Subject: Re: iproute uses too small of a receive buffer

From: Ben Greear <[email-masked]>
Date: Tue, 27 Oct 2009 16:30:31 -0700

On 10/27/2009 04:24 PM, Stephen Hemminger wrote:
> On Tue, 27 Oct 2009 16:16:52 -0700
> Ben Greear<[email-masked]>  wrote:
>
>> I have a very busy system with a bunch of xorp router processes (mis)configured.
>>
>> This thing is rapidly making route changes for whatever reason.
>>
>> The 'ip monitor route' command was failing:
>>
>> [root@i7-dqc-1 ]# ip monitor route
>> netlink receive error No buffer space available (105)
>> Dump terminated
>>
>>
>> It is only using a 32k rcv buffer, and it seems the OS was
>> overdriving it.
>>
>> Please consider making the rcv buffer larger, perhaps something
>> like this (inline is white-space damaged...attachment should apply
>> if deemed useful.):
>>
>> Signed-off-by:  Ben Greear<[email-masked]>
>>
>> diff --git a/lib/libnetlink.c b/lib/libnetlink.c
>> index b68e2fd..95a7d1d 100644
>> --- a/lib/libnetlink.c
>> +++ b/lib/libnetlink.c
>> @@ -38,7 +38,7 @@ int rtnl_open_byproto(struct rtnl_handle *rth, unsigned subscriptions,
>>    {
>>           socklen_t addr_len;
>>           int sndbuf = 32768;
>> -       int rcvbuf = 32768;
>> +       int rcvbuf = 3276800;
>>
>>           memset(rth, 0, sizeof(*rth));
>>
>>
>> Thanks,
>> Ben
>>
>
> Just having larger buffer isn't guarantee of success. Allocating
> a huge buffer is not going to work on embedded.
>
> Why not have it continue after one error.

Probably the right way is to give a cmd-line arg to set the buffer size
and also continue if the error is ENOBUFs (but print some error out
so users know they have issues).  I can make the attempt if that
sounds good to you.

Thanks,
Ben

-- 
Ben Greear <[email-masked]>
Candela Technologies Inc  http://www.candelatech.com