When reverse path filtering is in strict mode on Linux, using an exit
node blocks all network connectivity. This change adds a warning about
this to `tailscale status` and the logs.
Example in `tailscale status`:
```
- not connected to home DERP region 22
- The following issues on your machine will likely make usage of exit nodes impossible: [interface "eth0" has strict reverse-path filtering enabled], please set rp_filter=2 instead of rp_filter=1; see https://github.com/tailscale/tailscale/issues/3310
```
Example in the logs:
```
2024/02/21 21:17:07 health("overall"): error: multiple errors:
not in map poll
The following issues on your machine will likely make usage of exit nodes impossible: [interface "eth0" has strict reverse-path filtering enabled], please set rp_filter=2 instead of rp_filter=1; see https://github.com/tailscale/tailscale/issues/3310
```
Updates #3310
Signed-off-by: Anton Tolchanov <anton@tailscale.com>
This commit updates our IP forwarding parsing logic to allow the less
common but still valid value of `2` to be parsed as `true`, which fixes
an error some users encountered.
Fixes#8375
Signed-off-by: Ross Zurowski <ross@rosszurowski.com>
This updates all source files to use a new standard header for copyright
and license declaration. Notably, copyright no longer includes a date,
and we now use the standard SPDX-License-Identifier header.
This commit was done almost entirely mechanically with perl, and then
some minimal manual fixes.
Updates #6865
Signed-off-by: Will Norris <will@tailscale.com>
Combine the code between `LocalBackend.CheckIPForwarding` and
`controlclient.ipForwardingBroken`.
Fixes#4300
Signed-off-by: Maisem Ali <maisem@tailscale.com>
