add panic handlers

Author: marten-seemann

client.go

@@ -5,6 +5,8 @@ import (
 	"fmt"
 	"math/rand"
 	"net"
+	"os"
+	"runtime/debug"
 	"strings"
 	"time"
 
@@ -108,7 +110,14 @@ func applyOpts(options ...ClientOption) clientOpts {
 	return conf
 }
 
-func (c *client) run(ctx context.Context, params *lookupParams) error {
+func (c *client) run(ctx context.Context, params *lookupParams) (err error) {
+	defer func() {
+		if rerr := recover(); rerr != nil {
+			fmt.Fprintf(os.Stderr, "caught panic: %s\n%s\n", rerr, debug.Stack())
+			err = fmt.Errorf("panic in zeroconf run loop: %s", rerr)
+		}
+	}()
+
 	ctx, cancel := context.WithCancel(ctx)
 	done := make(chan struct{})
 	go func() {
@@ -118,7 +127,7 @@ func (c *client) run(ctx context.Context, params *lookupParams) error {
 
 	// If previous probe was ok, it should be fine now. In case of an error later on,
 	// the entries' queue is closed.
-	err := c.periodicQuery(ctx, params)
+	err = c.periodicQuery(ctx, params)
 	cancel()
 	<-done
 	return err
@@ -165,6 +174,12 @@ var cleanupFreq = 10 * time.Second
 
 // Start listeners and waits for the shutdown signal from exit channel
 func (c *client) mainloop(ctx context.Context, params *lookupParams) {
+	defer func() {
+		if rerr := recover(); rerr != nil {
+			fmt.Fprintf(os.Stderr, "caught panic: %s\n%s\n", rerr, debug.Stack())
+		}
+	}()
+
 	// start listening for responses
 	msgCh := make(chan *dns.Msg, 32)
 	if c.ipv4conn != nil {
@@ -313,6 +328,12 @@ func (c *client) shutdown() {
 // Data receiving routine reads from connection, unpacks packets into dns.Msg
 // structures and sends them to a given msgCh channel
 func (c *client) recv(ctx context.Context, l interface{}, msgCh chan *dns.Msg) {
+	defer func() {
+		if rerr := recover(); rerr != nil {
+			fmt.Fprintf(os.Stderr, "caught panic: %s\n%s\n", rerr, debug.Stack())
+		}
+	}()
+
 	var readFrom func([]byte) (n int, src net.Addr, err error)
 
 	switch pConn := l.(type) {

server.go

@@ -6,6 +6,7 @@ import (
 	"math/rand"
 	"net"
 	"os"
+	"runtime/debug"
 	"strings"
 	"sync"
 	"time"
@@ -309,7 +310,14 @@ func (s *Server) recv6(c *ipv6.PacketConn) {
 }
 
 // parsePacket is used to parse an incoming packet
-func (s *Server) parsePacket(packet []byte, ifIndex int, from net.Addr) error {
+func (s *Server) parsePacket(packet []byte, ifIndex int, from net.Addr) (err error) {
+	defer func() {
+		if rerr := recover(); rerr != nil {
+			fmt.Fprintf(os.Stderr, "caught panic: %s\n%s\n", rerr, debug.Stack())
+			err = fmt.Errorf("panic in mDNS packet handling: %s", rerr)
+		}
+	}()
+
 	var msg dns.Msg
 	if err := msg.Unpack(packet); err != nil {
 		// log.Printf("[ERR] zeroconf: Failed to unpack packet: %v", err)
@@ -548,8 +556,14 @@ func (s *Server) serviceTypeName(resp *dns.Msg, ttl uint32) {
 }
 
 // Perform probing & announcement
-//TODO: implement a proper probing & conflict resolution
+// TODO: implement a proper probing & conflict resolution
 func (s *Server) probe() {
+	defer func() {
+		if rerr := recover(); rerr != nil {
+			fmt.Fprintf(os.Stderr, "caught panic: %s\n%s\n", rerr, debug.Stack())
+		}
+	}()
+
 	defer s.refCount.Done()
 
 	q := new(dns.Msg)