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From 7fcfc0e4d6949ff32df3ed749bad8eb419cebbda Mon Sep 17 00:00:00 2001
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Message-Id: <7fcfc0e4d6949ff32df3ed749bad8eb419cebbda.1628790091.git.aclaudi@redhat.com>
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In-Reply-To: <650694eb0120722499207078f965442ef7343bb1.1628790091.git.aclaudi@redhat.com>
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References: <650694eb0120722499207078f965442ef7343bb1.1628790091.git.aclaudi@redhat.com>
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From: Andrea Claudi <aclaudi@redhat.com>
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Date: Wed, 11 Aug 2021 14:49:33 +0200
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Subject: [PATCH] tc: u32: Fix key folding in sample option
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Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1979425
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Upstream Status: iproute2.git commit 9b7ea92b
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commit 9b7ea92b9e3feff2876f772ace01148b7406839c
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Author: Phil Sutter <phil@nwl.cc>
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Date: Wed Aug 4 11:18:28 2021 +0200
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tc: u32: Fix key folding in sample option
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In between Linux kernel 2.4 and 2.6, key folding for hash tables changed
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in kernel space. When iproute2 dropped support for the older algorithm,
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the wrong code was removed and kernel 2.4 folding method remained in
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place. To get things functional for recent kernels again, restoring the
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old code alone was not sufficient - additional byteorder fixes were
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needed.
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While being at it, make use of ffs() and thereby align the code with how
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kernel determines the shift width.
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Fixes: 267480f55383c ("Backout the 2.4 utsname hash patch.")
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Signed-off-by: Phil Sutter <phil@nwl.cc>
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Signed-off-by: Stephen Hemminger <stephen@networkplumber.org>
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Signed-off-by: Andrea Claudi <aclaudi@redhat.com>
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---
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tc/f_u32.c | 11 ++++++++---
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1 file changed, 8 insertions(+), 3 deletions(-)
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diff --git a/tc/f_u32.c b/tc/f_u32.c
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index 2ed5254a..a5747f67 100644
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--- a/tc/f_u32.c
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+++ b/tc/f_u32.c
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@@ -978,6 +978,13 @@ show_k:
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goto show_k;
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}
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+static __u32 u32_hash_fold(struct tc_u32_key *key)
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+{
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+ __u8 fshift = key->mask ? ffs(ntohl(key->mask)) - 1 : 0;
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+
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+ return ntohl(key->val & key->mask) >> fshift;
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+}
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+
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static int u32_parse_opt(struct filter_util *qu, char *handle,
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int argc, char **argv, struct nlmsghdr *n)
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{
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@@ -1110,9 +1117,7 @@ static int u32_parse_opt(struct filter_util *qu, char *handle,
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}
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NEXT_ARG();
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}
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- hash = sel2.keys[0].val & sel2.keys[0].mask;
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- hash ^= hash >> 16;
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- hash ^= hash >> 8;
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+ hash = u32_hash_fold(&sel2.keys[0]);
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htid = ((hash % divisor) << 12) | (htid & 0xFFF00000);
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sample_ok = 1;
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continue;
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--
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2.31.1
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