From 25392fac9488bcae5c451500df2e2945430484a6 Mon Sep 17 00:00:00 2001 From: Lutz Donnerhacke Date: Fri, 2 Jul 2021 23:41:25 +0200 Subject: [PATCH] libalias: Fix splay comparsion bug Comparing elements in a tree requires transitiviy. If a < b and b < c then a must be smaller than c. This way the tree elements are always pairwise comparable. Tristate comparsion functions returning values lower, equal, or greater than zero, are usually implemented by a simple subtraction of the operands. If the size of the operands are equal to the size of the result, integer modular arithmetics kick in and violates the transitivity. Example: Working on byte with 0, 120, and 240. Now computing the differences: 120 - 0 = 120 240 - 120 = 120 240 - 0 = -16 MFC after: 3 days --- sys/netinet/libalias/alias_db.h | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-) diff --git a/sys/netinet/libalias/alias_db.h b/sys/netinet/libalias/alias_db.h index ec0b69c01f8..971ca305c1a 100644 --- a/sys/netinet/libalias/alias_db.h +++ b/sys/netinet/libalias/alias_db.h @@ -351,10 +351,10 @@ static inline int cmp_out(struct alias_link *a, struct alias_link *b) { int i = a->src_port - b->src_port; if (i != 0) return (i); - i = a->src_addr.s_addr - b->src_addr.s_addr; - if (i != 0) return (i); - i = a->dst_addr.s_addr - b->dst_addr.s_addr; - if (i != 0) return (i); + if (a->src_addr.s_addr > b->src_addr.s_addr) return (1); + if (a->src_addr.s_addr < b->src_addr.s_addr) return (-1); + if (a->dst_addr.s_addr > b->dst_addr.s_addr) return (1); + if (a->dst_addr.s_addr < b->dst_addr.s_addr) return (-1); i = a->dst_port - b->dst_port; if (i != 0) return (i); i = a->link_type - b->link_type; @@ -368,8 +368,9 @@ cmp_in(struct group_in *a, struct group_in *b) { if (i != 0) return (i); i = a->link_type - b->link_type; if (i != 0) return (i); - i = a->alias_addr.s_addr - b->alias_addr.s_addr; - return (i); + if (a->alias_addr.s_addr > b->alias_addr.s_addr) return (1); + if (a->alias_addr.s_addr < b->alias_addr.s_addr) return (-1); + return (0); } SPLAY_PROTOTYPE(splay_in, group_in, in, cmp_in);