Bug ID 667404: Fragmented IP over IPsec tunnels might capture mcp flows and provoke restarts

Last Modified: Sep 13, 2023

Affected Product(s):
BIG-IP TMOS(all modules)

Known Affected Versions:
11.6.1, 11.6.2, 11.6.3, 11.6.3.1, 11.6.3.2, 11.6.3.3, 11.6.3.4, 11.6.4, 11.6.5, 11.6.5.1, 11.6.5.2, 11.6.5.3, 12.0.0, 12.0.0 HF1, 12.1.0 HF1, 12.0.0 HF2, 12.1.0 HF2, 12.0.0 HF3, 12.0.0 HF4, 12.1.1 HF1, 12.1.1 HF2, 12.1.2 HF1, 12.1.2 HF2, 12.1.0, 12.1.1, 12.1.2, 12.1.3, 12.1.3.1, 13.0.0, 13.0.0 HF1, 13.0.0 HF2, 13.0.0 HF3, 13.0.1

Fixed In:
13.1.0, 12.1.3.2

Opened: Jun 01, 2017

Severity: 2-Critical

Related Article: K77576404

Symptoms

If fragmented IP packets match an IPsec policy, then get forwarded to another tmm for actual processing, the flow lookup might accidentally grab a stale flow_key for another connflow, including internal MCP flows. When that happens, if IPsec does tunnel those flows, internal MCP heartbeats later miss and cause tmm restarts.

Impact

Tmm restarts. Traffic disrupted while tmm restarts.

Conditions

-- Packet fragmentation. -- Packets are serviced by IPsec due to a matching policy for those packets.

Workaround

You can prevent this using either of the following methods: -- If you can, arrange that fragmented packets are re-assembled before reaching IPsec policy handling. -- Modify MTU configuration so fragmentation does not happen. Note: There is no mitigation when fragmented packets reach IPsec and need forwarding from one tmm to another.

Fix Information

Now fragmented packets are handled correctly, and other flows cannot experience interference.

Behavior Change

Guides & references

K10134038: F5 Bug Tracker Filter Names and Tips