From c1e196c1c6485fc5caa1798e20f6e8f61e2c4dce Mon Sep 17 00:00:00 2001
From: mzz2017 <2017@duck.com>
Date: Tue, 31 Jan 2023 19:54:11 +0800
Subject: [PATCH] fix: zero question dns packet causes panic

---
 component/control/dns.go        |  5 ++++-
 component/control/kern/tproxy.c |  3 ++-
 component/control/udp.go        | 22 ++++++++++++++--------
 3 files changed, 20 insertions(+), 10 deletions(-)

diff --git a/component/control/dns.go b/component/control/dns.go
index 65961be..4dbd60b 100644
--- a/component/control/dns.go
+++ b/component/control/dns.go
@@ -64,6 +64,9 @@ func (c *ControlPlane) BatchUpdateDomainRouting(cache *dnsCache) error {
 }
 
 func (c *ControlPlane) LookupDnsRespCache(msg *dnsmessage.Message) (resp []byte) {
+	if len(msg.Questions) == 0 {
+		return nil
+	}
 	q := msg.Questions[0]
 	if msg.Response {
 		return nil
@@ -101,7 +104,7 @@ func (c *ControlPlane) DnsRespHandler(data []byte) (newData []byte, err error) {
 	}
 
 	// Check healthy.
-	if !msg.Response || msg.RCode != dnsmessage.RCodeSuccess {
+	if !msg.Response || msg.RCode != dnsmessage.RCodeSuccess || len(msg.Questions) == 0 {
 		return data, nil
 	}
 	// Check req type.
diff --git a/component/control/kern/tproxy.c b/component/control/kern/tproxy.c
index b92fef4..53360df 100644
--- a/component/control/kern/tproxy.c
+++ b/component/control/kern/tproxy.c
@@ -960,7 +960,7 @@ static int routing(__u32 flag[6], void *l4_hdr, __be32 saddr[4],
         good_subrule = true;
       }
     } else if (match_set->type == MatchType_ProcessName) {
-      if ((equal_ipv6_format(match_set->pname, _pname))){
+      if ((equal_ipv6_format(match_set->pname, _pname))) {
         good_subrule = true;
       }
     } else if (match_set->type == MatchType_Final) {
@@ -1990,6 +1990,7 @@ static int __always_inline update_map_elem_by_sk(struct sock *sk) {
   struct pid_pname val;
   __builtin_memset(&val, 0, sizeof(struct pid_pname));
   val.pid = bpf_get_current_pid_tgid() >> 32;
+//  struct task_struct *t = (void *)bpf_get_current_task();
   if ((ret = bpf_get_current_comm(val.pname, sizeof(val.pname)))) {
     return ret;
   }
diff --git a/component/control/udp.go b/component/control/udp.go
index 32cf079..04c17cf 100644
--- a/component/control/udp.go
+++ b/component/control/udp.go
@@ -9,6 +9,7 @@ import (
 	"encoding/binary"
 	"fmt"
 	"github.com/mzz2017/softwind/pool"
+	"github.com/sirupsen/logrus"
 	"github.com/v2rayA/dae/common/consts"
 	"golang.org/x/net/dns/dnsmessage"
 	"net"
@@ -117,10 +118,12 @@ func (c *ControlPlane) handlePkt(data []byte, lConn *net.UDPConn, lAddrPort neti
 			if err = sendPktWithHdr(resp, dest, lConn, lAddrPort); err != nil {
 				return fmt.Errorf("failed to write cached DNS resp: %w", err)
 			}
-			q := dnsMessage.Questions[0]
-			c.log.Debugf("UDP(DNS) %v <-[%v]-> Cache: %v %v",
-				lAddrPort.String(), outbound.Name, q.Name, q.Type,
-			)
+			if c.log.IsLevelEnabled(logrus.DebugLevel) && len(dnsMessage.Questions) > 0 {
+				q := dnsMessage.Questions[0]
+				c.log.Debugf("UDP(DNS) %v <-[%v]-> Cache: %v %v",
+					lAddrPort.String(), outbound.Name, q.Name, q.Type,
+				)
+			}
 			return nil
 		} else {
 			c.log.Debugf("Modify dns target %v to upstream: %v", addrHdr.Dest.String(), c.dnsUpstream.String())
@@ -128,10 +131,13 @@ func (c *ControlPlane) handlePkt(data []byte, lConn *net.UDPConn, lAddrPort neti
 			// NOTICE: Routing was calculated in advance by the eBPF program.
 			dummyFrom = &addrHdr.Dest
 			dest = c.dnsUpstream
-			q := dnsMessage.Questions[0]
-			c.log.Debugf("UDP(DNS) %v <-[%v]-> %v: %v %v",
-				lAddrPort.String(), outbound.Name, dest.String(), q.Name, q.Type,
-			)
+
+			if c.log.IsLevelEnabled(logrus.DebugLevel) && len(dnsMessage.Questions) > 0 {
+				q := dnsMessage.Questions[0]
+				c.log.Debugf("UDP(DNS) %v <-[%v]-> %v: %v %v",
+					lAddrPort.String(), outbound.Name, dest.String(), q.Name, q.Type,
+				)
+			}
 		}
 	} else {
 		// TODO: Set-up ip to domain mapping and show domain if possible.