1 /* 2 * Copyright (c) 2007 The DragonFly Project. All rights reserved. 3 * 4 * This code is derived from software contributed to The DragonFly Project 5 * by Matthew Dillon <dillon@backplane.com> 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in 15 * the documentation and/or other materials provided with the 16 * distribution. 17 * 3. Neither the name of The DragonFly Project nor the names of its 18 * contributors may be used to endorse or promote products derived 19 * from this software without specific, prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 22 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 23 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 24 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 25 * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 26 * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING, 27 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; 28 * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 29 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 30 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 31 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 * 34 * $DragonFly: src/sys/netinet/ip_id.c,v 1.8 2007/11/23 22:29:51 dillon Exp $ 35 */ 36 37 /* 38 * Random ip sequence number generator. Use the system PRNG to shuffle the 39 * 65536 entry ID space. We reshuffle the front-side of the array as we 40 * index through it, guarenteeing an id will not be reused for at least 41 * 32768 calls. 42 */ 43 #include <sys/param.h> 44 #include <sys/systm.h> 45 #include <sys/kernel.h> 46 #include <sys/random.h> 47 #include <sys/globaldata.h> 48 49 #include <net/netmsg2.h> 50 #include <net/netisr2.h> 51 52 #include <netinet/ip_var.h> 53 54 #define IPRANDCOUNT 32 55 56 typedef struct iprandinfo { 57 short randdata[IPRANDCOUNT]; 58 int randidx; 59 int isidx; 60 } *iprandinfo_t __cachealign; 61 62 struct iprandinfo iprandcpu[MAXCPU]; 63 64 static u_int16_t ip_shuffle[65536]; 65 66 static void 67 ip_idinit_handler(netmsg_t msg) 68 { 69 int i; 70 71 for (i = 0; i < 65536; ++i) 72 ip_randomid(); 73 74 /* Done! */ 75 netisr_replymsg(&msg->base, 0); 76 } 77 78 /* 79 * Initialize the shuffle. We assume that the system PRNG won't be all that 80 * good this early in the boot sequence but use it anyway. The ids will be 81 * reshuffled as they are popped and the PRNG should be better then. 82 */ 83 static void 84 ip_idinit_shuffle(void *dummy __unused) 85 { 86 struct netmsg_base msg; 87 int i; 88 89 for (i = 0; i < 65536; ++i) 90 ip_shuffle[i] = i; 91 for (i = 0; i < ncpus; ++i) { 92 netmsg_init(&msg, NULL, &curthread->td_msgport, 0, 93 ip_idinit_handler); 94 netisr_domsg(&msg, i); 95 iprandcpu[i].isidx = i * (65536 / ncpus_fit); 96 } 97 } 98 99 SYSINIT(ipshuffle, SI_SUB_PSEUDO, SI_ORDER_ANY, ip_idinit_shuffle, NULL); 100 101 /* 102 * Return a random IP id. Use a forward shuffle over half the index 103 * space to avoid duplicates occuring too quickly. Since the initial 104 * shuffle may not have had a good random basis we returned the element 105 * at the shuffle target instead of the current element. 106 */ 107 u_int16_t 108 ip_randomid(void) 109 { 110 globaldata_t gd = mycpu; 111 iprandinfo_t info; 112 u_int16_t si, r; 113 int i1, i2; 114 115 info = &iprandcpu[gd->gd_cpuid]; 116 117 /* 118 * Reload random array efficiently 119 */ 120 if (info->randidx == 0) { 121 info->randidx = IPRANDCOUNT; 122 read_random_unlimited(info->randdata, sizeof(info->randdata)); 123 } 124 125 /* 126 * Get random number (si) and calculate shuffle. The shuffle 127 * is calculated such that the cpus do not interfere with each 128 * other. 129 */ 130 si = info->randdata[--info->randidx]; 131 i1 = (info->isidx & 0xFFFF & ~ncpus_fit_mask) | gd->gd_cpuid; 132 i2 = ((i1 + (si & 0x7FFF)) & 0xFFFF & ~ncpus_fit_mask) | gd->gd_cpuid; 133 134 /* 135 * Do the shuffle, bump isidx taking into account the cpu 136 * partitioning. 137 */ 138 r = ip_shuffle[i2]; 139 ip_shuffle[i2] = ip_shuffle[i1]; 140 ip_shuffle[i1] = r; 141 info->isidx += ncpus_fit; 142 143 return (r); 144 } 145