Updates rotateLocked so that we hold the activeStderrWriteForTest write
lock around the dup2Stderr call, rather than acquiring it only after
dup2 was already compelete. This ensures no stderrWriteForTest calls
can race with the dup2 syscall. The now unused waitIdleStderrForTest has
been removed.
On macOS, dup2 and write on the same file descriptor are not atomic with
respect to each other, when rotateLocked called dup2Stderr to redirect
the stderr fd to a new file, concurrent goroutines calling
stderrWriteForTest could observe the fd in a transiently invalid state,
resulting in the bad file descripter.
Fixestailscale/corp#36953
Signed-off-by: James Scott <jim@tailscale.com>
Extracts tsaddr.IsTailscaleIPv4 out of tsaddr.IsTailscaleIP.
This will allow for checking valid Tailscale assigned IPv4 addresses
without checking IPv6 addresses.
Updates #14168
Updates tailscale/corp#24620
Signed-off-by: James Scott <jim@tailscale.com>
James ScottandGitHub