tailscale/wgengine/magicsock
Josh Bleecher Snyder 3c543c103a wgengine/magicsock: unify initial bind and rebind
We had two separate code paths for the initial UDP listener bind
and any subsequent rebinds.

IPv6 got left out of the rebind code.
Rather than duplicate it there, unify the two code paths.
Then improve the resulting code:

* Rebind had nested listen attempts to try the user-specified port first,
  and then fall back to :0 if that failed. Convert that into a loop.
* Initial bind tried only the user-specified port.
  Rebind tried the user-specified port and 0.
  But there are actually three ports of interest:
  The one the user specified, the most recent port in use, and 0.
  We now try all three in order, as appropriate.
* In the extremely rare case in which binding to port 0 fails,
  use a dummy net.PacketConn whose reads block until close.
  This will keep the wireguard-go receive func goroutine alive.

As a pleasant side-effect of this, if we decide that
we need to resuscitate #1796, it will now be much easier.

Fixes #1799

Co-authored-by: David Anderson <danderson@tailscale.com>
Signed-off-by: Josh Bleecher Snyder <josharian@gmail.com>
2021-04-28 10:39:28 -07:00
..
discopingpurpose_string.go wgengine/magicsock: make discoPingPurpose a stringer 2020-09-14 14:29:28 -07:00
legacy.go wgengine/magicsock: mark some legacy debug log output as verbose 2021-03-18 08:17:59 -07:00
magicsock_test.go tailcfg: add Endpoint, EndpointType, MapRequest.EndpointType 2021-04-13 10:12:14 -07:00
magicsock.go wgengine/magicsock: unify initial bind and rebind 2021-04-28 10:39:28 -07:00