add test for magic packets

.github/workflows/cicd.yml

@@ -68,7 +68,7 @@ jobs:
           echo "image_created=$(date -u +%Y-%m-%dT%H:%M:%SZ)" >> "$GITHUB_OUTPUT"
 
       - name: Configure AWS credentials (OIDC)
-        uses: aws-actions/configure-aws-credentials@e6de054238d6b7531b4efff3b6587d9aade6a06c # v6.2.3
+        uses: aws-actions/configure-aws-credentials@254c19bd240aabef8777f48595e9d2d7b972184b # v6.2.1
         with:
           role-to-assume: arn:aws:iam::${{ secrets.AWS_ACCOUNT_ID }}:role/${{ secrets.AWS_ROLE_NAME }}
           role-duration-seconds: 3600
@@ -95,7 +95,7 @@ jobs:
       contents: write
     steps:
       - name: Checkout repository
-        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
         with:
           fetch-depth: 0
 
@@ -158,7 +158,7 @@ jobs:
 
     steps:
       - name: Checkout code
-        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
         with:
           fetch-depth: 0
 
@@ -243,14 +243,14 @@ jobs:
       #  uses: docker/setup-buildx-action@bb05f3f5519dd87d3ba754cc423b652a5edd6d2c # v4.2.0
 
       - name: Log in to Docker Hub
-        uses: docker/login-action@abd2ef45e78c5afb21d64d4ca52ee8550d9572c7 # v4.5.1
+        uses: docker/login-action@c99871dec2022cc055c062a10cc1a1310835ceb4 # v4.3.0
         with:
           registry: docker.io
           username: ${{ secrets.DOCKER_HUB_USERNAME }}
           password: ${{ secrets.DOCKER_HUB_ACCESS_TOKEN }}
 
       - name: Log in to GHCR
-        uses: docker/login-action@abd2ef45e78c5afb21d64d4ca52ee8550d9572c7 # v4.5.1
+        uses: docker/login-action@c99871dec2022cc055c062a10cc1a1310835ceb4 # v4.3.0
         with:
           registry: ghcr.io
           username: ${{ github.actor }}
@@ -309,7 +309,7 @@ jobs:
       IMAGE_CREATED: ${{ needs.pre-run.outputs.image_created }}
     steps:
       - name: Checkout code
-        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
         with:
           fetch-depth: 0
 
@@ -368,14 +368,14 @@ jobs:
           echo "Checked out $(git rev-parse --short HEAD) for tag ${TAG}"
 
       - name: Log in to Docker Hub
-        uses: docker/login-action@abd2ef45e78c5afb21d64d4ca52ee8550d9572c7 # v4.5.1
+        uses: docker/login-action@c99871dec2022cc055c062a10cc1a1310835ceb4 # v4.3.0
         with:
           registry: docker.io
           username: ${{ secrets.DOCKER_HUB_USERNAME }}
           password: ${{ secrets.DOCKER_HUB_ACCESS_TOKEN }}
 
       - name: Log in to GHCR
-        uses: docker/login-action@abd2ef45e78c5afb21d64d4ca52ee8550d9572c7 # v4.5.1
+        uses: docker/login-action@c99871dec2022cc055c062a10cc1a1310835ceb4 # v4.3.0
         with:
           registry: ghcr.io
           username: ${{ github.actor }}
@@ -434,7 +434,7 @@ jobs:
       IMAGE_CREATED: ${{ needs.pre-run.outputs.image_created }}
     steps:
       - name: Checkout code
-        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
         with:
           fetch-depth: 0
 
@@ -483,14 +483,14 @@ jobs:
           echo "Checked out $(git rev-parse --short HEAD) for tag ${TAG}"
 
       - name: Log in to Docker Hub
-        uses: docker/login-action@abd2ef45e78c5afb21d64d4ca52ee8550d9572c7 # v4.5.1
+        uses: docker/login-action@c99871dec2022cc055c062a10cc1a1310835ceb4 # v4.3.0
         with:
           registry: docker.io
           username: ${{ secrets.DOCKER_HUB_USERNAME }}
           password: ${{ secrets.DOCKER_HUB_ACCESS_TOKEN }}
 
       - name: Log in to GHCR
-        uses: docker/login-action@abd2ef45e78c5afb21d64d4ca52ee8550d9572c7 # v4.5.1
+        uses: docker/login-action@c99871dec2022cc055c062a10cc1a1310835ceb4 # v4.3.0
         with:
           registry: ghcr.io
           username: ${{ github.actor }}
@@ -556,14 +556,14 @@ jobs:
       #PUBLISH_MINOR:  ${{ github.event_name == 'workflow_dispatch' && inputs.publish_minor  || vars.PUBLISH_MINOR  }}
     steps:
       - name: Log in to Docker Hub
-        uses: docker/login-action@abd2ef45e78c5afb21d64d4ca52ee8550d9572c7 # v4.5.1
+        uses: docker/login-action@c99871dec2022cc055c062a10cc1a1310835ceb4 # v4.3.0
         with:
           registry: docker.io
           username: ${{ secrets.DOCKER_HUB_USERNAME }}
           password: ${{ secrets.DOCKER_HUB_ACCESS_TOKEN }}
 
       - name: Log in to GHCR
-        uses: docker/login-action@abd2ef45e78c5afb21d64d4ca52ee8550d9572c7 # v4.5.1
+        uses: docker/login-action@c99871dec2022cc055c062a10cc1a1310835ceb4 # v4.3.0
         with:
           registry: ghcr.io
           username: ${{ github.actor }}
@@ -642,7 +642,7 @@ jobs:
       IMAGE_CREATED: ${{ needs.pre-run.outputs.image_created }}
     steps:
       - name: Checkout code
-        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
         with:
           fetch-depth: 0
 
@@ -656,19 +656,19 @@ jobs:
           echo "Checked out $(git rev-parse --short HEAD) for tag ${TAG}"
 
       - name: Install Go
-        uses: actions/setup-go@b7ad1dad31e06c5925ef5d2fc7ad053ef454303e # v7.0.0
+        uses: actions/setup-go@924ae3a1cded613372ab5595356fb5720e22ba16 # v6.5.0
         with:
           go-version-file: go.mod
 
       - name: Log in to Docker Hub
-        uses: docker/login-action@abd2ef45e78c5afb21d64d4ca52ee8550d9572c7 # v4.5.1
+        uses: docker/login-action@c99871dec2022cc055c062a10cc1a1310835ceb4 # v4.3.0
         with:
           registry: docker.io
           username: ${{ secrets.DOCKER_HUB_USERNAME }}
           password: ${{ secrets.DOCKER_HUB_ACCESS_TOKEN }}
 
       - name: Log in to GHCR
-        uses: docker/login-action@abd2ef45e78c5afb21d64d4ca52ee8550d9572c7 # v4.5.1
+        uses: docker/login-action@c99871dec2022cc055c062a10cc1a1310835ceb4 # v4.3.0
         with:
           registry: ghcr.io
           username: ${{ github.actor }}
@@ -912,7 +912,7 @@ jobs:
           done
 
       - name: Create GitHub Release (draft)
-        uses: softprops/action-gh-release@3d0d9888cb7fd7b750713d6e236d1fcb99157228 # v3.0.2
+        uses: softprops/action-gh-release@718ea10b132b3b2eba29c1007bb80653f286566b # v3.0.1
         with:
           tag_name: ${{ env.TAG }}
           generate_release_notes: true
@@ -940,7 +940,7 @@ jobs:
     permissions: write-all
     steps:
       - name: Configure AWS credentials (OIDC)
-        uses: aws-actions/configure-aws-credentials@e6de054238d6b7531b4efff3b6587d9aade6a06c # v6.2.3
+        uses: aws-actions/configure-aws-credentials@254c19bd240aabef8777f48595e9d2d7b972184b # v6.2.1
         with:
           role-to-assume: arn:aws:iam::${{ secrets.AWS_ACCOUNT_ID }}:role/${{ secrets.AWS_ROLE_NAME }}
           role-duration-seconds: 3600

.github/workflows/nix-build.yml

@@ -13,7 +13,7 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v7.0.1
+        uses: actions/checkout@v7
 
       - name: Install Nix
         uses: DeterminateSystems/nix-installer-action@main

.github/workflows/nix-dependabot-update-hash.yml

@@ -16,7 +16,7 @@ jobs:
 
     steps:
       - name: Checkout repository
-        uses: actions/checkout@v7.0.1
+        uses: actions/checkout@v7
         with:
           ref: ${{ github.head_ref }}
           token: ${{ secrets.GITHUB_TOKEN }}

.github/workflows/stale-bot.yml

@@ -14,7 +14,7 @@ jobs:
   stale:
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/stale@1e223db275d687790206a7acac4d1a11bd6fe629 # v10.4.0
+      - uses: actions/stale@eb5cf3af3ac0a1aa4c9c45633dd1ae542a27a899 # v10.3.0
         with:
           days-before-stale: 14
           days-before-close: 14

.github/workflows/test.yml

@@ -14,10 +14,10 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Checkout repository
-        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
 
       - name: Set up Go
-        uses: actions/setup-go@b7ad1dad31e06c5925ef5d2fc7ad053ef454303e # v7.0.0
+        uses: actions/setup-go@924ae3a1cded613372ab5595356fb5720e22ba16 # v6.5.0
         with:
           go-version-file: go.mod
 
@@ -42,10 +42,10 @@ jobs:
           - go-build-release-windows-amd64
     steps:
       - name: Checkout repository
-        uses: actions/checkout@3d3c42e5aac5ba805825da76410c181273ba90b1 # v7.0.1
+        uses: actions/checkout@9c091bb21b7c1c1d1991bb908d89e4e9dddfe3e0 # v7.0.0
 
       - name: Set up Go
-        uses: actions/setup-go@b7ad1dad31e06c5925ef5d2fc7ad053ef454303e # v7.0.0
+        uses: actions/setup-go@924ae3a1cded613372ab5595356fb5720e22ba16 # v6.5.0
         with:
           go-version-file: go.mod
 

bind/shared_bind.go

@@ -683,6 +683,23 @@ func (b *SharedBind) receiveIPv4Simple(conn *net.UDPConn, bufs [][]byte, sizes [
 	}
 }
 
+// IsMagicPacket reports whether payload is one of our connectivity-test magic
+// packets (a MagicTestRequest or MagicTestResponse). These packets are meant to
+// travel directly between physical UDP sockets and must never be encapsulated by
+// WireGuard - e.g. if OS routing mistakenly sends one into a WireGuard TUN
+// interface (because the destination falls inside a routed tunnel subnet), it
+// should be dropped there rather than tunneled, which would otherwise make a
+// LAN-local endpoint test falsely appear to succeed over the tunnel.
+func IsMagicPacket(payload []byte) bool {
+	if len(payload) >= MagicTestRequestLen && bytes.HasPrefix(payload, MagicTestRequest) {
+		return true
+	}
+	if len(payload) >= MagicTestResponseLen && bytes.HasPrefix(payload, MagicTestResponse) {
+		return true
+	}
+	return false
+}
+
 // handleMagicPacket checks if the packet is a magic test packet and responds if so.
 // Returns true if the packet was a magic packet and was handled (should not be passed to WireGuard).
 func (b *SharedBind) handleMagicPacket(data []byte, addr *net.UDPAddr) bool {

clients/clients.go

@@ -35,10 +35,11 @@ import (
 )
 
 type WgConfig struct {
-	IpAddress string   `json:"ipAddress"`
-	Peers     []Peer   `json:"peers"`
-	Targets   []Target `json:"targets"`
-	ChainId   string   `json:"chainId"`
+	IpAddress string     `json:"ipAddress"`
+	Peers     []Peer     `json:"peers"`
+	Targets   []Target   `json:"targets"`
+	Certs     []CertData `json:"certs"`
+	ChainId   string     `json:"chainId"`
 }
 
 type Target struct {
@@ -53,6 +54,23 @@ type Target struct {
 	HTTPTargets    []netstack2.HTTPTarget `json:"httpTargets,omitempty"` // for http protocol, list of downstream services to load balance across
 	TLSCert        string                 `json:"tlsCert,omitempty"`     // PEM-encoded certificate for incoming HTTPS termination
 	TLSKey         string                 `json:"tlsKey,omitempty"`      // PEM-encoded private key for incoming HTTPS termination
+	TLSCertID      string                 `json:"tlsCertId,omitempty"`   // references an entry in the sync message's Certs list instead of inlining TLSCert/TLSKey
+}
+
+// CertData is a single shared TLS certificate/key pair, referenced by ID from
+// one or more Targets via TLSCertID. Sent once per sync message so that many
+// targets backed by the same certificate (e.g. a wildcard cert) don't each
+// carry a full copy of the PEM data.
+type CertData struct {
+	ID   string `json:"id"`
+	Cert string `json:"cert"`
+	Key  string `json:"key"`
+}
+
+// CertPair holds the resolved PEM certificate/key material for a CertData entry.
+type CertPair struct {
+	Cert string
+	Key  string
 }
 
 type PortRange struct {
@@ -122,6 +140,11 @@ type WireGuardService struct {
 
 	// connection blocking: when true, all new incoming connections are dropped
 	blocked atomic.Bool
+
+	// certs resolves TLSCertID references on incoming Targets to their PEM
+	// cert/key material. Replaced wholesale on every full sync.
+	certs   map[string]CertPair
+	certsMu sync.RWMutex
 }
 
 // generateChainId generates a random chain ID for deduplicating round-trip messages.
@@ -196,6 +219,8 @@ func NewWireGuardService(interfaceName string, port uint16, mtu int, host string
 	wsClient.RegisterHandler("newt/wg/targets/add", service.handleAddTarget)
 	wsClient.RegisterHandler("newt/wg/targets/remove", service.handleRemoveTarget)
 	wsClient.RegisterHandler("newt/wg/targets/update", service.handleUpdateTarget)
+	wsClient.RegisterHandler("newt/certs/add", service.handleAddCerts)
+	wsClient.RegisterHandler("newt/certs/remove", service.handleRemoveCerts)
 
 	return service, nil
 }
@@ -544,6 +569,7 @@ func (s *WireGuardService) handleConfig(msg websocket.WSMessage) {
 	}
 
 	s.config = config
+	s.SetCerts(config.Certs)
 
 	if s.stopGetConfig != nil {
 		s.stopGetConfig()
@@ -568,6 +594,107 @@ func (s *WireGuardService) handleConfig(msg websocket.WSMessage) {
 	logger.Info("Client connectivity setup. Ready to accept connections from clients!")
 }
 
+// SetCerts replaces the TLSCertID lookup table used by resolveTLS. The server
+// sends the complete set of referenced certs on every full sync, so this is a
+// wholesale replacement rather than an incremental merge.
+func (s *WireGuardService) SetCerts(certs []CertData) {
+	m := make(map[string]CertPair, len(certs))
+	for _, c := range certs {
+		m[c.ID] = CertPair{Cert: c.Cert, Key: c.Key}
+	}
+	s.certsMu.Lock()
+	s.certs = m
+	s.certsMu.Unlock()
+}
+
+// resolveTLS returns the PEM cert/key to use for target's incoming HTTPS
+// termination: target.TLSCertID looked up in the certs table if set, falling
+// back to the target's own inline TLSCert/TLSKey otherwise.
+func (s *WireGuardService) resolveTLS(target Target) (cert, key string) {
+	if target.TLSCertID == "" {
+		return target.TLSCert, target.TLSKey
+	}
+	s.certsMu.RLock()
+	pair, ok := s.certs[target.TLSCertID]
+	s.certsMu.RUnlock()
+	if !ok {
+		logger.Warn("No cert found for tlsCertId %s, falling back to inline cert on target", target.TLSCertID)
+		return target.TLSCert, target.TLSKey
+	}
+	return pair.Cert, pair.Key
+}
+
+// AddCerts upserts the given certs into the lookup table used by resolveTLS,
+// without discarding any certs already present. Used for incremental cert
+// pushes (e.g. after a renewal) outside of a full newt/sync or
+// newt/wg/receive-config, which replace the table wholesale via SetCerts.
+func (s *WireGuardService) AddCerts(certs []CertData) {
+	if len(certs) == 0 {
+		return
+	}
+	s.certsMu.Lock()
+	if s.certs == nil {
+		s.certs = make(map[string]CertPair, len(certs))
+	}
+	for _, c := range certs {
+		s.certs[c.ID] = CertPair{Cert: c.Cert, Key: c.Key}
+	}
+	s.certsMu.Unlock()
+}
+
+// RemoveCerts deletes the given cert IDs from the lookup table, e.g. once the
+// server knows no target references them anymore.
+func (s *WireGuardService) RemoveCerts(ids []string) {
+	if len(ids) == 0 {
+		return
+	}
+	s.certsMu.Lock()
+	for _, id := range ids {
+		delete(s.certs, id)
+	}
+	s.certsMu.Unlock()
+}
+
+// handleAddCerts processes a "newt/certs/add" message: an array of CertData
+// to upsert into the cert lookup table.
+func (s *WireGuardService) handleAddCerts(msg websocket.WSMessage) {
+	jsonData, err := json.Marshal(msg.Data)
+	if err != nil {
+		logger.Info("Error marshaling cert add data: %v", err)
+		return
+	}
+
+	var certs []CertData
+	if err := json.Unmarshal(jsonData, &certs); err != nil {
+		logger.Warn("Error unmarshaling cert add data: %v", err)
+		return
+	}
+
+	s.AddCerts(certs)
+	logger.Info("Added %d certs", len(certs))
+}
+
+// handleRemoveCerts processes a "newt/certs/remove" message: {ids: [...]}
+// naming the cert IDs to drop from the lookup table.
+func (s *WireGuardService) handleRemoveCerts(msg websocket.WSMessage) {
+	jsonData, err := json.Marshal(msg.Data)
+	if err != nil {
+		logger.Info("Error marshaling cert remove data: %v", err)
+		return
+	}
+
+	var data struct {
+		IDs []string `json:"ids"`
+	}
+	if err := json.Unmarshal(jsonData, &data); err != nil {
+		logger.Warn("Error unmarshaling cert remove data: %v", err)
+		return
+	}
+
+	s.RemoveCerts(data.IDs)
+	logger.Info("Removed %d certs", len(data.IDs))
+}
+
 // Sync synchronizes the clients WireGuard peers and targets with the desired state
 // received as part of the main newt/sync message.
 func (s *WireGuardService) Sync(peers []Peer, targets []Target) {
@@ -680,6 +807,7 @@ func (s *WireGuardService) syncTargets(desiredTargets []Target) error {
 				continue
 			}
 
+			tlsCert, tlsKey := s.resolveTLS(target)
 			rules = append(rules, netstack2.SubnetRule{
 				SourcePrefix: sourcePrefix,
 				DestPrefix:   destPrefix,
@@ -689,8 +817,8 @@ func (s *WireGuardService) syncTargets(desiredTargets []Target) error {
 				ResourceId:   target.ResourceId,
 				Protocol:     target.Protocol,
 				HTTPTargets:  target.HTTPTargets,
-				TLSCert:      target.TLSCert,
-				TLSKey:       target.TLSKey,
+				TLSCert:      tlsCert,
+				TLSKey:       tlsKey,
 			})
 		}
 	}
@@ -976,6 +1104,7 @@ func (s *WireGuardService) ensureTargets(targets []Target) error {
 			if err != nil {
 				return fmt.Errorf("invalid CIDR %s: %v", sp, err)
 			}
+			tlsCert, tlsKey := s.resolveTLS(target)
 			s.tnet.AddProxySubnetRule(netstack2.SubnetRule{
 				SourcePrefix: sourcePrefix,
 				DestPrefix:   destPrefix,
@@ -985,8 +1114,8 @@ func (s *WireGuardService) ensureTargets(targets []Target) error {
 				ResourceId:   target.ResourceId,
 				Protocol:     target.Protocol,
 				HTTPTargets:  target.HTTPTargets,
-				TLSCert:      target.TLSCert,
-				TLSKey:       target.TLSKey,
+				TLSCert:      tlsCert,
+				TLSKey:       tlsKey,
 			})
 			logger.Info("Added target subnet from %s to %s rewrite to %s with port ranges: %v", sp, target.DestPrefix, target.RewriteTo, target.PortRange)
 		}
@@ -1380,6 +1509,7 @@ func (s *WireGuardService) handleAddTarget(msg websocket.WSMessage) {
 				logger.Info("Invalid CIDR %s: %v", sp, err)
 				continue
 			}
+			tlsCert, tlsKey := s.resolveTLS(target)
 			s.tnet.AddProxySubnetRule(netstack2.SubnetRule{
 				SourcePrefix: sourcePrefix,
 				DestPrefix:   destPrefix,
@@ -1389,8 +1519,8 @@ func (s *WireGuardService) handleAddTarget(msg websocket.WSMessage) {
 				ResourceId:   target.ResourceId,
 				Protocol:     target.Protocol,
 				HTTPTargets:  target.HTTPTargets,
-				TLSCert:      target.TLSCert,
-				TLSKey:       target.TLSKey,
+				TLSCert:      tlsCert,
+				TLSKey:       tlsKey,
 			})
 			logger.Info("Added target subnet from %s to %s rewrite to %s with port ranges: %v", sp, target.DestPrefix, target.RewriteTo, target.PortRange)
 		}
@@ -1509,6 +1639,7 @@ func (s *WireGuardService) handleUpdateTarget(msg websocket.WSMessage) {
 				logger.Info("Invalid CIDR %s: %v", sp, err)
 				continue
 			}
+			tlsCert, tlsKey := s.resolveTLS(target)
 			s.tnet.AddProxySubnetRule(netstack2.SubnetRule{
 				SourcePrefix: sourcePrefix,
 				DestPrefix:   destPrefix,
@@ -1518,8 +1649,8 @@ func (s *WireGuardService) handleUpdateTarget(msg websocket.WSMessage) {
 				ResourceId:   target.ResourceId,
 				Protocol:     target.Protocol,
 				HTTPTargets:  target.HTTPTargets,
-				TLSCert:      target.TLSCert,
-				TLSKey:       target.TLSKey,
+				TLSCert:      tlsCert,
+				TLSKey:       tlsKey,
 			})
 			logger.Info("Added target subnet from %s to %s rewrite to %s with port ranges: %v", sp, target.DestPrefix, target.RewriteTo, target.PortRange)
 		}

exitnode/exitnode.go

@@ -0,0 +1,176 @@
+// Package exitnode implements the exit-node ping dance run before
+// registering with the server: request the candidate exit nodes, ping each
+// one over HTTP, and report the results so the server can pick the best one.
+// It is shared between newt and olm, which both register the same way.
+package exitnode
+
+import (
+	"net/http"
+	"strings"
+	"time"
+
+	"github.com/fosrl/newt/logger"
+)
+
+// ExitNodeData is the payload the server sends in response to a
+// "*/ping/request" message.
+type ExitNodeData struct {
+	ExitNodes []ExitNode `json:"exitNodes"`
+	ChainId   string     `json:"chainId"`
+}
+
+// ExitNode is a candidate exit node offered by the server for ping selection.
+type ExitNode struct {
+	ID                     int     `json:"exitNodeId"`
+	Name                   string  `json:"exitNodeName"`
+	Endpoint               string  `json:"endpoint"`
+	Weight                 float64 `json:"weight"`
+	WasPreviouslyConnected bool    `json:"wasPreviouslyConnected"`
+}
+
+// ExitNodePingResult is the measured latency (or error) for one exit node,
+// sent back to the server in the "*/wg/register" message's pingResults field.
+type ExitNodePingResult struct {
+	ExitNodeID             int     `json:"exitNodeId"`
+	LatencyMs              int64   `json:"latencyMs"`
+	Weight                 float64 `json:"weight"`
+	Error                  string  `json:"error,omitempty"`
+	Name                   string  `json:"exitNodeName"`
+	Endpoint               string  `json:"endpoint"`
+	WasPreviouslyConnected bool    `json:"wasPreviouslyConnected"`
+}
+
+// PingExitNodes pings the given exit nodes over HTTP and returns a per-node
+// ExitNodePingResult suitable for inclusion in a wg/register message's
+// pingResults field, so the server can select the best exit node.
+//
+// If there's only one exit node, or preferEndpoint names one of them, the
+// matching node is returned immediately with LatencyMs 0 and no pinging is
+// done. Otherwise every node is pinged pingAttempts times over HTTP GET
+// <endpoint>/ping and the average latency of successful attempts is used.
+//
+// When alreadyConnected is true, a node flagged WasPreviouslyConnected is
+// excluded from the results as long as at least one other healthy node is
+// available, biasing reconnects toward switching away from a possibly
+// degraded node.
+func PingExitNodes(exitNodes []ExitNode, preferEndpoint string, alreadyConnected bool) []ExitNodePingResult {
+	if len(exitNodes) == 0 {
+		return nil
+	}
+
+	if len(exitNodes) == 1 || preferEndpoint != "" {
+		selected := exitNodes[0]
+		if preferEndpoint != "" {
+			for _, node := range exitNodes {
+				if node.Endpoint == preferEndpoint {
+					selected = node
+					break
+				}
+			}
+		}
+
+		logger.Debug("Only one exit node available, using it directly: %s", selected.Endpoint)
+
+		return []ExitNodePingResult{
+			{
+				ExitNodeID:             selected.ID,
+				LatencyMs:              0,
+				Weight:                 selected.Weight,
+				Error:                  "",
+				Name:                   selected.Name,
+				Endpoint:               selected.Endpoint,
+				WasPreviouslyConnected: selected.WasPreviouslyConnected,
+			},
+		}
+	}
+
+	type nodeResult struct {
+		Node    ExitNode
+		Latency time.Duration
+		Err     error
+	}
+
+	results := make([]nodeResult, len(exitNodes))
+	const pingAttempts = 3
+	for i, node := range exitNodes {
+		var totalLatency time.Duration
+		var lastErr error
+		successes := 0
+		httpClient := &http.Client{
+			Timeout: 5 * time.Second,
+		}
+		url := node.Endpoint
+		if !strings.HasPrefix(url, "http://") && !strings.HasPrefix(url, "https://") {
+			url = "http://" + url
+		}
+		if !strings.HasSuffix(url, "/ping") {
+			url = strings.TrimRight(url, "/") + "/ping"
+		}
+		for j := 0; j < pingAttempts; j++ {
+			start := time.Now()
+			resp, err := httpClient.Get(url)
+			latency := time.Since(start)
+			if err != nil {
+				lastErr = err
+				logger.Warn("Failed to ping exit node %d (%s) attempt %d: %v", node.ID, url, j+1, err)
+				continue
+			}
+			resp.Body.Close()
+			totalLatency += latency
+			successes++
+		}
+		var avgLatency time.Duration
+		if successes > 0 {
+			avgLatency = totalLatency / time.Duration(successes)
+		}
+		if successes == 0 {
+			results[i] = nodeResult{Node: node, Latency: 0, Err: lastErr}
+		} else {
+			results[i] = nodeResult{Node: node, Latency: avgLatency, Err: nil}
+		}
+	}
+
+	var pingResults []ExitNodePingResult
+	for _, res := range results {
+		errMsg := ""
+		if res.Err != nil {
+			errMsg = res.Err.Error()
+		}
+		pingResults = append(pingResults, ExitNodePingResult{
+			ExitNodeID:             res.Node.ID,
+			LatencyMs:              res.Latency.Milliseconds(),
+			Weight:                 res.Node.Weight,
+			Error:                  errMsg,
+			Name:                   res.Node.Name,
+			Endpoint:               res.Node.Endpoint,
+			WasPreviouslyConnected: res.Node.WasPreviouslyConnected,
+		})
+	}
+
+	if alreadyConnected {
+		var filteredPingResults []ExitNodePingResult
+		previouslyConnectedNodeIdx := -1
+		for i, res := range pingResults {
+			if res.WasPreviouslyConnected {
+				previouslyConnectedNodeIdx = i
+			}
+		}
+		goodNodeCount := 0
+		for i, res := range pingResults {
+			if i != previouslyConnectedNodeIdx && res.LatencyMs > 0 && res.Error == "" {
+				goodNodeCount++
+			}
+		}
+		if previouslyConnectedNodeIdx != -1 && goodNodeCount > 0 {
+			for i, res := range pingResults {
+				if i != previouslyConnectedNodeIdx {
+					filteredPingResults = append(filteredPingResults, res)
+				}
+			}
+			pingResults = filteredPingResults
+			logger.Info("Excluding previously connected exit node from ping results due to other available nodes")
+		}
+	}
+
+	return pingResults
+}

netstack2/http_handler.go

@@ -3,9 +3,15 @@ package netstack2
 import (
 	"bufio"
 	"context"
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
 	"crypto/tls"
+	"crypto/x509"
+	"crypto/x509/pkix"
 	"errors"
 	"fmt"
+	"math/big"
 	"net"
 	"net/http"
 	"net/http/httputil"
@@ -65,6 +71,13 @@ type HTTPHandler struct {
 	// of the PEM certificate and key. Parsing a keypair is relatively expensive
 	// and the same cert is likely reused across many connections.
 	tlsCache sync.Map // map[string]*tls.Config
+
+	// fallbackTLSOnce/fallbackTLSCfg hold a lazily-generated self-signed
+	// certificate used when a rule's configured cert/key fails to parse, so
+	// that a misconfigured rule degrades to a browser cert warning instead of
+	// silently dropping every connection.
+	fallbackTLSOnce sync.Once
+	fallbackTLSCfg  *tls.Config
 }
 
 // ---------------------------------------------------------------------------
@@ -262,7 +275,13 @@ func (h *HTTPHandler) getTLSConfig(rule *SubnetRule) (*tls.Config, error) {
 
 	cert, err := tls.X509KeyPair([]byte(rule.TLSCert), []byte(rule.TLSKey))
 	if err != nil {
-		return nil, fmt.Errorf("failed to parse TLS keypair: %w", err)
+		// A misconfigured rule (bad/missing PEM data) must not take the whole
+		// connection down: fall back to a self-signed cert so the handshake
+		// still completes and the request reaches handleRequest, which routes
+		// independently of the cert. Clients will see a cert warning instead
+		// of a silent connection reset.
+		logger.Warn("HTTP handler: falling back to self-signed cert for rule (invalid configured keypair): %v", err)
+		return h.getFallbackTLSConfig(), nil
 	}
 	cfg := &tls.Config{
 		Certificates: []tls.Certificate{cert},
@@ -273,6 +292,57 @@ func (h *HTTPHandler) getTLSConfig(rule *SubnetRule) (*tls.Config, error) {
 	return actual.(*tls.Config), nil
 }
 
+// getFallbackTLSConfig returns a *tls.Config backed by a self-signed
+// certificate, generated once and reused for the lifetime of the handler.
+func (h *HTTPHandler) getFallbackTLSConfig() *tls.Config {
+	h.fallbackTLSOnce.Do(func() {
+		cert, err := generateSelfSignedCert()
+		if err != nil {
+			// Generation of an in-memory self-signed cert has no external
+			// dependencies and should never fail; if it somehow does, there
+			// is no sensible fallback left, so surface it loudly.
+			logger.Error("HTTP handler: failed to generate fallback self-signed cert: %v", err)
+			return
+		}
+		h.fallbackTLSCfg = &tls.Config{Certificates: []tls.Certificate{cert}}
+	})
+	return h.fallbackTLSCfg
+}
+
+// generateSelfSignedCert creates a fresh, in-memory self-signed TLS
+// certificate/key pair valid for one year, used as a fallback when a rule's
+// configured certificate cannot be parsed.
+func generateSelfSignedCert() (tls.Certificate, error) {
+	priv, err := ecdsa.GenerateKey(elliptic.P256(), rand.Reader)
+	if err != nil {
+		return tls.Certificate{}, fmt.Errorf("failed to generate private key: %w", err)
+	}
+
+	serialNumber, err := rand.Int(rand.Reader, new(big.Int).Lsh(big.NewInt(1), 128))
+	if err != nil {
+		return tls.Certificate{}, fmt.Errorf("failed to generate serial number: %w", err)
+	}
+
+	template := x509.Certificate{
+		SerialNumber: serialNumber,
+		Subject:      pkix.Name{CommonName: "newt-fallback"},
+		NotBefore:    time.Now().Add(-time.Hour),
+		NotAfter:     time.Now().AddDate(1, 0, 0),
+		KeyUsage:     x509.KeyUsageDigitalSignature | x509.KeyUsageKeyEncipherment,
+		ExtKeyUsage:  []x509.ExtKeyUsage{x509.ExtKeyUsageServerAuth},
+	}
+
+	derBytes, err := x509.CreateCertificate(rand.Reader, &template, &template, &priv.PublicKey, priv)
+	if err != nil {
+		return tls.Certificate{}, fmt.Errorf("failed to create certificate: %w", err)
+	}
+
+	return tls.Certificate{
+		Certificate: [][]byte{derBytes},
+		PrivateKey:  priv,
+	}, nil
+}
+
 // getProxy returns a cached *httputil.ReverseProxy for the given target,
 // creating one on first use. Reusing the proxy preserves its http.Transport
 // connection pool, avoiding repeated TCP/TLS handshakes to the downstream.

network/interface.go

@@ -167,3 +167,95 @@ func configureLinux(interfaceName string, ip net.IP, ipNet *net.IPNet) error {
 
 	return nil
 }
+
+// AddSecondaryAddress adds an additional IP address (given as CIDR, e.g. "10.10.0.5/32")
+// to an already-configured interface. It also records the address in the shared
+// NetworkSettings (see AddIPv4Address) so mobile (iOS/Android) packet-tunnel providers
+// pick it up on their next settings poll - those platforms have no OS-level interface
+// to configure directly, so this is the only way they learn about the address.
+func AddSecondaryAddress(interfaceName string, addr string) error {
+	ip, ipNet, err := net.ParseCIDR(addr)
+	if err != nil {
+		return fmt.Errorf("invalid IP address: %v", err)
+	}
+
+	mask := net.IP(ipNet.Mask).String()
+	AddIPv4Address(ip.String(), mask)
+
+	if interfaceName == "" {
+		return nil
+	}
+
+	switch runtime.GOOS {
+	case "linux":
+		return configureLinux(interfaceName, ip, ipNet)
+	case "darwin":
+		return configureDarwin(interfaceName, ip, ipNet)
+	case "windows":
+		return configureWindows(interfaceName, ip, ipNet)
+	default:
+		return nil
+	}
+}
+
+// RemoveSecondaryAddress removes an IP address (given as CIDR) previously added with
+// AddSecondaryAddress, including from the shared NetworkSettings used by mobile
+// packet-tunnel providers.
+func RemoveSecondaryAddress(interfaceName string, addr string) error {
+	ip, ipNet, err := net.ParseCIDR(addr)
+	if err != nil {
+		return fmt.Errorf("invalid IP address: %v", err)
+	}
+
+	RemoveIPv4Address(ip.String())
+
+	if interfaceName == "" {
+		return nil
+	}
+
+	switch runtime.GOOS {
+	case "linux":
+		return removeLinuxAddress(interfaceName, ip, ipNet)
+	case "darwin":
+		return removeDarwinAddress(interfaceName, ip, ipNet)
+	case "windows":
+		return removeWindowsAddress(interfaceName, ip, ipNet)
+	default:
+		return nil
+	}
+}
+
+func removeLinuxAddress(interfaceName string, ip net.IP, ipNet *net.IPNet) error {
+	link, err := netlink.LinkByName(interfaceName)
+	if err != nil {
+		return fmt.Errorf("failed to get interface %s: %v", interfaceName, err)
+	}
+
+	addr := &netlink.Addr{
+		IPNet: &net.IPNet{
+			IP:   ip,
+			Mask: ipNet.Mask,
+		},
+	}
+
+	if err := netlink.AddrDel(link, addr); err != nil {
+		return fmt.Errorf("failed to remove IP address: %v", err)
+	}
+
+	return nil
+}
+
+func removeDarwinAddress(interfaceName string, ip net.IP, ipNet *net.IPNet) error {
+	prefix, _ := ipNet.Mask.Size()
+	ipStr := fmt.Sprintf("%s/%d", ip.String(), prefix)
+
+	cmd := exec.Command("/sbin/ifconfig", interfaceName, "inet", ipStr, "-alias")
+	logger.Info("Running command: %v", cmd)
+
+	out, err := cmd.CombinedOutput()
+	if err != nil {
+		return fmt.Errorf("ifconfig command failed: %v, output: %s", err, out)
+	}
+
+	return nil
+}

network/interface_notwindows.go

@@ -10,3 +10,7 @@ import (
 func configureWindows(interfaceName string, ip net.IP, ipNet *net.IPNet) error {
 	return fmt.Errorf("configureWindows called on non-Windows platform")
 }
+
+func removeWindowsAddress(interfaceName string, ip net.IP, ipNet *net.IPNet) error {
+	return fmt.Errorf("removeWindowsAddress called on non-Windows platform")
+}

network/interface_windows.go

@@ -61,3 +61,35 @@ func configureWindows(interfaceName string, ip net.IP, ipNet *net.IPNet) error {
 
 	return nil
 }
+
+func removeWindowsAddress(interfaceName string, ip net.IP, ipNet *net.IPNet) error {
+	iface, err := net.InterfaceByName(interfaceName)
+	if err != nil {
+		return fmt.Errorf("failed to get interface %s: %v", interfaceName, err)
+	}
+
+	luid, err := winipcfg.LUIDFromIndex(uint32(iface.Index))
+	if err != nil {
+		return fmt.Errorf("failed to get LUID for interface %s: %v", interfaceName, err)
+	}
+
+	maskBits, _ := ipNet.Mask.Size()
+
+	var addr netip.Addr
+	if ip4 := ip.To4(); ip4 != nil {
+		addr, _ = netip.AddrFromSlice(ip4)
+	} else {
+		addr, _ = netip.AddrFromSlice(ip)
+	}
+	if !addr.IsValid() {
+		return fmt.Errorf("failed to convert IP address")
+	}
+	prefix := netip.PrefixFrom(addr, maskBits)
+
+	logger.Info("Removing IP address %s from interface %s", prefix.String(), interfaceName)
+	if err := luid.DeleteIPAddress(prefix); err != nil {
+		return fmt.Errorf("failed to remove IP address: %v", err)
+	}
+
+	return nil
+}

network/settings.go

@@ -81,6 +81,45 @@ func SetIPv4Settings(addresses []string, subnetMasks []string) {
 	logger.Info("Set IPv4 addresses: %v, subnet masks: %v", addresses, subnetMasks)
 }
 
+// AddIPv4Address appends an additional IPv4 address/subnet mask pair to the
+// tunnel's network settings. This is how a secondary interface address gets
+// exposed to mobile (iOS/Android) packet-tunnel providers, which read the
+// full IPv4Addresses/IPv4SubnetMasks arrays (not just the first entry) and
+// re-apply them on every settings poll.
+func AddIPv4Address(address string, subnetMask string) {
+	networkSettingsMutex.Lock()
+	defer networkSettingsMutex.Unlock()
+
+	for _, a := range networkSettings.IPv4Addresses {
+		if a == address {
+			logger.Info("IPv4 address already exists: %s", address)
+			return
+		}
+	}
+
+	networkSettings.IPv4Addresses = append(networkSettings.IPv4Addresses, address)
+	networkSettings.IPv4SubnetMasks = append(networkSettings.IPv4SubnetMasks, subnetMask)
+	incrementor++
+	logger.Info("Added IPv4 address: %s/%s", address, subnetMask)
+}
+
+// RemoveIPv4Address removes a previously added secondary IPv4 address.
+func RemoveIPv4Address(address string) {
+	networkSettingsMutex.Lock()
+	defer networkSettingsMutex.Unlock()
+
+	for i, a := range networkSettings.IPv4Addresses {
+		if a == address {
+			networkSettings.IPv4Addresses = append(networkSettings.IPv4Addresses[:i], networkSettings.IPv4Addresses[i+1:]...)
+			networkSettings.IPv4SubnetMasks = append(networkSettings.IPv4SubnetMasks[:i], networkSettings.IPv4SubnetMasks[i+1:]...)
+			incrementor++
+			logger.Info("Removed IPv4 address: %s", address)
+			return
+		}
+	}
+	logger.Info("IPv4 address not found for removal: %s", address)
+}
+
 // SetIPv4IncludedRoutes sets the included IPv4 routes
 func SetIPv4IncludedRoutes(routes []IPv4Route) {
 	networkSettingsMutex.Lock()

newt/data.go

@@ -144,6 +144,7 @@ func (n *Newt) handleSync(msg websocket.WSMessage) {
 
 	// Sync clients WireGuard peers and targets, if clients are set up
 	if n.wgService != nil {
+		n.wgService.SetCerts(syncData.Certs)
 		n.wgService.Sync(syncData.Peers, syncData.ClientTargets)
 	}
 

newt/handlers.go

@@ -10,13 +10,13 @@ import (
 	"net/http"
 	"os"
 	"os/signal"
-	"strings"
 	"syscall"
 	"time"
 
 	"github.com/fosrl/newt/authdaemon"
 	"github.com/fosrl/newt/browsergateway"
 	"github.com/fosrl/newt/docker"
+	"github.com/fosrl/newt/exitnode"
 	"github.com/fosrl/newt/healthcheck"
 	"github.com/fosrl/newt/internal/state"
 	"github.com/fosrl/newt/internal/telemetry"
@@ -140,129 +140,7 @@ func (n *Newt) registerHandlers(ctx context.Context) {
 			return
 		}
 
-		if len(exitNodes) == 1 || n.config.PreferEndpoint != "" {
-			logger.Debug("Only one exit node available, using it directly: %s", exitNodes[0].Endpoint)
-
-			if n.config.PreferEndpoint != "" {
-				for _, node := range exitNodes {
-					if node.Endpoint == n.config.PreferEndpoint {
-						exitNodes[0] = node
-						break
-					}
-				}
-			}
-
-			pingResults := []ExitNodePingResult{
-				{
-					ExitNodeID:             exitNodes[0].ID,
-					LatencyMs:              0,
-					Weight:                 exitNodes[0].Weight,
-					Error:                  "",
-					Name:                   exitNodes[0].Name,
-					Endpoint:               exitNodes[0].Endpoint,
-					WasPreviouslyConnected: exitNodes[0].WasPreviouslyConnected,
-				},
-			}
-
-			chainId := generateChainId()
-			n.pendingRegisterChainId = chainId
-			n.stopFunc = n.client.SendMessageInterval(topicWGRegister, map[string]interface{}{
-				"publicKey":   n.publicKey.String(),
-				"pingResults": pingResults,
-				"newtVersion": n.config.Version,
-				"chainId":     chainId,
-			}, 2*time.Second)
-
-			return
-		}
-
-		type nodeResult struct {
-			Node    ExitNode
-			Latency time.Duration
-			Err     error
-		}
-
-		results := make([]nodeResult, len(exitNodes))
-		const pingAttempts = 3
-		for i, node := range exitNodes {
-			var totalLatency time.Duration
-			var lastErr error
-			successes := 0
-			httpClient := &http.Client{
-				Timeout: 5 * time.Second,
-			}
-			url := node.Endpoint
-			if !strings.HasPrefix(url, "http://") && !strings.HasPrefix(url, "https://") {
-				url = "http://" + url
-			}
-			if !strings.HasSuffix(url, "/ping") {
-				url = strings.TrimRight(url, "/") + "/ping"
-			}
-			for j := 0; j < pingAttempts; j++ {
-				start := time.Now()
-				resp, err := httpClient.Get(url)
-				latency := time.Since(start)
-				if err != nil {
-					lastErr = err
-					logger.Warn("Failed to ping exit node %d (%s) attempt %d: %v", node.ID, url, j+1, err)
-					continue
-				}
-				resp.Body.Close()
-				totalLatency += latency
-				successes++
-			}
-			var avgLatency time.Duration
-			if successes > 0 {
-				avgLatency = totalLatency / time.Duration(successes)
-			}
-			if successes == 0 {
-				results[i] = nodeResult{Node: node, Latency: 0, Err: lastErr}
-			} else {
-				results[i] = nodeResult{Node: node, Latency: avgLatency, Err: nil}
-			}
-		}
-
-		var pingResults []ExitNodePingResult
-		for _, res := range results {
-			errMsg := ""
-			if res.Err != nil {
-				errMsg = res.Err.Error()
-			}
-			pingResults = append(pingResults, ExitNodePingResult{
-				ExitNodeID:             res.Node.ID,
-				LatencyMs:              res.Latency.Milliseconds(),
-				Weight:                 res.Node.Weight,
-				Error:                  errMsg,
-				Name:                   res.Node.Name,
-				Endpoint:               res.Node.Endpoint,
-				WasPreviouslyConnected: res.Node.WasPreviouslyConnected,
-			})
-		}
-
-		if n.connected {
-			var filteredPingResults []ExitNodePingResult
-			previouslyConnectedNodeIdx := -1
-			for i, res := range pingResults {
-				if res.WasPreviouslyConnected {
-					previouslyConnectedNodeIdx = i
-				}
-			}
-			goodNodeCount := 0
-			for i, res := range pingResults {
-				if i != previouslyConnectedNodeIdx && res.LatencyMs > 0 && res.Error == "" {
-					goodNodeCount++
-				}
-			}
-			if previouslyConnectedNodeIdx != -1 && goodNodeCount > 0 {
-				for i, res := range pingResults {
-					if i != previouslyConnectedNodeIdx {
-						filteredPingResults = append(filteredPingResults, res)
-					}
-				}
-				pingResults = filteredPingResults
-				logger.Info("Excluding previously connected exit node from ping results due to other available nodes")
-			}
-		}
+		pingResults := exitnode.PingExitNodes(exitNodes, n.config.PreferEndpoint, n.connected)
 
 		chainId := generateChainId()
 		n.pendingRegisterChainId = chainId

newt/types.go

@@ -2,6 +2,7 @@ package newt
 
 import (
 	wgclients "github.com/fosrl/newt/clients"
+	"github.com/fosrl/newt/exitnode"
 	"github.com/fosrl/newt/healthcheck"
 )
 
@@ -35,28 +36,14 @@ type TargetData struct {
 	Targets []string `json:"targets"`
 }
 
-type ExitNodeData struct {
-	ExitNodes []ExitNode `json:"exitNodes"`
-	ChainId   string     `json:"chainId"`
-}
-
-type ExitNode struct {
-	ID                     int     `json:"exitNodeId"`
-	Name                   string  `json:"exitNodeName"`
-	Endpoint               string  `json:"endpoint"`
-	Weight                 float64 `json:"weight"`
-	WasPreviouslyConnected bool    `json:"wasPreviouslyConnected"`
-}
-
-type ExitNodePingResult struct {
-	ExitNodeID             int     `json:"exitNodeId"`
-	LatencyMs              int64   `json:"latencyMs"`
-	Weight                 float64 `json:"weight"`
-	Error                  string  `json:"error,omitempty"`
-	Name                   string  `json:"exitNodeName"`
-	Endpoint               string  `json:"endpoint"`
-	WasPreviouslyConnected bool    `json:"wasPreviouslyConnected"`
-}
+// ExitNodeData, ExitNode and ExitNodePingResult are aliases for the shared
+// exit-node ping dance types in package exitnode, kept here so existing code
+// in this package can keep referring to them unqualified.
+type (
+	ExitNodeData       = exitnode.ExitNodeData
+	ExitNode           = exitnode.ExitNode
+	ExitNodePingResult = exitnode.ExitNodePingResult
+)
 
 type BlueprintResult struct {
 	Success bool   `json:"success"`
@@ -70,5 +57,6 @@ type SyncData struct {
 	RemoteExitNodeSubnets []string               `json:"remoteExitNodeSubnets"`
 	Peers                 []wgclients.Peer       `json:"peers"`
 	ClientTargets         []wgclients.Target     `json:"clientTargets"`
+	Certs                 []wgclients.CertData   `json:"certs"`
 	BrowserGatewayTargets []BrowserGatewayTarget `json:"browserGatewayTargets"`
 }

websocket/client.go

@@ -28,6 +28,15 @@ import (
 	"go.opentelemetry.io/otel"
 )
 
+// writeDeadline bounds how long a websocket write may block before it is
+// treated as a failure. Without this, a write to a TCP connection whose
+// underlying network interface has disappeared (e.g. laptop sleep/resume,
+// Wi-Fi roam) can sit buffered in the kernel for minutes without erroring.
+// This matters even with the read-deadline/pong machinery below: if the
+// WriteJSON call in sendPing blocks, execution never reaches the
+// WriteControl ping that would otherwise trigger that read-side detection.
+const writeDeadline = 10 * time.Second
+
 type Client struct {
 	conn              *websocket.Conn
 	config            *Config
@@ -257,6 +266,9 @@ func (c *Client) SendMessage(messageType string, data interface{}) error {
 
 	c.writeMux.Lock()
 	defer c.writeMux.Unlock()
+	if err := c.conn.SetWriteDeadline(time.Now().Add(writeDeadline)); err != nil {
+		return err
+	}
 	if err := c.conn.WriteJSON(msg); err != nil {
 		return err
 	}
@@ -277,6 +289,9 @@ func (c *Client) SendMessageNoLog(messageType string, data interface{}) error {
 
 	c.writeMux.Lock()
 	defer c.writeMux.Unlock()
+	if err := c.conn.SetWriteDeadline(time.Now().Add(writeDeadline)); err != nil {
+		return err
+	}
 	if err := c.conn.WriteJSON(msg); err != nil {
 		return err
 	}
@@ -760,14 +775,17 @@ func (c *Client) sendPing() {
 		c.writeMux.Unlock()
 		return
 	}
-	err := c.conn.WriteJSON(pingMsg)
+	err := c.conn.SetWriteDeadline(time.Now().Add(writeDeadline))
+	if err == nil {
+		err = c.conn.WriteJSON(pingMsg)
+	}
 	if err == nil {
 		telemetry.IncWSMessage(c.metricsContext(), "out", "ping")
 		// Protocol-level ping: a standards-compliant server replies with a PONG,
 		// which refreshes the read deadline. This is what lets us notice a
 		// half-open connection where writes still succeed (buffered) but the
 		// peer is gone.
-		_ = c.conn.WriteControl(websocket.PingMessage, nil, time.Now().Add(10*time.Second))
+		_ = c.conn.WriteControl(websocket.PingMessage, nil, time.Now().Add(writeDeadline))
 	}
 	c.writeMux.Unlock()