// SPDX-License-Identifier: GPL-2.0
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/* IPVS: Maglev Hashing scheduling module
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*
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* Authors: Inju Song <inju.song@navercorp.com>
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*
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*/
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/* The mh algorithm is to assign a preference list of all the lookup
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* table positions to each destination and populate the table with
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* the most-preferred position of destinations. Then it is to select
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* destination with the hash key of source IP address through looking
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* up a the lookup table.
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*
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* The algorithm is detailed in:
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* [3.4 Consistent Hasing]
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https://www.usenix.org/system/files/conference/nsdi16/nsdi16-paper-eisenbud.pdf
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*
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*/
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#define KMSG_COMPONENT "IPVS"
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#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt
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#include <linux/ip.h>
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#include <linux/slab.h>
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#include <linux/module.h>
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#include <linux/kernel.h>
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#include <linux/skbuff.h>
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#include <net/ip_vs.h>
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#include <linux/siphash.h>
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#include <linux/bitops.h>
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#include <linux/gcd.h>
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#define IP_VS_SVC_F_SCHED_MH_FALLBACK IP_VS_SVC_F_SCHED1 /* MH fallback */
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#define IP_VS_SVC_F_SCHED_MH_PORT IP_VS_SVC_F_SCHED2 /* MH use port */
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struct ip_vs_mh_lookup {
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struct ip_vs_dest __rcu *dest; /* real server (cache) */
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};
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struct ip_vs_mh_dest_setup {
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unsigned int offset; /* starting offset */
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unsigned int skip; /* skip */
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unsigned int perm; /* next_offset */
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int turns; /* weight / gcd() and rshift */
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};
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/* Available prime numbers for MH table */
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static int primes[] = {251, 509, 1021, 2039, 4093,
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8191, 16381, 32749, 65521, 131071};
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/* For IPVS MH entry hash table */
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#ifndef CONFIG_IP_VS_MH_TAB_INDEX
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#define CONFIG_IP_VS_MH_TAB_INDEX 12
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#endif
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#define IP_VS_MH_TAB_BITS (CONFIG_IP_VS_MH_TAB_INDEX / 2)
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#define IP_VS_MH_TAB_INDEX (CONFIG_IP_VS_MH_TAB_INDEX - 8)
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#define IP_VS_MH_TAB_SIZE primes[IP_VS_MH_TAB_INDEX]
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struct ip_vs_mh_state {
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struct rcu_head rcu_head;
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struct ip_vs_mh_lookup *lookup;
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struct ip_vs_mh_dest_setup *dest_setup;
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hsiphash_key_t hash1, hash2;
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int gcd;
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int rshift;
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};
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static inline void generate_hash_secret(hsiphash_key_t *hash1,
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hsiphash_key_t *hash2)
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{
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hash1->key[0] = 2654435761UL;
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hash1->key[1] = 2654435761UL;
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hash2->key[0] = 2654446892UL;
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hash2->key[1] = 2654446892UL;
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}
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/* Helper function to determine if server is unavailable */
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static inline bool is_unavailable(struct ip_vs_dest *dest)
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{
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return atomic_read(&dest->weight) <= 0 ||
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dest->flags & IP_VS_DEST_F_OVERLOAD;
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}
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/* Returns hash value for IPVS MH entry */
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static inline unsigned int
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ip_vs_mh_hashkey(int af, const union nf_inet_addr *addr,
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__be16 port, hsiphash_key_t *key, unsigned int offset)
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{
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unsigned int v;
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__be32 addr_fold = addr->ip;
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#ifdef CONFIG_IP_VS_IPV6
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if (af == AF_INET6)
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addr_fold = addr->ip6[0] ^ addr->ip6[1] ^
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addr->ip6[2] ^ addr->ip6[3];
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#endif
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v = (offset + ntohs(port) + ntohl(addr_fold));
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return hsiphash(&v, sizeof(v), key);
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}
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/* Reset all the hash buckets of the specified table. */
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static void ip_vs_mh_reset(struct ip_vs_mh_state *s)
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{
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int i;
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struct ip_vs_mh_lookup *l;
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struct ip_vs_dest *dest;
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l = &s->lookup[0];
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for (i = 0; i < IP_VS_MH_TAB_SIZE; i++) {
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dest = rcu_dereference_protected(l->dest, 1);
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if (dest) {
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ip_vs_dest_put(dest);
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RCU_INIT_POINTER(l->dest, NULL);
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}
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l++;
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}
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}
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static int ip_vs_mh_permutate(struct ip_vs_mh_state *s,
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struct ip_vs_service *svc)
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{
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struct list_head *p;
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struct ip_vs_mh_dest_setup *ds;
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struct ip_vs_dest *dest;
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int lw;
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/* If gcd is smaller then 1, number of dests or
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* all last_weight of dests are zero. So, skip
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* permutation for the dests.
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*/
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if (s->gcd < 1)
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return 0;
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/* Set dest_setup for the dests permutation */
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p = &svc->destinations;
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ds = &s->dest_setup[0];
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while ((p = p->next) != &svc->destinations) {
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dest = list_entry(p, struct ip_vs_dest, n_list);
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ds->offset = ip_vs_mh_hashkey(svc->af, &dest->addr,
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dest->port, &s->hash1, 0) %
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IP_VS_MH_TAB_SIZE;
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ds->skip = ip_vs_mh_hashkey(svc->af, &dest->addr,
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dest->port, &s->hash2, 0) %
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(IP_VS_MH_TAB_SIZE - 1) + 1;
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ds->perm = ds->offset;
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lw = atomic_read(&dest->last_weight);
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ds->turns = ((lw / s->gcd) >> s->rshift) ? : (lw != 0);
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ds++;
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}
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return 0;
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}
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static int ip_vs_mh_populate(struct ip_vs_mh_state *s,
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struct ip_vs_service *svc)
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{
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int n, c, dt_count;
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unsigned long *table;
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struct list_head *p;
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struct ip_vs_mh_dest_setup *ds;
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struct ip_vs_dest *dest, *new_dest;
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/* If gcd is smaller then 1, number of dests or
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* all last_weight of dests are zero. So, skip
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* the population for the dests and reset lookup table.
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*/
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if (s->gcd < 1) {
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ip_vs_mh_reset(s);
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return 0;
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}
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table = kcalloc(BITS_TO_LONGS(IP_VS_MH_TAB_SIZE),
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sizeof(unsigned long), GFP_KERNEL);
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if (!table)
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return -ENOMEM;
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p = &svc->destinations;
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n = 0;
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dt_count = 0;
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while (n < IP_VS_MH_TAB_SIZE) {
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if (p == &svc->destinations)
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p = p->next;
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ds = &s->dest_setup[0];
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while (p != &svc->destinations) {
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/* Ignore added server with zero weight */
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if (ds->turns < 1) {
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p = p->next;
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ds++;
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continue;
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}
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c = ds->perm;
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while (test_bit(c, table)) {
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/* Add skip, mod IP_VS_MH_TAB_SIZE */
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ds->perm += ds->skip;
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if (ds->perm >= IP_VS_MH_TAB_SIZE)
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ds->perm -= IP_VS_MH_TAB_SIZE;
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c = ds->perm;
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}
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__set_bit(c, table);
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dest = rcu_dereference_protected(s->lookup[c].dest, 1);
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new_dest = list_entry(p, struct ip_vs_dest, n_list);
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if (dest != new_dest) {
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if (dest)
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ip_vs_dest_put(dest);
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ip_vs_dest_hold(new_dest);
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RCU_INIT_POINTER(s->lookup[c].dest, new_dest);
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}
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if (++n == IP_VS_MH_TAB_SIZE)
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goto out;
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if (++dt_count >= ds->turns) {
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dt_count = 0;
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p = p->next;
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ds++;
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}
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}
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}
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out:
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kfree(table);
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return 0;
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}
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/* Get ip_vs_dest associated with supplied parameters. */
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static inline struct ip_vs_dest *
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ip_vs_mh_get(struct ip_vs_service *svc, struct ip_vs_mh_state *s,
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const union nf_inet_addr *addr, __be16 port)
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{
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unsigned int hash = ip_vs_mh_hashkey(svc->af, addr, port, &s->hash1, 0)
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% IP_VS_MH_TAB_SIZE;
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struct ip_vs_dest *dest = rcu_dereference(s->lookup[hash].dest);
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return (!dest || is_unavailable(dest)) ? NULL : dest;
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}
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/* As ip_vs_mh_get, but with fallback if selected server is unavailable */
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static inline struct ip_vs_dest *
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ip_vs_mh_get_fallback(struct ip_vs_service *svc, struct ip_vs_mh_state *s,
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const union nf_inet_addr *addr, __be16 port)
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{
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unsigned int offset, roffset;
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unsigned int hash, ihash;
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struct ip_vs_dest *dest;
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/* First try the dest it's supposed to go to */
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ihash = ip_vs_mh_hashkey(svc->af, addr, port,
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&s->hash1, 0) % IP_VS_MH_TAB_SIZE;
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dest = rcu_dereference(s->lookup[ihash].dest);
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if (!dest)
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return NULL;
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if (!is_unavailable(dest))
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return dest;
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IP_VS_DBG_BUF(6, "MH: selected unavailable server %s:%u, reselecting",
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IP_VS_DBG_ADDR(dest->af, &dest->addr), ntohs(dest->port));
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/* If the original dest is unavailable, loop around the table
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* starting from ihash to find a new dest
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*/
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for (offset = 0; offset < IP_VS_MH_TAB_SIZE; offset++) {
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roffset = (offset + ihash) % IP_VS_MH_TAB_SIZE;
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hash = ip_vs_mh_hashkey(svc->af, addr, port, &s->hash1,
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roffset) % IP_VS_MH_TAB_SIZE;
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dest = rcu_dereference(s->lookup[hash].dest);
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if (!dest)
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break;
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if (!is_unavailable(dest))
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return dest;
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IP_VS_DBG_BUF(6,
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"MH: selected unavailable server %s:%u (offset %u), reselecting",
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IP_VS_DBG_ADDR(dest->af, &dest->addr),
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ntohs(dest->port), roffset);
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}
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return NULL;
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}
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/* Assign all the hash buckets of the specified table with the service. */
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static int ip_vs_mh_reassign(struct ip_vs_mh_state *s,
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struct ip_vs_service *svc)
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{
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int ret;
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if (svc->num_dests > IP_VS_MH_TAB_SIZE)
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return -EINVAL;
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if (svc->num_dests >= 1) {
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s->dest_setup = kcalloc(svc->num_dests,
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sizeof(struct ip_vs_mh_dest_setup),
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GFP_KERNEL);
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if (!s->dest_setup)
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return -ENOMEM;
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}
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ip_vs_mh_permutate(s, svc);
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ret = ip_vs_mh_populate(s, svc);
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if (ret < 0)
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goto out;
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IP_VS_DBG_BUF(6, "MH: reassign lookup table of %s:%u\n",
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IP_VS_DBG_ADDR(svc->af, &svc->addr),
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ntohs(svc->port));
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out:
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if (svc->num_dests >= 1) {
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kfree(s->dest_setup);
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s->dest_setup = NULL;
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}
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return ret;
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}
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static int ip_vs_mh_gcd_weight(struct ip_vs_service *svc)
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{
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struct ip_vs_dest *dest;
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int weight;
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int g = 0;
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list_for_each_entry(dest, &svc->destinations, n_list) {
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weight = atomic_read(&dest->last_weight);
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if (weight > 0) {
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if (g > 0)
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g = gcd(weight, g);
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else
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g = weight;
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}
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}
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return g;
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}
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/* To avoid assigning huge weight for the MH table,
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* calculate shift value with gcd.
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*/
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static int ip_vs_mh_shift_weight(struct ip_vs_service *svc, int gcd)
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{
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struct ip_vs_dest *dest;
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int new_weight, weight = 0;
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int mw, shift;
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/* If gcd is smaller then 1, number of dests or
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* all last_weight of dests are zero. So, return
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* shift value as zero.
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*/
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if (gcd < 1)
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return 0;
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list_for_each_entry(dest, &svc->destinations, n_list) {
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new_weight = atomic_read(&dest->last_weight);
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if (new_weight > weight)
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weight = new_weight;
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}
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/* Because gcd is greater than zero,
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* the maximum weight and gcd are always greater than zero
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*/
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mw = weight / gcd;
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/* shift = occupied bits of weight/gcd - MH highest bits */
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shift = fls(mw) - IP_VS_MH_TAB_BITS;
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return (shift >= 0) ? shift : 0;
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}
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static void ip_vs_mh_state_free(struct rcu_head *head)
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{
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struct ip_vs_mh_state *s;
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s = container_of(head, struct ip_vs_mh_state, rcu_head);
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kfree(s->lookup);
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kfree(s);
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}
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static int ip_vs_mh_init_svc(struct ip_vs_service *svc)
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{
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int ret;
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struct ip_vs_mh_state *s;
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/* Allocate the MH table for this service */
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s = kzalloc(sizeof(*s), GFP_KERNEL);
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if (!s)
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return -ENOMEM;
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s->lookup = kcalloc(IP_VS_MH_TAB_SIZE, sizeof(struct ip_vs_mh_lookup),
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GFP_KERNEL);
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if (!s->lookup) {
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kfree(s);
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return -ENOMEM;
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}
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generate_hash_secret(&s->hash1, &s->hash2);
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s->gcd = ip_vs_mh_gcd_weight(svc);
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s->rshift = ip_vs_mh_shift_weight(svc, s->gcd);
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IP_VS_DBG(6,
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"MH lookup table (memory=%zdbytes) allocated for current service\n",
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sizeof(struct ip_vs_mh_lookup) * IP_VS_MH_TAB_SIZE);
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/* Assign the lookup table with current dests */
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ret = ip_vs_mh_reassign(s, svc);
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if (ret < 0) {
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ip_vs_mh_reset(s);
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ip_vs_mh_state_free(&s->rcu_head);
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return ret;
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}
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/* No more failures, attach state */
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svc->sched_data = s;
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return 0;
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}
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static void ip_vs_mh_done_svc(struct ip_vs_service *svc)
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{
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struct ip_vs_mh_state *s = svc->sched_data;
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/* Got to clean up lookup entry here */
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ip_vs_mh_reset(s);
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call_rcu(&s->rcu_head, ip_vs_mh_state_free);
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IP_VS_DBG(6, "MH lookup table (memory=%zdbytes) released\n",
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sizeof(struct ip_vs_mh_lookup) * IP_VS_MH_TAB_SIZE);
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}
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static int ip_vs_mh_dest_changed(struct ip_vs_service *svc,
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struct ip_vs_dest *dest)
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{
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struct ip_vs_mh_state *s = svc->sched_data;
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s->gcd = ip_vs_mh_gcd_weight(svc);
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s->rshift = ip_vs_mh_shift_weight(svc, s->gcd);
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/* Assign the lookup table with the updated service */
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return ip_vs_mh_reassign(s, svc);
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}
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/* Helper function to get port number */
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static inline __be16
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ip_vs_mh_get_port(const struct sk_buff *skb, struct ip_vs_iphdr *iph)
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{
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__be16 _ports[2], *ports;
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/* At this point we know that we have a valid packet of some kind.
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* Because ICMP packets are only guaranteed to have the first 8
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* bytes, let's just grab the ports. Fortunately they're in the
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* same position for all three of the protocols we care about.
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*/
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switch (iph->protocol) {
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case IPPROTO_TCP:
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case IPPROTO_UDP:
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case IPPROTO_SCTP:
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ports = skb_header_pointer(skb, iph->len, sizeof(_ports),
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&_ports);
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if (unlikely(!ports))
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return 0;
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if (likely(!ip_vs_iph_inverse(iph)))
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return ports[0];
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else
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return ports[1];
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default:
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return 0;
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}
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}
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/* Maglev Hashing scheduling */
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static struct ip_vs_dest *
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ip_vs_mh_schedule(struct ip_vs_service *svc, const struct sk_buff *skb,
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struct ip_vs_iphdr *iph)
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{
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struct ip_vs_dest *dest;
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struct ip_vs_mh_state *s;
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__be16 port = 0;
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const union nf_inet_addr *hash_addr;
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hash_addr = ip_vs_iph_inverse(iph) ? &iph->daddr : &iph->saddr;
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IP_VS_DBG(6, "%s : Scheduling...\n", __func__);
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if (svc->flags & IP_VS_SVC_F_SCHED_MH_PORT)
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port = ip_vs_mh_get_port(skb, iph);
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s = (struct ip_vs_mh_state *)svc->sched_data;
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if (svc->flags & IP_VS_SVC_F_SCHED_MH_FALLBACK)
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dest = ip_vs_mh_get_fallback(svc, s, hash_addr, port);
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else
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dest = ip_vs_mh_get(svc, s, hash_addr, port);
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if (!dest) {
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ip_vs_scheduler_err(svc, "no destination available");
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return NULL;
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}
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IP_VS_DBG_BUF(6, "MH: source IP address %s:%u --> server %s:%u\n",
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IP_VS_DBG_ADDR(svc->af, hash_addr),
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ntohs(port),
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IP_VS_DBG_ADDR(dest->af, &dest->addr),
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ntohs(dest->port));
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return dest;
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}
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/* IPVS MH Scheduler structure */
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static struct ip_vs_scheduler ip_vs_mh_scheduler = {
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.name = "mh",
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.refcnt = ATOMIC_INIT(0),
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.module = THIS_MODULE,
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.n_list = LIST_HEAD_INIT(ip_vs_mh_scheduler.n_list),
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.init_service = ip_vs_mh_init_svc,
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.done_service = ip_vs_mh_done_svc,
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.add_dest = ip_vs_mh_dest_changed,
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.del_dest = ip_vs_mh_dest_changed,
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.upd_dest = ip_vs_mh_dest_changed,
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.schedule = ip_vs_mh_schedule,
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};
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static int __init ip_vs_mh_init(void)
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{
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return register_ip_vs_scheduler(&ip_vs_mh_scheduler);
|
}
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static void __exit ip_vs_mh_cleanup(void)
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{
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unregister_ip_vs_scheduler(&ip_vs_mh_scheduler);
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rcu_barrier();
|
}
|
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module_init(ip_vs_mh_init);
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module_exit(ip_vs_mh_cleanup);
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MODULE_DESCRIPTION("Maglev hashing ipvs scheduler");
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MODULE_LICENSE("GPL v2");
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MODULE_AUTHOR("Inju Song <inju.song@navercorp.com>");
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