iftop doesn't work with tun0?

[Zhang Weiwu]

As of 0.17, iftop change log says it being to support ppp interface,
while in my case it doesn't work for my tun0 which is created
by /etc/rc.d/ppp (DSL connection). Launch 'iftop -i tun0' does
correctly show up all active TCP connections and from/to address, but
bandwidth usage for every connection are always '0b'.

Any one hit this problem too or give me a hint? I googled but earliest
post about tun0 and iftop is on 2004, before release 0f v0.17 of iftop.
Again I am not sure if I should mail iftop developers, as maybe they
didn't design specifically for FreeBSD. Or, at least, perhaps someone
already successfully run iftop on ppp link and can tell me if this
behavior I saw is normal or not.

Thanks a lot in advance!

Below is example output of monitoring tun0. When working on fxp0 it's
100% correct.

            12.5Kb      25.0Kb      37.5Kb      50.0Kb 62.5Kb
└───────────┴───────────┴───────────┴───────────┴────────────
242.6.198.160    => 209.85.139.18        0b      0b      0b  
                 <=                      0b      0b      0b  
242.6.45.125     => 209.85.139.18        0b      0b      0b  
                 <=                      0b      0b      0b  
242.6.241.248    => 209.85.139.18        0b      0b      0b  
                 <=                      0b      0b      0b  
51.6.214.188     => 209.85.139.18        0b      0b      0b  
                 <=                      0b      0b      0b  
51.6.214.186     => 209.85.139.18        0b      0b      0b
                 <=                      0b      0b      0b
51.6.214.252     => 209.85.139.18        0b      0b      0b
                 <=                      0b      0b      0b
51.6.214.96      => 209.85.139.18        0b      0b      0b
                 <=                      0b      0b      0b

─────────────────────────────────────────────────────────────
TX:             cumm:     0B rates:k:    0b0b    0b      0b  
RX:                       0B             0b0b    0b      0b  
TOTAL:                    0B             0b0b    0b      0b