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[204.195.22.127]) by smtp.gmail.com with ESMTPSA id i126sm17991795pfb.32.2019.07.15.13.48.26 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Mon, 15 Jul 2019 13:48:27 -0700 (PDT) Date: Mon, 15 Jul 2019 13:48:20 -0700 From: Stephen Hemminger To: Andrea Claudi Cc: netdev@vger.kernel.org, dsahern@kernel.org Subject: Re: [PATCH iproute2] tc: util: constrain percentage in 0-100 interval Message-ID: <20190715134820.119e0cb8@hermes.lan> In-Reply-To: References: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Sat, 13 Jul 2019 11:44:07 +0200 Andrea Claudi wrote: > parse_percent() currently allows to specify negative percentages > or value above 100%. However this does not seems to make sense, > as the function is used for probabilities or bandiwidth rates. > > Moreover, using negative values leads to erroneous results > (using Bernoulli loss model as example): > > $ ip link add test type dummy > $ ip link set test up > $ tc qdisc add dev test root netem loss gemodel -10% limit 10 > $ tc qdisc show dev test > qdisc netem 800c: root refcnt 2 limit 10 loss gemodel p 90% r 10% 1-h 100% 1-k 0% > > Using values above 100% we have instead: > > $ ip link add test type dummy > $ ip link set test up > $ tc qdisc add dev test root netem loss gemodel 140% limit 10 > $ tc qdisc show dev test > qdisc netem 800f: root refcnt 2 limit 10 loss gemodel p 40% r 60% 1-h 100% 1-k 0% > > This commit changes parse_percent() with a check to ensure > percentage values stay between 1.0 and 0.0. > parse_percent_rate() function, which already employs a similar > check, is adjusted accordingly. > > With this check in place, we have: > > $ ip link add test type dummy > $ ip link set test up > $ tc qdisc add dev test root netem loss gemodel -10% limit 10 > Illegal "loss gemodel p" > > Fixes: 927e3cfb52b58 ("tc: B.W limits can now be specified in %.") > Signed-off-by: Andrea Claudi Looks good. Applied