* Fw: [Bug 84951] New: 8021q: kernel doesn't take into account ethernet header bytes for received packets
@ 2014-09-22 16:01 Stephen Hemminger
2014-09-24 14:36 ` Vlad Yasevich
2014-09-24 14:45 ` [PATCH] vlan: Fix receive statistics under-reporting Vladislav Yasevich
0 siblings, 2 replies; 5+ messages in thread
From: Stephen Hemminger @ 2014-09-22 16:01 UTC (permalink / raw)
To: netdev
I am inclined to think this is something that is just an incorrect
user expectation.
Begin forwarded message:
Date: Sun, 21 Sep 2014 11:47:22 -0700
From: "bugzilla-daemon@bugzilla.kernel.org" <bugzilla-daemon@bugzilla.kernel.org>
To: "stephen@networkplumber.org" <stephen@networkplumber.org>
Subject: [Bug 84951] New: 8021q: kernel doesn't take into account ethernet header bytes for received packets
https://bugzilla.kernel.org/show_bug.cgi?id=84951
Bug ID: 84951
Summary: 8021q: kernel doesn't take into account ethernet
header bytes for received packets
Product: Networking
Version: 2.5
Kernel Version: 3.16.1
Hardware: All
OS: Linux
Tree: Mainline
Status: NEW
Severity: normal
Priority: P1
Component: Other
Assignee: shemminger@linux-foundation.org
Reporter: g.djavadyan@gmail.com
Regression: No
Statistics exported by the kernel for received packets on 802.1q subinterfaces
don't consider Ethernet header bytes (dst MAC, src MAC, type). Statistics for
transmitted packets is not affected. The problem is more prominent on
high-speed links (>100Mb/s), as networking tools (nload, iftop, ...) display
lower bandwidth utilization (>5Mb/s difference) than a report from neighboring
routing device (FreeBSD, Cisco). Also, someone monitoring Linux router
interfaces will find that the router generates more information than it
receives.
Tested on CentOS kernel 2.6.32-431.29.2.el6.x86_64 and vanilla 3.16.1 with
drivers: bnx2, atl1c and igb.
How to reproduce:
1. Create dot1q subinterfaces on two boxes (vconfig add eth0 4040).
2. Assign IP addresses to subinterfaces.
3. Check the connection using ping.
4. Check the output from ifconfig eth0.4040 or 'cat
/sys/class/net/eth0.4040/statistics/rx_{packets,bytes}'.
5. Issue standard 56 byte payload ping using 'ping -c 1 neighboring_ip'.
6. Recheck statistics using step 4.
Expected results:
Received packets value should increase by 1 and received bytes value should
increase by 98.
dst MAC - 6
src MAC - 6
ethertype - 2
IP header - 20
ICMP header - 8
ICMP Payload - 56
Total: 98 bytes.
Actual results:
Received packets value increases by 1 and received bytes value increases by 84
bytes.
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^ permalink raw reply [flat|nested] 5+ messages in thread* Re: Fw: [Bug 84951] New: 8021q: kernel doesn't take into account ethernet header bytes for received packets
2014-09-22 16:01 Fw: [Bug 84951] New: 8021q: kernel doesn't take into account ethernet header bytes for received packets Stephen Hemminger
@ 2014-09-24 14:36 ` Vlad Yasevich
2014-09-24 14:45 ` [PATCH] vlan: Fix receive statistics under-reporting Vladislav Yasevich
1 sibling, 0 replies; 5+ messages in thread
From: Vlad Yasevich @ 2014-09-24 14:36 UTC (permalink / raw)
To: Stephen Hemminger, netdev
On 09/22/2014 12:01 PM, Stephen Hemminger wrote:
> I am inclined to think this is something that is just an incorrect
> user expectation.
Looks like a valid bug. vlan just uses skb->len which already had
the eth header stripped off, so it will always under-report 12 bytes
per packet.
-vlad
>
> Begin forwarded message:
>
> Date: Sun, 21 Sep 2014 11:47:22 -0700
> From: "bugzilla-daemon@bugzilla.kernel.org" <bugzilla-daemon@bugzilla.kernel.org>
> To: "stephen@networkplumber.org" <stephen@networkplumber.org>
> Subject: [Bug 84951] New: 8021q: kernel doesn't take into account ethernet header bytes for received packets
>
>
> https://bugzilla.kernel.org/show_bug.cgi?id=84951
>
> Bug ID: 84951
> Summary: 8021q: kernel doesn't take into account ethernet
> header bytes for received packets
> Product: Networking
> Version: 2.5
> Kernel Version: 3.16.1
> Hardware: All
> OS: Linux
> Tree: Mainline
> Status: NEW
> Severity: normal
> Priority: P1
> Component: Other
> Assignee: shemminger@linux-foundation.org
> Reporter: g.djavadyan@gmail.com
> Regression: No
>
> Statistics exported by the kernel for received packets on 802.1q subinterfaces
> don't consider Ethernet header bytes (dst MAC, src MAC, type). Statistics for
> transmitted packets is not affected. The problem is more prominent on
> high-speed links (>100Mb/s), as networking tools (nload, iftop, ...) display
> lower bandwidth utilization (>5Mb/s difference) than a report from neighboring
> routing device (FreeBSD, Cisco). Also, someone monitoring Linux router
> interfaces will find that the router generates more information than it
> receives.
>
> Tested on CentOS kernel 2.6.32-431.29.2.el6.x86_64 and vanilla 3.16.1 with
> drivers: bnx2, atl1c and igb.
>
> How to reproduce:
>
> 1. Create dot1q subinterfaces on two boxes (vconfig add eth0 4040).
> 2. Assign IP addresses to subinterfaces.
> 3. Check the connection using ping.
> 4. Check the output from ifconfig eth0.4040 or 'cat
> /sys/class/net/eth0.4040/statistics/rx_{packets,bytes}'.
> 5. Issue standard 56 byte payload ping using 'ping -c 1 neighboring_ip'.
> 6. Recheck statistics using step 4.
>
> Expected results:
>
> Received packets value should increase by 1 and received bytes value should
> increase by 98.
>
> dst MAC - 6
> src MAC - 6
> ethertype - 2
> IP header - 20
> ICMP header - 8
> ICMP Payload - 56
> Total: 98 bytes.
>
>
> Actual results:
>
> Received packets value increases by 1 and received bytes value increases by 84
> bytes.
>
^ permalink raw reply [flat|nested] 5+ messages in thread* [PATCH] vlan: Fix receive statistics under-reporting
2014-09-22 16:01 Fw: [Bug 84951] New: 8021q: kernel doesn't take into account ethernet header bytes for received packets Stephen Hemminger
2014-09-24 14:36 ` Vlad Yasevich
@ 2014-09-24 14:45 ` Vladislav Yasevich
2014-09-24 15:08 ` Eric Dumazet
1 sibling, 1 reply; 5+ messages in thread
From: Vladislav Yasevich @ 2014-09-24 14:45 UTC (permalink / raw)
To: netdev; +Cc: stephen, Vladislav Yasevich
Vlan devices uder-report 14 bytes per packet in the recieve statistics.
This is because the ETH_HLEN bytes of data has been pulled off the skb
by the time it gets to the vlan receive code. When accounting for
receive butes, add ETH_HLEN back.
See also https://bugzilla.kernel.org/show_bug.cgi?id=84951
Signed-off-by: Vladislav Yasevich <vyasevic@redhat.com>
---
net/8021q/vlan_core.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/8021q/vlan_core.c b/net/8021q/vlan_core.c
index 90cc2bd..8bc5d46 100644
--- a/net/8021q/vlan_core.c
+++ b/net/8021q/vlan_core.c
@@ -54,7 +54,7 @@ bool vlan_do_receive(struct sk_buff **skbp)
u64_stats_update_begin(&rx_stats->syncp);
rx_stats->rx_packets++;
- rx_stats->rx_bytes += skb->len;
+ rx_stats->rx_bytes += skb->len + ETH_HLEN;
if (skb->pkt_type == PACKET_MULTICAST)
rx_stats->rx_multicast++;
u64_stats_update_end(&rx_stats->syncp);
--
1.9.3
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH] vlan: Fix receive statistics under-reporting
2014-09-24 14:45 ` [PATCH] vlan: Fix receive statistics under-reporting Vladislav Yasevich
@ 2014-09-24 15:08 ` Eric Dumazet
2014-09-24 16:45 ` Vlad Yasevich
0 siblings, 1 reply; 5+ messages in thread
From: Eric Dumazet @ 2014-09-24 15:08 UTC (permalink / raw)
To: Vladislav Yasevich; +Cc: netdev, stephen, Vladislav Yasevich
On Wed, 2014-09-24 at 10:45 -0400, Vladislav Yasevich wrote:
> Vlan devices uder-report 14 bytes per packet in the recieve statistics.
> This is because the ETH_HLEN bytes of data has been pulled off the skb
> by the time it gets to the vlan receive code. When accounting for
> receive butes, add ETH_HLEN back.
>
> See also https://bugzilla.kernel.org/show_bug.cgi?id=84951
>
> Signed-off-by: Vladislav Yasevich <vyasevic@redhat.com>
> ---
> net/8021q/vlan_core.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/net/8021q/vlan_core.c b/net/8021q/vlan_core.c
> index 90cc2bd..8bc5d46 100644
> --- a/net/8021q/vlan_core.c
> +++ b/net/8021q/vlan_core.c
> @@ -54,7 +54,7 @@ bool vlan_do_receive(struct sk_buff **skbp)
>
> u64_stats_update_begin(&rx_stats->syncp);
> rx_stats->rx_packets++;
> - rx_stats->rx_bytes += skb->len;
> + rx_stats->rx_bytes += skb->len + ETH_HLEN;
> if (skb->pkt_type == PACKET_MULTICAST)
> rx_stats->rx_multicast++;
> u64_stats_update_end(&rx_stats->syncp);
I do not think this patch is general enough, it doesn't handle GRO for
example.
And should not the vlan tag also be accounted ?
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: [PATCH] vlan: Fix receive statistics under-reporting
2014-09-24 15:08 ` Eric Dumazet
@ 2014-09-24 16:45 ` Vlad Yasevich
0 siblings, 0 replies; 5+ messages in thread
From: Vlad Yasevich @ 2014-09-24 16:45 UTC (permalink / raw)
To: Eric Dumazet, Vladislav Yasevich; +Cc: netdev, stephen
On 09/24/2014 11:08 AM, Eric Dumazet wrote:
> On Wed, 2014-09-24 at 10:45 -0400, Vladislav Yasevich wrote:
>> Vlan devices uder-report 14 bytes per packet in the recieve statistics.
>> This is because the ETH_HLEN bytes of data has been pulled off the skb
>> by the time it gets to the vlan receive code. When accounting for
>> receive butes, add ETH_HLEN back.
>>
>> See also https://bugzilla.kernel.org/show_bug.cgi?id=84951
>>
>> Signed-off-by: Vladislav Yasevich <vyasevic@redhat.com>
>> ---
>> net/8021q/vlan_core.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/net/8021q/vlan_core.c b/net/8021q/vlan_core.c
>> index 90cc2bd..8bc5d46 100644
>> --- a/net/8021q/vlan_core.c
>> +++ b/net/8021q/vlan_core.c
>> @@ -54,7 +54,7 @@ bool vlan_do_receive(struct sk_buff **skbp)
>>
>> u64_stats_update_begin(&rx_stats->syncp);
>> rx_stats->rx_packets++;
>> - rx_stats->rx_bytes += skb->len;
>> + rx_stats->rx_bytes += skb->len + ETH_HLEN;
>> if (skb->pkt_type == PACKET_MULTICAST)
>> rx_stats->rx_multicast++;
>> u64_stats_update_end(&rx_stats->syncp);
>
>
> I do not think this patch is general enough, it doesn't handle GRO for
> example.
I just looked at more software devices (including encapsulators) and
find that macvlan appears to be the only anomaly.
Everyone appears to be using skb->len directly and dropping ETH_HLEN.
Macvlan tries to be "extra smart" and adds the ETH_HLEN back in.
Definitely this patch isn't enough all by itself. I might be better
to make it consistent the other way around.
>
> And should not the vlan tag also be accounted ?
>
>
I don't think so. We don't do it on TX.
-vlad
^ permalink raw reply [flat|nested] 5+ messages in thread
end of thread, other threads:[~2014-09-24 17:45 UTC | newest]
Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2014-09-22 16:01 Fw: [Bug 84951] New: 8021q: kernel doesn't take into account ethernet header bytes for received packets Stephen Hemminger
2014-09-24 14:36 ` Vlad Yasevich
2014-09-24 14:45 ` [PATCH] vlan: Fix receive statistics under-reporting Vladislav Yasevich
2014-09-24 15:08 ` Eric Dumazet
2014-09-24 16:45 ` Vlad Yasevich
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