broken HTTP_PROXY handling on jenkins-slave (JNLP)
The proxy exclusion list (http.nonProxyHosts, no_proxy) is not taken into account on the jenkins-slave side.
This has been observed in our jenkins master/slave environment which uses JNLP.

Support for HTTP_PROXY handling on jenkins-slave side has been added with jenkins version 1.606.
Unfortunately that does not take the proxy exclusion list into account (e.g. defined by no_proxy env variable on linux).
This forces the slave to always use the proxy. Even for destinations which would be excluded by no_proxy.

Jenkins uses org.jenkins-ci.main:remoting for handling http proxy functionality.
Jenkins includes version 2.53.2 of org.jenkins-ci.main:remoting which contains the error described above.

possible solution:
1.) create new release of org.jenkins-ci.main:remoting which already contains the fix in it's master branch.
2.) update jenkins' to use this new version of org.jenkins-ci.main:remoting

see also:

• commit of fix in master branch of org.jenkins-ci.main:remoting
  https://github.com/jenkinsci/remoting/commit/56d30acb89f5626320d6b47585053674a5fdfb78