Move Linux client & common packages into a public repo.

portlist/portlist_linux.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 (
+	"bufio"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"os"
+	"sort"
+	"strconv"
+	"strings"
+)
+
+// Reading the sockfiles on Linux is very fast, so we can do it often.
+const POLL_SECONDS = 1
+
+// TODO(apenwarr): Include IPv6 ports eventually.
+// Right now we don't route IPv6 anyway so it's better to exclude them.
+var sockfiles = []string{"/proc/net/tcp", "/proc/net/udp"}
+
+func listPorts() (List, error) {
+	l := []Port{}
+
+	for pi, fname := range sockfiles {
+		proto := protos[pi]
+
+		f, err := os.Open(fname)
+		if err != nil {
+			return nil, fmt.Errorf("%s: %s", fname, err)
+		}
+		defer f.Close()
+		r := bufio.NewReader(f)
+
+		// skip header row
+		_, err = r.ReadString('\n')
+		if err != nil {
+			return nil, err
+		}
+
+		for err == nil {
+			line, err := r.ReadString('\n')
+			if err == io.EOF {
+				break
+			}
+			if err != nil {
+				return nil, err
+			}
+
+			// sl local rem ... inode
+			words := strings.Fields(line)
+			local := words[1]
+			rem := words[2]
+			inode := words[9]
+
+			if rem != "00000000:0000" {
+				// not a "listener" port
+				continue
+			}
+
+			portv, err := strconv.ParseUint(local[9:], 16, 16)
+			if err != nil {
+				return nil, fmt.Errorf("%#v: %s", local[9:], err)
+			}
+			inodev := fmt.Sprintf("socket:[%s]", inode)
+			l = append(l, Port{
+				Proto: proto,
+				Port:  uint16(portv),
+				inode: inodev,
+			})
+		}
+	}
+
+	sort.Slice(l, func(i, j int) bool {
+		return (&l[i]).lessThan(&l[j])
+	})
+
+	return l, nil
+}
+
+func addProcesses(pl []Port) ([]Port, error) {
+	pm := map[string]*Port{}
+	for k := range pl {
+		pm[pl[k].inode] = &pl[k]
+	}
+
+	pdir, err := os.Open("/proc")
+	if err != nil {
+		return nil, fmt.Errorf("/proc: %s", err)
+	}
+	defer pdir.Close()
+
+	for {
+		pids, err := pdir.Readdirnames(100)
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			return nil, fmt.Errorf("/proc: %s", err)
+		}
+
+		for _, pid := range pids {
+			_, err := strconv.ParseInt(pid, 10, 64)
+			if err != nil {
+				// not a pid, ignore it.
+				// /proc has lots of non-pid stuff in it.
+				continue
+			}
+			fddir, err := os.Open(fmt.Sprintf("/proc/%s/fd", pid))
+			if err != nil {
+				// Can't open fd list for this pid. Maybe
+				// don't have access. Ignore it.
+				continue
+			}
+			defer fddir.Close()
+
+			for {
+				fds, err := fddir.Readdirnames(100)
+				if err == io.EOF {
+					break
+				}
+				if err != nil {
+					return nil, fmt.Errorf("readdir: %s", err)
+				}
+				for _, fd := range fds {
+					target, err := os.Readlink(fmt.Sprintf("/proc/%s/fd/%s", pid, fd))
+					if err != nil {
+						// Not a symlink or no permission.
+						// Skip it.
+						continue
+					}
+
+					// TODO(apenwarr): use /proc/*/cmdline instead of /comm?
+					// Unsure right now whether users will want the extra detail
+					// or not.
+					pe := pm[target]
+					if pe != nil {
+						comm, err := ioutil.ReadFile(fmt.Sprintf("/proc/%s/comm", pid))
+						if err != nil {
+							// Usually shouldn't happen. One possibility is
+							// the process has gone away, so let's skip it.
+							continue
+						}
+						pe.Process = strings.TrimSpace(string(comm))
+					}
+				}
+			}
+		}
+	}
+
+	return pl, nil
+}