Timeout to pcap_open_live() shouldn't be zero
guyharris opened this issue · comments
In prepare_capture(), pcap_open_live() is called with the third argument, which is the timeout, being 0.
The pcap man page says:
read timeout
If, when capturing, packets are delivered as soon as they
arrive, the application capturing the packets will be woken up
for each packet as it arrives, and might have to make one or
more calls to the operating system to fetch each packet.
If, instead, packets are not delivered as soon as they arrive,
but are delivered after a short delay (called a "read timeout"),
more than one packet can be accumulated before the packets are
delivered, so that a single wakeup would be done for multiple
packets, and each set of calls made to the operating system
would supply multiple packets, rather than a single packet.
This reduces the per-packet CPU overhead if packets are arriving
at a high rate, increasing the number of packets per second that
can be captured.
The read timeout is required so that an application won't wait
for the operating system's capture buffer to fill up before
packets are delivered; if packets are arriving slowly, that wait
could take an arbitrarily long period of time.
Not all platforms support a read timeout; on platforms that
don't, the read timeout is ignored. A zero value for the time-
out, on platforms that support a read timeout, will cause a read
to wait forever to allow enough packets to arrive, with no time-
out.
This means that on several platforms, including all the BSDs and OS X, httpry will not see any packets until enough packets arrive to fill BPF's buffer.
A non-zero value should be specified here; the value should probably be between 1 and 1000.
I'm assuming you're using the latest released version, which currently does use 0. However, the development version has this timeout value set to 1000. Of course, this means I need to stop procrastinating and release a new version...
Thanks!
Earlier today I released version 0.1.8 which includes this change. Hope that helps!