NFD

Eric Newberry wrote:

separate channels for each face

I was saying one channel for each local IPv4/v6 address, not for each face (the context was UDP channels)

However, this would require that NFD know which local endpoint it should use for a given connection. The open question is how this should be accomplished, particularly if there are multiple physical interfaces with non-loopback addresses on the system.

The "simple" answer is look at the kernel's IP routing table... except that it's not that simple. And I don't think we want to replicate the IP routing logic in NFD.

One alternative approach (for UDP) is to let the kernel do PMTU discovery, and react to "datagram too large" errors by fragmenting the packet via NDNLP. This would also be more accurate than just looking at the interface MTU.

Davide Pesavento wrote:

Eric Newberry wrote:

separate channels for each face

I was saying one channel for each local IPv4/v6 address, not for each face (the context was UDP channels)

Sorry, that's what I meant.

However, this would require that NFD know which local endpoint it should use for a given connection. The open question is how this should be accomplished, particularly if there are multiple physical interfaces with non-loopback addresses on the system.

The "simple" answer is look at the kernel's IP routing table... except that it's not that simple. And I don't think we want to replicate the IP routing logic in NFD.

I agree that this would be pretty complicated (and redundant).

Eric Newberry wrote:

this would require that NFD know which local endpoint it should use for a given connection.

Actually, why do we need to do that? Unless I forgot something, we can do the following: keep using a single channel on the "any" address and let the kernel pick the outgoing interface; then, once the face is created, query the socket's local endpoint and find it among all the addresses of all the known network interfaces (you can either maintain a reverse mapping address -> netif or search the address every time).

Davide Pesavento wrote:

Eric Newberry wrote:

this would require that NFD know which local endpoint it should use for a given connection.

Actually, why do we need to do that? Unless I forgot something, we can do the following: keep using a single channel on the "any" address and let the kernel pick the outgoing interface; then, once the face is created, query the socket's local endpoint and find it among all the addresses of all the known network interfaces (you can either maintain a reverse mapping address -> netif or search the address every time).

How would we check for changes in the MTU? Perhaps the Factory or Channel could connect to the MTU changed signal on all netifs and then iterate through all Transports to determine which ones needed to be updated?