When an Exit Node is used, we create a WFP rule to block all inbound and outbound traffic,
along with several rules to permit specific types of traffic. Notably, we allow all inbound and
outbound traffic to and from LocalRoutes specified in wgengine/router.Config. The list of allowed
routes always includes routes for internal interfaces, such as loopback and virtual Hyper-V/WSL2
interfaces, and may also include LAN routes if the "Allow local network access" option is enabled.
However, these permitting rules do not allow link-local multicast on the corresponding interfaces.
This results in broken mDNS/LLMNR, and potentially other similar issues, whenever an exit node is used.
In this PR, we update (*wf.Firewall).UpdatePermittedRoutes() to create rules allowing outbound and
inbound link-local multicast traffic to and from the permitted IP ranges, partially resolving the mDNS/LLMNR
and *.local name resolution issue.
Since Windows does not attempt to send mDNS/LLMNR queries if a catch-all NRPT rule is present,
it is still necessary to disable the creation of that rule using the disable-local-dns-override-via-nrpt nodeAttr.
Updates #13571
Signed-off-by: Nick Khyl <nickk@tailscale.com>
Of tests we wish we could easily add. One day.
Updates #13038
Change-Id: If44646f8d477674bbf2c9a6e58c3cd8f94a4e8df
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
Nick Khyl
Brad Fitzpatrick