Move Linux client & common packages into a public repo.

portlist/netstat.go

@@ -0,0 +1,155 @@
+// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package portlist
+
+import (
+	"fmt"
+	"sort"
+	"strconv"
+	"strings"
+
+	exec "tailscale.com/tempfork/osexec"
+)
+
+func parsePort(s string) int {
+	// a.b.c.d:1234 or [a:b:c:d]:1234
+	i1 := strings.LastIndexByte(s, ':')
+	// a.b.c.d.1234 or [a:b:c:d].1234
+	i2 := strings.LastIndexByte(s, '.')
+
+	i := i1
+	if i2 > i {
+		i = i2
+	}
+	if i < 0 {
+		// no match; weird
+		return -1
+	}
+
+	portstr := s[i+1 : len(s)]
+	if portstr == "*" {
+		return 0
+	}
+
+	port, err := strconv.ParseUint(portstr, 10, 16)
+	if err != nil {
+		// invalid port; weird
+		return -1
+	}
+
+	return int(port)
+}
+
+type nothing struct{}
+
+// Lowest common denominator parser for "netstat -na" format.
+// All of Linux, Windows, and macOS support -na and give similar-ish output
+// formats that we can parse without special detection logic.
+// Unfortunately, options to filter by proto or state are non-portable,
+// so we'll filter for ourselves.
+func parsePortsNetstat(output string) List {
+	m := map[Port]nothing{}
+	lines := strings.Split(string(output), "\n")
+
+	var lastline string
+	var lastport Port
+	for _, line := range lines {
+		trimline := strings.TrimSpace(line)
+		cols := strings.Fields(trimline)
+		if len(cols) < 1 {
+			continue
+		}
+		protos := strings.ToLower(cols[0])
+		var proto, laddr, raddr string
+		if strings.HasPrefix(protos, "tcp") {
+			if len(cols) < 4 {
+				continue
+			}
+			proto = "tcp"
+			laddr = cols[len(cols)-3]
+			raddr = cols[len(cols)-2]
+			state := cols[len(cols)-1]
+			if !strings.HasPrefix(state, "LISTEN") {
+				// not interested in non-listener sockets
+				continue
+			}
+		} else if strings.HasPrefix(protos, "udp") {
+			if len(cols) < 3 {
+				continue
+			}
+			proto = "udp"
+			laddr = cols[len(cols)-2]
+			raddr = cols[len(cols)-1]
+		} else if protos[0] == '[' && len(trimline) > 2 {
+			// Windows: with netstat -nab, appends a line like:
+			//  [description]
+			// after the port line.
+			p := lastport
+			delete(m, lastport)
+			proc := trimline[1 : len(trimline)-1]
+			if proc == "svchost.exe" && lastline != "" {
+				p.Process = lastline
+			} else {
+				if strings.HasSuffix(proc, ".exe") {
+					p.Process = proc[:len(proc)-4]
+				} else {
+					p.Process = proc
+				}
+			}
+			m[p] = nothing{}
+		} else {
+			// not interested in other protocols
+			lastline = trimline
+			continue
+		}
+
+		lport := parsePort(laddr)
+		rport := parsePort(raddr)
+		if rport != 0 || lport <= 0 {
+			// not interested in "connected" sockets
+			continue
+		}
+
+		p := Port{
+			Proto: proto,
+			Port:  uint16(lport),
+		}
+		m[p] = nothing{}
+		lastport = p
+		lastline = ""
+	}
+
+	l := []Port{}
+	for p := range m {
+		l = append(l, p)
+	}
+	sort.Slice(l, func(i, j int) bool {
+		return (&l[i]).lessThan(&l[j])
+	})
+
+	return l
+}
+
+func listPortsNetstat(args string) (List, error) {
+	exe, err := exec.LookPath("netstat")
+	if err != nil {
+		return nil, fmt.Errorf("netstat: lookup: %v", err)
+	}
+	c := exec.Cmd{
+		Path: exe,
+		Args: []string{exe, args},
+	}
+	output, err := c.Output()
+	if err != nil {
+		xe, ok := err.(*exec.ExitError)
+		stderr := ""
+		if ok {
+			stderr = strings.TrimSpace(string(xe.Stderr))
+		}
+		return nil, fmt.Errorf("netstat: %v (%q)", err, stderr)
+	}
+
+	return parsePortsNetstat(string(output)), nil
+}