Revert "tun: default pin_threads off"

This reverts commit fcf59343bd66dd3c879c8293c1429e95d9fd3ee2.

examples/config.yml

@@ -267,9 +267,8 @@ tun:
 
   # Linux only. pin_threads pins each tun reader/encrypt OS thread to a single CPU. This keeps every goroutine's
   # batched sends flowing through one XPS-selected NIC TX ring, so packets within a flow stay ordered on the wire
-  # instead of being sprayed across multiple TX rings and reordered. Off by default; pinning takes CPUs away from
-  # the scheduler, which can hurt hosts that share cores with other workloads. Not reloadable.
-  #pin_threads: false
+  # instead of being sprayed across multiple TX rings and reordered. Not reloadable.
+  #pin_threads: true
 
   # Linux only. cpu_affinity overrides which CPUs the tun reader threads pin to: a list of CPU IDs, one per routine
   # (see the top-level `routines` setting). Lists shorter than `routines` are modulo-cycled across the queues; extra

interface.go

@@ -59,7 +59,7 @@ type InterfaceConfig struct {
 	// pin-to-(i % NumCPU) behavior. Only consulted when PinThreads is true.
 	CpuAffinity []int
 	// PinThreads controls whether each TUN reader OS thread is pinned to a
-	// single CPU (via tun.pin_threads, default false). Pinning keeps each
+	// single CPU (via tun.pin_threads, default true). Pinning keeps each
 	// goroutine's sendmmsg on one XPS-selected NIC TX ring so per-flow
 	// packets stay ordered on the wire.
 	PinThreads bool
@@ -94,7 +94,7 @@ type Interface struct {
 	// Only consulted when pinThreads is true.
 	cpuAffinity []int
 	// pinThreads controls whether listenIn pins each TUN reader OS thread to
-	// a CPU at all (tun.pin_threads, default false). When false, threads are
+	// a CPU at all (tun.pin_threads, default true). When false, threads are
 	// left free to migrate as on stock nebula.
 	pinThreads bool
 	// ecnEnabled gates RFC 6040 underlay ECN propagation. When true,

main.go

@@ -236,7 +236,7 @@ func Main(c *config.C, configTest bool, buildVersion string, l *slog.Logger, dev
 		punchy:                punchy,
 		ConntrackCacheTimeout: conntrackCacheTimeout,
 		CpuAffinity:           parseCpuAffinity(c, l, routines),
-		PinThreads:            c.GetBool("tun.pin_threads", false),
+		PinThreads:            c.GetBool("tun.pin_threads", true),
 		l:                     l,
 	}