Add peer-share toggle to lantern-core (Share My Connection PR 3/4)

PR 3 of 4 implementing the lantern-side wiring for "Share My
Connection". Bumps radiance to fisk/peer-localbackend tip so we can
reference the new PeerShareEnabledKey setting; that bump is provisional
and should be re-pinned to a release tag once radiance #460 merges.

* lantern-core/core.go: new PeerShare interface (mirrors Ads /
  SmartRouting), embedded in Core. SetPeerShareEnabled patches
  PeerShareEnabledKey via the radiance ipc client; IsPeerShareEnabled
  reads the snapshot.
* lantern-core/ffi/ffi.go: new //export setPeerProxyEnabled and
  //export isPeerProxyEnabled, mirroring setBlockAdsEnabled exactly.
  The Dart FFI binding name uses "PeerProxy" to match the existing
  user-facing naming in the lantern repo (vpn_setting.dart toggle was
  drafted as "Peer Proxy").
* lantern-core/mobile/mobile.go: SetPeerShareEnabled / IsPeerShareEnabled
  for the gomobile-bind surface so Android can toggle once Dart wires
  it up in PR 4.

The lifecycle path:

  Dart toggle → setPeerProxyEnabled(enabled)
  → LanternCore.SetPeerShareEnabled
  → ipc.Client.PatchSettings({PeerShareEnabledKey: ...})
  → radiance LocalBackend.PatchSettings dispatch
  → peer.Client.Start / Stop

ffigen regen for the Dart bindings happens in PR 4 alongside the Dart
wire-through and rollback logic.

go test ./lantern-core/... and golangci-lint --new-from-rev=origin/main
both clean.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: 2 people

go.mod

@@ -25,7 +25,7 @@ replace github.com/quic-go/qpack => github.com/quic-go/qpack v0.5.1
 require (
 	github.com/alecthomas/assert/v2 v2.3.0
 	github.com/getlantern/lantern-server-provisioner v0.0.0-20251031121934-8ea031fccfa9
-	github.com/getlantern/radiance v0.0.0-20260529193818-b9df7d613b1a
+	github.com/getlantern/radiance v0.0.0-20260529195140-5959bbef7f5a
 	github.com/sagernet/sing-box v1.12.22
 	golang.org/x/mobile v0.0.0-20250711185624-d5bb5ecc55c0
 	golang.org/x/sys v0.41.0

go.sum

@@ -261,8 +261,8 @@ github.com/getlantern/pluriconfig v0.0.0-20251126214241-8cc8bc561535 h1:rtDmW8YL
 github.com/getlantern/pluriconfig v0.0.0-20251126214241-8cc8bc561535/go.mod h1:WKJEdjMOD4IuTRYwjQHjT4bmqDl5J82RShMLxPAvi0Q=
 github.com/getlantern/publicip v0.0.0-20260328175246-2c460fe80c6b h1:gMYJzEhLrmIqQ+JnjiYNm+UyUDalK3WUmVyecFwmV5g=
 github.com/getlantern/publicip v0.0.0-20260328175246-2c460fe80c6b/go.mod h1:NpfXdK4ldEKkjQ4P1R+DBF4ua5VFOlxmgHROTnYrApg=
-github.com/getlantern/radiance v0.0.0-20260529193818-b9df7d613b1a h1:BUnZxaaUJbDmILeIOj+/4qlUQrgD8hdV1+67fkLvdqY=
-github.com/getlantern/radiance v0.0.0-20260529193818-b9df7d613b1a/go.mod h1:SOXeNVsbdP1v9yYRbuJLB9tV9DpPI77HN+iSecuC9kM=
+github.com/getlantern/radiance v0.0.0-20260529195140-5959bbef7f5a h1:+KfogporLkmRnJv+PK/nlBZgs249Dk+kFteV0OeIeuY=
+github.com/getlantern/radiance v0.0.0-20260529195140-5959bbef7f5a/go.mod h1:XgUaooT08sJg1gINkX5/RhvkjBWwgO9KexMU8z0FVs8=
 github.com/getlantern/samizdat v0.0.3-0.20260529191731-5ea8ae61ddbf h1:KxiMF+oG0rTtuBi7GiIaHfccYOf69rLJ/VnO5myoYc4=
 github.com/getlantern/samizdat v0.0.3-0.20260529191731-5ea8ae61ddbf/go.mod h1:uEeykQSW2/6rTjfPlj3MTTo59poSHXfAHTGgzYDkbr0=
 github.com/getlantern/semconv v0.0.0-20260327040646-21845dda05cb h1:c5YM7b3a4r2J8Eh89KkI6M/iTFe6Bi+b8AJlfkKdFq4=

lantern-core/core.go

@@ -153,6 +153,11 @@ type SmartRouting interface {
 	IsSmartRoutingEnabled() bool
 }
 
+type PeerShare interface {
+	SetPeerShareEnabled(bool) error
+	IsPeerShareEnabled() bool
+}
+
 type VPN interface {
 	ConnectVPN(tag string) error
 	SelectServer(tag string) error
@@ -169,6 +174,7 @@ type Core interface {
 	SplitTunnel
 	Ads
 	SmartRouting
+	PeerShare
 	VPN
 	Client() *ipc.Client
 }
@@ -454,6 +460,16 @@ func (lc *LanternCore) IsSmartRoutingEnabled() bool {
 	return b
 }
 
+func (lc *LanternCore) SetPeerShareEnabled(enabled bool) error {
+	_, err := lc.client.PatchSettings(lc.ctx, settings.Settings{settings.PeerShareEnabledKey: enabled})
+	return err
+}
+
+func (lc *LanternCore) IsPeerShareEnabled() bool {
+	b, _ := lc.settings()[settings.PeerShareEnabledKey].(bool)
+	return b
+}
+
 func (lc *LanternCore) IsTelemetryEnabled() bool {
 	b, _ := lc.settings()[settings.TelemetryKey].(bool)
 	return b

lantern-core/ffi/ffi.go

@@ -1352,6 +1352,29 @@ func isSmartRoutingEnabled() C.int {
 	return 0
 }
 
+//export setPeerProxyEnabled
+func setPeerProxyEnabled(enabled C.int) *C.char {
+	return runOnGoStack(func() *C.char {
+		c, errStr := requireCore()
+		if errStr != nil {
+			return errStr
+		}
+		if err := c.SetPeerShareEnabled(enabled != 0); err != nil {
+			return SendError(err)
+		}
+		return C.CString("ok")
+	})
+}
+
+//export isPeerProxyEnabled
+func isPeerProxyEnabled() C.int {
+	c, _ := requireCore()
+	if c != nil && c.IsPeerShareEnabled() {
+		return 1
+	}
+	return 0
+}
+
 //export getSplitTunnelState
 func getSplitTunnelState() *C.char {
 	return runOnGoStack(func() *C.char {

lantern-core/mobile/mobile.go

@@ -203,6 +203,23 @@ func SetSmartRoutingEnabled(enabled bool) error {
 	})
 }
 
+func SetPeerShareEnabled(enabled bool) error {
+	slog.Info("peer-share: SetPeerShareEnabled", "enabled", enabled)
+	return withCore(func(c lanterncore.Core) error {
+		return c.SetPeerShareEnabled(enabled)
+	})
+}
+
+func IsPeerShareEnabled() bool {
+	ok, err := withCoreR(func(c lanterncore.Core) (bool, error) {
+		return c.IsPeerShareEnabled(), nil
+	})
+	if err != nil {
+		return false
+	}
+	return ok
+}
+
 func IsSmartRoutingEnabled() bool {
 	ok, err := withCoreR(func(c lanterncore.Core) (bool, error) {
 		return c.IsSmartRoutingEnabled(), nil