Connections stall, fail, or take a long time to complete due to excessive TCP retransmissions
Issue
- When using iptables, a lot of retransmissions are performed, the connection is reset.
- When using firewalld, connections are stalled (hung) for long periods of time and may be reset.
- TCP packets/segments containing select acknowledgement (SACK) options are ignored when iptables is being used
- System is not sending TCP Fast Retransmissions/Retransmits after receiving three Duplicate Acknowledgements when iptables is used
- SCP transfers are intermittently failing
- TCP transfer stalls and eventually disconnects with "broken pipe" (
EPIPE) message - In Wireshark/tshark, SACK Left Edge (SRE) and SACK Right Edge (SRE) on Dup-ACK packets are much larger than the relative SEQ and ACK numbers
Environment
- Red Hat Enterprise Linux
- TCP (Transmission Control Protocol)
- SACK (Selective Acknowledgements)
- iptables or firewalld firewall
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