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wgengine/magicsock: make debugNeverDirectUDP influence remote peer decisions

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By dropping inbound disco.Ping messages received over direct UDP paths.

Fixes #18560

Signed-off-by: Jordan Whited <jordan@tailscale.com>
This commit is contained in:
Jordan Whited
2026-01-29 15:41:55 -08:00
committed by Jordan Whited
parent 3ce13eb2b9
commit 3b6d542923
2 changed files with 6 additions and 1 deletions
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wgengine/magicsock/debugknobs.go
+2 -1
View File
@@ -62,7 +62,8 @@ var (
// //
//lint:ignore U1000 used on Linux/Darwin only //lint:ignore U1000 used on Linux/Darwin only
debugPMTUD = envknob.RegisterBool("TS_DEBUG_PMTUD") debugPMTUD = envknob.RegisterBool("TS_DEBUG_PMTUD")
// debugNeverDirectUDP disables the use of direct UDP connections, forcing // debugNeverDirectUDP disables the use of direct UDP connections by
// suppressing/dropping inbound/outbound [disco.Ping] messages, forcing
// all peer communication over DERP or peer relay. // all peer communication over DERP or peer relay.
debugNeverDirectUDP = envknob.RegisterBool("TS_DEBUG_NEVER_DIRECT_UDP") debugNeverDirectUDP = envknob.RegisterBool("TS_DEBUG_NEVER_DIRECT_UDP")
// Hey you! Adding a new debugknob? Make sure to stub it out in the // Hey you! Adding a new debugknob? Make sure to stub it out in the
wgengine/magicsock/magicsock.go
+4
View File
@@ -2555,6 +2555,10 @@ func (c *Conn) handlePingLocked(dm *disco.Ping, src epAddr, di *discoInfo, derpN
// This is a naked [disco.Ping] without a VNI. // This is a naked [disco.Ping] without a VNI.
if debugNeverDirectUDP() && !isDerp {
return
}
// If we can figure out with certainty which node key this disco // If we can figure out with certainty which node key this disco
// message is for, eagerly update our [epAddr]<>node and disco<>node // message is for, eagerly update our [epAddr]<>node and disco<>node
// mappings to make p2p path discovery faster in simple // mappings to make p2p path discovery faster in simple