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ipvs: improved SH fallback strategy 

Improve the SH fallback realserver selection strategy.

With sh and sh-fallback, if a realserver is down, this attempts to
distribute the traffic that would have gone to that server evenly
among the remaining servers.

Signed-off-by: Alexander Frolkin <avf@eldamar.org.uk>
Acked-by: Julian Anastasov <ja@ssi.bg>
Signed-off-by: Simon Horman <horms@verge.net.au>
This commit is contained in:
Alexander Frolkin 2013-09-27 11:06:23 +01:00 committed by Simon Horman
parent 9e4e948a3e
commit 1255ce5f10
1 changed files with 29 additions and 10 deletions
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39
net/netfilter/ipvs/ip_vs_sh.c
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@ -115,27 +115,46 @@ ip_vs_sh_get(struct ip_vs_service *svc, struct ip_vs_sh_state *s,
}
/* As ip_vs_sh_get, but with fallback if selected server is unavailable */
/* As ip_vs_sh_get, but with fallback if selected server is unavailable
*
* The fallback strategy loops around the table starting from a "random"
* point (in fact, it is chosen to be the original hash value to make the
* algorithm deterministic) to find a new server.
*/
static inline struct ip_vs_dest *
ip_vs_sh_get_fallback(struct ip_vs_service *svc, struct ip_vs_sh_state *s,
const union nf_inet_addr *addr, __be16 port)
{
unsigned int offset;
unsigned int hash;
unsigned int offset, roffset;
unsigned int hash, ihash;
struct ip_vs_dest *dest;
/* first try the dest it's supposed to go to */
ihash = ip_vs_sh_hashkey(svc->af, addr, port, 0);
dest = rcu_dereference(s->buckets[ihash].dest);
if (!dest)
return NULL;
if (!is_unavailable(dest))
return dest;
IP_VS_DBG_BUF(6, "SH: selected unavailable server %s:%d, reselecting",
IP_VS_DBG_ADDR(svc->af, &dest->addr), ntohs(dest->port));
/* if the original dest is unavailable, loop around the table
* starting from ihash to find a new dest
*/
for (offset = 0; offset < IP_VS_SH_TAB_SIZE; offset++) {
hash = ip_vs_sh_hashkey(svc->af, addr, port, offset);
roffset = (offset + ihash) % IP_VS_SH_TAB_SIZE;
hash = ip_vs_sh_hashkey(svc->af, addr, port, roffset);
dest = rcu_dereference(s->buckets[hash].dest);
if (!dest)
break;
if (is_unavailable(dest))
IP_VS_DBG_BUF(6, "SH: selected unavailable server "
"%s:%d (offset %d)",
IP_VS_DBG_ADDR(svc->af, &dest->addr),
ntohs(dest->port), offset);
else
if (!is_unavailable(dest))
return dest;
IP_VS_DBG_BUF(6, "SH: selected unavailable "
"server %s:%d (offset %d), reselecting",
IP_VS_DBG_ADDR(svc->af, &dest->addr),
ntohs(dest->port), roffset);
}
return NULL;