Fix tc-tbf burst value in bytes

[hustcat]

According to iproute2, we should calculate the buffer in bytes for rate and burst both. But the current burst is in bit unit.

[rosenhouse]

@hustcat this change looks right, but it broke some tests. Could you fix that up?

[hustcat]

@rosenhouse Updated, PTAL

[rosenhouse]

LGTM, Thanks!

[squeed]

Hmm. I tested the original bandwidth plugin and it seemed to create the correct values, at least when I viewed the queues. But I don't know enough about this stuff.

[hustcat]

@squeed This is my test with original bandwidth tool before this PR:

• Create veth pair

# ip netns add netns1
# ip link add veth_host type veth peer name veth_con
# ip link set veth_con netns netns1
# ip link show veth_host
2719: veth_host@if2718: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT qlen 1000
    link/ether b2:1d:56:6a:ff:3c brd ff:ff:ff:ff:ff:ff link-netnsid 5

• Set rate to 8000bit and burt to 80bit by bandwidth

# cat bandwidth.conf 
{
"cniVersion": "0.3.1",
"name": "slowdown",
"type": "bandwidth",
"ingressRate": 8000,
"ingressBurst": 80,
"egressRate": 8000,
"egressBurst": 80,
"prevResult": {"cniVersion":"0.3.1", "interfaces": [{"name": "veth_host","mac": "b2:1d:56:6a:ff:3c", "sandbox": ""}]}
}

# CNI_PATH=`pwd`/bin CNI_COMMAND=ADD CNI_NETNS=/var/run/netns/netns1 CNI_CONTAINERID=netns1 CNI_IFNAME=veth_con CNI_ARGS="" bin/bandwidth < bandwidth.conf
{
    "cniVersion": "0.3.1",
    "interfaces": [
        {
            "name": "veth_host",
            "mac": "b2:1d:56:6a:ff:3c"
        },
        {
            "name": "5026",
            "mac": "7a:49:f8:e0:ff:9e"
        }
    ],
    "dns": {}
}

# ./tc -r qdisc show dev veth_host
qdisc tbf 1:[00010000] root refcnt 2 rate 8Kbit burst 80b [001312d0] lat 25.0ms limit 105b 
qdisc ingress ffff:[ffff0000] parent ffff:fff1 ---------------- 

• Set rate to 8000bit and burt to 80bit(=10b) by tc

# tc qdisc delete dev veth_host root handle 1:
# tc qdisc delete dev veth_host ingress


# tc qdisc add dev veth_host handle 1: root tbf rate 8kbit burst 10b latency 25ms

# ./tc  -r qdisc show dev veth_host                                                 
qdisc tbf 1:[00010000] root refcnt 2 rate 8Kbit burst 10b [0002625a] lat 25.0ms limit 35b

As we can see, the values of burst and limit are not same between the bandwidth and tc ouput.

[hustcat]

Maybe we should make ingressBurst and egressBurst use byte as unit directly, but not bit. See here.

[squeed]

Ahh, I see. Thanks for the explanation. I definitely want to keep the config API the same (bits), so your fix seems right.

[matthewdupre]

Haven't tried it, but it all looks right and consistent.