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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link="#0563C1" vlink="#954F72"><div class=WordSection1><p class=MsoNormal>Hi all,<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>This will only be relevant to folks using Myricom cards, but I wanted to share something I learned today…<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>As I’m sure you know, Myricom provides a libpcap wrapper around its native SNF APIs. I had been unsure for a while how the pcap.buffer-size YAML setting was used within SNF. My testing yielded no noticeable difference in Suricata when adjusting this value, however I wanted to be sure. I tracked this value to a call to pcap_set_buffer_size (a libpcap API) within the Suricata source code. I then began an exchange with Myricom support regarding how SNF handles the pcap_set_buffer_size() API. Here was the response:<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoPlainText style='text-indent:.5in'><span style='font-size:10.0pt'>“The libpcap interface to Sniffer10G ignores the pcap_set_buffer_size() value. The call to snf_open() uses zero as the dataring_size which informs the Sniffer library to use a default value or the value from the SNF_DATARING_SIZE environment variable.”<o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>They also cited a pull request to add support for setting the SNF_DATARING_SIZE using the value from pcap_set_buffer_size().<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoPlainText><span style='font-size:10.0pt'> “I've submitted this change to the libpcap maintainers at <a href="https://github.com/the-tcpdump-group/libpcap/compare/master...myri:master">https://github.com/the-tcpdump-group/libpcap/compare/master...myri:master</a> as pull request 435.”<o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>In summary, the pcap.buffer-size YAML setting is currently ignored when using Myricom SNF, however a future release should provide support for using the pcap.buffer-size to set the SNF_DATARING_SIZE from within the YAML file instead of an environment variable.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Hope this helps!<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Zach<o:p></o:p></p><p class=MsoNormal><b><span style='font-size:12.0pt;font-family:"Franklin Gothic Book","sans-serif"'>________________________<o:p></o:p></span></b></p><p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Franklin Gothic Book","sans-serif"'>Zach Rasmor<o:p></o:p></span></b></p><p class=MsoNormal><span style='font-size:9.0pt;font-family:"Franklin Gothic Book","sans-serif"'>Senior Software Engineer<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:9.0pt;font-family:"Franklin Gothic Book","sans-serif"'>Lockheed Martin CIRT<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:9.0pt;font-family:"Franklin Gothic Book","sans-serif"'>700 N Frederick Ave | Gaithersburg, MD 20879<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:9.0pt;font-family:"Franklin Gothic Book","sans-serif"'>Email: <a href="mailto:zachary.r.rasmor@lmco.com"><span style='color:blue'>zachary.r.rasmor@lmco.com</span></a><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:9.0pt;font-family:"Franklin Gothic Book","sans-serif"'>Office: 301.240.6116<o:p></o:p></span></p><p class=MsoNormal><o:p> </o:p></p></div></body></html>