Add a wrapper that uses anet on Android, but net on other platforms.
### Purpose
Fixes
https://forum.syncthing.net/t/workaround-for-android-local-discovery/20403/12
### Testing
Run two Syncthing instances with Global Discovery disabled. Pair them
with each other, don't hardcode their addresses, and verify they
connect.
Before:
- Local discovery on Android 10+ is broken. The phone receives local
discovery packets from other devices running Syncthing on the same
network, e.g. a computer. But it doesn't send its own local discovery
packets.
- Startup of the beacon/broadcast.go and beacon/multicast.go "services"
subsequently fail, see the log entries of "service.go" with "2 of 2
failures, backing off".
Root cause:
- Android 10+ restricts determining the network interfaces for privacy
reasons. The interfaces and IP addresses cannot be determined.
- There's a bug in the go "net" library. I can actually get the
interfaces, but the fix was not implemented by the go team.
Workaround:
- The "community" found a workaround by creating a light wrapper around
"net" called "anet" library.
- "anet" adjusts the behaviour on Android 10+ and gets the interfaces
plus their IP addresses, as required by Syncthing.
After:
- By using the "anet" lib, Syncthing is able to get the interface ip
addresses and put them into the "AllAddresses" string array.
- The "AllAddresses" string array is then announced on the local
discovery multicast and broadcast packets, if enabled in Syncthing's
config.
- By correctly getting the interfaces and IP addresses using "anet" in
"beacon/broadcast.go" and "beacon/multicast.go", the services start up
fine again.
Verification:
- I've built "libSyncthingNative.so" with this PR applied for Android
and put it into Syncthing-Fork v1.29.7.5 for testing. My two phones,
Android 10 and Android 15 (arm64-v8a) immediately discovered each other
using local discovery.
- I can see the "sent XX bytes" and "recv XX bytes" on both phones in
the log filtering for "SyncthingNativeCode" :-).
Personal note:
- Please go light on me, and, if it's not demanded too much of your
time, please help me on this. I am no go programmer. Most things you
think are easy or common sense aren't part of my knowledge set. I'd just
like to help and hope we somehow can drive this home together to fix the
problem.
----
ref: https://github.com/Catfriend1/syncthing-android/pull/1501
ref: https://github.com/Catfriend1/syncthing-android/issues/1500
ref: https://github.com/wlynxg/anet/blob/main/interface.go &
https://github.com/wlynxg/anet/blob/main/interface_android.go
With that fix, I can see the broadcast/multicast lines again and my
phone can be discovered by other phones running the Syncthing app which
wasn't possible before on Android 10+.
```
[ET76H] .346892 broadcast.go:107: DEBUG: sent 185 bytes to 192.168.x.255:21027
[ET76H] .347114 multicast.go:86: DEBUG: sent 185 bytes to [ff12::8384]:21027 on wlan0
```
---------
Co-authored-by: Marcus B Spencer <marcus@marcusspencer.us>
With VPNs and stuff we can get a single failure on an interface that
supposedly supports broadcasts without it being fatal.
GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/4415
This implements a new debug/trace infrastructure based on a slightly
hacked up logger. Instead of the traditional "if debug { ... }" I've
rewritten the logger to have no-op Debugln and Debugf, unless debugging
has been enabled for a given "facility". The "facility" is just a
string, typically a package name.
This will be slightly slower than before; but not that much as it's
mostly a function call that returns immediately. For the cases where it
matters (the Debugln takes a hex.Dump() of something for example, and
it's not in a very occasional "if err != nil" branch) there is an
l.ShouldDebug(facility) that is fast enough to be used like the old "if
debug".
The point of all this is that we can now toggle debugging for the
various packages on and off at runtime. There's a new method
/rest/system/debug that can be POSTed a set of facilities to enable and
disable debug for, or GET from to get a list of facilities with
descriptions and their current debug status.
Similarly a /rest/system/log?since=... can grab the latest log entries,
up to 250 of them (hardcoded constant in main.go) plus the initial few.
Not implemented in this commit (but planned) is a simple debug GUI
available on /debug that shows the current log in an easily pasteable
format and has checkboxes to enable the various debug facilities.
The debug instructions to a user then becomes "visit this URL, check
these boxes, reproduce your problem, copy and paste the log". The actual
log viewer on the hypothetical /debug URL can poll regularly for new log
entries and this bypass the 250 line limit.
The existing STTRACE=foo variable is still obeyed and just sets the
start state of the system.
This makes it possible to run multiple instances on the same box, all
receiving local discovery packets. Tested on Mac, Windows, supposed to
work on at least Linux too. For Windows, there may be issues with XP and
earlier, but meh...
Marcus B Spencer
Catfriend1andMarcus B Spencer
Jakob Borg
bt90
greatroar
Simon Frei
Alex Xu
Lukas Lihotzki
Jakob Borg
Audrius Butkevicius