Dear Yutaka,
   I found a possible bug.

Free from this bug: 9.1.1

9.1.2  to 9.5.0 no check

Affected: 9.5.1 - 9.5.2 - 9.5.3
 
Landscape:
Delegate configured for a FTP proxy in cascade mode:

/firewall/# delegated -P21 SERVER=ftp PERMIT="ftp:*:/internal/"
/internal/# delegated -P21 SERVER=ftp PROXY=/firewall/:21

The problem appear on firewall log:

with 9.5.3

03/22 11:44:25.07 [8807] 2+0/11/8: ## ftp-conndata: NOT bound#1 err=98
03/22 11:44:25.07 [8807] 2+0/11/8: ftp_conndata: connected 
217.172.X.X:53795->217.172.X.X/217.172.X.X:30794 [22](0.0)
03/22 11:44:25.07 [8807] 2+0/11/8: -- with PASV
03/22 11:44:25.07 [8807] 2+0/11/8: PORT [0,0,0,0,0,0] >> 200 PORT 
command successful [translated to PASV by DeleGate].^M
03/22 11:44:25.08 [8807] 2+0/12/9: FTP-CACHE: STOR [SkypeSetup.exe] = [][]:0
03/22 11:44:25.08 [8807] 2+0/12/9: -- PASVserv to XDCclnt
03/22 11:44:25.08 [8807] 2+0/12/9: --- XDC data_relay SERVER (STOR).
03/22 11:44:25.15 [8807] 2+0/12/9: relayABORT[1 0 1]: recvPeek: 0.000 
pcc=31 [32 59 46 A 4D 44 42 6D 70 00 00 00 00 XA 4C 41 71 6F 74 39 2B
41 4E 39 43 48 6B 48 4D 63 44]
03/22 11:44:25.15 [8807] 2+0/12/9: relayABORT[2 0 1]: recvPeek: 0.000 
pcc=31 [2F 30 00 00 00 00 XE 56 69 2B 79 44 70 00 00 00 00 XC 65 4C 38
 59 6C 56 2F 44 50 53 69 52 59]
03/22 11:44:25.17 [8807] 2+0/12/9: relayABORT[3 0 1]: recvPeek: 0.000 
pcc=31 [41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 41 A 41 41
41 41 41 41 41 41 41 41 41 41]
03/22 11:44:25.17 [8807] 2+0/12/9: relayABORT[4 0 1]: recvPeek: 0.000 
pcc=31 [2F 7A 5A 59 41 2F 30 00 00 00 00 XF 4E 6C 67 44 2F 7A 5A 59 41
 2F 30 00 00 00 00 XF 4E 6C 67]

etc...
 

Instead with 9.1.1 (works!)

03/22 11:46:49.38 [9072] 3+0/9/9: ## ftp-conndata: NOT bound#1 err=98
03/22 11:46:49.39 [9072] 3+0/9/9: ftp_conndata: connected 
217.172.X.X:57385->217.172.5.12/217.172.X.X:5389 [21](0.0)
03/22 11:46:49.39 [9072] 3+0/9/9: -- with PASV
03/22 11:46:49.39 [9072] 3+0/9/9: PORT [0,0,0,0,0,0] >> 200 PORT command 
successful [translated to PASV by DeleGate].^M
03/22 11:46:49.40 [9072] 3+0/10/10: FTP-CACHE: STOR [ica32pkg.msi] = [][]:0
03/22 11:46:49.40 [9072] 3+0/10/10: -- PASVserv to XDCclnt
03/22 11:46:49.40 [9072] 3+0/10/10: --- XDC data_relay SERVER (STOR).



Cheers
Stefano