The reason they weren't working was because the cmd/tta agent in the
guest was dialing out to the test and the vnet couldn't map its global
unicast IPv6 address to a node as it was just using a
map[netip.Addr]*node and blindly trusting the *node was
populated. Instead, it was nil, so the agent connection fetching
didn't work for its RoundTripper and the test could never drive the
node. That map worked for IPv4 but for IPv6 we need to use the method
that takes into account the node's IPv6 SLAAC address. Most call sites
had been converted but I'd missed that one.
Also clean up some debug, and prohibit nodes' link-local unicast
addresses from dialing 2000::/3 directly for now. We can allow that to
be configured opt-in later (some sort of IPv6 NAT mode. Whatever it's
called.) That mode was working on accident, but was confusing: Linux
would do source address selection from link local for the first few
seconds and then after SLAAC and DAD, switch to using the global
unicast source address. Be consistent for now and force it to use the
global unicast.
Updates #13038
Change-Id: I85e973aaa38b43c14611943ff45c7c825ee9200a
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
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