A TCP client is not able to connect to a RHEL server: SYN is answered by challenge ACK and RST is ignored.

Solution Verified - Updated -

Issue

A customer application is from time to time not able to connect to RHEL hosted IMAP server. Sometimes an SYN and all its retransmissions are answered by a challenge ACK and RSTs are ignored. Connection is then timing out from the application point of view and failed connection attempt can be seen in the application log.

Environment

  • Red Hat Enterprise Linux (RHEL)
    • RHEL-8.4.z (kernel-4.18.0-305.76.1)
    • RHEL-8.7 GA (kernel-4.18.0-425)
    • RHEL-9.1 GA (kernel-5.14.0-162)

Subscriber exclusive content

A Red Hat subscription provides unlimited access to our knowledgebase, tools, and much more.

Current Customers and Partners

Log in for full access

Log In

New to Red Hat?

Learn more about Red Hat subscriptions

Using a Red Hat product through a public cloud?

How to access this content