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POExtract tcpdump data with awk
 

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    <p>I'm trying to set up a pipeline to extract, via awk, certain fields and the ascii data (source IP, target IP, and payload) from each packet in a stream of packets captured by tcpdump, but I'm having difficulty. I think the problem is that the payload are arbitrary and it's hard to find a fixed structure one can use to filter it into a record via awk. Here's my current command: </p> <pre><code>sudo tcpdump -i en1 -A -q -l | awk ' { print "fields are $3 $5 $8} ' </code></pre> <p>Here is a single line of the output I'm trying to filter:</p> <pre><code> 12:45:23.890302 IP 10.0.1.3.52695 &gt; weblnb.fogcreek.com.http: tcp 739 E....M@.@... T.........P-.....&amp;..... 2U......GET /default.asp?pg=pgRss&amp;ixDiscussGroup=5 HTTP/1.1 Host: discuss.joelonsoftware.com User-Agent: Vienna/2.6.0.2601 Accept: */* Accept-Encoding: gzip Accept-Language: en-us Cookie: __utma=261409944.1875583.1351297139.1362842383.1362868129.78; __utmz=261409944.1358134504.43.4.utmcsr=joelonsoftware.com|utmccn=(referral)|utmcmd=referral|utmcct=/; fb_SessionId=qc48cvnjvacl3jeo76l8qv69emn119; DBID=LTOJIXRXTFAPXDGFBKCAYLVCILYFCA; fbToken=lqdf3avvfodabtfvd5c4drt18107B8; sUniqueID=20121026230417-66.117.217.10-slb5btkgb5; __utma=131697940.47826445.1351869116.1360335377.1361680499.5; __utmz=131697940.1361680499.5.2.utmccn=(referral)|utmcsr=statcounter.com|utmcct=/p8568424/exit_link_activity/|utmcmd=referral Connection: keep-alive </code></pre> <p>The desired output from this filter is </p> <pre><code>10.0.1.3.52695 weblnb.fogcreek.com.http: { E....M@.@... T.........P-.....&amp;..... 2U......GET /default.asp?pg=pgRss&amp;ixDiscussGroup=5 HTTP/1.1 Host: discuss.joelonsoftware.com User-Agent: Vienna/2.6.0.2601 Accept: */* Accept-Encoding: gzip Accept-Language: en-us Cookie: __utma=261409944.1875583.1351297139.1362842383.1362868129.78; __utmz=261409944.1358134504.43.4.utmcsr=joelonsoftware.com|utmccn=(referral)|utmcmd=referral|utmcct=/; fb_SessionId=qc48cvnjvacl3jeo76l8qv69emn119; DBID=LTOJIXRXTFAPXDGFBKCAYLVCILYFCA; fbToken=lqdf3avvfodabtfvd5c4drt18107B8; sUniqueID=20121026230417-66.117.217.10-slb5btkgb5; __utma=131697940.47826445.1351869116.1360335377.1361680499.5; __utmz=131697940.1361680499.5.2.utmccn=(referral)|utmcsr=statcounter.com|utmcct=/p8568424/exit_link_activity/|utmcmd=referral Connection: keep-alive} </code></pre> <p>Note: the level of abstraction here is not limited to the single specific example above. The general structure of the filtered output should look like this: </p> <pre><code>$sourceip $targetip {$raw_packet_data/payload,_could_be_http_stream_or_just_plain_gibberish} </code></pre> <p>The ending demarcation of the payload field should be the start of the next packet, cf. $sourceip. </p> <p>And the awk filter should capture every line of the tcpdump output stream in this fashion, not just a single line. </p> <p>Any suggestions on how to implement this? </p>
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    1. USKevin Walzer
    1. USKevin Walzer
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    1. COCan you add the expected output, it's not clear how you want the results to look.
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      1. USChris Seymour
 

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