Re: Mcast packet loss 2.6.8.1 kernel

From: Ahmed Kadwa
Date: Thu Nov 15 2007 - 02:44:22 EST


Thanks for the response David,

Heres output of netstat -s before and after my app data:

I have advised management to upgrade the kernel, but we have too many
custom drivers on this embedded system :-(. It would take way too long
to get everything working again.

cat /proc/sys/net/core/netdev_max_backlog = 300
set to 1000 also, with no effect

tried setting device to eth0 in ip_mreq struct for IP_ADD_MEMBERSHIP
sock option, no change to packet loss.

output of netstat after startup and before tx of packets
/flash/sbin/netstat -s
Ip:
1199 total packets received
0 forwarded
0 incoming packets discarded
884 incoming packets delivered
666 requests sent out
316 reassemblies required
16 packets reassembled ok
Icmp:
59 ICMP messages received
0 input ICMP message failed.
ICMP input histogram:
destination unreachable: 10
echo requests: 48
echo replies: 1
58 ICMP messages sent
0 ICMP messages failed
ICMP output histogram:
destination unreachable: 10
echo replies: 48

Tcp:
8 active connections openings
4 passive connection openings
0 failed connection attempts
0 connection resets received
4 connections established
747 segments received
535 segments send out
0 segments retransmited
0 bad segments received.
0 resets sent
Udp:
54 packets received
10 packets to unknown port received.
0 packet receive errors
64 packets sent
error parsing /proc/net/snmp: Success

after data tx:
/flash/sbin/netstat -s
Ip:
5469 total packets received
0 forwarded
0 incoming packets discarded
5138 incoming packets delivered
4801 requests sent out
316 reassemblies required
16 packets reassembled ok

Icmp:
140 ICMP messages received
0 input ICMP message failed.
ICMP input histogram:
destination unreachable: 10
echo requests: 129
echo replies: 1
139 ICMP messages sent
0 ICMP messages failed
ICMP output histogram:
destination unreachable: 10
echo replies: 129
Tcp:
8 active connections openings
4 passive connection openings
0 failed connection attempts
0 connection resets received
4 connections established
2925 segments received
3590 segments send out
0 segments retransmited
0 bad segments received.
0 resets sent
Udp:
2040 packets received
10 packets to unknown port received.
0 packet receive errors
1057 packets sent
error parsing /proc/net/snmp: Success

/flash/sbin/netstat -g
IPv4 Group Memberships
Interface RefCnt Group
--------------- ------ ---------------------
lo 1 224.0.0.1
eth0 1 231.10.11.1
eth0 1 224.0.0.1
eth1 1 224.0.0.1

I am a bit slow and cant make much out of this output though. My app
showed 7 messages lost.

cat /proc/net/dev
Inter-| Receive |
face |bytes packets errs drop fifo frame compressed multicast|
lo: 1136388 1049 0 0 0 0 0 0
eth0: 1432490 4333 0 0 0 0 0 1025
eth1: 526993 1113 0 0 0 0 0 73
tunl0: 0 0 0 0 0 0 0 0

This makes more sense to me, as I can see the multicast packets received
on eth0. The multicast packets include my data + data from mrouted

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