README: dashboard screenshot from v0.9.0

The card puts the address websites see next to the server's address.
Through a full tunnel both are the server's, and the card says
"You are protected"; directly or through a split tunnel it says
"Not protected", with the visitor's address and its location.

README.md

@@ -9,13 +9,42 @@ binary, with a web interface, a JSON API and a native iPhone app.
 
 GHOSTWIRE sets up the WireGuard server, manages peers (add, change, disable,
 remove), hands out client configs as a download or QR code, and records traffic
-and connection history per peer. There are no install scripts and no
+and connection history per peer. There are no dependencies on the server:
-dependencies on the server: the binary installs, updates and removes itself.
+the binary installs, updates and removes itself.
 
-![Dashboard with peers online, traffic of the last 24 hours, the peer list and recent activity](screenshots/dashboard.png)
+## Quick start
+
+On a Linux server, run:
+
+```sh
+curl -fsSL https://ghostwi.re/install | sh
+```
+
+The short link leads to the script on Gitea. The same script can also be
+fetched directly from Gitea or from the GitHub mirror:
+
+```sh
+curl -fsSL https://git.redetzke.aero/Redetzke/GHOSTWIRE/raw/branch/main/install.sh | sh
+curl -fsSL https://raw.githubusercontent.com/danielredetzke/GHOSTWIRE/main/install.sh | sh
+```
+
+It downloads the latest release for the server's architecture, checks it
+against `SHA256SUMS` and starts the [install](#install), which asks a few
+questions and changes nothing until you confirm.
+
+> **Coming from pivpn?** GHOSTWIRE takes over a pivpn WireGuard server with
+> the [quick start](#quick-start) command above. Your phones and laptops keep their
+> current configs and reconnect on their own, with nothing to re-scan or
+> re-send. See [Moving from pivpn](#moving-from-pivpn).
+
+![Dashboard with the protection check, peers online, traffic of the last 24 hours, the peer list and recent activity](screenshots/dashboard.png)
 
 ## Features
 
+- **pivpn takeover:** install finds a pivpn WireGuard server and takes over
+  its key, networks and every client with its keys and addresses, so devices
+  keep working without new configs. pivpn comes back by itself if the switch
+  fails. [Details](#moving-from-pivpn).
 - **One file of state:** everything lives in `config.json`. The kernel is
   reconciled to it, so there is no `/etc/wireguard`, no `wg-quick` and no
   `wireguard-tools`.
@@ -28,6 +57,9 @@ dependencies on the server: the binary installs, updates and removes itself.
   server has a global IPv6 address.
 - **Traffic history:** kept in `stats.json`, hourly for 48 h and daily for
   400 days by default (Settings → Logs & history).
+- **Protection check:** the dashboard shows the address websites see for your
+  browser next to the server's. The same address means you are behind the
+  VPN; a peer that only routes the VPN network counts as not protected.
 - **Live view:** the speed of every peer right now, updated every 2 seconds,
   with the last 2 minutes as a chart. Kept in memory only.
 - **Connection history:** every online session per peer, with start, duration,
@@ -97,7 +129,15 @@ make test
 
 ## Install
 
-The binary installs itself. Copy it to the server and run it as root:
+The quickest way is the [one-line install](#quick-start). Arguments after
+`sh -s --` are passed on to `install` and skip their questions:
+
+```sh
+curl -fsSL https://ghostwi.re/install | sh -s -- -domain vpn.example.net -email you@example.net
+```
+
+The binary installs itself, so you can also copy it to the server and run it
+as root:
 
 ```sh
 scp dist/amd64/GHOSTWIRE server:/tmp/
@@ -154,6 +194,8 @@ sudo /tmp/GHOSTWIRE install -y -domain vpn.example.net -email you@example.net -p
 | `-email` | none |
 | `-endpoint` | the domain |
 | `-port` | 51820, or the current port when already installed |
+| `-import-pivpn` | off: see [Moving from pivpn](#moving-from-pivpn) |
+| `-no-wait` | off: after a pivpn takeover, don't wait for devices to reconnect |
 
 The admin password is then read from standard input, e.g.
 `echo "$PASSWORD" | sudo ./GHOSTWIRE install -y …`. Every value is checked
@@ -179,11 +221,35 @@ Then open `https://vpn.example.net` and sign in as `admin`. Add more users
 under Settings → Users. Root is needed only for the commands below, never for
 the running service.
 
+## Moving from pivpn
+
+On a server that runs pivpn's WireGuard, a new install offers to take it
+over. Devices keep their current config: GHOSTWIRE takes pivpn's server key,
+port, MTU, tunnel networks (IPv4 and IPv6), endpoint, DNS, AllowedIPs and
+keepalive, and every client with its public key, preshared key and addresses.
+Clients pivpn switched off are imported switched off, with the note
+"Imported from pivpn". Client private keys, which pivpn keeps in
+`/etc/wireguard/configs`, are not read or stored.
+
+After the summary, install notes which peers are connected, stops pivpn's
+WireGuard (`systemctl disable --now wg-quick@wg0`), starts GHOSTWIRE on the
+same `wg0` and waits up to 30 s for those peers to come back. Devices that
+send traffic reconnect after about 15 s; an idle device reconnects the next
+time it sends something. The wait only reports: Enter skips it, and so does
+`-no-wait` in scripts. If the service does not stay running, install puts
+pivpn back as it was.
+
+Without a terminal, the takeover needs `-import-pivpn`; install refuses to
+run next to pivpn otherwise. pivpn's files stay as they were. Manage peers in
+GHOSTWIRE from then on, delete `/etc/wireguard/configs` once everything works,
+and don't run `pivpn uninstall`, which removes WireGuard packages. To go back
+to pivpn: `GHOSTWIRE uninstall`, then `systemctl enable --now wg-quick@wg0`.
+
 ## Commands (as root)
 
 | Command | What it does |
 |---|---|
-| `GHOSTWIRE install [-domain d] [-email e] [-endpoint h] [-port p] [-y]` | Sets up and starts the service, as above. Asks for the settings no flag gave; `-y` never asks. |
+| `GHOSTWIRE install [-domain d] [-email e] [-endpoint h] [-port p] [-import-pivpn] [-no-wait] [-y]` | Sets up and starts the service, as above. Asks for the settings no flag gave; `-y` never asks. On a pivpn server it takes over pivpn's WireGuard (see above). |
 | `GHOSTWIRE update [-force]` | Run from the new binary, e.g. `sudo /tmp/GHOSTWIRE update`. Checks that it can read the current `config.json` (nothing changes if not), backs up the config to `config.json.bak-<old version>` (keeping the newest 3 such copies), replaces the binary, updates the unit if needed and restarts. If the new version does not stay up, the old binary and config are put back and restarted. It refuses older versions without `-force`. |
 | `GHOSTWIRE uninstall [-purge] [-y]` | Stops and removes the service, `wg0` and the firewall table. `-purge` also deletes `/opt/ghostwire` and the user. |
 | `GHOSTWIRE passwd [username]` | Sets a user's password (default: the first user) and reloads the running service. The way back in if you are locked out. |

api.go

@@ -34,6 +34,7 @@ type App struct {
 	started  time.Time
 	shutdown func()   // graceful stop; systemd restarts the service
 	webAddrs []string // the addresses the web server listens on now
+	endpoint endpointIPs
 }
 
 // --- helpers ---
@@ -389,6 +390,7 @@ func (a *App) status(w http.ResponseWriter, r *http.Request) {
 		"traffic24h": map[string]int64{"down": d24, "up": u24},
 		"traffic30d": map[string]int64{"down": d30, "up": u30},
 		"topPeer30d": top,
+		"visitor":    a.visitor(r, cfg),
 	})
 }
 
@@ -560,7 +562,7 @@ func (a *App) patchServer(w http.ResponseWriter, r *http.Request) {
 	err = a.store.Update(func(c *Config) error {
 		s := &c.Server
 		before := s.clientFacing()
-		oldV4 := s.IPv4
+		oldV4, oldV6 := s.IPv4, s.IPv6
 		for _, f := range []struct {
 			key string
 			dst any
@@ -583,6 +585,11 @@ func (a *App) patchServer(w http.ResponseWriter, r *http.Request) {
 				return err
 			}
 		}
+		if s.IPv6 != oldV6 {
+			for i := range c.Peers {
+				c.Peers[i].IPv6 = "" // pivpn's addresses are in the old network
+			}
+		}
 		reissue = before != s.clientFacing()
 		return nil
 	})
@@ -703,7 +710,7 @@ func (a *App) peerView(c *Config, p *Peer) peerView {
 		Created:      p.Created, ConfigIssued: p.ConfigIssued, Setup: viewSetup(p.Setup), Stats: a.stats.Summary(p.ID),
 	}
 	if c.Server.IPv6Enabled {
-		v.IPv6 = mapIPv6(netip.MustParsePrefix(c.Server.IPv6), netip.MustParseAddr(p.IPv4)).String()
+		v.IPv6 = peerIPv6(c, p).String()
 	}
 	return v
 }
@@ -1037,7 +1044,8 @@ func (a *App) issueConfig(w http.ResponseWriter, r *http.Request) {
 		}
 		now := time.Now().UTC()
 		// A config issued here replaces any pending link.
-		p.PublicKey, p.ConfigIssued, p.Setup, name = pub, &now, nil, p.Name
+		// The new config gets the mapped IPv6 address.
+		p.PublicKey, p.ConfigIssued, p.Setup, p.IPv6, name = pub, &now, nil, "", p.Name
 		if p.PresharedKey != "" {
 			p.PresharedKey = psk.String()
 		}

app.css

@@ -218,6 +218,22 @@ fieldset { border: 0; margin: 0; padding: 0; min-width: 0; display: flex; flex-d
 @media (max-width: 1000px) { .hcbody { grid-template-columns: minmax(0, 1fr); } }
 @media (max-width: 640px) { .hcrow { grid-template-columns: 8px minmax(0, 1fr); } .hcrow .v { grid-column: 2; } }
 
+/* visitor: the address websites see next to the server's */
+.visitor { display: flex; flex-wrap: wrap; align-items: stretch; gap: 16px 24px; }
+.vstate { flex: 1 1 340px; min-width: 0; display: flex; gap: 14px; align-items: flex-start; }
+.vstate h2 { margin: 2px 0 4px; font-size: 18px; font-weight: 600; }
+.vstate p { margin: 0; color: var(--ink-2); font-size: 13px; max-width: 62ch; }
+.vicon { flex: none; width: 40px; height: 40px; border-radius: 50%; display: grid; place-items: center; }
+.visitor.ok .vicon { background: #e6f5e6; color: #0b7a0b; }
+.visitor.ok h2 { color: #0b6b0b; }
+.visitor.off .vicon { background: var(--warn-bg); color: var(--warn-ink); }
+.visitor.off h2 { color: var(--warn-ink); }
+.vaddrs { flex: 2 1 420px; min-width: 0; display: grid; grid-template-columns: repeat(auto-fit, minmax(200px, 1fr)); gap: 12px; }
+.visitor .hcaddr { padding: 12px 16px; }
+.visitor .hcaddr .v.mono { font-size: 20px; }
+.visitor.ok .hcaddr { background: #eef7ee; box-shadow: inset 0 0 0 1px #c5e3c5; }
+.visitor.off .hcaddr:first-child { background: var(--warn-bg); box-shadow: inset 0 0 0 1px #f0d2ad; }
+
 /* updates */
 .upvers { display: grid; grid-template-columns: repeat(auto-fit, minmax(180px, 1fr)); gap: 12px; margin-top: 14px; }
 .upbox { background: var(--ground); border-radius: 10px; padding: 12px 14px; display: flex; flex-direction: column; gap: 2px; min-width: 0; }

app.js

@@ -51,6 +51,8 @@
     plus: '<path d="M12 5v14M5 12h14"/>',
     key: '<circle cx="8" cy="15" r="4"/><path d="M11 12l9-9M17 6l3 3M14 9l2 2"/>',
     log: '<rect x="4" y="3" width="16" height="18" rx="2"/><path d="M8 8h8M8 12h8M8 16h5"/>',
+    shield: '<path d="M12 3l7 3v5c0 4.5-3 8.3-7 10-4-1.7-7-5.5-7-10V6z"/><path d="M8.5 12l2.5 2.5 4.5-5"/>',
+    shieldoff: '<path d="M12 3l7 3v5c0 4.5-3 8.3-7 10-4-1.7-7-5.5-7-10V6z"/><path d="M12 8v4.5M12 15.8h.01"/>',
     logout: '<path d="M14 4h4a2 2 0 0 1 2 2v12a2 2 0 0 1-2 2h-4"/><path d="M10 16l-4-4 4-4M6 12h10"/>',
   };
 
@@ -1033,6 +1035,37 @@
   // RANGES are the time ranges offered above the traffic charts.
   const RANGES = [['24h', '24 h'], ['7d', '7 days'], ['30d', '30 days']];
 
+  // visitorCard shows the address websites see for this browser next to the
+  // server's: the same address means the browser is behind the VPN.
+  function visitorCard(v) {
+    if (!v) return null;
+    const addr = (label, value, note) => h('div', { class: 'hcaddr' },
+      h('span', { class: 'l' }, label), h('span', { class: 'v mono' }, value || 'Unknown'), h('span', { class: 'n' }, note));
+    const server = addr('Server IP address', v.serverIP, v.protected ? 'Same address: you are behind the VPN' : 'Different address: you are not behind the VPN');
+    if (v.protected) {
+      return h('section', { class: 'card visitor ok', 'aria-labelledby': 'vis' },
+        h('div', { class: 'vstate' },
+          h('span', { class: 'vicon' }, icon('shield', 22, 1.8)),
+          h('div', null,
+            h('h2', { id: 'vis' }, 'You are protected'),
+            h('p', null, v.peer
+              ? ['This browser is connected through the tunnel as ', peerLink(v.peer), '. All its traffic goes out through this server, so websites see the server\'s address, not yours.']
+              : 'This browser\'s traffic goes out through this server, so websites see the server\'s address, not yours.'))),
+        h('div', { class: 'vaddrs' }, addr('Your IP address', v.ip, 'What websites see'), server));
+    }
+    const where = v.peer ? 'Tunnel address of ' + v.peer.name
+      : v.location ? [v.location.countryName, v.location.network].filter(Boolean).join(' · ') : 'What websites see';
+    return h('section', { class: 'card visitor off', 'aria-labelledby': 'vis' },
+      h('div', { class: 'vstate' },
+        h('span', { class: 'vicon' }, icon('shieldoff', 22, 1.8)),
+        h('div', null,
+          h('h2', { id: 'vis' }, 'Not protected'),
+          h('p', null, v.peer
+            ? ['This browser uses the tunnel as ', peerLink(v.peer), ' only for the VPN network. Its other traffic skips the VPN, so websites see your own address.']
+            : 'This browser connects directly, not through the VPN. Websites see your own address. Turn on the tunnel on this device to browse through this server.'))),
+      h('div', { class: 'vaddrs' }, addr('Your IP address', v.ip, where), server));
+  }
+
   async function viewDashboard(wrap) {
     let range = '24h';
     const draw = async () => {
@@ -1063,10 +1096,9 @@
       fill(wrap,
         h('div', { class: 'head' },
           h('div', null, h('h1', null, 'Dashboard'),
-            h('p', { class: 'sub' }, 'Endpoint ', h('span', { class: 'mono' }, st.endpoint), ' · network ', h('span', { class: 'mono' }, st.ipv4))),
+            h('p', { class: 'sub' }, 'Endpoint ', h('span', { class: 'mono' }, st.endpoint), ' · network ', h('span', { class: 'mono' }, st.ipv4)))),
-          h('div', { class: 'actions' },
+
-            h('a', { class: 'btn', href: '#/server' }, 'Server config'),
+        visitorCard(st.visitor),
-            h('a', { class: 'btn primary', href: '#/peers/new' }, icon('plus', 16, 2), 'Add peer'))),
 
         failing.length ? h('div', { class: 'notice err', role: 'alert' },
           h('div', null, h('strong', null, 'Needs attention: '), failing.map((c) => c.name + ' (' + c.detail + ')').join(' · ')),

clientconf.go

@@ -52,7 +52,7 @@ func peerAddresses(c *Config, p *Peer) []netip.Prefix {
 	v4 := netip.MustParseAddr(p.IPv4)
 	out := []netip.Prefix{netip.PrefixFrom(v4, 32)}
 	if c.Server.IPv6Enabled {
-		out = append(out, netip.PrefixFrom(mapIPv6(netip.MustParsePrefix(c.Server.IPv6), v4), 128))
+		out = append(out, netip.PrefixFrom(peerIPv6(c, p), 128))
 	}
 	return out
 }
@@ -77,7 +77,7 @@ func clientConfig(c *Config, p *Peer, privateKey string) string {
 	addr := fmt.Sprintf("%s/%d", v4, v4net.Bits())
 	if c.Server.IPv6Enabled {
 		v6net := netip.MustParsePrefix(c.Server.IPv6)
-		addr += fmt.Sprintf(",%s/%d", mapIPv6(v6net, v4), v6net.Bits())
+		addr += fmt.Sprintf(",%s/%d", peerIPv6(c, p), v6net.Bits())
 	}
 	if privateKey == "" {
 		privateKey = "<the private key of this device>"

config.go

@@ -172,16 +172,20 @@ type ClientDefaults struct {
 // Peer is one client. Its private key is never stored: it is shown once when
 // the config is issued.
 type Peer struct {
-	ID           string   `json:"id"`
+	ID           string `json:"id"`
-	Name         string   `json:"name"`
+	Name         string `json:"name"`
-	Note         string   `json:"note"`
+	Note         string `json:"note"`
-	Enabled      bool     `json:"enabled"`
+	Enabled      bool   `json:"enabled"`
-	PublicKey    string   `json:"publicKey"`
+	PublicKey    string `json:"publicKey"`
-	PresharedKey string   `json:"presharedKey,omitempty"`
+	PresharedKey string `json:"presharedKey,omitempty"`
-	IPv4         string   `json:"ipv4"`
+	IPv4         string `json:"ipv4"`
-	DNS          []string `json:"dns,omitempty"`        // nil = server default
+	// IPv6 is set only for a peer imported from pivpn, which numbers IPv6
-	AllowedIPs   []string `json:"allowedIPs,omitempty"` // nil = server default
+	// differently: its device keeps the address until the config is issued
-	Keepalive    *int     `json:"keepalive,omitempty"`  // nil = server default
+	// here. Empty means the address mapped from IPv4 (see mapIPv6).
+	IPv6       string   `json:"ipv6,omitempty"`
+	DNS        []string `json:"dns,omitempty"`        // nil = server default
+	AllowedIPs []string `json:"allowedIPs,omitempty"` // nil = server default
+	Keepalive  *int     `json:"keepalive,omitempty"`  // nil = server default
 	// LatencyCheck says when the server pings the peer through the tunnel:
 	// "" (off), "active" (while the device sends traffic) or "always".
 	LatencyCheck string     `json:"latencyCheck,omitempty"`
@@ -473,6 +477,7 @@ func (c *Config) validate() error {
 
 	names := map[string]bool{}
 	ips := map[netip.Addr]bool{}
+	ips6 := map[netip.Addr]bool{}
 	keys := map[string]bool{}
 	for _, p := range c.Peers {
 		if err := validatePeerName(p.Name); err != nil {
@@ -493,6 +498,17 @@ func (c *Config) validate() error {
 			return fmt.Errorf("address %s is used twice", ip)
 		}
 		ips[ip] = true
+		if p.IPv6 != "" {
+			a, err := netip.ParseAddr(p.IPv6)
+			if err != nil || !a.Is6() || !v6.Contains(a) || a == v6.Addr() {
+				return fmt.Errorf("peer %q: IPv6 address %s is outside %s", p.Name, p.IPv6, v6)
+			}
+		}
+		if a := peerIPv6(c, &p); ips6[a] {
+			return fmt.Errorf("IPv6 address %s is used twice", a)
+		} else {
+			ips6[a] = true
+		}
 		if p.hasKey() && keys[p.PublicKey] {
 			return fmt.Errorf("peer %q: public key is used by another peer", p.Name)
 		}

install.sh

@@ -0,0 +1,69 @@
+#!/bin/sh
+# Downloads the latest GHOSTWIRE release, checks it against SHA256SUMS and
+# runs its install command. Usage:
+#
+#   curl -fsSL https://ghostwi.re/install | sh
+#   curl -fsSL https://ghostwi.re/install | sh -s -- -y -domain vpn.example.net -email you@example.net
+#
+# ghostwi.re/install redirects to this file on Gitea; the GitHub mirror has it
+# at raw.githubusercontent.com/danielredetzke/GHOSTWIRE/main/install.sh.
+#
+# Arguments are passed on to "GHOSTWIRE install". Everything is wrapped in
+# main so that a cut-off download runs nothing.
+set -eu
+
+GITEA=https://git.redetzke.aero/Redetzke/GHOSTWIRE
+GITEA_API=https://git.redetzke.aero/api/v1/repos/Redetzke/GHOSTWIRE/releases/latest
+GITHUB=https://github.com/danielredetzke/GHOSTWIRE
+GITHUB_API=https://api.github.com/repos/danielredetzke/GHOSTWIRE/releases/latest
+
+die() { echo "GHOSTWIRE: $*" >&2; exit 1; }
+
+latest() { curl -fsSL "$1" 2>/dev/null | sed -n 's/.*"tag_name": *"\([^"]*\)".*/\1/p'; }
+
+main() {
+	[ "$(uname -s)" = Linux ] || die "runs on Linux only"
+	case "$(uname -m)" in
+	x86_64 | amd64) arch=amd64 ;;
+	aarch64 | arm64) arch=arm64 ;;
+	armv7l | armv8l) arch=armv7 ;;
+	*) die "no build for $(uname -m)" ;;
+	esac
+	command -v curl >/dev/null || die "needs curl"
+	command -v sha256sum >/dev/null || die "needs sha256sum"
+
+	sudo=
+	if [ "$(id -u)" -ne 0 ]; then
+		command -v sudo >/dev/null || die "run as root or install sudo"
+		sudo=sudo
+	fi
+
+	# Gitea first, GitHub if it is not reachable.
+	repo=$GITEA
+	version=$(latest "$GITEA_API")
+	if [ -z "$version" ]; then
+		repo=$GITHUB
+		version=$(latest "$GITHUB_API")
+	fi
+	[ -n "$version" ] || die "could not find the latest release"
+
+	file=GHOSTWIRE-$version-linux-$arch
+	tmp=$(mktemp -d)
+	trap 'rm -rf "$tmp"' EXIT
+	echo "Downloading GHOSTWIRE $version ($arch) from $repo"
+	curl -fsSL -o "$tmp/$file" "$repo/releases/download/$version/$file"
+	curl -fsSL -o "$tmp/SHA256SUMS" "$repo/releases/download/$version/SHA256SUMS"
+	(cd "$tmp" && grep " $file\$" SHA256SUMS | sha256sum -c --status) ||
+		die "checksum of $file does not match SHA256SUMS"
+	mv "$tmp/$file" "$tmp/GHOSTWIRE"
+	chmod 755 "$tmp/GHOSTWIRE"
+
+	# The script itself arrives on stdin, so the questions read the terminal.
+	if [ -t 1 ] && [ -r /dev/tty ]; then
+		$sudo "$tmp/GHOSTWIRE" install "$@" </dev/tty
+	else
+		$sudo "$tmp/GHOSTWIRE" install "$@"
+	fi
+}
+
+main "$@"

installask.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"bufio"
+	"cmp"
 	"context"
 	"errors"
 	"fmt"
@@ -17,10 +18,11 @@ import (
 type installPlan struct {
 	domain, email, endpoint string
 	port                    int
-	noDomain                bool   // turn an existing domain off (self-signed certificate)
+	noDomain                bool        // turn an existing domain off (self-signed certificate)
-	noEmail                 bool   // remove an existing Let's Encrypt email
+	noEmail                 bool        // remove an existing Let's Encrypt email
-	passwordHash            string // asked in the terminal; empty: asked later
+	passwordHash            string      // asked in the terminal; empty: asked later
-	ipv4                    string // tunnel network of a new install
+	ipv4                    string      // tunnel network of a new install
+	pivpn                   *pivpnSetup // pivpn's WireGuard server to take over
 }
 
 var domainRe = regexp.MustCompile(`^([a-zA-Z0-9]([a-zA-Z0-9-]{0,61}[a-zA-Z0-9])?\.)+[a-zA-Z]{2,63}$`)
@@ -80,6 +82,10 @@ func (p installPlan) changes() bool {
 	return p.domain != "" || p.email != "" || p.endpoint != "" || p.port != 0 || p.noDomain || p.noEmail || p.passwordHash != ""
 }
 
+// errPivpnDeclined ends an install whose admin keeps pivpn: both would use
+// the same interface.
+var errPivpnDeclined = errors.New("install cancelled; nothing was changed. GHOSTWIRE and pivpn cannot both run the WireGuard interface: remove pivpn first, or install again and take it over")
+
 func (p installPlan) apply(c *Config) {
 	if p.noDomain {
 		if c.Web.TLS.Mode == "acme" {
@@ -113,7 +119,7 @@ func (p installPlan) apply(c *Config) {
 // reissueCount is the number of devices whose config stops working because
 // the endpoint host or port changes.
 func (p installPlan) reissueCount(cur *Config, existing bool) int {
-	if !existing {
+	if !existing && p.pivpn == nil {
 		return 0
 	}
 	next := cur.clone()
@@ -189,6 +195,25 @@ func askInstall(in io.Reader, cur *Config, existing bool, given map[string]bool,
 		fmt.Println("Press Enter to accept the value in [brackets].")
 	}
 
+	// pivpn: taken over first, so its settings become the defaults below.
+	if p.pivpn != nil && !given["import-pivpn"] {
+		s := cur.Server
+		nets := s.IPv4
+		if s.IPv6Enabled {
+			nets += " + " + s.IPv6
+		}
+		fmt.Println("\npivpn found")
+		fmt.Printf("  %s · %s · UDP %d · %s\n", s.Interface, nets, s.ListenPort, cmp.Or(s.Endpoint, "no endpoint"))
+		fmt.Printf("  %s: %s\n", plural(len(p.pivpn.Peers), "client"), cmp.Or(p.pivpn.names(), "none"))
+		ok, err := pr.confirm("  Take over this WireGuard server? The devices keep working without new configs.")
+		if err != nil {
+			return p, err
+		}
+		if !ok {
+			return p, errPivpnDeclined
+		}
+	}
+
 	// Web interface
 	fmt.Println("\nWeb interface")
 	curDomain := ""
@@ -328,7 +353,7 @@ func askInstall(in io.Reader, cur *Config, existing bool, given map[string]bool,
 
 func printInstallSummary(cur *Config, existing bool, p installPlan) {
 	next := cur.clone()
-	if !existing {
+	if !existing && p.pivpn == nil {
 		next.Server.IPv4 = p.ipv4
 		next.Server.IPv6Enabled = hasGlobalIPv6()
 	}
@@ -366,7 +391,10 @@ func printInstallSummary(cur *Config, existing bool, p installPlan) {
 		ep += fmt.Sprintf("   (was %s — %d existing device(s) need a new config)", endpointString(cur), n)
 	}
 	tunnel := next.Server.IPv4
-	if !existing {
+	switch {
+	case p.pivpn != nil:
+		tunnel += " (from pivpn)"
+	case !existing:
 		tunnel += " (random free range)"
 	}
 	if next.Server.IPv6Enabled {
@@ -395,4 +423,21 @@ func printInstallSummary(cur *Config, existing bool, p installPlan) {
 	if p.passwordHash != "" {
 		fmt.Printf("  Admin           %s (password set)\n", next.Users[0].Username)
 	}
+	if pv := p.pivpn; pv != nil {
+		s := next.Server
+		fmt.Printf("  From pivpn      server key, %s with their keys and addresses,\n", plural(len(pv.Peers), "peer"))
+		fmt.Printf("                  DNS %s · keepalive %d s · MTU %d\n", strings.Join(s.ClientDefaults.DNS, ", "), s.ClientDefaults.Keepalive, s.MTU)
+		for _, r := range pv.Renamed {
+			fmt.Printf("  Renamed         %s → %s (names here: 1–32 letters, digits, . @ _ -)\n", r[0], r[1])
+		}
+		fmt.Printf("  Not taken       client private keys in %s (never stored here)\n", pv.ClientKeys)
+	}
+}
+
+// plural writes "1 peer" or "5 peers".
+func plural(n int, word string) string {
+	if n == 1 {
+		return "1 " + word
+	}
+	return strconv.Itoa(n) + " " + word + "s"
 }

ipam.go

@@ -122,6 +122,15 @@ func nextFreeIPv4(c *Config) (netip.Addr, error) {
 // capacity is the number of peer addresses in the tunnel network.
 func capacity(n netip.Prefix) int { return 1<<(32-n.Bits()) - 3 }
 
+// peerIPv6 is the peer's IPv6 tunnel address: the one kept from pivpn, or
+// the one mapped from its IPv4 address.
+func peerIPv6(c *Config, p *Peer) netip.Addr {
+	if a, err := netip.ParseAddr(p.IPv6); err == nil {
+		return a
+	}
+	return mapIPv6(netip.MustParsePrefix(c.Server.IPv6), netip.MustParseAddr(p.IPv4))
+}
+
 // mapIPv6 puts the 32 bits of an IPv4 address into the low bits of the IPv6
 // network: 10.84.12.8 in fd11:5ee:bad:c0de::/64 becomes fd11:5ee:bad:c0de::a54:c08.
 func mapIPv6(v6net netip.Prefix, v4 netip.Addr) netip.Addr {

kernel_linux.go

@@ -368,8 +368,10 @@ func (k *linuxKernel) Checks(c *Config) []Check {
 
 func (k *linuxKernel) Down(c *Config) error {
 	var errs []error
-	if link, err := netlink.LinkByName(c.Server.Interface); err == nil {
+	if c.Server.Interface != "" {
-		errs = append(errs, netlink.LinkDel(link))
+		if link, err := netlink.LinkByName(c.Server.Interface); err == nil {
+			errs = append(errs, netlink.LinkDel(link))
+		}
 	}
 	errs = append(errs, removeFirewall())
 	return errors.Join(errs...)

main_test.go

@@ -1607,3 +1607,42 @@ func TestApplyOrder(t *testing.T) {
 		t.Fatalf("the kernel ended with %q, not the newest config; applies: %q", last, k.applied)
 	}
 }
+
+func TestClassifyVisitor(t *testing.T) {
+	c := testConfig(t)
+	c.Peers = []Peer{
+		{ID: "full", Name: "phone", IPv4: "10.84.12.2", Enabled: true},
+		{ID: "split", Name: "laptop", IPv4: "10.84.12.3", Enabled: true, AllowedIPs: []string{"10.84.12.0/24"}},
+		{ID: "off", Name: "old", IPv4: "10.84.12.4"},
+	}
+	server := netip.MustParseAddr("203.0.113.10")
+	none := func(netip.Addr) bool { return false }
+	lan := func(ip netip.Addr) bool { return ip == netip.MustParseAddr("192.168.1.5") }
+	for _, tc := range []struct {
+		ip        string
+		own       func(netip.Addr) bool
+		protected bool
+		shown     string
+		peer      string
+	}{
+		{"10.84.12.2", none, true, "203.0.113.10", "phone"},                          // full tunnel
+		{"10.84.12.3", none, false, "10.84.12.3", "laptop"},                          // split tunnel
+		{"10.84.12.4", none, false, "10.84.12.4", ""},                                // disabled peer
+		{"203.0.113.10", none, true, "203.0.113.10", ""},                             // looped back through the router
+		{"192.168.1.5", lan, true, "203.0.113.10", ""},                               // the server's own address
+		{"198.51.100.77", none, false, "198.51.100.77", ""},                          // directly
+		{"127.0.0.1", func(netip.Addr) bool { return true }, false, "127.0.0.1", ""}, // local proxy
+	} {
+		v := classifyVisitor(c, netip.MustParseAddr(tc.ip), server, tc.own)
+		name := ""
+		if v.Peer != nil {
+			name = v.Peer.Name
+		}
+		if v.Protected != tc.protected || v.IP != tc.shown || name != tc.peer || v.ServerIP != "203.0.113.10" {
+			t.Errorf("%s: got %+v", tc.ip, v)
+		}
+	}
+	if !fullTunnel([]string{"0.0.0.0/1", "128.0.0.0/1"}, false) || fullTunnel([]string{"::/0"}, false) || !fullTunnel([]string{"::/0"}, true) {
+		t.Error("fullTunnel")
+	}
+}

pivpn.go

@@ -0,0 +1,354 @@
+package main
+
+import (
+	"bufio"
+	"cmp"
+	"errors"
+	"fmt"
+	"net/netip"
+	"os"
+	"path/filepath"
+	"slices"
+	"strconv"
+	"strings"
+	"time"
+
+	"golang.zx2c4.com/wireguard/wgctrl/wgtypes"
+)
+
+// A new install can take over a WireGuard server set up by pivpn: the
+// server key, the network and every client with its public key, preshared
+// key and addresses, so the devices keep their configs. pivpn keeps the
+// client private keys in /etc/wireguard/configs; they are not read.
+
+const (
+	pivpnSetupVars = "etc/pivpn/wireguard/setupVars.conf"
+	pivpnNote      = "Imported from pivpn"
+)
+
+// pivpnSetup is what install takes over from pivpn.
+type pivpnSetup struct {
+	Dev        string // the interface, wg0
+	Server     Server
+	Peers      []Peer
+	Renamed    [][2]string // pivpn name, name here
+	ClientKeys string      // where pivpn keeps the client configs with private keys
+}
+
+// readPivpn reads pivpn's WireGuard setup under root ("/" on a server). It
+// returns nil and no error when pivpn's WireGuard is not installed.
+func readPivpn(root string) (*pivpnSetup, error) {
+	vars, err := readSetupVars(filepath.Join(root, pivpnSetupVars))
+	if errors.Is(err, os.ErrNotExist) {
+		return nil, nil
+	}
+	if err != nil {
+		return nil, err
+	}
+	s := &pivpnSetup{Dev: cmp.Or(vars["pivpnDEV"], "wg0")}
+	if checkIfName(s.Dev) != nil {
+		return nil, fmt.Errorf("pivpn: interface name %q is not usable", s.Dev)
+	}
+	confPath := filepath.Join(root, "etc/wireguard", s.Dev+".conf")
+	conf, err := parseWgConf(confPath)
+	if err != nil {
+		return nil, fmt.Errorf("pivpn: %w", err)
+	}
+	s.ClientKeys = "/etc/wireguard/configs"
+	created := readClientsTxt(filepath.Join(root, "etc/wireguard/configs/clients.txt"))
+
+	// Server
+	srv := &s.Server
+	srv.Interface = s.Dev
+	if _, err := wgtypes.ParseKey(conf.privateKey); err != nil {
+		return nil, fmt.Errorf("pivpn: %s: the server key is missing or invalid", confPath)
+	}
+	srv.PrivateKey = conf.privateKey
+	srv.KeyCreated = fileTime(filepath.Join(root, "etc/wireguard/keys/server_priv"), confPath)
+	if srv.ListenPort = conf.listenPort; srv.ListenPort == 0 {
+		srv.ListenPort, _ = strconv.Atoi(vars["pivpnPORT"])
+	}
+	if srv.MTU = conf.mtu; srv.MTU == 0 {
+		srv.MTU, _ = strconv.Atoi(vars["pivpnMTU"])
+	}
+	for _, a := range conf.address {
+		if a.Addr().Is4() {
+			srv.IPv4 = a.Masked().String()
+		} else {
+			srv.IPv6, srv.IPv6Enabled = a.Masked().String(), true
+		}
+	}
+	if srv.IPv4 == "" {
+		return nil, fmt.Errorf("pivpn: %s has no IPv4 Address line", confPath)
+	}
+	if h := vars["pivpnHOST"]; checkEndpoint(h) == nil {
+		srv.Endpoint = h
+	}
+	srv.NAT, srv.PeerToPeer, srv.OpenPort = true, true, true
+	for _, k := range []string{"pivpnDNS1", "pivpnDNS2"} {
+		if a, err := netip.ParseAddr(vars[k]); err == nil {
+			srv.ClientDefaults.DNS = append(srv.ClientDefaults.DNS, a.String())
+		}
+	}
+	for _, v := range strings.Split(vars["ALLOWED_IPS"], ",") {
+		if p, err := netip.ParsePrefix(strings.TrimSpace(v)); err == nil {
+			srv.ClientDefaults.AllowedIPs = append(srv.ClientDefaults.AllowedIPs, p.Masked().String())
+		}
+	}
+	srv.ClientDefaults.Keepalive, _ = strconv.Atoi(vars["pivpnPERSISTENTKEEPALIVE"])
+
+	// Clients
+	v6net, _ := netip.ParsePrefix(srv.IPv6)
+	taken := map[string]bool{}
+	for _, cl := range conf.clients {
+		pub, err := wgtypes.ParseKey(cl.publicKey)
+		if err != nil {
+			return nil, fmt.Errorf("pivpn: client %q has no valid public key", cl.name)
+		}
+		p := Peer{ID: newID(), Name: cl.name, Note: pivpnNote, Enabled: !cl.disabled, PublicKey: pub.String()}
+		if cl.presharedKey != "" {
+			psk, err := wgtypes.ParseKey(cl.presharedKey)
+			if err != nil {
+				return nil, fmt.Errorf("pivpn: client %q has an invalid preshared key", cl.name)
+			}
+			p.PresharedKey = psk.String()
+		}
+		for _, a := range cl.allowedIPs {
+			switch {
+			case a.Addr().Is4() && p.IPv4 == "":
+				p.IPv4 = a.Addr().String()
+			case a.Addr().Is6() && p.IPv6 == "" && v6net.IsValid() && v6net.Contains(a.Addr()):
+				p.IPv6 = a.Addr().String()
+			}
+		}
+		if p.IPv4 == "" {
+			return nil, fmt.Errorf("pivpn: client %q has no IPv4 address", cl.name)
+		}
+		// Keep pivpn's IPv6 address only where it differs from the mapped one.
+		if v4, err := netip.ParseAddr(p.IPv4); err == nil && v6net.IsValid() && p.IPv6 == mapIPv6(v6net, v4).String() {
+			p.IPv6 = ""
+		}
+		t, ok := created[cl.name]
+		if !ok {
+			t = srv.KeyCreated
+		}
+		t = t.UTC()
+		p.Created, p.ConfigIssued = t, &t
+		if name := usableName(cl.name, taken); name != cl.name {
+			s.Renamed = append(s.Renamed, [2]string{cl.name, name})
+			p.Name = name
+		}
+		taken[strings.ToLower(p.Name)] = true
+		s.Peers = append(s.Peers, p)
+	}
+	return s, nil
+}
+
+// apply puts the pivpn setup into a fresh config.
+func (s *pivpnSetup) apply(c *Config) {
+	cd := c.Server.ClientDefaults
+	c.Server = s.Server
+	// Settings pivpn left empty keep GHOSTWIRE's defaults.
+	if c.Server.ClientDefaults.DNS == nil {
+		c.Server.ClientDefaults.DNS = cd.DNS
+	}
+	if c.Server.ClientDefaults.AllowedIPs == nil {
+		c.Server.ClientDefaults.AllowedIPs = cd.AllowedIPs
+	}
+	if c.Server.IPv6 == "" {
+		// IPv4-only pivpn: IPv6 stays off, with the network GHOSTWIRE
+		// would pick, ready for when it is switched on.
+		c.Server.IPv6 = "fd11:5ee:bad:c0de::/64"
+	}
+	c.Peers = slices.Clone(s.Peers)
+	c.applyDefaults()
+}
+
+// names lists the clients for the takeover question.
+func (s *pivpnSetup) names() string {
+	var out []string
+	for _, p := range s.Peers {
+		n := p.Name
+		if !p.Enabled {
+			n += " (off)"
+		}
+		out = append(out, n)
+	}
+	return strings.Join(out, ", ")
+}
+
+func checkIfName(n string) error {
+	if n == "" || len(n) > 15 || strings.ContainsAny(n, "/ \t") {
+		return errors.New("bad interface name")
+	}
+	return nil
+}
+
+// usableName turns a pivpn client name into one GHOSTWIRE accepts and that
+// is not taken yet.
+func usableName(name string, taken map[string]bool) string {
+	b := []rune{}
+	for _, r := range name {
+		if r < 128 && (r == '.' || r == '@' || r == '_' || r == '-' || r >= '0' && r <= '9' || r >= 'a' && r <= 'z' || r >= 'A' && r <= 'Z') {
+			b = append(b, r)
+		} else {
+			b = append(b, '-')
+		}
+	}
+	n := strings.TrimLeft(string(b), "-.")
+	if n == "" || strings.Trim(n, "0123456789") == "" || n == "server" {
+		n = "peer-" + n
+	}
+	n = strings.TrimRight(n, "-")
+	if len(n) > 32 {
+		n = n[:32]
+	}
+	base := n
+	for i := 1; taken[strings.ToLower(n)] || validatePeerName(n) != nil; i++ {
+		suffix := "-" + strconv.Itoa(i)
+		n = base
+		if len(n)+len(suffix) > 32 {
+			n = n[:32-len(suffix)]
+		}
+		n += suffix
+		if i > 1000 {
+			break
+		}
+	}
+	return n
+}
+
+// readSetupVars reads pivpn's KEY=VALUE file; values may be quoted.
+func readSetupVars(path string) (map[string]string, error) {
+	b, err := os.ReadFile(path)
+	if err != nil {
+		return nil, err
+	}
+	out := map[string]string{}
+	for _, line := range strings.Split(string(b), "\n") {
+		k, v, ok := strings.Cut(strings.TrimSpace(line), "=")
+		if !ok || strings.HasPrefix(k, "#") {
+			continue
+		}
+		v = strings.TrimSpace(v)
+		if len(v) >= 2 && (v[0] == '"' || v[0] == '\'') && v[len(v)-1] == v[0] {
+			v = v[1 : len(v)-1]
+		}
+		out[strings.TrimSpace(k)] = v
+	}
+	return out, nil
+}
+
+type wgClient struct {
+	name, publicKey, presharedKey string
+	allowedIPs                    []netip.Prefix
+	disabled                      bool
+}
+
+type wgConf struct {
+	privateKey      string
+	listenPort, mtu int
+	address         []netip.Prefix
+	clients         []wgClient
+}
+
+// parseWgConf reads pivpn's wg0.conf: the [Interface] section, then one
+// "### begin NAME ###" … "### end NAME ###" block per client. pivpn turns a
+// client off by prefixing each line of its block with "#[disabled] ".
+func parseWgConf(path string) (*wgConf, error) {
+	f, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+	c := &wgConf{}
+	var cur *wgClient
+	sc := bufio.NewScanner(f)
+	for sc.Scan() {
+		line := strings.TrimSpace(sc.Text())
+		disabled := false
+		if rest, ok := strings.CutPrefix(line, "#[disabled]"); ok {
+			line, disabled = strings.TrimSpace(rest), true
+		}
+		if name, ok := strings.CutPrefix(line, "### begin "); ok {
+			c.clients = append(c.clients, wgClient{name: strings.TrimSpace(strings.TrimSuffix(name, "###"))})
+			cur = &c.clients[len(c.clients)-1]
+			continue
+		}
+		if strings.HasPrefix(line, "### end ") {
+			cur = nil
+			continue
+		}
+		if line == "" || strings.HasPrefix(line, "#") || strings.HasPrefix(line, "[") {
+			continue
+		}
+		k, v, ok := strings.Cut(line, "=")
+		if !ok {
+			continue
+		}
+		k, v = strings.ToLower(strings.TrimSpace(k)), strings.TrimSpace(v)
+		if cur != nil {
+			cur.disabled = cur.disabled || disabled
+			switch k {
+			case "publickey":
+				cur.publicKey = v
+			case "presharedkey":
+				cur.presharedKey = v
+			case "allowedips":
+				cur.allowedIPs = parsePrefixes(v)
+			}
+			continue
+		}
+		switch k {
+		case "privatekey":
+			c.privateKey = v
+		case "listenport":
+			c.listenPort, _ = strconv.Atoi(v)
+		case "mtu":
+			c.mtu, _ = strconv.Atoi(v)
+		case "address":
+			c.address = parsePrefixes(v)
+		}
+	}
+	return c, sc.Err()
+}
+
+func parsePrefixes(v string) []netip.Prefix {
+	var out []netip.Prefix
+	for _, s := range strings.Split(v, ",") {
+		if p, err := netip.ParsePrefix(strings.TrimSpace(s)); err == nil {
+			out = append(out, p)
+		}
+	}
+	return out
+}
+
+// readClientsTxt returns when each client was created: clients.txt has
+// "NAME PUBLICKEY UNIXTIME" per line.
+func readClientsTxt(path string) map[string]time.Time {
+	out := map[string]time.Time{}
+	b, err := os.ReadFile(path)
+	if err != nil {
+		return out
+	}
+	for _, line := range strings.Split(string(b), "\n") {
+		f := strings.Fields(line)
+		if len(f) < 3 {
+			continue
+		}
+		if n, err := strconv.ParseInt(f[2], 10, 64); err == nil && n > 0 {
+			out[f[0]] = time.Unix(n, 0)
+		}
+	}
+	return out
+}
+
+// fileTime is the modification time of the first file that exists.
+func fileTime(paths ...string) time.Time {
+	for _, p := range paths {
+		if st, err := os.Stat(p); err == nil {
+			return st.ModTime().UTC()
+		}
+	}
+	return time.Now().UTC()
+}

pivpn_test.go

@@ -0,0 +1,335 @@
+package main
+
+import (
+	"errors"
+	"fmt"
+	"net/netip"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+	"time"
+
+	"golang.zx2c4.com/wireguard/wgctrl/wgtypes"
+)
+
+// pivpnFixture writes a pivpn WireGuard layout under a temp root, in the
+// format pivpn v4 writes (checked against a real install, Ubuntu 24.04).
+type pivpnClient struct {
+	name, v6 string
+	ipv4     string
+	psk      bool
+	disabled bool
+}
+
+func pivpnFixture(t *testing.T, ipv6 bool, clients []pivpnClient) (root string, serverKey wgtypes.Key, pubs map[string]string) {
+	t.Helper()
+	root = t.TempDir()
+	must := func(err error) {
+		if err != nil {
+			t.Fatal(err)
+		}
+	}
+	for _, d := range []string{"etc/pivpn/wireguard", "etc/wireguard/configs", "etc/wireguard/keys"} {
+		must(os.MkdirAll(filepath.Join(root, d), 0o755))
+	}
+	v6 := "0"
+	if ipv6 {
+		v6 = "1"
+	}
+	vars := `USING_UFW=0
+IPv4dev=eth0
+VPN=wireguard
+pivpnPORT=51820
+pivpnDNS1=9.9.9.9
+pivpnDNS2=149.112.112.112
+pivpnHOST=vpn.example.net
+pivpnPROTO=udp
+pivpnMTU=1420
+pivpnPERSISTENTKEEPALIVE=25
+pivpnDEV=wg0
+pivpnNET=10.6.0.0
+subnetClass=24
+pivpnenableipv6=` + v6 + `
+pivpnNETv6="fd11:5ee:bad:c0de::"
+subnetClassv6=64
+ALLOWED_IPS="0.0.0.0/0, ::0/0"
+INSTALLED_PACKAGES=(wireguard-tools qrencode)
+`
+	must(os.WriteFile(filepath.Join(root, pivpnSetupVars), []byte(vars), 0o644))
+	serverKey, _ = wgtypes.GeneratePrivateKey()
+	var conf, txt strings.Builder
+	addr := "10.6.0.1/24"
+	if ipv6 {
+		addr += ",fd11:5ee:bad:c0de::a06:1/64"
+	}
+	fmt.Fprintf(&conf, "[Interface]\nPrivateKey = %s\nAddress = %s\nMTU = 1420\nListenPort = 51820\n", serverKey, addr)
+	pubs = map[string]string{}
+	for _, c := range clients {
+		k, _ := wgtypes.GeneratePrivateKey()
+		pubs[c.name] = k.PublicKey().String()
+		var b strings.Builder
+		fmt.Fprintf(&b, "### begin %s ###\n[Peer]\nPublicKey = %s\n", c.name, k.PublicKey())
+		if c.psk {
+			psk, _ := wgtypes.GenerateKey()
+			fmt.Fprintf(&b, "PresharedKey = %s\n", psk)
+		}
+		fmt.Fprintf(&b, "AllowedIPs = %s/32", c.ipv4)
+		if ipv6 {
+			fmt.Fprintf(&b, ",%s/128", c.v6)
+		}
+		fmt.Fprintf(&b, "\n### end %s ###\n", c.name)
+		block := b.String()
+		if c.disabled {
+			block = "#[disabled] " + strings.ReplaceAll(strings.TrimSuffix(block, "\n"), "\n", "\n#[disabled] ") + "\n"
+		}
+		conf.WriteString(block)
+		fmt.Fprintf(&txt, "%s %s 1700000000 167116802\n", c.name, k.PublicKey())
+	}
+	must(os.WriteFile(filepath.Join(root, "etc/wireguard/wg0.conf"), []byte(conf.String()), 0o644))
+	must(os.WriteFile(filepath.Join(root, "etc/wireguard/configs/clients.txt"), []byte(txt.String()), 0o644))
+	return root, serverKey, pubs
+}
+
+func importedConfig(t *testing.T, s *pivpnSetup) *Config {
+	t.Helper()
+	c := &Config{}
+	c.applyDefaults()
+	s.apply(c)
+	if err := c.validate(); err != nil {
+		t.Fatalf("imported config does not validate: %v", err)
+	}
+	return c
+}
+
+func TestPivpnImport(t *testing.T) {
+	// No pivpn: nothing to import, no error.
+	if s, err := readPivpn(t.TempDir()); s != nil || err != nil {
+		t.Fatalf("empty root: %v %v", s, err)
+	}
+
+	clients := []pivpnClient{
+		{name: "iphone-alex", ipv4: "10.6.0.2", v6: "fd11:5ee:bad:c0de::a06:2", psk: true},
+		{name: "nas-office", ipv4: "10.6.0.5", v6: "fd11:5ee:bad:c0de::a06:5", psk: false},
+		{name: "phone-guest", ipv4: "10.6.0.6", v6: "fd11:5ee:bad:c0de::a06:6", psk: true, disabled: true},
+		// Hand-edited: an IPv6 address that is not the mapped one.
+		{name: "old-laptop", ipv4: "10.6.0.7", v6: "fd11:5ee:bad:c0de::7", psk: true},
+	}
+	root, key, pubs := pivpnFixture(t, true, clients)
+	s, err := readPivpn(root)
+	if err != nil || s == nil {
+		t.Fatal(err)
+	}
+	c := importedConfig(t, s)
+	srv := c.Server
+	if srv.PrivateKey != key.String() || srv.ListenPort != 51820 || srv.MTU != 1420 || srv.Interface != "wg0" ||
+		srv.IPv4 != "10.6.0.0/24" || srv.IPv6 != "fd11:5ee:bad:c0de::/64" || !srv.IPv6Enabled ||
+		srv.Endpoint != "vpn.example.net" || !srv.NAT || !srv.PeerToPeer || !srv.OpenPort {
+		t.Fatalf("server: %+v", srv)
+	}
+	cd := srv.ClientDefaults
+	if strings.Join(cd.DNS, ",") != "9.9.9.9,149.112.112.112" || strings.Join(cd.AllowedIPs, ",") != "0.0.0.0/0,::/0" || cd.Keepalive != 25 {
+		t.Fatalf("client defaults: %+v", cd)
+	}
+	if len(c.Peers) != 4 {
+		t.Fatalf("want 4 peers, got %d", len(c.Peers))
+	}
+	by := map[string]*Peer{}
+	for i := range c.Peers {
+		by[c.Peers[i].Name] = &c.Peers[i]
+	}
+	ph := by["iphone-alex"]
+	if ph.PublicKey != pubs["iphone-alex"] || ph.PresharedKey == "" || ph.IPv4 != "10.6.0.2" || ph.IPv6 != "" ||
+		!ph.Enabled || ph.Note != pivpnNote || !ph.Created.Equal(time.Unix(1700000000, 0)) || ph.ConfigIssued == nil {
+		t.Fatalf("iphone-alex: %+v", ph)
+	}
+	if by["nas-office"].PresharedKey != "" {
+		t.Error("nas-office had no preshared key")
+	}
+	if by["phone-guest"].Enabled {
+		t.Error("a #[disabled] client must be imported switched off")
+	}
+	if by["old-laptop"].IPv6 != "fd11:5ee:bad:c0de::7" {
+		t.Errorf("a non-mapped IPv6 address must be kept, got %q", by["old-laptop"].IPv6)
+	}
+
+	// Each device's own pivpn config keeps working: the server accepts its
+	// key, preshared key and both addresses.
+	for _, cl := range clients {
+		p := by[cl.name]
+		got := []string{}
+		for _, a := range peerAddresses(c, p) {
+			got = append(got, a.String())
+		}
+		want := cl.ipv4 + "/32 " + cl.v6 + "/128"
+		if strings.Join(got, " ") != want {
+			t.Errorf("%s: server allows %v, the device uses %s", cl.name, got, want)
+		}
+	}
+	// A config issued here gets the mapped address and drops the kept one.
+	conf := clientConfig(c, by["old-laptop"], "")
+	if !strings.Contains(conf, "fd11:5ee:bad:c0de::7/64") {
+		t.Errorf("config before re-issue should keep pivpn's address:\n%s", conf)
+	}
+
+	// IPv4-only pivpn.
+	root4, _, _ := pivpnFixture(t, false, clients[:1])
+	s4, err := readPivpn(root4)
+	if err != nil {
+		t.Fatal(err)
+	}
+	c4 := importedConfig(t, s4)
+	if c4.Server.IPv6Enabled || c4.Peers[0].IPv6 != "" {
+		t.Fatalf("IPv4-only import: %+v %+v", c4.Server, c4.Peers[0])
+	}
+
+	// A wg0.conf without clients imports the server alone.
+	root0, _, _ := pivpnFixture(t, true, nil)
+	s0, err := readPivpn(root0)
+	if err != nil || len(importedConfig(t, s0).Peers) != 0 {
+		t.Fatalf("no clients: %v", err)
+	}
+
+	// Broken files are refused before anything changes.
+	broken := func(edit func(string) string) error {
+		r, _, _ := pivpnFixture(t, true, clients[:1])
+		p := filepath.Join(r, "etc/wireguard/wg0.conf")
+		b, _ := os.ReadFile(p)
+		_ = os.WriteFile(p, []byte(edit(string(b))), 0o644)
+		_, err := readPivpn(r)
+		return err
+	}
+	if broken(func(s string) string { return strings.Replace(s, "PrivateKey = ", "PrivateKey = x", 1) }) == nil {
+		t.Error("a bad server key must be refused")
+	}
+	if broken(func(s string) string { return strings.Replace(s, "\nPublicKey = ", "\nPublicKey = x", 1) }) == nil {
+		t.Error("a bad client key must be refused")
+	}
+	if err := broken(func(s string) string { return strings.Replace(s, "AllowedIPs = 10.6.0.2/32,", "AllowedIPs = ", 1) }); err == nil {
+		t.Error("a client without IPv4 must be refused")
+	}
+	r, _, _ := pivpnFixture(t, true, nil)
+	_ = os.Remove(filepath.Join(r, "etc/wireguard/wg0.conf"))
+	if _, err := readPivpn(r); err == nil || errors.Is(err, os.ErrNotExist) && !strings.Contains(err.Error(), "pivpn") {
+		t.Errorf("a missing wg0.conf must be an error: %v", err)
+	}
+}
+
+func TestPivpnNames(t *testing.T) {
+	taken := map[string]bool{"phone": true}
+	for in, want := range map[string]string{
+		"iphone-alex": "iphone-alex",
+		"phone":       "phone-1",
+		"server":      "peer-server",
+		"12345":       "peer-12345",
+		"-dash":       "dash",
+		"a-very-long-client-name-from-pivpn-2025": "a-very-long-client-name-from-piv",
+		"Ümlaut": "mlaut",
+	} {
+		if got := usableName(in, taken); got != want || validatePeerName(got) != nil {
+			t.Errorf("usableName(%q) = %q, want %q", in, got, want)
+		}
+	}
+
+	// Two pivpn names that become the same here are both kept, renamed.
+	root, _, _ := pivpnFixture(t, true, []pivpnClient{
+		{name: "Phone", ipv4: "10.6.0.2", v6: "fd11:5ee:bad:c0de::a06:2"},
+		{name: "phone", ipv4: "10.6.0.3", v6: "fd11:5ee:bad:c0de::a06:3"},
+	})
+	s, err := readPivpn(root)
+	if err != nil {
+		t.Fatal(err)
+	}
+	c := importedConfig(t, s)
+	if c.Peers[0].Name != "Phone" || c.Peers[1].Name != "phone-1" || len(s.Renamed) != 1 || s.Renamed[0] != [2]string{"phone", "phone-1"} {
+		t.Fatalf("renames: %v %v", []string{c.Peers[0].Name, c.Peers[1].Name}, s.Renamed)
+	}
+}
+
+func TestPivpnInstallQuestion(t *testing.T) {
+	root, _, _ := pivpnFixture(t, true, []pivpnClient{
+		{name: "iphone-alex", ipv4: "10.6.0.2", v6: "fd11:5ee:bad:c0de::a06:2", psk: true},
+	})
+	s, err := readPivpn(root)
+	if err != nil {
+		t.Fatal(err)
+	}
+	cur := importedConfig(t, s)
+	hash, _ := hashPassword("a long test password")
+	cur.Users[0].PasswordHash = hash
+
+	// Yes, then Enter keeps pivpn's endpoint and port: no device needs a new config.
+	p, err := askInstall(strings.NewReader("y\n\n\n\ny\n"), cur, false, map[string]bool{}, installPlan{pivpn: s})
+	if err != nil || p.endpoint != "" || p.port != 0 || p.reissueCount(cur, false) != 0 {
+		t.Fatalf("Enter should keep pivpn's settings: %+v %v", p, err)
+	}
+	// A new port means the device needs a new config.
+	p, err = askInstall(strings.NewReader("y\n\n\n51900\ny\n"), cur, false, map[string]bool{}, installPlan{pivpn: s})
+	if err != nil || p.reissueCount(cur, false) != 1 {
+		t.Fatalf("a new port should need a new config: %+v %v", p, err)
+	}
+	// No: nothing changes, and install explains why.
+	if _, err := askInstall(strings.NewReader("n\n"), cur, false, map[string]bool{}, installPlan{pivpn: s}); !errors.Is(err, errPivpnDeclined) {
+		t.Fatalf("want errPivpnDeclined, got %v", err)
+	}
+	// -import-pivpn answers the question.
+	if _, err := askInstall(strings.NewReader("\n\n\ny\n"), cur, false, map[string]bool{"import-pivpn": true}, installPlan{pivpn: s}); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestPeerIPv6Kept(t *testing.T) {
+	c := testConfig(t)
+	c.Server.IPv6Enabled = true
+	c.Peers = []Peer{{ID: "a", Name: "a", IPv4: "10.84.12.2", PublicKey: "k1", IPv6: "fd11:5ee:bad:c0de::2"}}
+	if err := c.validate(); err != nil {
+		t.Fatal(err)
+	}
+	for _, bad := range []string{"10.84.12.9", "fd00::2", "fd11:5ee:bad:c0de::", "not an address"} {
+		c.Peers[0].IPv6 = bad
+		if c.validate() == nil {
+			t.Errorf("IPv6 %q should be refused", bad)
+		}
+	}
+	// Two peers on the same IPv6 address.
+	c.Peers[0].IPv6 = mapIPv6(netip.MustParsePrefix(c.Server.IPv6), netip.MustParseAddr("10.84.12.3")).String()
+	c.Peers = append(c.Peers, Peer{ID: "b", Name: "b", IPv4: "10.84.12.3", PublicKey: "k2"})
+	if c.validate() == nil {
+		t.Error("an IPv6 address used twice should be refused")
+	}
+}
+
+func TestPivpnWaitBack(t *testing.T) {
+	pv := &pivpnSetup{Peers: []Peer{{Name: "a", PublicKey: "ka"}, {Name: "b", PublicKey: "kb"}}}
+	since := time.Now()
+	after := since.Add(time.Second)
+	sample := func(back ...string) func() ([]PeerSample, error) {
+		return func() ([]PeerSample, error) {
+			var out []PeerSample
+			for _, k := range back {
+				out = append(out, PeerSample{PublicKey: k, LastHandshake: after})
+			}
+			// A handshake from before the switch does not count.
+			return append(out, PeerSample{PublicKey: "kb", LastHandshake: since.Add(-time.Minute)}), nil
+		}
+	}
+	// Everyone back: returns at once.
+	start := time.Now()
+	back, skipped := waitBack(pv, []string{"a", "b"}, sample("ka", "kb"), since, time.Minute, time.Millisecond, nil)
+	if len(back) != 2 || skipped || time.Since(start) > time.Second {
+		t.Fatalf("all back: %v %v", back, skipped)
+	}
+	// One missing: waits for the timeout.
+	back, skipped = waitBack(pv, []string{"a", "b"}, sample("ka"), since, 50*time.Millisecond, 5*time.Millisecond, nil)
+	if len(back) != 1 || back[0] != "a" || skipped {
+		t.Fatalf("timeout: %v %v", back, skipped)
+	}
+	// Enter: returns at once, marked skipped.
+	skip := make(chan struct{})
+	close(skip)
+	start = time.Now()
+	back, skipped = waitBack(pv, []string{"a", "b"}, sample("ka"), time.Now(), time.Minute, time.Second, skip)
+	if !skipped || time.Since(start) > time.Second {
+		t.Fatalf("skip: %v %v", back, skipped)
+	}
+}

setup.go

@@ -1,7 +1,9 @@
 package main
 
 import (
+	"bufio"
 	"bytes"
+	"cmp"
 	"crypto/sha256"
 	"errors"
 	"flag"
@@ -37,9 +39,10 @@ func usage() {
 	fmt.Fprintf(os.Stderr, `%s %s — WireGuard server manager
 
 Usage (as root):
-  %s install [-domain vpn.example.net] [-email you@example.net] [-endpoint host] [-port 51820] [-y]
+  %s install [-domain vpn.example.net] [-email you@example.net] [-endpoint host] [-port 51820] [-import-pivpn] [-no-wait] [-y]
         set up user, folder, config, sysctls and systemd service; start it.
-        In a terminal it asks for the settings no flag gave; -y never asks
+        In a terminal it asks for the settings no flag gave; -y never asks.
+        On a pivpn server it offers to take over pivpn's WireGuard and clients
   %s update [-force]
         replace the installed binary with this one and restart
   %s uninstall [-purge] [-y]
@@ -379,6 +382,8 @@ func cmdInstall(args []string) error {
 	endpoint := fs.String("endpoint", "", "host or IP clients connect to (default: the domain)")
 	port := fs.Int("port", 0, "UDP port WireGuard listens on (default: 51820, or the current port when already installed)")
 	yes := fs.Bool("y", false, "do not ask; use the flags and defaults")
+	importPivpn := fs.Bool("import-pivpn", false, "take over pivpn's WireGuard server and clients (new installs only)")
+	noWait := fs.Bool("no-wait", false, "after a pivpn takeover, do not wait for connected devices to come back")
 	_ = fs.Parse(args)
 	given := map[string]bool{}
 	fs.Visit(func(f *flag.Flag) { given[f.Name] = true })
@@ -402,14 +407,40 @@ func cmdInstall(args []string) error {
 	if err := plan.check(); err != nil {
 		return err
 	}
+	interactive := !*yes && term.IsTerminal(int(os.Stdin.Fd()))
+
+	// pivpn: a new install takes over its WireGuard server, or stops, since
+	// both would run the same interface.
+	var pv *pivpnSetup
 	if !existing {
+		if pv, err = readPivpn("/"); err != nil {
+			return err
+		}
+	}
+	switch {
+	case *importPivpn && existing:
+		return fmt.Errorf("-import-pivpn works only on a new install, and %s exists", configFile)
+	case *importPivpn && pv == nil:
+		return fmt.Errorf("-import-pivpn: pivpn's WireGuard setup was not found (/%s)", pivpnSetupVars)
+	case pv != nil && !interactive && !*importPivpn:
+		return fmt.Errorf("pivpn runs WireGuard on %s here; add -import-pivpn to take it over, or remove pivpn first", pv.Dev)
+	}
+	if pv != nil {
+		pv.apply(cur)
+		if err := cur.validate(); err != nil {
+			return fmt.Errorf("pivpn's setup cannot be taken over, nothing changed: %w", err)
+		}
+		plan.pivpn = pv
+	}
+
+	if !existing && pv == nil {
 		n, err := randomSubnet(24)
 		if err != nil {
 			return err
 		}
 		plan.ipv4 = n.String()
 	}
-	if !*yes && term.IsTerminal(int(os.Stdin.Fd())) {
+	if interactive {
 		if plan, err = askInstall(os.Stdin, cur, existing, given, plan); err != nil {
 			return err
 		}
@@ -453,8 +484,15 @@ func cmdInstall(args []string) error {
 		}
 	}
 
-	// Config: created with defaults (server key, the chosen subnet) if missing.
+	// Config: created with defaults (server key, the chosen subnet) if
-	if !existing {
+	// missing, or with everything taken over from pivpn.
+	switch {
+	case pv != nil:
+		step("Creating %s from pivpn (%s)", configFile, plural(len(pv.Peers), "peer"))
+		if err := writeFileAtomic(configFile, cur, 0o600); err != nil {
+			return err
+		}
+	case !existing:
 		step("Creating %s", configFile)
 		initial := fmt.Sprintf("{\"server\": {\"ipv4\": %q}}\n", plan.ipv4)
 		if err := os.WriteFile(configFile, []byte(initial), 0o600); err != nil {
@@ -491,17 +529,179 @@ func cmdInstall(args []string) error {
 		return err
 	}
 
+	// pivpn hands over its interface: note who is connected, then stop it.
+	var connected []string
+	var switched time.Time
+	if pv != nil {
+		connected = pivpnConnected(pv)
+		step("Peers connected to pivpn right now: %s", cmp.Or(strings.Join(connected, ", "), "none"))
+		step("Stopping pivpn's WireGuard (systemctl disable --now wg-quick@%s)", pv.Dev)
+		if err := sh("systemctl", "disable", "--now", "wg-quick@"+pv.Dev); err != nil {
+			return err
+		}
+		switched = time.Now()
+	}
+
 	step("Starting %s", serviceName)
-	if err := sh("systemctl", "enable", serviceName); err != nil {
+	err = sh("systemctl", "enable", serviceName)
+	if err == nil {
+		err = restartAndVerify()
+	}
+	if err != nil {
+		if pv != nil {
+			fmt.Fprintln(os.Stderr, " ", err)
+			return pivpnBack(pv, store.Get(), err)
+		}
 		return err
 	}
-	if err := restartAndVerify(); err != nil {
+	if pv != nil {
-		return err
+		waitForPeers(pv, connected, switched, *noWait, interactive)
 	}
 	printWhereToGo(store.Get())
+	if pv != nil {
+		fmt.Printf("\npivpn is still installed but no longer runs %s. Manage the peers here from now on.\n", pv.Dev)
+		fmt.Printf("Its files in /etc/wireguard and /etc/pivpn are untouched, including the client\n")
+		fmt.Printf("configs with private keys. Once everything works, delete %s.\n", pv.ClientKeys)
+		fmt.Printf("Don't run \"pivpn uninstall\": it removes WireGuard packages and firewall rules.\n")
+	}
 	return nil
 }
 
+// pivpnConnected names the peers with a handshake in the last 3 minutes.
+func pivpnConnected(pv *pivpnSetup) []string {
+	k, err := newKernel()
+	if err != nil {
+		return nil
+	}
+	defer k.Close()
+	samples, err := k.Sample(pv.Dev)
+	if err != nil {
+		return nil
+	}
+	var out []string
+	for _, p := range pv.Peers {
+		for _, s := range samples {
+			if s.PublicKey == p.PublicKey && !s.LastHandshake.IsZero() && time.Since(s.LastHandshake) < onlineWindow {
+				out = append(out, p.Name)
+			}
+		}
+	}
+	return out
+}
+
+// waitForPeers waits up to 30 s for the peers that were connected to pivpn
+// to make a handshake with the new service. It only reports: a device that
+// is idle may take minutes to send its next packet. Enter in a terminal
+// skips the rest of the wait; -no-wait skips it entirely.
+func waitForPeers(pv *pivpnSetup, names []string, since time.Time, noWait, interactive bool) {
+	switch {
+	case len(names) == 0:
+		step("No peer was connected before the switch; devices connect when they come back online.")
+		return
+	case noWait:
+		step("Not waiting for %s (-no-wait).", strings.Join(names, ", "))
+		fmt.Printf("  %s\n", onlineLater(len(names)))
+		return
+	}
+	k, err := newKernel()
+	if err != nil {
+		return
+	}
+	defer k.Close()
+	var skip <-chan struct{}
+	hint := ""
+	if interactive {
+		ch := make(chan struct{})
+		go func() {
+			_, _ = bufio.NewReader(os.Stdin).ReadString('\n')
+			close(ch)
+		}()
+		skip, hint = ch, " (Enter skips)"
+	}
+	step("Waiting up to 30 s for %s to come back%s", strings.Join(names, ", "), hint)
+	back, skipped := waitBack(pv, names, func() ([]PeerSample, error) { return k.Sample(pv.Dev) }, since, 30*time.Second, 2*time.Second, skip)
+	secs := int(time.Since(since).Round(time.Second).Seconds())
+	var missing []string
+	for _, n := range names {
+		if !slices.Contains(back, n) {
+			missing = append(missing, n)
+		}
+	}
+	switch {
+	case len(missing) == 0:
+		step("%d of %d peers that were connected before are back (after %d s)", len(back), len(names), secs)
+		return
+	case skipped:
+		step("Skipped after %d s: %d of %d back so far", secs, len(back), len(names))
+		fmt.Printf("  %s not back yet.\n  %s\n", strings.Join(missing, ", "), onlineLater(len(missing)))
+	default:
+		step("%d of %d are back after %d s", len(back), len(names), secs)
+		fmt.Printf("  %s not back yet. A device that is idle can take a few minutes to send its next\n", strings.Join(missing, ", "))
+		fmt.Printf("  packet. %s\n", onlineLater(len(missing)))
+	}
+}
+
+// waitBack polls the kernel until every named peer made a handshake after
+// since, the timeout passes or skip is closed. It returns the peers that are
+// back and whether the wait was skipped.
+func waitBack(pv *pivpnSetup, names []string, sample func() ([]PeerSample, error), since time.Time, timeout, every time.Duration, skip <-chan struct{}) (back []string, skipped bool) {
+	key := map[string]string{}
+	for _, p := range pv.Peers {
+		key[p.Name] = p.PublicKey
+	}
+	deadline := time.After(time.Until(since.Add(timeout)))
+	tick := time.NewTicker(every)
+	defer tick.Stop()
+	for {
+		back = back[:0]
+		if samples, err := sample(); err == nil {
+			for _, n := range names {
+				for _, s := range samples {
+					if s.PublicKey == key[n] && s.LastHandshake.After(since) {
+						back = append(back, n)
+					}
+				}
+			}
+		}
+		if len(back) == len(names) {
+			return back, false
+		}
+		select {
+		case <-skip:
+			return back, true
+		case <-deadline:
+			return back, false
+		case <-tick.C:
+		}
+	}
+}
+
+// onlineLater tells where peers that are not back yet will show up.
+func onlineLater(n int) string {
+	if n == 1 {
+		return "It shows as online on the Peers page once it is back."
+	}
+	return "They show as online on the Peers page once they are back."
+}
+
+// pivpnBack undoes the takeover after the service failed to start: it stops
+// the service, removes its interface, firewall table and the config it was
+// given, and starts pivpn's WireGuard again. Without the config, the next
+// install offers the takeover again instead of fighting pivpn for wg0.
+func pivpnBack(pv *pivpnSetup, c *Config, cause error) error {
+	_ = sh("systemctl", "disable", "--now", serviceName)
+	if k, err := newKernel(); err == nil {
+		_ = k.Down(c)
+		k.Close()
+	}
+	_ = os.Remove(configFile)
+	step("Starting pivpn's WireGuard again (systemctl enable --now wg-quick@%s)", pv.Dev)
+	if err := sh("systemctl", "enable", "--now", "wg-quick@"+pv.Dev); err != nil {
+		return fmt.Errorf("install failed, and starting pivpn's WireGuard again failed too: %v (original error: %w)", err, cause)
+	}
+	return fmt.Errorf("install failed; pivpn runs %s as before: %w", pv.Dev, cause)
+}
+
 func chownTree(root string, uid, gid int) error {
 	return filepath.Walk(root, func(p string, _ os.FileInfo, err error) error {
 		if err != nil {
@@ -663,9 +863,11 @@ func cmdUninstall(args []string) error {
 
 	step("Removing the WireGuard interface and firewall table")
 	c, err := loadConfigFile(configFile)
-	if err != nil {
+	if _, statErr := os.Stat(configFile); err != nil || statErr != nil {
+		// Without a config of ours, e.g. after a pivpn takeover was undone,
+		// the interface may belong to someone else: only the firewall table
+		// goes.
 		c = &Config{}
-		c.applyDefaults()
 	}
 	if k, err := newKernel(); err == nil {
 		if err := k.Down(c); err != nil {

setuplink.go

@@ -260,7 +260,7 @@ func (a *App) setupRedeem(w http.ResponseWriter, r *http.Request) {
 		}
 		now := time.Now().UTC()
 		id, hadKey = p.ID, p.hasKey()
-		p.PublicKey, p.ConfigIssued, p.Setup = k.PublicKey().String(), &now, nil
+		p.PublicKey, p.ConfigIssued, p.Setup, p.IPv6 = k.PublicKey().String(), &now, nil, ""
 		if p.PresharedKey != "" {
 			p.PresharedKey = psk.String()
 		}

visitor.go

@@ -0,0 +1,145 @@
+package main
+
+import (
+	"context"
+	"net"
+	"net/http"
+	"net/netip"
+	"sync"
+	"time"
+)
+
+// visitorView tells the dashboard whether the browser asking is behind the
+// VPN. Behind it, websites see the server's address, so the card shows the
+// visitor's address next to the server's: the same means protected.
+type visitorView struct {
+	Protected bool     `json:"protected"`
+	IP        string   `json:"ip"`       // what websites see; the server's address when protected
+	ServerIP  string   `json:"serverIP"` // empty when the endpoint does not resolve
+	Peer      *peerRef `json:"peer"`     // the peer whose tunnel the request came through
+	Location  *GeoInfo `json:"location"` // of IP, when not protected
+}
+
+type peerRef struct {
+	ID   string `json:"id"`
+	Name string `json:"name"`
+}
+
+// classifyVisitor decides on the address the server sees (remoteIP).
+// Through the tunnel that is the peer's tunnel address; the peer is
+// protected when its AllowedIPs send all traffic of that family through
+// the server. A server behind NAT may instead see its own or its public
+// address, when the request loops back through the router.
+func classifyVisitor(c *Config, ip, server netip.Addr, own func(netip.Addr) bool) visitorView {
+	v := visitorView{IP: ip.String()}
+	if server.IsValid() {
+		v.ServerIP = server.String()
+	}
+	if p := peerByTunnelAddr(c, ip); p != nil {
+		v.Peer = &peerRef{ID: p.ID, Name: p.Name}
+		v.Protected = fullTunnel(peerAllowedIPs(c, p), ip.Is6())
+	} else if !ip.IsLoopback() && !ip.IsLinkLocalUnicast() && (ip == server || own(ip)) {
+		v.Protected = true
+	}
+	if v.Protected && server.IsValid() {
+		v.IP = v.ServerIP
+	}
+	return v
+}
+
+func peerByTunnelAddr(c *Config, ip netip.Addr) *Peer {
+	for i := range c.Peers {
+		p := &c.Peers[i]
+		if !p.Enabled {
+			continue
+		}
+		for _, a := range peerAddresses(c, p) {
+			if a.Addr() == ip {
+				return p
+			}
+		}
+	}
+	return nil
+}
+
+// fullTunnel reports whether AllowedIPs route all IPv4 (or IPv6) traffic
+// into the tunnel: 0.0.0.0/0, ::/0, or the two halves some clients use.
+func fullTunnel(allowed []string, v6 bool) bool {
+	halves := 0
+	for _, s := range allowed {
+		p, err := netip.ParsePrefix(s)
+		if err != nil || p.Addr().Is6() != v6 {
+			continue
+		}
+		switch p.Bits() {
+		case 0:
+			return true
+		case 1:
+			halves++
+		}
+	}
+	return halves >= 2
+}
+
+// ownAddr reports whether ip is an address of this machine.
+func ownAddr(ip netip.Addr) bool {
+	addrs, err := net.InterfaceAddrs()
+	if err != nil {
+		return false
+	}
+	for _, a := range addrs {
+		if n, ok := a.(*net.IPNet); ok {
+			if x, ok := netip.AddrFromSlice(n.IP); ok && x.Unmap() == ip {
+				return true
+			}
+		}
+	}
+	return false
+}
+
+// endpointIPs resolves the WireGuard endpoint, the address websites see
+// behind the VPN, and keeps the answer for a few minutes.
+type endpointIPs struct {
+	mu    sync.Mutex
+	host  string
+	addrs []netip.Addr
+	at    time.Time
+}
+
+func (e *endpointIPs) lookup(host string, v6 bool) netip.Addr {
+	if ip, err := netip.ParseAddr(host); err == nil {
+		return ip.Unmap()
+	}
+	e.mu.Lock()
+	defer e.mu.Unlock()
+	if host != e.host || time.Since(e.at) > 10*time.Minute {
+		ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
+		addrs, _ := net.DefaultResolver.LookupNetIP(ctx, "ip", host)
+		cancel()
+		e.host, e.addrs, e.at = host, addrs, time.Now()
+	}
+	var other netip.Addr
+	for _, a := range e.addrs {
+		a = a.Unmap()
+		if a.Is6() == v6 {
+			return a
+		}
+		if !other.IsValid() {
+			other = a
+		}
+	}
+	return other
+}
+
+func (a *App) visitor(r *http.Request, c *Config) visitorView {
+	ip, err := netip.ParseAddr(remoteIP(r))
+	if err != nil {
+		return visitorView{IP: remoteIP(r)}
+	}
+	ip = ip.Unmap()
+	v := classifyVisitor(c, ip, a.endpoint.lookup(c.Server.Endpoint, ip.Is6()), ownAddr)
+	if !v.Protected && v.Peer == nil {
+		v.Location = a.geo.Lookup(v.IP)
+	}
+	return v
+}