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[PATCH] ipvs: SH fallback and L4 hashing

To: Julian Anastasov <ja@xxxxxx>, lvs-devel@xxxxxxxxxxxxxxx
Subject: [PATCH] ipvs: SH fallback and L4 hashing
Cc: Wensong Zhang <wensong@xxxxxxxxxxxx>, Simon Horman <horms@xxxxxxxxxxxx>, netdev@xxxxxxxxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx
From: Alexander Frolkin <avf@xxxxxxxxxxxxxx>
Date: Wed, 19 Jun 2013 10:54:25 +0100
By default the SH scheduler rejects connections that are hashed onto a
realserver of weight 0.  This patch adds a flag to make SH choose a
different realserver in this case, instead of rejecting the connection.

The patch also adds a flag to make SH include the source port (TCP, UDP,
SCTP) in the hash as well as the source address.  This basically allows
for deterministic round-robin load balancing (i.e., where any director
in a cluster of directors with identical config will send the same
packet the same way).

The flags are service flags (IP_VS_SVC_F_SCHED*) so that these options
can be set per service.  They are set using a new option to ipvsadm.

Signed-off-by: Alexander Frolkin <avf@xxxxxxxxxxxxxx>
---
The patch is against the ipvs-next tree.

diff --git a/include/uapi/linux/ip_vs.h b/include/uapi/linux/ip_vs.h
index a245377..2945822 100644
--- a/include/uapi/linux/ip_vs.h
+++ b/include/uapi/linux/ip_vs.h
@@ -20,6 +20,12 @@
 #define IP_VS_SVC_F_PERSISTENT 0x0001          /* persistent port */
 #define IP_VS_SVC_F_HASHED     0x0002          /* hashed entry */
 #define IP_VS_SVC_F_ONEPACKET  0x0004          /* one-packet scheduling */
+#define IP_VS_SVC_F_SCHED1     0x0008          /* scheduler flag 1 */
+#define IP_VS_SVC_F_SCHED2     0x0010          /* scheduler flag 2 */
+#define IP_VS_SVC_F_SCHED3     0x0020          /* scheduler flag 3 */
+
+#define IP_VS_SVC_F_SCHED_SH_FALLBACK  IP_VS_SVC_F_SCHED1 /* SH fallback */
+#define IP_VS_SVC_F_SCHED_SH_PORT      IP_VS_SVC_F_SCHED2 /* SH use port */
 
 /*
  *      Destination Server Flags
diff --git a/net/netfilter/ipvs/ip_vs_sh.c b/net/netfilter/ipvs/ip_vs_sh.c
index e0130f8..b7e2c5a 100644
--- a/net/netfilter/ipvs/ip_vs_sh.c
+++ b/net/netfilter/ipvs/ip_vs_sh.c
@@ -48,6 +48,10 @@
 
 #include <net/ip_vs.h>
 
+#include <net/tcp.h>
+#include <linux/udp.h>
+#include <linux/sctp.h>
+
 
 /*
  *      IPVS SH bucket
@@ -71,10 +75,19 @@ struct ip_vs_sh_state {
        struct rcu_head                 rcu_head;
 };
 
+/* Helper function to determine if server is unavailable */
+static inline bool is_unavailable(struct ip_vs_dest *dest)
+{
+       return atomic_read(&dest->weight) <= 0 ||
+              dest->flags & IP_VS_DEST_F_OVERLOAD;
+}
+
 /*
  *     Returns hash value for IPVS SH entry
  */
-static inline unsigned int ip_vs_sh_hashkey(int af, const union nf_inet_addr 
*addr)
+static inline unsigned int
+ip_vs_sh_hashkey(int af, const union nf_inet_addr *addr,
+                __be16 port, unsigned int offset)
 {
        __be32 addr_fold = addr->ip;
 
@@ -83,7 +96,8 @@ static inline unsigned int ip_vs_sh_hashkey(int af, const 
union nf_inet_addr *ad
                addr_fold = addr->ip6[0]^addr->ip6[1]^
                            addr->ip6[2]^addr->ip6[3];
 #endif
-       return (ntohl(addr_fold)*2654435761UL) & IP_VS_SH_TAB_MASK;
+       return (offset + (ntohs(port) + ntohl(addr_fold))*2654435761UL) &
+               IP_VS_SH_TAB_MASK;
 }
 
 
@@ -91,12 +105,42 @@ static inline unsigned int ip_vs_sh_hashkey(int af, const 
union nf_inet_addr *ad
  *      Get ip_vs_dest associated with supplied parameters.
  */
 static inline struct ip_vs_dest *
-ip_vs_sh_get(int af, struct ip_vs_sh_state *s, const union nf_inet_addr *addr)
+ip_vs_sh_get(struct ip_vs_service *svc, struct ip_vs_sh_state *s,
+            const union nf_inet_addr *addr, __be16 port)
 {
-       return rcu_dereference(s->buckets[ip_vs_sh_hashkey(af, addr)].dest);
+       unsigned int hash = ip_vs_sh_hashkey(svc->af, addr, port, 0);
+       struct ip_vs_dest *dest = rcu_dereference(s->buckets[hash].dest);
+
+       return (!dest || is_unavailable(dest)) ? NULL : dest;
 }
 
 
+/* As ip_vs_sh_get, but with fallback if selected server is unavailable */
+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;
+       struct ip_vs_dest *dest;
+
+       for (offset = 0; offset < IP_VS_SH_TAB_SIZE; offset++) {
+               hash = ip_vs_sh_hashkey(svc->af, addr, port, offset);
+               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
+                       return dest;
+       }
+
+       return NULL;
+}
+
 /*
  *      Assign all the hash buckets of the specified table with the service.
  */
@@ -213,13 +257,33 @@ static int ip_vs_sh_dest_changed(struct ip_vs_service 
*svc,
 }
 
 
-/*
- *      If the dest flags is set with IP_VS_DEST_F_OVERLOAD,
- *      consider that the server is overloaded here.
- */
-static inline int is_overloaded(struct ip_vs_dest *dest)
+/* Helper function to get port number */
+static inline __be16
+ip_vs_sh_get_port(const struct sk_buff *skb, struct ip_vs_iphdr *iph)
 {
-       return dest->flags & IP_VS_DEST_F_OVERLOAD;
+       __be16 port;
+       struct tcphdr _tcph, *th;
+       struct udphdr _udph, *uh;
+       sctp_sctphdr_t _sctph, *sh;
+
+       switch (iph->protocol) {
+       case IPPROTO_TCP:
+               th = skb_header_pointer(skb, iph->len, sizeof(_tcph), &_tcph);
+               port = th->source;
+               break;
+       case IPPROTO_UDP:
+               uh = skb_header_pointer(skb, iph->len, sizeof(_udph), &_udph);
+               port = uh->source;
+               break;
+       case IPPROTO_SCTP:
+               sh = skb_header_pointer(skb, iph->len, sizeof(_sctph), &_sctph);
+               port = sh->source;
+               break;
+       default:
+               port = 0;
+       }
+
+       return port;
 }
 
 
@@ -232,15 +296,21 @@ ip_vs_sh_schedule(struct ip_vs_service *svc, const struct 
sk_buff *skb,
 {
        struct ip_vs_dest *dest;
        struct ip_vs_sh_state *s;
+       __be16 port = 0;
 
        IP_VS_DBG(6, "ip_vs_sh_schedule(): Scheduling...\n");
 
+       if (svc->flags & IP_VS_SVC_F_SCHED_SH_PORT)
+               port = ip_vs_sh_get_port(skb, iph);
+
        s = (struct ip_vs_sh_state *) svc->sched_data;
-       dest = ip_vs_sh_get(svc->af, s, &iph->saddr);
-       if (!dest
-           || !(dest->flags & IP_VS_DEST_F_AVAILABLE)
-           || atomic_read(&dest->weight) <= 0
-           || is_overloaded(dest)) {
+
+       if (svc->flags & IP_VS_SVC_F_SCHED_SH_FALLBACK)
+               dest = ip_vs_sh_get_fallback(svc, s, &iph->saddr, port);
+       else
+               dest = ip_vs_sh_get(svc, s, &iph->saddr, port);
+
+       if (!dest) {
                ip_vs_scheduler_err(svc, "no destination available");
                return NULL;
        }
--
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