From: Inju Song Date: Tue, 27 Mar 2018 14:15:18 +0000 (+0900) Subject: netfilter: ipvs: Add Maglev hashing scheduler X-Git-Tag: v5.15~8692^2~308^2~10^2~2 X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=039f32e8cdea29b4d0680df7a83817b5ec4166e1;p=platform%2Fkernel%2Flinux-starfive.git netfilter: ipvs: Add Maglev hashing scheduler Implements the Google's Maglev hashing algorithm as a IPVS scheduler. Basically it provides consistent hashing but offers some special features about disruption and load balancing. 1) minimal disruption: when the set of destinations changes, a connection will likely be sent to the same destination as it was before. 2) load balancing: each destination will receive an almost equal number of connections. Seel also for detail: [3.4 Consistent Hasing] in https://www.usenix.org/system/files/conference/nsdi16/nsdi16-paper-eisenbud.pdf Signed-off-by: Inju Song Signed-off-by: Julian Anastasov Signed-off-by: Simon Horman --- diff --git a/net/netfilter/ipvs/ip_vs_mh.c b/net/netfilter/ipvs/ip_vs_mh.c new file mode 100644 index 0000000..0f795b1 --- /dev/null +++ b/net/netfilter/ipvs/ip_vs_mh.c @@ -0,0 +1,540 @@ +// SPDX-License-Identifier: GPL-2.0 +/* IPVS: Maglev Hashing scheduling module + * + * Authors: Inju Song + * + */ + +/* The mh algorithm is to assign a preference list of all the lookup + * table positions to each destination and populate the table with + * the most-preferred position of destinations. Then it is to select + * destination with the hash key of source IP address through looking + * up a the lookup table. + * + * The algorithm is detailed in: + * [3.4 Consistent Hasing] +https://www.usenix.org/system/files/conference/nsdi16/nsdi16-paper-eisenbud.pdf + * + */ + +#define KMSG_COMPONENT "IPVS" +#define pr_fmt(fmt) KMSG_COMPONENT ": " fmt + +#include +#include +#include +#include +#include + +#include + +#include +#include +#include + +#define IP_VS_SVC_F_SCHED_MH_FALLBACK IP_VS_SVC_F_SCHED1 /* MH fallback */ +#define IP_VS_SVC_F_SCHED_MH_PORT IP_VS_SVC_F_SCHED2 /* MH use port */ + +struct ip_vs_mh_lookup { + struct ip_vs_dest __rcu *dest; /* real server (cache) */ +}; + +struct ip_vs_mh_dest_setup { + unsigned int offset; /* starting offset */ + unsigned int skip; /* skip */ + unsigned int perm; /* next_offset */ + int turns; /* weight / gcd() and rshift */ +}; + +/* Available prime numbers for MH table */ +static int primes[] = {251, 509, 1021, 2039, 4093, + 8191, 16381, 32749, 65521, 131071}; + +/* For IPVS MH entry hash table */ +#ifndef CONFIG_IP_VS_MH_TAB_INDEX +#define CONFIG_IP_VS_MH_TAB_INDEX 12 +#endif +#define IP_VS_MH_TAB_BITS (CONFIG_IP_VS_MH_TAB_INDEX / 2) +#define IP_VS_MH_TAB_INDEX (CONFIG_IP_VS_MH_TAB_INDEX - 8) +#define IP_VS_MH_TAB_SIZE primes[IP_VS_MH_TAB_INDEX] + +struct ip_vs_mh_state { + struct rcu_head rcu_head; + struct ip_vs_mh_lookup *lookup; + struct ip_vs_mh_dest_setup *dest_setup; + hsiphash_key_t hash1, hash2; + int gcd; + int rshift; +}; + +static inline void generate_hash_secret(hsiphash_key_t *hash1, + hsiphash_key_t *hash2) +{ + hash1->key[0] = 2654435761UL; + hash1->key[1] = 2654435761UL; + + hash2->key[0] = 2654446892UL; + hash2->key[1] = 2654446892UL; +} + +/* 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 MH entry */ +static inline unsigned int +ip_vs_mh_hashkey(int af, const union nf_inet_addr *addr, + __be16 port, hsiphash_key_t *key, unsigned int offset) +{ + unsigned int v; + __be32 addr_fold = addr->ip; + +#ifdef CONFIG_IP_VS_IPV6 + if (af == AF_INET6) + addr_fold = addr->ip6[0] ^ addr->ip6[1] ^ + addr->ip6[2] ^ addr->ip6[3]; +#endif + v = (offset + ntohs(port) + ntohl(addr_fold)); + return hsiphash(&v, sizeof(v), key); +} + +/* Reset all the hash buckets of the specified table. */ +static void ip_vs_mh_reset(struct ip_vs_mh_state *s) +{ + int i; + struct ip_vs_mh_lookup *l; + struct ip_vs_dest *dest; + + l = &s->lookup[0]; + for (i = 0; i < IP_VS_MH_TAB_SIZE; i++) { + dest = rcu_dereference_protected(l->dest, 1); + if (dest) { + ip_vs_dest_put(dest); + RCU_INIT_POINTER(l->dest, NULL); + } + l++; + } +} + +static int ip_vs_mh_permutate(struct ip_vs_mh_state *s, + struct ip_vs_service *svc) +{ + struct list_head *p; + struct ip_vs_mh_dest_setup *ds; + struct ip_vs_dest *dest; + int lw; + + /* If gcd is smaller then 1, number of dests or + * all last_weight of dests are zero. So, skip + * permutation for the dests. + */ + if (s->gcd < 1) + return 0; + + /* Set dest_setup for the dests permutation */ + p = &svc->destinations; + ds = &s->dest_setup[0]; + while ((p = p->next) != &svc->destinations) { + dest = list_entry(p, struct ip_vs_dest, n_list); + + ds->offset = ip_vs_mh_hashkey(svc->af, &dest->addr, + dest->port, &s->hash1, 0) % + IP_VS_MH_TAB_SIZE; + ds->skip = ip_vs_mh_hashkey(svc->af, &dest->addr, + dest->port, &s->hash2, 0) % + (IP_VS_MH_TAB_SIZE - 1) + 1; + ds->perm = ds->offset; + + lw = atomic_read(&dest->last_weight); + ds->turns = ((lw / s->gcd) >> s->rshift) ? : (lw != 0); + ds++; + } + + return 0; +} + +static int ip_vs_mh_populate(struct ip_vs_mh_state *s, + struct ip_vs_service *svc) +{ + int n, c, dt_count; + unsigned long *table; + struct list_head *p; + struct ip_vs_mh_dest_setup *ds; + struct ip_vs_dest *dest, *new_dest; + + /* If gcd is smaller then 1, number of dests or + * all last_weight of dests are zero. So, skip + * the population for the dests and reset lookup table. + */ + if (s->gcd < 1) { + ip_vs_mh_reset(s); + return 0; + } + + table = kcalloc(BITS_TO_LONGS(IP_VS_MH_TAB_SIZE), + sizeof(unsigned long), GFP_KERNEL); + if (!table) + return -ENOMEM; + + p = &svc->destinations; + n = 0; + dt_count = 0; + while (n < IP_VS_MH_TAB_SIZE) { + if (p == &svc->destinations) + p = p->next; + + ds = &s->dest_setup[0]; + while (p != &svc->destinations) { + /* Ignore added server with zero weight */ + if (ds->turns < 1) { + p = p->next; + ds++; + continue; + } + + c = ds->perm; + while (test_bit(c, table)) { + /* Add skip, mod IP_VS_MH_TAB_SIZE */ + ds->perm += ds->skip; + if (ds->perm >= IP_VS_MH_TAB_SIZE) + ds->perm -= IP_VS_MH_TAB_SIZE; + c = ds->perm; + } + + __set_bit(c, table); + + dest = rcu_dereference_protected(s->lookup[c].dest, 1); + new_dest = list_entry(p, struct ip_vs_dest, n_list); + if (dest != new_dest) { + if (dest) + ip_vs_dest_put(dest); + ip_vs_dest_hold(new_dest); + RCU_INIT_POINTER(s->lookup[c].dest, new_dest); + } + + if (++n == IP_VS_MH_TAB_SIZE) + goto out; + + if (++dt_count >= ds->turns) { + dt_count = 0; + p = p->next; + ds++; + } + } + } + +out: + kfree(table); + return 0; +} + +/* Get ip_vs_dest associated with supplied parameters. */ +static inline struct ip_vs_dest * +ip_vs_mh_get(struct ip_vs_service *svc, struct ip_vs_mh_state *s, + const union nf_inet_addr *addr, __be16 port) +{ + unsigned int hash = ip_vs_mh_hashkey(svc->af, addr, port, &s->hash1, 0) + % IP_VS_MH_TAB_SIZE; + struct ip_vs_dest *dest = rcu_dereference(s->lookup[hash].dest); + + return (!dest || is_unavailable(dest)) ? NULL : dest; +} + +/* As ip_vs_mh_get, but with fallback if selected server is unavailable */ +static inline struct ip_vs_dest * +ip_vs_mh_get_fallback(struct ip_vs_service *svc, struct ip_vs_mh_state *s, + const union nf_inet_addr *addr, __be16 port) +{ + 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_mh_hashkey(svc->af, addr, port, + &s->hash1, 0) % IP_VS_MH_TAB_SIZE; + dest = rcu_dereference(s->lookup[ihash].dest); + if (!dest) + return NULL; + if (!is_unavailable(dest)) + return dest; + + IP_VS_DBG_BUF(6, "MH: selected unavailable server %s:%u, reselecting", + IP_VS_DBG_ADDR(dest->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_MH_TAB_SIZE; offset++) { + roffset = (offset + ihash) % IP_VS_MH_TAB_SIZE; + hash = ip_vs_mh_hashkey(svc->af, addr, port, &s->hash1, + roffset) % IP_VS_MH_TAB_SIZE; + dest = rcu_dereference(s->lookup[hash].dest); + if (!dest) + break; + if (!is_unavailable(dest)) + return dest; + IP_VS_DBG_BUF(6, + "MH: selected unavailable server %s:%u (offset %u), reselecting", + IP_VS_DBG_ADDR(dest->af, &dest->addr), + ntohs(dest->port), roffset); + } + + return NULL; +} + +/* Assign all the hash buckets of the specified table with the service. */ +static int ip_vs_mh_reassign(struct ip_vs_mh_state *s, + struct ip_vs_service *svc) +{ + int ret; + + if (svc->num_dests > IP_VS_MH_TAB_SIZE) + return -EINVAL; + + if (svc->num_dests >= 1) { + s->dest_setup = kcalloc(svc->num_dests, + sizeof(struct ip_vs_mh_dest_setup), + GFP_KERNEL); + if (!s->dest_setup) + return -ENOMEM; + } + + ip_vs_mh_permutate(s, svc); + + ret = ip_vs_mh_populate(s, svc); + if (ret < 0) + goto out; + + IP_VS_DBG_BUF(6, "MH: reassign lookup table of %s:%u\n", + IP_VS_DBG_ADDR(svc->af, &svc->addr), + ntohs(svc->port)); + +out: + if (svc->num_dests >= 1) { + kfree(s->dest_setup); + s->dest_setup = NULL; + } + return ret; +} + +static int ip_vs_mh_gcd_weight(struct ip_vs_service *svc) +{ + struct ip_vs_dest *dest; + int weight; + int g = 0; + + list_for_each_entry(dest, &svc->destinations, n_list) { + weight = atomic_read(&dest->last_weight); + if (weight > 0) { + if (g > 0) + g = gcd(weight, g); + else + g = weight; + } + } + return g; +} + +/* To avoid assigning huge weight for the MH table, + * calculate shift value with gcd. + */ +static int ip_vs_mh_shift_weight(struct ip_vs_service *svc, int gcd) +{ + struct ip_vs_dest *dest; + int new_weight, weight = 0; + int mw, shift; + + /* If gcd is smaller then 1, number of dests or + * all last_weight of dests are zero. So, return + * shift value as zero. + */ + if (gcd < 1) + return 0; + + list_for_each_entry(dest, &svc->destinations, n_list) { + new_weight = atomic_read(&dest->last_weight); + if (new_weight > weight) + weight = new_weight; + } + + /* Because gcd is greater than zero, + * the maximum weight and gcd are always greater than zero + */ + mw = weight / gcd; + + /* shift = occupied bits of weight/gcd - MH highest bits */ + shift = fls(mw) - IP_VS_MH_TAB_BITS; + return (shift >= 0) ? shift : 0; +} + +static void ip_vs_mh_state_free(struct rcu_head *head) +{ + struct ip_vs_mh_state *s; + + s = container_of(head, struct ip_vs_mh_state, rcu_head); + kfree(s->lookup); + kfree(s); +} + +static int ip_vs_mh_init_svc(struct ip_vs_service *svc) +{ + int ret; + struct ip_vs_mh_state *s; + + /* Allocate the MH table for this service */ + s = kzalloc(sizeof(*s), GFP_KERNEL); + if (!s) + return -ENOMEM; + + s->lookup = kcalloc(IP_VS_MH_TAB_SIZE, sizeof(struct ip_vs_mh_lookup), + GFP_KERNEL); + if (!s->lookup) { + kfree(s); + return -ENOMEM; + } + + generate_hash_secret(&s->hash1, &s->hash2); + s->gcd = ip_vs_mh_gcd_weight(svc); + s->rshift = ip_vs_mh_shift_weight(svc, s->gcd); + + IP_VS_DBG(6, + "MH lookup table (memory=%zdbytes) allocated for current service\n", + sizeof(struct ip_vs_mh_lookup) * IP_VS_MH_TAB_SIZE); + + /* Assign the lookup table with current dests */ + ret = ip_vs_mh_reassign(s, svc); + if (ret < 0) { + ip_vs_mh_reset(s); + ip_vs_mh_state_free(&s->rcu_head); + return ret; + } + + /* No more failures, attach state */ + svc->sched_data = s; + return 0; +} + +static void ip_vs_mh_done_svc(struct ip_vs_service *svc) +{ + struct ip_vs_mh_state *s = svc->sched_data; + + /* Got to clean up lookup entry here */ + ip_vs_mh_reset(s); + + call_rcu(&s->rcu_head, ip_vs_mh_state_free); + IP_VS_DBG(6, "MH lookup table (memory=%zdbytes) released\n", + sizeof(struct ip_vs_mh_lookup) * IP_VS_MH_TAB_SIZE); +} + +static int ip_vs_mh_dest_changed(struct ip_vs_service *svc, + struct ip_vs_dest *dest) +{ + struct ip_vs_mh_state *s = svc->sched_data; + + s->gcd = ip_vs_mh_gcd_weight(svc); + s->rshift = ip_vs_mh_shift_weight(svc, s->gcd); + + /* Assign the lookup table with the updated service */ + return ip_vs_mh_reassign(s, svc); +} + +/* Helper function to get port number */ +static inline __be16 +ip_vs_mh_get_port(const struct sk_buff *skb, struct ip_vs_iphdr *iph) +{ + __be16 _ports[2], *ports; + + /* At this point we know that we have a valid packet of some kind. + * Because ICMP packets are only guaranteed to have the first 8 + * bytes, let's just grab the ports. Fortunately they're in the + * same position for all three of the protocols we care about. + */ + switch (iph->protocol) { + case IPPROTO_TCP: + case IPPROTO_UDP: + case IPPROTO_SCTP: + ports = skb_header_pointer(skb, iph->len, sizeof(_ports), + &_ports); + if (unlikely(!ports)) + return 0; + + if (likely(!ip_vs_iph_inverse(iph))) + return ports[0]; + else + return ports[1]; + default: + return 0; + } +} + +/* Maglev Hashing scheduling */ +static struct ip_vs_dest * +ip_vs_mh_schedule(struct ip_vs_service *svc, const struct sk_buff *skb, + struct ip_vs_iphdr *iph) +{ + struct ip_vs_dest *dest; + struct ip_vs_mh_state *s; + __be16 port = 0; + const union nf_inet_addr *hash_addr; + + hash_addr = ip_vs_iph_inverse(iph) ? &iph->daddr : &iph->saddr; + + IP_VS_DBG(6, "%s : Scheduling...\n", __func__); + + if (svc->flags & IP_VS_SVC_F_SCHED_MH_PORT) + port = ip_vs_mh_get_port(skb, iph); + + s = (struct ip_vs_mh_state *)svc->sched_data; + + if (svc->flags & IP_VS_SVC_F_SCHED_MH_FALLBACK) + dest = ip_vs_mh_get_fallback(svc, s, hash_addr, port); + else + dest = ip_vs_mh_get(svc, s, hash_addr, port); + + if (!dest) { + ip_vs_scheduler_err(svc, "no destination available"); + return NULL; + } + + IP_VS_DBG_BUF(6, "MH: source IP address %s:%u --> server %s:%u\n", + IP_VS_DBG_ADDR(svc->af, hash_addr), + ntohs(port), + IP_VS_DBG_ADDR(dest->af, &dest->addr), + ntohs(dest->port)); + + return dest; +} + +/* IPVS MH Scheduler structure */ +static struct ip_vs_scheduler ip_vs_mh_scheduler = { + .name = "mh", + .refcnt = ATOMIC_INIT(0), + .module = THIS_MODULE, + .n_list = LIST_HEAD_INIT(ip_vs_mh_scheduler.n_list), + .init_service = ip_vs_mh_init_svc, + .done_service = ip_vs_mh_done_svc, + .add_dest = ip_vs_mh_dest_changed, + .del_dest = ip_vs_mh_dest_changed, + .upd_dest = ip_vs_mh_dest_changed, + .schedule = ip_vs_mh_schedule, +}; + +static int __init ip_vs_mh_init(void) +{ + return register_ip_vs_scheduler(&ip_vs_mh_scheduler); +} + +static void __exit ip_vs_mh_cleanup(void) +{ + unregister_ip_vs_scheduler(&ip_vs_mh_scheduler); + rcu_barrier(); +} + +module_init(ip_vs_mh_init); +module_exit(ip_vs_mh_cleanup); +MODULE_DESCRIPTION("Maglev hashing ipvs scheduler"); +MODULE_LICENSE("GPL v2"); +MODULE_AUTHOR("Inju Song ");