Scan web servers to see if the change compression behaviour when the HTTP Via header is added.

viascan is used to test one of more origin web servers to see if they give different results when asking for gzipped content when an HTTP Via header is or is not present.

It expects to receive one or more lines on stdin that consist of comma separated entries representing an HTTP Host header value and the name of an origin web server to which to send an HTTP request. For example,

 echo "www.cloudflare.com,cloudflare.com" | ./viascan

would connect to cloudflare.com and do a GET for / with the Host header set to www.cloudflare.com. The origin can be an IP address.

viascan outputs one comma-separated line per input line.

For example, the above might output:

 cloudflare.com,www.cloudflare.com,t,t,t,2038,2038,gzip,gzip,
 cloudflare-nginx,cloudflare-nginx

Breaking that down:

cloudflare.com, Origin server contacted

www.cloudflare.com, Host header sent

t, t if the origin server name resolved

t, t if a GET / with no Via header worked

t, t if a GET / with a Via header worked

2038, Size in bytes of the response to GET / with no Via

2038, Size in bytes of the response to GET / with Via

gzip, Content-Encoding in response with no Via header

gzip, Content-Encoding in response with a Via header

cloudflare-nginx, Server in response with no Via header

cloudflare-nginx Server in response with a Via header

-dump Dump requests and responses for debugging

-fields If set outputs a header line containing field names

-log File to write log information to

-resolver DNS resolver address (default 127.0.0.1)

-workers Number of concurrent workers (default 10)