Date: Fri, 6 Aug 2021 08:00:39 -0700 From: Gleb Smirnoff <glebius@freebsd.org> To: Lutz Donnerhacke <donner@freebsd.org> Cc: src-committers@freebsd.org, dev-commits-src-all@freebsd.org, dev-commits-src-main@freebsd.org Subject: Re: git: 25392fac9488 - main - libalias: Fix splay comparsion bug Message-ID: <YQ1Ol7UfATYcXMwa@FreeBSD.org> In-Reply-To: <202107022232.162MWUIY049889@gitrepo.freebsd.org> References: <202107022232.162MWUIY049889@gitrepo.freebsd.org>
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Lutz, Wouldn't declaring 'i' to u_short fix the root of the problem? On Fri, Jul 02, 2021 at 10:32:30PM +0000, Lutz Donnerhacke wrote: L> The branch main has been updated by donner: L> L> URL: https://cgit.FreeBSD.org/src/commit/?id=25392fac9488bcae5c451500df2e2945430484a6 L> L> commit 25392fac9488bcae5c451500df2e2945430484a6 L> Author: Lutz Donnerhacke <donner@FreeBSD.org> L> AuthorDate: 2021-07-02 21:41:25 +0000 L> Commit: Lutz Donnerhacke <donner@FreeBSD.org> L> CommitDate: 2021-07-02 22:31:53 +0000 L> L> libalias: Fix splay comparsion bug L> L> Comparing elements in a tree requires transitiviy. If a < b and b < c L> then a must be smaller than c. This way the tree elements are always L> pairwise comparable. L> L> Tristate comparsion functions returning values lower, equal, or L> greater than zero, are usually implemented by a simple subtraction of L> the operands. If the size of the operands are equal to the size of L> the result, integer modular arithmetics kick in and violates the L> transitivity. L> L> Example: L> Working on byte with 0, 120, and 240. Now computing the differences: L> 120 - 0 = 120 L> 240 - 120 = 120 L> 240 - 0 = -16 L> L> MFC after: 3 days L> sys/netinet/libalias/alias_db.h | 13 +++++++------ L> 1 file changed, 7 insertions(+), 6 deletions(-) L> L> diff --git a/sys/netinet/libalias/alias_db.h b/sys/netinet/libalias/alias_db.h L> index ec0b69c01f82..971ca305c1a6 100644 L> --- a/sys/netinet/libalias/alias_db.h L> +++ b/sys/netinet/libalias/alias_db.h L> @@ -351,10 +351,10 @@ static inline int L> cmp_out(struct alias_link *a, struct alias_link *b) { L> int i = a->src_port - b->src_port; L> if (i != 0) return (i); L> - i = a->src_addr.s_addr - b->src_addr.s_addr; L> - if (i != 0) return (i); L> - i = a->dst_addr.s_addr - b->dst_addr.s_addr; L> - if (i != 0) return (i); L> + if (a->src_addr.s_addr > b->src_addr.s_addr) return (1); L> + if (a->src_addr.s_addr < b->src_addr.s_addr) return (-1); L> + if (a->dst_addr.s_addr > b->dst_addr.s_addr) return (1); L> + if (a->dst_addr.s_addr < b->dst_addr.s_addr) return (-1); L> i = a->dst_port - b->dst_port; L> if (i != 0) return (i); L> i = a->link_type - b->link_type; L> @@ -368,8 +368,9 @@ cmp_in(struct group_in *a, struct group_in *b) { L> if (i != 0) return (i); L> i = a->link_type - b->link_type; L> if (i != 0) return (i); L> - i = a->alias_addr.s_addr - b->alias_addr.s_addr; L> - return (i); L> + if (a->alias_addr.s_addr > b->alias_addr.s_addr) return (1); L> + if (a->alias_addr.s_addr < b->alias_addr.s_addr) return (-1); L> + return (0); L> } L> SPLAY_PROTOTYPE(splay_in, group_in, in, cmp_in); L> -- Gleb Smirnoff
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