Adding masquerade_address_map client ip support

[nmweizi]

Signed-off-by: weizi nmweizi@gmail.com

Adding masquerade_address_map client ip masquerade_address_map = {"2.2.2.1":"2.2.2.1","4.4.4.1":"4.4.4.1"}

client-A -> nat device -> ftp server. <- nat device. <- client-B	client-A	nat device	ftp server	nat device	client-B
1.1.1.1	2.2.2.1	3.3.3.1	4.4.4.1	5.5.5.1

[giampaolo]

What's the story behind this? Why is this needed?

[nmweizi]

What's the story behind this? Why is this needed?

client-A | nat device A | ftp server | nat device B | client-B -- | -- | -- | -- | -- 1.1.1.1 | 2.2.2.1 | 3.3.3.1 | 4.4.4.1 | 5.5.5.1

1. The nat device only allows pasv mode for clients accessing the ftp server, and does not support alg.
2. ftp server connects two networks through nat.
3. The ftp server has a single network card, so the ftp server can only send masquerade_address based on client ip information.