|-6||IPv6 mode. The proxy will expect and use IPv6 addresses for all communication. Only the extended FTP modes EPSV and EPRT are allowed with IPv6. The proxy is in IPv4 mode by default.|
|-A||Only permit anonymous FTP connections. Either user "ftp" or user "anonymous" is allowed.|
|The proxy will use this as the source address for the control connection to a server.|
|Address where the proxy will listen for redirected control connections. The default is 127.0.0.1, or ::1 in IPv6 mode.|
|Debug level, ranging from 0 to 7. Higher is more verbose. The default is 5. (These levels correspond to the syslog(3) levels.)|
|-d||Do not daemonize. The process will stay in the foreground, logging to standard error.|
|Maximum number of concurrent FTP sessions. When the proxy reaches this limit, new connections are denied. The default is 100 sessions. The limit can be lowered to a minimum of 1, or raised to a maximum of 500.|
|Fixed server port. Only used in combination with -R . The default is port 21.|
|Port where the proxy will listen for redirected connections. The default is port 8021.|
|Create rules with queue queue appended, so that data connections can be queued.|
|Fixed server address, also known as reverse mode. The proxy will always connect to the same server, regardless of where the client wanted to connect to (before it was redirected). Use this option to proxy for a server behind NAT, or to forward all connections to another proxy.|
|-r||Rewrite sourceport to 20 in active mode to suit ancient clients that insist on this RFC property.|
|-T tag||The filter rules will add tag tag to data connections, and not match quick. This way alternative rules that use the tagged keyword can be implemented following the ftp-proxy anchor. These rules can use special pf(4) features like route-to, reply-to, label, rtable, overload, etc. that ftp-proxy does not implement itself.|
|Number of seconds that the control connection can be idle, before the proxy will disconnect. The maximum is 86400 seconds, which is also the default. Do not set this too low, because the control connection is usually idle when large data transfers are taking place.|
|-v||Set the log flag on pf rules committed by ftp-proxy. Use twice to set the log-all flag. The pf rules do not log by default.|
To make use of the proxy, pf.conf(5) needs the following rules. All anchors are mandatory. Adjust the rules as needed.
In the NAT section:nat-anchor "ftp-proxy/*" rdr-anchor "ftp-proxy/*" rdr pass on $int_if proto tcp from $lan to any port 21 -> \ 127.0.0.1 port 8021
In the rule section:anchor "ftp-proxy/*" pass out proto tcp from $proxy to any port 21
pf(4) does not allow the ruleset to be modified if the system is running at a securelevel(7) higher than 1. At that level ftp-proxy cannot add rules to the anchors and FTP data connections may get blocked.
Negotiated data connection ports below 1024 are not allowed.
The negotiated IP address for active modes is ignored for security reasons. This makes third party file transfers impossible.
ftp-proxy chroots to "/var/empty" and changes to user "proxy" to drop privileges.