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o Use Jenkins hash. With previous hash, for a single source IP address and

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sequential IP ID case (e.g. ping -f), distribution fell into 8-10 buckets
  out of 64. With Jenkins hash, distribution is even.
o Add random seed to the hash.

Sponsored by:	Nginx, Inc.
This commit is contained in:
Gleb Smirnoff 2015-04-10 06:55:43 +00:00
parent 1dbefcc00d
commit c047fd1b99
1 changed files with 7 additions and 4 deletions
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11
sys/netinet/ip_reass.c
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@ -39,6 +39,7 @@ __FBSDID("$FreeBSD$");
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/eventhandler.h>
#include <sys/hash.h>
#include <sys/mbuf.h>
#include <sys/malloc.h>
#include <sys/lock.h>
@ -64,8 +65,6 @@ SYSCTL_DECL(_net_inet_ip);
#define IPREASS_NHASH_LOG2 6
#define IPREASS_NHASH (1 << IPREASS_NHASH_LOG2)
#define IPREASS_HMASK (IPREASS_NHASH - 1)
#define IPREASS_HASH(x,y) \
(((((x) & 0xF) | ((((x) >> 8) & 0xF) << 4)) ^ (y)) & IPREASS_HMASK)
struct ipqbucket {
TAILQ_HEAD(ipqhead, ipq) head;
@ -74,6 +73,8 @@ struct ipqbucket {
static VNET_DEFINE(struct ipqbucket, ipq[IPREASS_NHASH]);
#define V_ipq VNET(ipq)
static VNET_DEFINE(uint32_t, ipq_hashseed);
#define V_ipq_hashseed VNET(ipq_hashseed)
#define IPQ_LOCK(i) mtx_lock(&V_ipq[i].lock)
#define IPQ_TRYLOCK(i) mtx_trylock(&V_ipq[i].lock)
@ -146,7 +147,7 @@ ip_reass(struct mbuf *m)
struct ipqhead *head;
int i, hlen, next;
u_int8_t ecn, ecn0;
u_short hash;
uint32_t hash;
#ifdef RSS
uint32_t rss_hash, rss_type;
#endif
@ -200,7 +201,8 @@ ip_reass(struct mbuf *m)
m->m_data += hlen;
m->m_len -= hlen;
hash = IPREASS_HASH(ip->ip_src.s_addr, ip->ip_id);
hash = ip->ip_src.s_addr ^ ip->ip_id;
hash = jenkins_hash32(&hash, 1, V_ipq_hashseed) & IPREASS_HMASK;
head = &V_ipq[hash].head;
IPQ_LOCK(hash);
@ -465,6 +467,7 @@ ipreass_init(void)
mtx_init(&V_ipq[i].lock, "IP reassembly", NULL,
MTX_DEF | MTX_DUPOK);
}
V_ipq_hashseed = arc4random();
V_maxfragsperpacket = 16;
V_ipq_zone = uma_zcreate("ipq", sizeof(struct ipq), NULL, NULL, NULL,
NULL, UMA_ALIGN_PTR, 0);