diff options
| author | Md. Islam <mislam4@kent.edu> | 2018-02-06 23:14:18 -0500 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2018-02-07 21:59:12 -0500 |
| commit | 043e337f555e610ad8237fd23522d97c968d72b9 (patch) | |
| tree | af44c2bc108f2bc7bc3f74390dbbc81f24a73e91 /net/sched/sch_netem.c | |
| parent | 62f94c2101f35cd45775df00ba09bde77580e26a (diff) | |
| download | lwn-043e337f555e610ad8237fd23522d97c968d72b9.tar.gz lwn-043e337f555e610ad8237fd23522d97c968d72b9.zip | |
sch_netem: Bug fixing in calculating Netem interval
In Kernel 4.15.0+, Netem does not work properly.
Netem setup:
tc qdisc add dev h1-eth0 root handle 1: netem delay 10ms 2ms
Result:
PING 172.16.101.2 (172.16.101.2) 56(84) bytes of data.
64 bytes from 172.16.101.2: icmp_seq=1 ttl=64 time=22.8 ms
64 bytes from 172.16.101.2: icmp_seq=2 ttl=64 time=10.9 ms
64 bytes from 172.16.101.2: icmp_seq=3 ttl=64 time=10.9 ms
64 bytes from 172.16.101.2: icmp_seq=5 ttl=64 time=11.4 ms
64 bytes from 172.16.101.2: icmp_seq=6 ttl=64 time=11.8 ms
64 bytes from 172.16.101.2: icmp_seq=4 ttl=64 time=4303 ms
64 bytes from 172.16.101.2: icmp_seq=10 ttl=64 time=11.2 ms
64 bytes from 172.16.101.2: icmp_seq=11 ttl=64 time=10.3 ms
64 bytes from 172.16.101.2: icmp_seq=7 ttl=64 time=4304 ms
64 bytes from 172.16.101.2: icmp_seq=8 ttl=64 time=4303 ms
Patch:
(rnd % (2 * sigma)) - sigma was overflowing s32. After applying the
patch, I found following output which is desirable.
PING 172.16.101.2 (172.16.101.2) 56(84) bytes of data.
64 bytes from 172.16.101.2: icmp_seq=1 ttl=64 time=21.1 ms
64 bytes from 172.16.101.2: icmp_seq=2 ttl=64 time=8.46 ms
64 bytes from 172.16.101.2: icmp_seq=3 ttl=64 time=9.00 ms
64 bytes from 172.16.101.2: icmp_seq=4 ttl=64 time=11.8 ms
64 bytes from 172.16.101.2: icmp_seq=5 ttl=64 time=8.36 ms
64 bytes from 172.16.101.2: icmp_seq=6 ttl=64 time=11.8 ms
64 bytes from 172.16.101.2: icmp_seq=7 ttl=64 time=8.11 ms
64 bytes from 172.16.101.2: icmp_seq=8 ttl=64 time=10.0 ms
64 bytes from 172.16.101.2: icmp_seq=9 ttl=64 time=11.3 ms
64 bytes from 172.16.101.2: icmp_seq=10 ttl=64 time=11.5 ms
64 bytes from 172.16.101.2: icmp_seq=11 ttl=64 time=10.2 ms
Reviewed-by: Stephen Hemminger <stephen@networkplumber.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/sched/sch_netem.c')
| -rw-r--r-- | net/sched/sch_netem.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/net/sched/sch_netem.c b/net/sched/sch_netem.c index 7bbc13b8ca47..7c179addebcd 100644 --- a/net/sched/sch_netem.c +++ b/net/sched/sch_netem.c @@ -327,7 +327,7 @@ static s64 tabledist(s64 mu, s32 sigma, /* default uniform distribution */ if (dist == NULL) - return (rnd % (2 * sigma)) - sigma + mu; + return ((rnd % (2 * sigma)) + mu) - sigma; t = dist->table[rnd % dist->size]; x = (sigma % NETEM_DIST_SCALE) * t; |