1 files changed, 57 insertions, 0 deletions
diff --git a/src/net/port_unix.go b/src/net/port_unix.go
new file mode 100644
index 0000000..b05b588
--- /dev/null
+++ b/src/net/port_unix.go
@@ -0,0 +1,57 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+//go:build unix || (js && wasm)
+
+// Read system port mappings from /etc/services
+
+package net
+
+import (
+	"internal/bytealg"
+	"sync"
+)
+
+var onceReadServices sync.Once
+
+func readServices() {
+	file, err := open("/etc/services")
+	if err != nil {
+		return
+	}
+	defer file.close()
+
+	for line, ok := file.readLine(); ok; line, ok = file.readLine() {
+		// "http 80/tcp www www-http # World Wide Web HTTP"
+		if i := bytealg.IndexByteString(line, '#'); i >= 0 {
+			line = line[:i]
+		}
+		f := getFields(line)
+		if len(f) < 2 {
+			continue
+		}
+		portnet := f[1] // "80/tcp"
+		port, j, ok := dtoi(portnet)
+		if !ok || port <= 0 || j >= len(portnet) || portnet[j] != '/' {
+			continue
+		}
+		netw := portnet[j+1:] // "tcp"
+		m, ok1 := services[netw]
+		if !ok1 {
+			m = make(map[string]int)
+			services[netw] = m
+		}
+		for i := 0; i < len(f); i++ {
+			if i != 1 { // f[1] was port/net
+				m[f[i]] = port
+			}
+		}
+	}
+}
+
+// goLookupPort is the native Go implementation of LookupPort.
+func goLookupPort(network, service string) (port int, err error) {
+	onceReadServices.Do(readServices)
+	return lookupPortMap(network, service)
+}