dhcrelay doesn't support the loopback as uplink interface
Add support for adding the loopback interface as uplink in dhcrelay agent
The Problem
As we know the loopback interfaces can have multiple ip addresses. And there is a case to use the loopback interface as uplink interface using -U option which is not supported yet in relay agent.
Solution
I request to do two changes in the project.
So I suggest ignore the fatal logging (Example: "Unsupported device type 128 for lo") in common/lpf.c file, add the case for ARPHRD_LOOPBACK type and handle as a ARPHRD_ETHER type interface.
Then change some functionality in relay/dhcrelay.c file.
When you specify the loopback interface as uplink using -U option and this interface has one more ip address, except the link local (127.0.0.1/8), use this ip address as outbound uplink "giaddr" in "DHCP Option 82" described in RFC3527.
These changes will not affect other functionality of relay agent.
Dear @tomek can you allocate me to the project and discuss this feature.
Contacts
Artashes Balabekyan
Software/Network engineer from Netris Inc.