Snort mailing list archives

Re: high packet loss - low throughput


From: Michal Purzynski <michal () rsbac org>
Date: Sun, 21 Jul 2013 12:23:12 +0200

On 7/21/13 2:01 AM, Y M wrote:
What are the configurations of the http_inspect preprocessor?

In our environment we have noticed better http traffic performance after tweaking the http_inspect preprocessor configurations in terms of request/response based on our environment, specifically when running Snort inline. What are the values of the memcap, server_flow_depth and client_flow_depth, decompress_depth, and max_gzip_mem?

memcap 1073741824
decompress_depth - not set, looks like an unlimited one
max_gzip_mem not set so most likely default

preprocessor http_inspect: global iis_unicode_map unicode.map 1252 compress_depth 65535 decompress_depth 65535
preprocessor http_inspect_server: server default \
http_methods { GET POST PUT SEARCH MKCOL COPY MOVE LOCK UNLOCK NOTIFY POLL BCOPY BDELETE BMOVE LINK UNLINK OPTIONS HEAD DELETE TRACE TRACK CONNECT SOURCE SUBSCRIBE UNSUBSCRIBE PROPFIND PROPPATCH BPROPFIND BPROPPATCH RPC_CONNECT PROXY_SUCCESS BITS_POST CCM_POST SMS_POST RPC_IN_DATA RPC_OUT_DATA RPC_ECHO_DATA } \
    chunk_length 500000 \
    server_flow_depth 0 \
    client_flow_depth 0 \
    post_depth 65495 \
    oversize_dir_length 500 \
    max_header_length 750 \
    max_headers 100 \
    max_spaces 200 \
    small_chunk_length { 10 5 } \
    non_rfc_char { 0x00 0x01 0x02 0x03 0x04 0x05 0x06 0x07 } \
    enable_cookie \
    extended_response_inspection \
    inspect_gzip \
    normalize_utf \
    unlimited_decompress \
    normalize_javascript \
    apache_whitespace no \
    ascii no \
    bare_byte no \
    directory no \
    double_decode no \
    iis_backslash no \
    iis_delimiter no \
    iis_unicode no \
    multi_slash no \
    utf_8 no \
    u_encode yes \
    webroot no

And a default set of ports.
Also, since this an SO deployment, did you use the iso image directly to build your sensors or built your own Ubuntu server and then added the SO repository? Note: the SO iso distribution is x64.

Did you also try to not to manually bind Snort processes to processors and just let the kernel do it? As I said earlier, a post I read somewhere suggested not to manually bind Snort processes to processors which involved pfring.
Like I said 5 times already (counted! :) I don't manually bind anything - tried that once and got a packet loss around 40-60%.
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