From ad6edf5ecda94ac89df8278871a29c3783ae85e4 Mon Sep 17 00:00:00 2001
From: David Anderson <danderson@tailscale.com>
Date: Wed, 3 Mar 2021 19:00:41 -0800
Subject: [PATCH] portlist: report a better process name for .Net on linux.

Fixes #1440.

Signed-off-by: David Anderson <danderson@tailscale.com>
---
 portlist/clean.go          | 34 ++++++++++++++++++++++++++++++
 portlist/clean_test.go     | 42 ++++++++++++++++++++++++++++++++++++++
 portlist/netstat.go        |  8 ++------
 portlist/portlist_linux.go |  9 ++++----
 4 files changed, 82 insertions(+), 11 deletions(-)
 create mode 100644 portlist/clean.go
 create mode 100644 portlist/clean_test.go

diff --git a/portlist/clean.go b/portlist/clean.go
new file mode 100644
index 000000000..aad350fe3
--- /dev/null
+++ b/portlist/clean.go
@@ -0,0 +1,34 @@
+// Copyright (c) 2021 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 (
+	"path/filepath"
+	"strings"
+)
+
+// argvSubject takes a command and its flags, and returns the
+// short/pretty name for the process. This is usually the basename of
+// the binary being executed, but can sometimes vary (e.g. so that we
+// don't report all Java programs as "java").
+func argvSubject(argv ...string) string {
+	if len(argv) == 0 {
+		return ""
+	}
+	ret := filepath.Base(argv[0])
+
+	// Handle special cases.
+	switch {
+	case ret == "mono" && len(argv) >= 2:
+		// .Net programs execute as `mono actualProgram.exe`.
+		ret = filepath.Base(argv[1])
+	}
+
+	// Remove common noise.
+	ret = strings.TrimSpace(ret)
+	ret = strings.TrimSuffix(ret, ".exe")
+
+	return ret
+}
diff --git a/portlist/clean_test.go b/portlist/clean_test.go
new file mode 100644
index 000000000..767071481
--- /dev/null
+++ b/portlist/clean_test.go
@@ -0,0 +1,42 @@
+// Copyright (c) 2021 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 "testing"
+
+func TestArgvSubject(t *testing.T) {
+	tests := []struct {
+		in   []string
+		want string
+	}{
+		{
+			in:   nil,
+			want: "",
+		},
+		{
+			in:   []string{"/usr/bin/sshd"},
+			want: "sshd",
+		},
+		{
+			in:   []string{"/bin/mono"},
+			want: "mono",
+		},
+		{
+			in:   []string{"/nix/store/x2cw2xjw98zdysf56bdlfzsr7cyxv0jf-mono-5.20.1.27/bin/mono", "/bin/exampleProgram.exe"},
+			want: "exampleProgram",
+		},
+		{
+			in:   []string{"/bin/mono", "/sbin/exampleProgram.bin"},
+			want: "exampleProgram.bin",
+		},
+	}
+
+	for _, test := range tests {
+		got := argvSubject(test.in...)
+		if got != test.want {
+			t.Errorf("argvSubject(%v) = %q, want %q", test.in, got, test.want)
+		}
+	}
+}
diff --git a/portlist/netstat.go b/portlist/netstat.go
index 02b1a5957..7eb8ed973 100644
--- a/portlist/netstat.go
+++ b/portlist/netstat.go
@@ -101,13 +101,9 @@ func parsePortsNetstat(output string) List {
 			delete(m, lastport)
 			proc := trimline[1 : len(trimline)-1]
 			if proc == "svchost.exe" && lastline != "" {
-				p.Process = lastline
+				p.Process = argvSubject(lastline)
 			} else {
-				if strings.HasSuffix(proc, ".exe") {
-					p.Process = proc[:len(proc)-4]
-				} else {
-					p.Process = proc
-				}
+				p.Process = argvSubject(proc)
 			}
 			m[p] = nothing{}
 		} else {
diff --git a/portlist/portlist_linux.go b/portlist/portlist_linux.go
index 8b7555872..cc22b3f1a 100644
--- a/portlist/portlist_linux.go
+++ b/portlist/portlist_linux.go
@@ -158,18 +158,17 @@ func addProcesses(pl []Port) ([]Port, error) {
 					continue
 				}
 
-				// TODO(apenwarr): use /proc/*/cmdline instead of /comm?
-				// Unsure right now whether users will want the extra detail
-				// or not.
 				pe := pm[string(targetBuf[:n])] // m[string([]byte)] avoids alloc
 				if pe != nil {
-					comm, err := ioutil.ReadFile(fmt.Sprintf("/proc/%s/comm", pid))
+					bs, err := ioutil.ReadFile(fmt.Sprintf("/proc/%s/cmdline", 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))
+
+					argv := strings.Split(strings.TrimSuffix(string(bs), "\x00"), "\x00")
+					pe.Process = argvSubject(argv...)
 				}
 			}
 		}