Hi, I'm in the process of merging v4-via-v6 into mainline babeld, and I need some advice about the default configuration.
V4-via-v6, is described here: https://datatracker.ietf.org/doc/html/draft-ietf-babel-v4viav6 It's a technique that allows an IPv6-only router to forward IPv4 packets, which makes it easier to administer a double-stack network, since only IPv6 addresses need to be allocated inside the network. However, a v4-via-v6 router needs to be able to originate ICMPv4 packets, and these packets need to have a source address. I haven't done extensive testing yet, but my preliminary investigations indicate that the Linux kernel behaves as follows: - if the router has an IPv4 address on at least one interface, the address is borrowed as the source of the ICMPv4 packet; - if the router has no IPv4 address at all, no ICMPv4 packet is sent, which may cause blackholes. The issue is describes in Section 3 of the draft, which suggests using the IPv4 dummy address 192.0.0.8 when no IPv4 address is available. Using the dummy address will require some minor surgery to the Linux kernel, and I haven't implemented it yet. So while we wait for somebody (me or someone else) to implement support for the dummy address, what should babeld's default behaviour be? 1. Disable v4-via-v6 by default, and assume that an administrator who enables it knows what they're doing? 2. Check for IPv4 addresses, and enable v4-via-v6 automatically if there is at least one IPv4 address? 3. 3=1+2, behave like (2), but allow overriding the daemon's decision? Any better ideas? -- Juliusz _______________________________________________ Babel-users mailing list [email protected] https://alioth-lists.debian.net/cgi-bin/mailman/listinfo/babel-users
