'--address' option on client side.

[Paul Slootman]

On Fri 26 Mar 2021, Harry Mangalam via rsync wrote:
> 
> I'm trying to improve a parallel rsync wrapper called parsyncfp (pfp)  in
> response to a user request.  He wants rsync to emit data on multiple
> interfaces (one interface per rsync instance). From the man page it seems
> like the '--address' option would do that and in fact using it as such does
> not result in an error, but it also does not result in both interfaces
> being used, either from pfp or when launched directly from different shells.
> 
> My route (working from home) shows the 2 wlan interfaces up with
> different IP #s:
> wlp3s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
>        inet 192.168.1.223  netmask 255.255.255.0  broadcast 192.168.1.255
> ...
> 
> wlx9cefd5fb0bb5: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
>        inet 192.168.1.186  netmask 255.255.255.0  broadcast 192.168.1.255

As both interfaces are on the same network, the kernel will use one
interface to transmit data to that network.

> and route shows:
> $ route
> 
> Kernel IP routing table
> Destination     Gateway         Genmask         Flags Metric Ref    Use
> Iface
> default         router.asus.com 0.0.0.0         UG    601    0        0
> wlx9cefd5fb0bb5
> default         router.asus.com 0.0.0.0         UG    602    0        0

Here you see wlx9cefd5fb0bb5 has a lower metric, hence it will
preferentially be used.

You need to dive deeper into linux policy based routing, to force
traffic e.g. from a particular IP address out over a certain interface.

This is totally outside the scope of rsync; there's nothing rsync can do
to influence this. You need the 'ip rule' and 'ip route' commands.


Paul