> Source: [sk170144](https://support.checkpoint.com/results/sk/sk170144)

# sk170144 - Security Gateway drops SYN or SYN-ACK TCP packets on 'out of state'

| Property | Value |
|----------|-------|
| Solution ID | sk170144 |
| Date Created | 2020-10-19 |
| Last Modified | 2025-11-30 |
| Technical Level | Advanced |
| Products | Security Gateway |
| Versions | R82, R81.20, R81.10 (EOS), R81 (EOS) |
| OS | Gaia |

## Symptoms

- * Security Gateway drops SYN or SYN-ACK TCP packets on 'out of state'.

* Kernel debug (fw ctl zdebug + drop) shows the following packet drops:  
  `
  [DATE TIME];[kern];[tid_0];[SIM-206609312];update_tcp_state: not empty[PPK0];`  
  `
  [DATE TIME];[kern];[tid_0];[SIM-206609312];do_inbound: Possible TCP state violation for ` -> dropping packet ;  
  [DATE TIME];[kern];[tid_0];[SIM-206609312];do_packet_finish: SIMPKT_IN_DROP vsid=0, conn:;

## Cause

The SYN or SYN-ACK packets have payload data. Usually, they do not contain any.  
Different functionality in R80.20 causes SecureXL to drop them as "Drop Out of State TCP Packets".

A new SecureXL kernel parameter was added: **asm_syn_packet_with_data**   
It behaves just like an equivalent FireWall kernel parameter that already exists: **asm_allow_syn_with_data**

## Solution

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