tree 05dfffbc156ab8c2995037279f1dee7b1396fd85
parent cd7e167a57ddd54edae5effb09022a8d7e955c7c
author Ruslan Ermilov <ru@nginx.com> 1541510989 +0300
committer Ruslan Ermilov <ru@nginx.com> 1541510989 +0300

HTTP/2: limit the number of idle state switches.

An attack that continuously switches HTTP/2 connection between
idle and active states can result in excessive CPU usage.
This is because when a connection switches to the idle state,
all of its memory pool caches are freed.

This change limits the maximum allowed number of idle state
switches to 10 * http2_max_requests (i.e., 10000 by default).
This limits possible CPU usage in one connection, and also
imposes a limit on the maximum lifetime of a connection.

Initially reported by Gal Goldshtein from F5 Networks.