feat: rewrite dns

.github/workflows/build.yml

@@ -34,15 +34,6 @@ jobs:
       if: matrix.arch == 'arm64'
       run: make clean && make build-bpf && GOOS=linux GOARCH=arm64 go build -o gotproxy ./cmd
 
-    - name: Set DNS to 1.1.1.1 (avoid 127.0.0.53)
-      if: matrix.arch == 'amd64'
-      run: |
-        set -e
-        sudo rm -f /etc/resolv.conf
-        printf "nameserver 1.1.1.1\nnameserver 1.0.0.1\noptions timeout:1 attempts:2\n" | sudo tee /etc/resolv.conf >/dev/null
-        echo "[INFO] /etc/resolv.conf:"
-        cat /etc/resolv.conf
-
     - name: Run proxy tests
       if: matrix.arch == 'amd64'
       run: sudo ./scripts/test_proxy.sh

README.md

@@ -43,6 +43,7 @@ sudo ./gotproxy [flags]
 | **--socks5-user** | SOCKS5 username (RFC1929). Must be set together with `--socks5-pass`. |
 | **--socks5-pass** | SOCKS5 password (RFC1929). Must be set together with `--socks5-user`. |
 | **--proto** | Proxy protocol selection: `both` (default) / `tcp` / `udp`. When set to `tcp`, only TCP traffic will be redirected; when set to `udp`, only UDP traffic will be redirected. |
+| **--no-dns53** | Disable automatic UDP DNS rewrite from `127.0.0.53:53` to `1.1.1.1:53` (enabled by default). |
 
 Features Under Development：
 IPv6 support
@@ -95,7 +96,7 @@ When multiple process/container filters are specified (such as `--container-name
 
 * The current implementation of UDP proxy is not perfect, and there may be issues in certain scenarios.
 
-* If your distro uses `127.0.0.53` for DNS, switch to a real upstream DNS , otherwise DNS may fail.
+* By default, UDP DNS destination `127.0.0.53:53` is automatically rewritten to `1.1.1.1:53`; set `--no-dns53` to turn this off.
 
 ## Thanks
 Some code is referenced from

README_CN.md

@@ -44,6 +44,7 @@ sudo ./gotproxy [flags]
 | **--socks5-user** | socks5 账号（RFC1929）。需要同时设置 `--socks5-pass`。 |
 | **--socks5-pass** | socks5 密码（RFC1929）。需要同时设置 `--socks5-user`。 |
 | **--proto** | 代理协议选择：`both`（默认）/ `tcp` / `udp`。当设置为 `tcp` 时只重定向 TCP 流量；设置为 `udp` 时只重定向 UDP 流量。 |
+| **--no-dns53** | 关闭 UDP DNS 对 `127.0.0.53:53` 的自动改写。默认会自动改写为 `1.1.1.1:53`。 |
 
 
 正在开发中的功能：
@@ -96,7 +97,7 @@ sudo ./gotproxy --container-name curl-test --pids 1234
 * 理论上应该根据5元组确定一个连接，但是考虑大多数情况目前只根据协议类型和源端口进行连接映射。
 * 在根据进程名称进行代理的场景中，如果进程启动了子进程并使用了execve执行一个新命令，会无法进行代理。
 * 目前的udp代理实现并不完善，某些场景下可能存在问题。
-* 如果你的 Linux 发行版使用 `127.0.0.53` 作为 DNS 需要将 DNS 指向真实的上游服务器，否则可能出现域名解析异常。
+* 默认会将 UDP DNS 目标 `127.0.0.53:53` 自动改写为 `1.1.1.1:53`；如需关闭可设置 `--no-dns53`。
 
 ## 感谢
 一些代码引用自：

cmd/cmd.go

@@ -21,6 +21,7 @@ var (
 	socks5User      string
 	socks5Pass      string
 	proto           string
+	noDNS53         bool
 )
 
 var rootCmd = &cobra.Command{
@@ -101,4 +102,5 @@ func init() {
 	rootCmd.PersistentFlags().StringVar(&socks5User, "socks5-user", "", "The SOCKS5 username. Requires --socks5-pass.")
 	rootCmd.PersistentFlags().StringVar(&socks5Pass, "socks5-pass", "", "The SOCKS5 password. Requires --socks5-user.")
 	rootCmd.PersistentFlags().StringVar(&proto, "proto", "both", "Proxy protocol: both|tcp|udp")
+	rootCmd.PersistentFlags().BoolVar(&noDNS53, "no-dns53", false, "Disable UDP DNS destination rewrite from 127.0.0.53:53 to 1.1.1.1:53")
 }

cmd/udpProxy.go

@@ -15,6 +15,11 @@ import (
 
 const udpReadTimeout = 5 * time.Second
 
+const (
+	localDNSStubAddr = "127.0.0.53:53"
+	publicDNSAddr    = "1.1.1.1:53"
+)
+
 // StartUDPProxy listens on addr (UDP) and forwards packets to original destinations
 // looked up from the BPF map (key = client addr, value = original dst ip:port).
 func StartUDPProxy(addr string, udpMap *ebpf.Map) {
@@ -55,6 +60,7 @@ func handleUDPPacket(proxyConn *net.UDPConn, clientAddr *net.UDPAddr, payload []
 		log.Printf("UDP proxy: lookup original dest for %s: %v", clientAddr, err)
 		return
 	}
+	targetAddr = maybeRewriteLocalDNSStub(targetAddr)
 	fmt.Printf("UDP Original destination: %s\n", targetAddr)
 
 	var remoteConn net.Conn
@@ -94,6 +100,17 @@ func handleUDPPacket(proxyConn *net.UDPConn, clientAddr *net.UDPAddr, payload []
 	}
 }
 
+func maybeRewriteLocalDNSStub(targetAddr string) string {
+	if noDNS53 {
+		return targetAddr
+	}
+	if targetAddr != localDNSStubAddr {
+		return targetAddr
+	}
+	log.Printf("UDP proxy: rewrite DNS destination %s -> %s", localDNSStubAddr, publicDNSAddr)
+	return publicDNSAddr
+}
+
 // getUDPOriginalDest looks up the BPF map with key (clientIP, clientPort) and returns "ip:port".
 // BPF stores: key src_ip (network order), src_port (host); value dst_ip (network order), dst_port (host).
 func getUDPOriginalDest(clientAddr *net.UDPAddr, udpMap *ebpf.Map) (string, error) {