388909a12a
o Unlike xor, in Jenkins hash every bit of input affects virtually every bit of output, thus salting the hash actually works. With xor salting only provides a false sense of security, since if hash(x) collides with hash(y), then of course, hash(x) ^ salt would also collide with hash(y) ^ salt. [1] o Jenkins provides much better distribution than xor, very close to ideal. TCP connection setup/teardown benchmark has shown a 10% increase with default hash size, and with bigger hashes that still provide possibility for collisions. With enormous hash size, when dataset is by an order of magnitude smaller than hash size, the benchmark has shown 4% decrease in performance decrease, which is expected and acceptable. Noticed by: Jeffrey Knockel <jeffk cs.unm.edu> [1] Benchmarks by: jch Reviewed by: jch, pkelsey, delphij Security: strengthens protection against hash collision DoS Sponsored by: Nginx, Inc.
139 lines
4.7 KiB
C
139 lines
4.7 KiB
C
/*-
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* Copyright (c) 1982, 1986, 1993, 1994, 1995
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* The Regents of the University of California. All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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*
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* @(#)tcp_var.h 8.4 (Berkeley) 5/24/95
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* $FreeBSD$
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*/
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#ifndef _NETINET_TCP_SYNCACHE_H_
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#define _NETINET_TCP_SYNCACHE_H_
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#ifdef _KERNEL
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void syncache_init(void);
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#ifdef VIMAGE
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void syncache_destroy(void);
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#endif
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void syncache_unreach(struct in_conninfo *, struct tcphdr *);
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int syncache_expand(struct in_conninfo *, struct tcpopt *,
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struct tcphdr *, struct socket **, struct mbuf *);
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void syncache_add(struct in_conninfo *, struct tcpopt *,
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struct tcphdr *, struct inpcb *, struct socket **, struct mbuf *,
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void *, void *);
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void syncache_chkrst(struct in_conninfo *, struct tcphdr *);
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void syncache_badack(struct in_conninfo *);
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int syncache_pcbcount(void);
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int syncache_pcblist(struct sysctl_req *req, int max_pcbs, int *pcbs_exported);
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struct syncache {
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TAILQ_ENTRY(syncache) sc_hash;
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struct in_conninfo sc_inc; /* addresses */
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int sc_rxttime; /* retransmit time */
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u_int16_t sc_rxmits; /* retransmit counter */
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u_int32_t sc_tsreflect; /* timestamp to reflect */
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u_int32_t sc_ts; /* our timestamp to send */
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u_int32_t sc_tsoff; /* ts offset w/ syncookies */
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u_int32_t sc_flowlabel; /* IPv6 flowlabel */
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tcp_seq sc_irs; /* seq from peer */
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tcp_seq sc_iss; /* our ISS */
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struct mbuf *sc_ipopts; /* source route */
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u_int16_t sc_peer_mss; /* peer's MSS */
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u_int16_t sc_wnd; /* advertised window */
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u_int8_t sc_ip_ttl; /* IPv4 TTL */
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u_int8_t sc_ip_tos; /* IPv4 TOS */
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u_int8_t sc_requested_s_scale:4,
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sc_requested_r_scale:4;
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u_int16_t sc_flags;
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#if defined(TCP_OFFLOAD) || !defined(TCP_OFFLOAD_DISABLE)
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struct toedev *sc_tod; /* entry added by this TOE */
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void *sc_todctx; /* TOE driver context */
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#endif
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struct label *sc_label; /* MAC label reference */
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struct ucred *sc_cred; /* cred cache for jail checks */
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void *sc_pspare; /* TCP_SIGNATURE */
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u_int32_t sc_spare[2]; /* UTO */
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};
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/*
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* Flags for the sc_flags field.
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*/
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#define SCF_NOOPT 0x01 /* no TCP options */
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#define SCF_WINSCALE 0x02 /* negotiated window scaling */
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#define SCF_TIMESTAMP 0x04 /* negotiated timestamps */
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/* MSS is implicit */
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#define SCF_UNREACH 0x10 /* icmp unreachable received */
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#define SCF_SIGNATURE 0x20 /* send MD5 digests */
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#define SCF_SACK 0x80 /* send SACK option */
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#define SCF_ECN 0x100 /* send ECN setup packet */
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struct syncache_head {
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struct mtx sch_mtx;
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TAILQ_HEAD(sch_head, syncache) sch_bucket;
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struct callout sch_timer;
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int sch_nextc;
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u_int sch_length;
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struct tcp_syncache *sch_sc;
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};
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#define SYNCOOKIE_SECRET_SIZE 16
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#define SYNCOOKIE_LIFETIME 15 /* seconds */
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struct syncookie_secret {
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volatile u_int oddeven;
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uint8_t key[2][SYNCOOKIE_SECRET_SIZE];
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struct callout reseed;
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u_int lifetime;
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};
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struct tcp_syncache {
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struct syncache_head *hashbase;
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uma_zone_t zone;
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u_int hashsize;
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u_int hashmask;
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u_int bucket_limit;
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u_int cache_limit;
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u_int rexmt_limit;
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uint32_t hash_secret;
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struct vnet *vnet;
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struct syncookie_secret secret;
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};
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/* Internal use for the syncookie functions. */
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union syncookie {
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uint8_t cookie;
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struct {
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uint8_t odd_even:1,
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sack_ok:1,
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wscale_idx:3,
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mss_idx:3;
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} flags;
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};
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#endif /* _KERNEL */
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#endif /* !_NETINET_TCP_SYNCACHE_H_ */
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