTE_MULTIPATH
spin_lock_bh(&fib_multipath_lock);
fi->fib_power -= nexthop_nh->nh_power;
nexthop_nh->nh_power = 0;
spin_unlock_bh(&fib_multipath_lock);
#endif
dead++;
}
#ifdef CONFIG_IP_ROUTE_MULTIPATH
@ -1345,6 +1401,8 @@ int fib_sync_down_dev(struct net_device *dev, unsigned long event)
}
ret++;
}
fib_rebalance(fi);
}
return ret;
@ -1467,20 +1525,15 @@ int fib_sync_up(struct net_device *dev, unsigned int nh_flags)
!__in_dev_get_rtnl(dev))
continue;
alive++;
#ifdef CONFIG_IP_ROUTE_MULTIPATH
spin_lock_bh(&fib_multipath_lock);
nexthop_nh->nh_power = 0;
nexthop_nh->nh_flags &= ~nh_flags;
spin_unlock_bh(&fib_multipath_lock);
#else
nexthop_nh->nh_flags &= ~nh_flags;
#endif
} endfor_nexthops(fi)
if (alive > 0) {
fi->fib_flags &= ~nh_flags;
ret++;
}
fib_rebalance(fi);
}
return ret;
@ -1488,62 +1541,19 @@ int fib_sync_up(struct net_device *dev, unsigned int nh_flags)
#ifdef CONFIG_IP_ROUTE_MULTIPATH
/*
* The algorithm is suboptimal, but it provides really
* fair weighted route distribution.
*/
void fib_select_multipath(struct fib_result *res)
void fib_select_multipath(struct fib_result *res, int hash)
{
struct fib_info *fi = res->fi;
struct in_device *in_dev;
int w;
spin_lock_bh(&fib_multipath_lock);
if (fi->fib_power <= 0) {
int power = 0;
change_nexthops(fi) {
in_dev = __in_dev_get_rcu(nexthop_nh->nh_dev);
if (nexthop_nh->nh_flags & RTNH_F_DEAD)
continue;
if (in_dev &&
IN_DEV_IGNORE_ROUTES_WITH_LINKDOWN(in_dev) &&
nexthop_nh->nh_flags & RTNH_F_LINKDOWN)
continue;
power += nexthop_nh->nh_weight;
nexthop_nh->nh_power = nexthop_nh->nh_weight;
} endfor_nexthops(fi);
fi->fib_power = power;
if (power <= 0) {
spin_unlock_bh(&fib_multipath_lock);
/* Race condition: route has just become dead. */
res->nh_sel = 0;
return;
}
}
for_nexthops(fi) {
if (hash > atomic_read(&nh->nh_upper_bound))
continue;
/* w should be random number [0..fi->fib_power-1],
* it is pretty bad approximation.
*/
w = jiffies % fi->fib_power;
change_nexthops(fi) {
if (!(nexthop_nh->nh_flags & RTNH_F_DEAD) &&
nexthop_nh->nh_power) {
w -= nexthop_nh->nh_power;
if (w <= 0) {
nexthop_nh->nh_power--;
fi->fib_power--;
res->nh_sel = nhsel;
spin_unlock_bh(&fib_multipath_lock);
return;
}
}
res->nh_sel = nhsel;
return;
} endfor_nexthops(fi);
/* Race condition: route has just become dead. */
res->nh_sel = 0;
spin_unlock_bh(&fib_multipath_lock);
}
#endif

16
net/ipv4/route.c
View File

@ -1658,8 +1658,12 @@ static int ip_mkroute_input(struct sk_buff *skb,
__be32 daddr, __be32 saddr, u32 tos)
{
#ifdef CONFIG_IP_ROUTE_MULTIPATH
if (res->fi && res->fi->fib_nhs > 1)
fib_select_multipath(res);
if (res->fi && res->fi->fib_nhs > 1) {
int h;
h = fib_multipath_hash(saddr, daddr);
fib_select_multipath(res, h);
}
#endif
/* create a routing cache entry */
@ -2189,8 +2193,12 @@ struct rtable *__ip_route_output_key(struct net *net, struct flowi4 *fl4)
}
#ifdef CONFIG_IP_ROUTE_MULTIPATH
if (res.fi->fib_nhs > 1 && fl4->flowi4_oif == 0)
fib_select_multipath(&res);
if (res.fi->fib_nhs > 1 && fl4->flowi4_oif == 0) {
int h;
h = fib_multipath_hash(fl4->saddr, fl4->daddr);
fib_select_multipath(&res, h);
}
else
#endif
if (!res.prefixlen &&