2006 March | John Leach's Blog

Condoleezza Rice Liverpool/Blackburn protests
March 30th, 2006

George Bush’s No 2, Condoleezza Rice, is coming to En-ger-land. She’s not leading an invasion (ha!), she was invited by Jack Straw. During her time here she’ll be visiting Liverpool and Blackburn. Get yourself down to the organised protests on Friday 31st March in Liverpool and Saturday 1st April in Blackburn. Read more at www.condiwatch.co.uk.

UPDATE: I took some photos on Friday night at the Royal Philharmonic in Liverpool. I hearby throw this set of photos into the public domain. Do with them as you wish.

ANOTHER UPDATE: Fixed the link to the rest of the photos. Duh

Tags: blackburn, Condoleezza Rice, jack straw, liverpool, protest, war, war criminal
Posted in Photoblog, Politics | No Comments »
Lighttpd and Ruby on Rails: Secure and Fast Downloading
March 16th, 2006

When controlling access to files on a webserver developers often use the web application itself as a file server. The request comes in, the script checks for some session authentication variable or something, then streams the file from disk (hopefully from outside the webroot) to the browser.

The problem with this from a performance standpoint is that a thread/process of the web application has to be running for the entire duration of the download. With a busy webserver serving many concurrent downloads, this is an immense overhead. The web server itself should be orders of magnitude faster at serving files directly than via a web application, but you can’t just stick the files in a different directory and hope nobody finds the secret urls. The new web server on the block, Lighttpd, has some clever solutions for this problem.
Read the rest of this entry »

Tags: http, lighttpd, performance, Security
Posted in Ruby on Rails, Tech | 3 Comments »

TCP, NAT and 2MSL mismatch

March 8th, 2006

We have a client that connects over the NHS internal network to a server hosted at our site. We have lots of clients like this, but these are slightly different because they NAT all their machines to one IP before it gets to us.

Recently they complained about connection problems and after lots of investigation we managed to get a packet capture of the problem (IPs changed of course):

 1  0.00 192.168.0.1 -> 10.0.0.254 TCP 2268 > 80 [SYN]
 2  0.00 10.0.0.254 -> 192.168.0.1 TCP 80 > 2268 [SYN, ACK]
 3  0.01 192.168.0.1 -> 10.0.0.254 TCP 2268 > 80 [ACK]
 4  0.08 192.168.0.1 -> 10.0.0.254 HTTP POST
 5  0.24 10.0.0.254 -> 192.168.0.1 TCP 80 > 2268 [ACK]
 6  0.23 192.168.0.1 -> 10.0.0.254 HTTP Continuation
 7  0.24 10.0.0.254 -> 192.168.0.1 HTTP HTTP/1.1 200 OK 1365
 8  0.24 10.0.0.254 -> 192.168.0.1 HTTP Continuation
 9  0.24 10.0.0.254 -> 192.168.0.1 TCP 80 > 2268 [FIN, ACK]
10  0.29 192.168.0.1 -> 10.0.0.254 TCP 2268 > 80 [ACK]
11  0.31 192.168.0.1 -> 10.0.0.254 TCP 2268 > 80 [FIN, ACK]
12  0.31 10.0.0.254 -> 192.168.0.1 TCP 80 > 2268 [ACK]
13  0.34 192.168.0.1 -> 10.0.0.254 TCP 2268 > 80 [ACK]
14 68.26 192.168.0.1 -> 10.0.0.254 TCP 2268 > 80 [SYN]
15 71.18 192.168.0.1 -> 10.0.0.254 TCP 2268 > 80 [SYN]
16 77.13 192.168.0.1 -> 10.0.0.254 TCP 2268 > 80 [SYN]
17 98.25 192.168.0.1 -> 10.0.0.254 TCP 2268 > 80 [RST, CWR]

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Tags: cisco, NAT, network, networking, tcp, tcpip, troubleshooting

Posted in Networks and Firewalls, Tech | No Comments »

Condoleezza Rice Liverpool/Blackburn protests

Lighttpd and Ruby on Rails: Secure and Fast Downloading

TCP, NAT and 2MSL mismatch

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Condoleezza Rice Liverpool/Blackburn protests

Lighttpd and Ruby on Rails: Secure and Fast Downloading

TCP, NAT and 2MSL mismatch

John Leach

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