Refactor socksopts per functionality, not per build flag

network/v2/sockopts_congestion.go

@@ -0,0 +1,20 @@
+//go:build linux
+
+package network
+
+import (
+	"syscall"
+
+	"golang.org/x/sys/unix"
+)
+
+// setCongestionControl sets BBR as the TCP congestion control algorithm.
+// BBR provides better throughput over lossy and high-latency links compared
+// to the default cubic, which is especially beneficial for mobile and
+// home internet clients. This is best-effort: silently ignored if the
+// kernel does not have tcp_bbr available.
+func setCongestionControl(conn syscall.RawConn) {
+	conn.Control(func(fd uintptr) { //nolint: errcheck
+		unix.SetsockoptString(int(fd), unix.IPPROTO_TCP, unix.TCP_CONGESTION, "bbr") //nolint: errcheck
+	})
+}

network/v2/sockopts_congestion_stub.go

@@ -0,0 +1,7 @@
+//go:build !linux
+
+package network
+
+import "syscall"
+
+func setCongestionControl(conn syscall.RawConn) {}

network/v2/sockopts_reuseaddr.go

@@ -1,5 +1,4 @@
 //go:build !windows
-// +build !windows
 
 package network
 

network/v2/sockopts_reuseaddr_stub.go

@@ -1,5 +1,4 @@
 //go:build windows
-// +build windows
 
 package network
 

network/v2/sockopts_usertimeout.go

@@ -46,13 +46,3 @@ func setTCPUserTimeout(conn syscall.RawConn, cfg net.KeepAliveConfig) {
 		unix.SetsockoptInt(int(fd), unix.IPPROTO_TCP, unix.TCP_USER_TIMEOUT, int(timeout.Milliseconds())) //nolint: errcheck
 	})
 }
-
-func setCongestionControl(conn syscall.RawConn) {
-	conn.Control(func(fd uintptr) { //nolint: errcheck
-		// BBR provides better throughput over lossy and high-latency links compared
-		// to the default cubic, which is especially beneficial for mobile and
-		// home internet clients. This is best-effort: silently ignored if the
-		// kernel does not have tcp_bbr available.
-		unix.SetsockoptString(int(fd), unix.IPPROTO_TCP, unix.TCP_CONGESTION, "bbr") //nolint: errcheck
-	})
-}

network/v2/sockopts_usertimeout_stub.go

@@ -7,5 +7,4 @@ import (
 	"syscall"
 )
 
-func setCongestionControl(conn syscall.RawConn)                       {}
 func setTCPUserTimeout(conn syscall.RawConn, cfg net.KeepAliveConfig) {}