mirror of https://github.com/tailscale/tailscale/
ipn/ipnauth: start splitting ipnserver into new ipnauth package
We're trying to gut 90% of the ipnserver package. A lot will get deleted, some will move to LocalBackend, and a lot is being moved into this new ipn/ipnauth package which will be leaf-y and testable. This is a baby step towards moving some stuff to ipnauth. Update #6417 Updates tailscale/corp#8051 Change-Id: I28bc2126764f46597d92a2d72565009dc6927ee0 Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>pull/6471/head
Brad Fitzpatrick
2 years ago
committed by
Brad Fitzpatrick
parent
5f6fec0eba
commit
7bff7345cc
@ -0,0 +1,204 @@
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// Copyright (c) 2022 Tailscale Inc & AUTHORS All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package ipnauth controls access to the LocalAPI.
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package ipnauth
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import (
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"errors"
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"fmt"
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"net"
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"net/netip"
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"os"
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"os/user"
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"runtime"
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"strconv"
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"syscall"
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"inet.af/peercred"
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"tailscale.com/net/netstat"
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"tailscale.com/safesocket"
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"tailscale.com/types/logger"
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"tailscale.com/util/groupmember"
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"tailscale.com/util/pidowner"
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"tailscale.com/util/winutil"
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"tailscale.com/version/distro"
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)
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// ConnIdentity represents the owner of a localhost TCP or unix socket connection
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// connecting to the LocalAPI.
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type ConnIdentity struct {
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conn net.Conn
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notWindows bool // runtime.GOOS != "windows"
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// Fields used when NotWindows:
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isUnixSock bool // Conn is a *net.UnixConn
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creds *peercred.Creds // or nil
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// Used on Windows:
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// TODO(bradfitz): merge these into the peercreds package and
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// use that for all.
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pid int
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userID string
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user *user.User
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}
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func (ci *ConnIdentity) UserID() string { return ci.userID }
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func (ci *ConnIdentity) User() *user.User { return ci.user }
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func (ci *ConnIdentity) Pid() int { return ci.pid }
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func (ci *ConnIdentity) IsUnixSock() bool { return ci.isUnixSock }
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func (ci *ConnIdentity) NotWindows() bool { return ci.notWindows }
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func (ci *ConnIdentity) Creds() *peercred.Creds { return ci.creds }
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// GetConnIdentity returns the localhost TCP connection's identity information
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// (pid, userid, user). If it's not Windows (for now), it returns a nil error
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// and a ConnIdentity with NotWindows set true. It's only an error if we expected
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// to be able to map it and couldn't.
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func GetConnIdentity(logf logger.Logf, c net.Conn) (ci *ConnIdentity, err error) {
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ci = &ConnIdentity{conn: c}
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if runtime.GOOS != "windows" { // for now; TODO: expand to other OSes
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ci.notWindows = true
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_, ci.isUnixSock = c.(*net.UnixConn)
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ci.creds, _ = peercred.Get(c)
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return ci, nil
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}
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la, err := netip.ParseAddrPort(c.LocalAddr().String())
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if err != nil {
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return ci, fmt.Errorf("parsing local address: %w", err)
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}
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ra, err := netip.ParseAddrPort(c.RemoteAddr().String())
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if err != nil {
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return ci, fmt.Errorf("parsing local remote: %w", err)
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}
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if !la.Addr().IsLoopback() || !ra.Addr().IsLoopback() {
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return ci, errors.New("non-loopback connection")
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}
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tab, err := netstat.Get()
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if err != nil {
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return ci, fmt.Errorf("failed to get local connection table: %w", err)
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}
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pid := peerPid(tab.Entries, la, ra)
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if pid == 0 {
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return ci, errors.New("no local process found matching localhost connection")
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}
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ci.pid = pid
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uid, err := pidowner.OwnerOfPID(pid)
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if err != nil {
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var hint string
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if runtime.GOOS == "windows" {
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hint = " (WSL?)"
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}
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return ci, fmt.Errorf("failed to map connection's pid to a user%s: %w", hint, err)
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}
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ci.userID = uid
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u, err := LookupUserFromID(logf, uid)
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if err != nil {
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return ci, fmt.Errorf("failed to look up user from userid: %w", err)
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}
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ci.user = u
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return ci, nil
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}
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// LookupUserFromID is a wrapper around os/user.LookupId that works around some
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// issues on Windows. On non-Windows platforms it's identical to user.LookupId.
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func LookupUserFromID(logf logger.Logf, uid string) (*user.User, error) {
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u, err := user.LookupId(uid)
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if err != nil && runtime.GOOS == "windows" && errors.Is(err, syscall.Errno(0x534)) {
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// The below workaround is only applicable when uid represents a
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// valid security principal. Omitting this check causes us to succeed
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// even when uid represents a deleted user.
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if !winutil.IsSIDValidPrincipal(uid) {
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return nil, err
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}
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logf("[warning] issue 869: os/user.LookupId failed; ignoring")
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// Work around https://github.com/tailscale/tailscale/issues/869 for
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// now. We don't strictly need the username. It's just a nice-to-have.
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// So make up a *user.User if their machine is broken in this way.
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return &user.User{
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Uid: uid,
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Username: "unknown-user-" + uid,
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Name: "unknown user " + uid,
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}, nil
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}
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return u, err
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}
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// IsReadonlyConn reports whether the connection should be considered read-only,
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// meaning it's not allowed to change the state of the node.
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//
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// Read-only also means it's not allowed to access sensitive information, which
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// admittedly doesn't follow from the name. Consider this "IsUnprivileged".
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// Also, Windows doesn't use this. For Windows it always returns false.
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//
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// TODO(bradfitz): rename it? Also make Windows use this.
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func (ci *ConnIdentity) IsReadonlyConn(operatorUID string, logf logger.Logf) bool {
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if runtime.GOOS == "windows" {
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// Windows doesn't need/use this mechanism, at least yet. It
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// has a different last-user-wins auth model.
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return false
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}
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const ro = true
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const rw = false
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if !safesocket.PlatformUsesPeerCreds() {
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return rw
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}
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creds := ci.creds
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if creds == nil {
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logf("connection from unknown peer; read-only")
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return ro
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}
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uid, ok := creds.UserID()
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if !ok {
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logf("connection from peer with unknown userid; read-only")
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return ro
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}
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if uid == "0" {
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logf("connection from userid %v; root has access", uid)
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return rw
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}
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if selfUID := os.Getuid(); selfUID != 0 && uid == strconv.Itoa(selfUID) {
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logf("connection from userid %v; connection from non-root user matching daemon has access", uid)
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return rw
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}
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if operatorUID != "" && uid == operatorUID {
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logf("connection from userid %v; is configured operator", uid)
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return rw
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}
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if yes, err := isLocalAdmin(uid); err != nil {
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logf("connection from userid %v; read-only; %v", uid, err)
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return ro
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} else if yes {
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logf("connection from userid %v; is local admin, has access", uid)
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return rw
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}
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logf("connection from userid %v; read-only", uid)
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return ro
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}
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func isLocalAdmin(uid string) (bool, error) {
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u, err := user.LookupId(uid)
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if err != nil {
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return false, err
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}
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var adminGroup string
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switch {
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case runtime.GOOS == "darwin":
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adminGroup = "admin"
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case distro.Get() == distro.QNAP:
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adminGroup = "administrators"
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default:
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return false, fmt.Errorf("no system admin group found")
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}
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return groupmember.IsMemberOfGroup(adminGroup, u.Username)
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}
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func peerPid(entries []netstat.Entry, la, ra netip.AddrPort) int {
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for _, e := range entries {
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if e.Local == ra && e.Remote == la {
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return e.Pid
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}
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}
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return 0
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}
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