sflow module and increasing useragent

Mark Moseley moseleymark at gmail.com
Wed Aug 10 16:55:54 UTC 2011

On Tue, Aug 9, 2011 at 10:37 PM, Neil Mckee <neil.mckee.ca at gmail.com> wrote:
> It looks like it may be (erroneously!) ignoring that limit and sending the whole user-agent string.  Thanks for pointing it out.
> If you are using sflowtool to print the output at the collector then it's probably chopping the field there,  so you would just need to tweak sflowtool/src/sflow.h file and recompile sflowtool.
> The user-agent can be kilobytes long in some cases.   How many bytes is enough?   Please submit comments to the HTTP thread on http://groups.google.com/group/sflow.
> Neil
> On Aug 9, 2011, at 6:21 PM, Mark Moseley wrote:
>> If I wanted to increase the amount of bytes logged by the sflow module
>> for the user agent to, say, 128 bytes, what would I need to change?
>> I tried changing this:
>> (in ngx_http_sflow.h)
>> but I still get the user agent truncated at 64 bytes. Nor does it seem
>> like SFLHTTP_MAX_USERAGENT_LEN is used anywhere in the code (or any
>> SFLHTTP_MAX_* define).
>> I'm sure I could whack on it long enough to get it to work, but I ask
>> mainly because I don't want to cause some buffer/format/etc overflow
>> somewhere else down the line. Thanks!

Thanks for the info. That did the trick. I wrongly assumed the limit
was being applied in the module itself.

BTW, is there anywhere that has info on APIs for host sflow? I've been
googling to no avail. The perl Net::sFlow module chokes badly
(presumably just expecting standard sflow), and I've not been able to
track down a python module (which is what I'm really interested in).
Just asking since we have this thread going, but I can repost to the
google group if you think it'd be better asked there. Thanks!

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