SSL-VPN Bad compression stub decompression header byte: 102

Question

Hi, 
 
 I am seeing a lot of theese when making remote access with SSL-VPN through the XG (Connenction to the XG from outside) 
 Bad compression stub decompression header byte: 102 
 When theese occur data traffic is halted, but connection is not dropped (vpn) 
 Running SFOS 17 MR5 
 I have compression enbled in XG SSL-VPN configuration. 
 UPDATE: 
 Read on openvpn.net, there there is some issues with the comp-lzo parameter. 
 In the config from the XG, comp-lzo is set to no 
 Switched to "comp-lzo yes" 
 For now, everything works as supposed, will return later on :-)

Matt Heyse · Answer

At firmware 17.5.9 -With VPN Compression on 
 All versions of 2.4.x (2.4.1, 2.4.6. 2.48-current) all give the "Bad compression stub decompression header byte: 102" error 
 Regardless of the Client Compression Option, and syntax style 
 
 compress-lzo yes 
 compress-lzo no 
 compress lzo 
 compress lz4 
 compress 
 Same options as above but with the '--' prefix (--compress lzo) 
 
 It always errors 
 
 Unknown said: At firmware 17.5.2, OpenVPN still using 2.3.6 
 Client 2.3.6, Does not have the Error and is much Faster than 2.4.x when browsing a File Share 
 Client 2.3.18 [Apr-2018 -current for 2.3.x] is even faster with no noticeable lag when browsing a File Share 
 Both 2.3.x versions don't give this Error, with or without adding the Compression option 
 Bulk Copy performance seems unchanged between 2.3.x and a erroring 2.4.x client. 
 Upgrading to the earliest 2.4.x (2.4.0 [Jan-2017 older than 2.3.18]) It errors always. My suggestion is to use Client 2.3.18 openvpn-install-2.3.18-I602-x86_64.exe untill Sophos fixes whatever is wrong with their compression settings