/* * Random policy for multipath. * * * Version: $Id: multipath_random.c,v 1.1.2.3 2004/09/21 08:42:11 elueck Exp $ * * Authors: Einar Lueck * * This program is free software; you can redistribute it and/or * modify it under the terms of the GNU General Public License * as published by the Free Software Foundation; either version * 2 of the License, or (at your option) any later version. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define MULTIPATH_MAX_CANDIDATES 40 /* interface to random number generation */ static unsigned int RANDOM_SEED = 93186752; static inline unsigned int random(unsigned int ubound) { static unsigned int a = 1588635695, q = 2, r = 1117695901; RANDOM_SEED = a*(RANDOM_SEED % q) - r*(RANDOM_SEED / q); return RANDOM_SEED % ubound; } static void random_select_route(const struct flowi *flp, struct rtable *first, struct rtable **rp) { struct rtable *rt; struct rtable *decision; unsigned char candidate_count = 0; /* count all candidate */ for (rt = rcu_dereference(first); rt; rt = rcu_dereference(rt->u.rt_next)) { if ((rt->u.dst.flags & DST_BALANCED) != 0 && multipath_comparekeys(&rt->fl, flp)) ++candidate_count; } /* choose a random candidate */ decision = first; if (candidate_count > 1) { unsigned char i = 0; unsigned char candidate_no = (unsigned char) random(candidate_count); /* find chosen candidate and adjust GC data for all candidates * to ensure they stay in cache */ for (rt = first; rt; rt = rt->u.rt_next) { if ((rt->u.dst.flags & DST_BALANCED) != 0 && multipath_comparekeys(&rt->fl, flp)) { rt->u.dst.lastuse = jiffies; if (i == candidate_no) decision = rt; if (i >= candidate_count) break; i++; } } } decision->u.dst.__use++; *rp = decision; } static struct ip_mp_alg_ops random_ops = { .mp_alg_select_route = random_select_route, }; static int __init random_init(void) { return multipath_alg_register(&random_ops, IP_MP_ALG_RANDOM); } static void __exit random_exit(void) { multipath_alg_unregister(&random_ops, IP_MP_ALG_RANDOM); } module_init(random_init); module_exit(random_exit); MODULE_LICENSE("GPL");