Merge branch 'main' of github.com:fosrl/gerbil

Bump golang.org/x/crypto from 0.42.0 to 0.43.0 in the prod-minor-updates group

.github/DISCUSSION_TEMPLATE/feature-requests.yml

@@ -0,0 +1,47 @@
+body:
+    - type: textarea
+      attributes:
+          label: Summary
+          description: A clear and concise summary of the requested feature.
+      validations:
+          required: true
+
+    - type: textarea
+      attributes:
+          label: Motivation
+          description: |
+              Why is this feature important?
+              Explain the problem this feature would solve or what use case it would enable.
+      validations:
+          required: true
+
+    - type: textarea
+      attributes:
+          label: Proposed Solution
+          description: |
+              How would you like to see this feature implemented?
+              Provide as much detail as possible about the desired behavior, configuration, or changes.
+      validations:
+          required: true
+
+    - type: textarea
+      attributes:
+          label: Alternatives Considered
+          description: Describe any alternative solutions or workarounds you've thought about.
+      validations:
+          required: false
+
+    - type: textarea
+      attributes:
+          label: Additional Context
+          description: Add any other context, mockups, or screenshots about the feature request here.
+      validations:
+          required: false
+
+    - type: markdown
+      attributes:
+          value: |
+              Before submitting, please:
+              - Check if there is an existing issue for this feature.
+              - Clearly explain the benefit and use case.
+              - Be as specific as possible to help contributors evaluate and implement.

.github/ISSUE_TEMPLATE/1.bug_report.yml

@@ -0,0 +1,51 @@
+name: Bug Report
+description: Create a bug report
+labels: []
+body:
+    - type: textarea
+      attributes:
+          label: Describe the Bug
+          description: A clear and concise description of what the bug is.
+      validations:
+          required: true
+
+    - type: textarea
+      attributes:
+          label: Environment
+          description: Please fill out the relevant details below for your environment.
+          value: |
+              - OS Type & Version: (e.g., Ubuntu 22.04)
+              - Pangolin Version:
+              - Gerbil Version:
+              - Traefik Version:
+              - Newt Version:
+              - Olm Version: (if applicable)
+      validations:
+          required: true
+
+    - type: textarea
+      attributes:
+          label: To Reproduce
+          description: |
+              Steps to reproduce the behavior, please provide a clear description of how to reproduce the issue, based on the linked minimal reproduction. Screenshots can be provided in the issue body below.
+
+              If using code blocks, make sure syntax highlighting is correct and double-check that the rendered preview is not broken.
+      validations:
+          required: true
+
+    - type: textarea
+      attributes:
+          label: Expected Behavior
+          description: A clear and concise description of what you expected to happen.
+      validations:
+          required: true
+
+    - type: markdown
+      attributes:
+          value: |
+              Before posting the issue go through the steps you've written down to make sure the steps provided are detailed and clear.
+
+    - type: markdown
+      attributes:
+          value: |
+              Contributors should be able to follow the steps provided in order to reproduce the bug.

.github/ISSUE_TEMPLATE/config.yml

@@ -0,0 +1,8 @@
+blank_issues_enabled: false
+contact_links:
+    - name: Need help or have questions?
+      url: https://github.com/orgs/fosrl/discussions
+      about: Ask questions, get help, and discuss with other community members
+    - name: Request a Feature
+      url: https://github.com/orgs/fosrl/discussions/new?category=feature-requests
+      about: Feature requests should be opened as discussions so others can upvote and comment

.github/workflows/cicd.yml

@@ -12,7 +12,7 @@ jobs:
 
         steps:
             - name: Checkout code
-              uses: actions/checkout@v4
+              uses: actions/checkout@v5
 
             - name: Set up QEMU
               uses: docker/setup-qemu-action@v3
@@ -31,7 +31,7 @@ jobs:
               run: echo "TAG=${GITHUB_REF#refs/tags/}" >> $GITHUB_ENV
 
             - name: Install Go
-              uses: actions/setup-go@v5
+              uses: actions/setup-go@v6
               with:
                   go-version: 1.25
 

.github/workflows/test.yml

@@ -11,10 +11,10 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@v5
 
       - name: Set up Go
-        uses: actions/setup-go@v5
+        uses: actions/setup-go@v6
         with:
           go-version: '1.25'
 

Dockerfile

@@ -16,18 +16,13 @@ COPY . .
 RUN CGO_ENABLED=0 GOOS=linux go build -o /gerbil
 
 # Start a new stage from scratch
-FROM ubuntu:24.04 AS runner
+FROM alpine:3.22 AS runner
 
-RUN apt-get update && apt-get install -y iptables iproute2 && rm -rf /var/lib/apt/lists/*
+RUN apk add --no-cache iptables iproute2
 
-# Copy the pre-built binary file from the previous stage and the entrypoint script
 COPY --from=builder /gerbil /usr/local/bin/
 COPY entrypoint.sh /
 
 RUN chmod +x /entrypoint.sh
-
-# Copy the entrypoint script
 ENTRYPOINT ["/entrypoint.sh"]
-
-# Command to run the executable
 CMD ["gerbil"]

README.md

@@ -20,7 +20,7 @@ Gerbil will create the peers defined in the config on the WireGuard interface. T
 
 ### Report Bandwidth
 
-Bytes transmitted in and out of each peer are collected every 10 seconds, and incremental usage is reported via the "reportBandwidthTo" endpoint. This can be used to track data usage of each peer on the remote server.
+Bytes transmitted in and out of each peer are collected every 10 seconds, and incremental usage is reported via the api endpoint. This can be used to track data usage of each peer on the remote server.
 
 ### Handle client relaying
 
@@ -51,7 +51,7 @@ Note: You must use either `config` or `remoteConfig` to configure WireGuard.
 
 - `reportBandwidthTo` (optional): **DEPRECATED** - Use `remoteConfig` instead. Remote HTTP endpoint to send peer bandwidth data
 - `interface` (optional): Name of the WireGuard interface created by Gerbil. Default: `wg0`
-- `listen` (optional): Port to listen on for HTTP server. Default: `:3003`
+- `listen` (optional): Port to listen on for HTTP server. Default: `:3004`
 - `log-level` (optional): The log level to use (DEBUG, INFO, WARN, ERROR, FATAL). Default: `INFO`
 - `mtu` (optional): MTU of the WireGuard interface. Default: `1280`
 - `notify` (optional): URL to notify on peer changes
@@ -84,7 +84,7 @@ Example:
 
 ```bash
 ./gerbil \
---reachableAt=http://gerbil:3003 \
+--reachableAt=http://gerbil:3004 \
 --generateAndSaveKeyTo=/var/config/key \
 --remoteConfig=http://pangolin:3001/api/v1/
 ```

go.mod

@@ -3,8 +3,9 @@ module github.com/fosrl/gerbil
 go 1.25
 
 require (
+	github.com/patrickmn/go-cache v2.1.0+incompatible
 	github.com/vishvananda/netlink v1.3.1
-	golang.org/x/crypto v0.36.0
+	golang.org/x/crypto v0.43.0
 	golang.zx2c4.com/wireguard/wgctrl v0.0.0-20230429144221-925a1e7659e6
 )
 
@@ -14,10 +15,9 @@ require (
 	github.com/mdlayher/genetlink v1.3.2 // indirect
 	github.com/mdlayher/netlink v1.7.2 // indirect
 	github.com/mdlayher/socket v0.4.1 // indirect
-	github.com/patrickmn/go-cache v2.1.0+incompatible // indirect
 	github.com/vishvananda/netns v0.0.5 // indirect
-	golang.org/x/net v0.38.0 // indirect
+	golang.org/x/net v0.45.0 // indirect
 	golang.org/x/sync v0.1.0 // indirect
-	golang.org/x/sys v0.31.0 // indirect
+	golang.org/x/sys v0.37.0 // indirect
 	golang.zx2c4.com/wireguard v0.0.0-20230325221338-052af4a8072b // indirect
 )

go.sum

@@ -16,16 +16,16 @@ github.com/vishvananda/netlink v1.3.1 h1:3AEMt62VKqz90r0tmNhog0r/PpWKmrEShJU0wJW
 github.com/vishvananda/netlink v1.3.1/go.mod h1:ARtKouGSTGchR8aMwmkzC0qiNPrrWO5JS/XMVl45+b4=
 github.com/vishvananda/netns v0.0.5 h1:DfiHV+j8bA32MFM7bfEunvT8IAqQ/NzSJHtcmW5zdEY=
 github.com/vishvananda/netns v0.0.5/go.mod h1:SpkAiCQRtJ6TvvxPnOSyH3BMl6unz3xZlaprSwhNNJM=
-golang.org/x/crypto v0.36.0 h1:AnAEvhDddvBdpY+uR+MyHmuZzzNqXSe/GvuDeob5L34=
+golang.org/x/crypto v0.43.0 h1:dduJYIi3A3KOfdGOHX8AVZ/jGiyPa3IbBozJ5kNuE04=
-golang.org/x/crypto v0.36.0/go.mod h1:Y4J0ReaxCR1IMaabaSMugxJES1EpwhBHhv2bDHklZvc=
+golang.org/x/crypto v0.43.0/go.mod h1:BFbav4mRNlXJL4wNeejLpWxB7wMbc79PdRGhWKncxR0=
-golang.org/x/net v0.38.0 h1:vRMAPTMaeGqVhG5QyLJHqNDwecKTomGeqbnfZyKlBI8=
+golang.org/x/net v0.45.0 h1:RLBg5JKixCy82FtLJpeNlVM0nrSqpCRYzVU1n8kj0tM=
-golang.org/x/net v0.38.0/go.mod h1:ivrbrMbzFq5J41QOQh0siUuly180yBYtLp+CKbEaFx8=
+golang.org/x/net v0.45.0/go.mod h1:ECOoLqd5U3Lhyeyo/QDCEVQ4sNgYsqvCZ722XogGieY=
 golang.org/x/sync v0.1.0 h1:wsuoTGHzEhffawBOhz5CYhcrV4IdKZbEyZjBMuTp12o=
 golang.org/x/sync v0.1.0/go.mod h1:RxMgew5VJxzue5/jJTE5uejpjVlOe/izrB70Jof72aM=
 golang.org/x/sys v0.2.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
 golang.org/x/sys v0.10.0/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
-golang.org/x/sys v0.31.0 h1:ioabZlmFYtWhL+TRYpcnNlLwhyxaM9kWTDEmfnprqik=
+golang.org/x/sys v0.37.0 h1:fdNQudmxPjkdUTPnLn5mdQv7Zwvbvpaxqs831goi9kQ=
-golang.org/x/sys v0.31.0/go.mod h1:BJP2sWEmIv4KK5OTEluFJCKSidICx8ciO85XgH3Ak8k=
+golang.org/x/sys v0.37.0/go.mod h1:OgkHotnGiDImocRcuBABYBEXf8A9a87e/uXjp9XT3ks=
 golang.zx2c4.com/wireguard v0.0.0-20230325221338-052af4a8072b h1:J1CaxgLerRR5lgx3wnr6L04cJFbWoceSK9JWBdglINo=
 golang.zx2c4.com/wireguard v0.0.0-20230325221338-052af4a8072b/go.mod h1:tqur9LnfstdR9ep2LaJT4lFUl0EjlHtge+gAjmsHUG4=
 golang.zx2c4.com/wireguard/wgctrl v0.0.0-20230429144221-925a1e7659e6 h1:CawjfCvYQH2OU3/TnxLx97WDSUDRABfT18pCOYwc2GE=

main.go

@@ -121,6 +121,7 @@ func main() {
 		localProxyAddr       string
 		localProxyPort       int
 		localOverridesStr    string
+		trustedUpstreamsStr  string
 		proxyProtocol        bool
 	)
 
@@ -138,6 +139,7 @@ func main() {
 	localProxyAddr = os.Getenv("LOCAL_PROXY")
 	localProxyPortStr := os.Getenv("LOCAL_PROXY_PORT")
 	localOverridesStr = os.Getenv("LOCAL_OVERRIDES")
+	trustedUpstreamsStr = os.Getenv("TRUSTED_UPSTREAMS")
 	proxyProtocolStr := os.Getenv("PROXY_PROTOCOL")
 
 	if interfaceName == "" {
@@ -150,7 +152,7 @@ func main() {
 		flag.StringVar(&remoteConfigURL, "remoteConfig", "", "URL of the Pangolin server")
 	}
 	if listenAddr == "" {
-		flag.StringVar(&listenAddr, "listen", ":3003", "Address to listen on")
+		flag.StringVar(&listenAddr, "listen", "", "DEPRECATED (overridden by reachableAt): Address to listen on")
 	}
 	// DEPRECATED AND UNSED: reportBandwidthTo
 	// allow reportBandwidthTo to be passed but dont do anything with it just thow it away
@@ -160,9 +162,11 @@ func main() {
 	if generateAndSaveKeyTo == "" {
 		flag.StringVar(&generateAndSaveKeyTo, "generateAndSaveKeyTo", "", "Path to save generated private key")
 	}
+
 	if reachableAt == "" {
 		flag.StringVar(&reachableAt, "reachableAt", "", "Endpoint of the http server to tell remote config about")
 	}
+
 	if logLevel == "" {
 		flag.StringVar(&logLevel, "log-level", "INFO", "Log level (DEBUG, INFO, WARN, ERROR, FATAL)")
 	}
@@ -197,6 +201,9 @@ func main() {
 	if localOverridesStr != "" {
 		flag.StringVar(&localOverridesStr, "local-overrides", "", "Comma-separated list of local overrides for SNI proxy")
 	}
+	if trustedUpstreamsStr == "" {
+		flag.StringVar(&trustedUpstreamsStr, "trusted-upstreams", "", "Comma-separated list of trusted upstream proxy domain names/IPs that can send PROXY protocol")
+	}
 
 	if proxyProtocolStr != "" {
 		proxyProtocol = strings.ToLower(proxyProtocolStr) == "true"
@@ -210,6 +217,22 @@ func main() {
 	logger.Init()
 	logger.GetLogger().SetLevel(parseLogLevel(logLevel))
 
+	// try to parse as http://host:port and set the listenAddr to the :port from this reachableAt.
+	if reachableAt != "" && listenAddr == "" {
+		if strings.HasPrefix(reachableAt, "http://") || strings.HasPrefix(reachableAt, "https://") {
+			parts := strings.Split(reachableAt, ":")
+			if len(parts) == 3 {
+				port := parts[2]
+				if strings.Contains(port, "/") {
+					port = strings.Split(port, "/")[0]
+				}
+				listenAddr = ":" + port
+			}
+		}
+	} else if listenAddr == "" {
+		listenAddr = ":3003"
+	}
+
 	mtuInt, err = strconv.Atoi(mtu)
 	if err != nil {
 		logger.Fatal("Failed to parse MTU: %v", err)
@@ -323,7 +346,16 @@ func main() {
 		logger.Info("Local overrides configured: %v", localOverrides)
 	}
 
-	proxySNI, err = proxy.NewSNIProxy(sniProxyPort, remoteConfigURL, key.PublicKey().String(), localProxyAddr, localProxyPort, localOverrides, proxyProtocol)
+	var trustedUpstreams []string
+	if trustedUpstreamsStr != "" {
+		trustedUpstreams = strings.Split(trustedUpstreamsStr, ",")
+		for i, upstream := range trustedUpstreams {
+			trustedUpstreams[i] = strings.TrimSpace(upstream)
+		}
+		logger.Info("Trusted upstreams configured: %v", trustedUpstreams)
+	}
+
+	proxySNI, err = proxy.NewSNIProxy(sniProxyPort, remoteConfigURL, key.PublicKey().String(), localProxyAddr, localProxyPort, localOverrides, proxyProtocol, trustedUpstreams)
 	if err != nil {
 		logger.Fatal("Failed to create proxy: %v", err)
 	}

proxy/proxy.go

@@ -11,6 +11,7 @@ import (
 	"log"
 	"net"
 	"net/http"
+	"strconv"
 	"strings"
 	"sync"
 	"time"
@@ -31,6 +32,16 @@ type RouteAPIResponse struct {
 	Endpoints []string `json:"endpoints"`
 }
 
+// ProxyProtocolInfo holds information parsed from incoming PROXY protocol header
+type ProxyProtocolInfo struct {
+	Protocol     string // TCP4 or TCP6
+	SrcIP        string
+	DestIP       string
+	SrcPort      int
+	DestPort     int
+	OriginalConn net.Conn // The original connection after PROXY protocol parsing
+}
+
 // SNIProxy represents the main proxy server
 type SNIProxy struct {
 	port            int
@@ -55,6 +66,9 @@ type SNIProxy struct {
 	// Track active tunnels by SNI
 	activeTunnels     map[string]*activeTunnel
 	activeTunnelsLock sync.Mutex
+
+	// Trusted upstream proxies that can send PROXY protocol
+	trustedUpstreams map[string]struct{}
 }
 
 type activeTunnel struct {
@@ -75,6 +89,194 @@ func (conn readOnlyConn) SetDeadline(t time.Time) error      { return nil }
 func (conn readOnlyConn) SetReadDeadline(t time.Time) error  { return nil }
 func (conn readOnlyConn) SetWriteDeadline(t time.Time) error { return nil }
 
+// parseProxyProtocolHeader parses a PROXY protocol v1 header from the connection
+func (p *SNIProxy) parseProxyProtocolHeader(conn net.Conn) (*ProxyProtocolInfo, net.Conn, error) {
+	// Check if the connection comes from a trusted upstream
+	remoteHost, _, err := net.SplitHostPort(conn.RemoteAddr().String())
+	if err != nil {
+		return nil, conn, fmt.Errorf("failed to parse remote address: %w", err)
+	}
+
+	// Resolve the remote IP to hostname to check if it's trusted
+	// For simplicity, we'll check the IP directly in trusted upstreams
+	// In production, you might want to do reverse DNS lookup
+	if _, isTrusted := p.trustedUpstreams[remoteHost]; !isTrusted {
+		// Not from trusted upstream, return original connection
+		return nil, conn, nil
+	}
+
+	// Set read timeout for PROXY protocol parsing
+	if err := conn.SetReadDeadline(time.Now().Add(5 * time.Second)); err != nil {
+		return nil, conn, fmt.Errorf("failed to set read deadline: %w", err)
+	}
+
+	// Read the first line (PROXY protocol header)
+	buffer := make([]byte, 512) // PROXY protocol header should be much smaller
+	n, err := conn.Read(buffer)
+	if err != nil {
+		// If we can't read from trusted upstream, treat as regular connection
+		logger.Debug("Could not read from trusted upstream %s, treating as regular connection: %v", remoteHost, err)
+		// Clear read timeout before returning
+		if clearErr := conn.SetReadDeadline(time.Time{}); clearErr != nil {
+			logger.Debug("Failed to clear read deadline: %v", clearErr)
+		}
+		return nil, conn, nil
+	}
+
+	// Find the end of the first line (CRLF)
+	headerEnd := bytes.Index(buffer[:n], []byte("\r\n"))
+	if headerEnd == -1 {
+		// No PROXY protocol header found, treat as regular TLS connection
+		// Return the connection with the buffered data prepended
+		logger.Debug("No PROXY protocol header from trusted upstream %s, treating as regular TLS connection", remoteHost)
+
+		// Clear read timeout
+		if err := conn.SetReadDeadline(time.Time{}); err != nil {
+			logger.Debug("Failed to clear read deadline: %v", err)
+		}
+
+		// Create a reader that includes the buffered data + original connection
+		newReader := io.MultiReader(bytes.NewReader(buffer[:n]), conn)
+		wrappedConn := &proxyProtocolConn{
+			Conn:   conn,
+			reader: newReader,
+		}
+		return nil, wrappedConn, nil
+	}
+
+	headerLine := string(buffer[:headerEnd])
+	remainingData := buffer[headerEnd+2 : n]
+
+	// Parse PROXY protocol line: "PROXY TCP4/TCP6 srcIP destIP srcPort destPort"
+	parts := strings.Fields(headerLine)
+	if len(parts) != 6 || parts[0] != "PROXY" {
+		// Check for PROXY UNKNOWN
+		if len(parts) == 2 && parts[0] == "PROXY" && parts[1] == "UNKNOWN" {
+			// PROXY UNKNOWN - use original connection info
+			return nil, conn, nil
+		}
+		// Invalid PROXY protocol, but might be regular TLS - treat as such
+		logger.Debug("Invalid PROXY protocol from trusted upstream %s, treating as regular TLS connection: %s", remoteHost, headerLine)
+
+		// Clear read timeout
+		if err := conn.SetReadDeadline(time.Time{}); err != nil {
+			logger.Debug("Failed to clear read deadline: %v", err)
+		}
+
+		// Return the connection with all buffered data prepended
+		newReader := io.MultiReader(bytes.NewReader(buffer[:n]), conn)
+		wrappedConn := &proxyProtocolConn{
+			Conn:   conn,
+			reader: newReader,
+		}
+		return nil, wrappedConn, nil
+	}
+
+	protocol := parts[1]
+	srcIP := parts[2]
+	destIP := parts[3]
+	srcPort, err := strconv.Atoi(parts[4])
+	if err != nil {
+		return nil, conn, fmt.Errorf("invalid source port in PROXY header: %s", parts[4])
+	}
+	destPort, err := strconv.Atoi(parts[5])
+	if err != nil {
+		return nil, conn, fmt.Errorf("invalid destination port in PROXY header: %s", parts[5])
+	}
+
+	// Create a new reader that includes remaining data + original connection
+	var newReader io.Reader
+	if len(remainingData) > 0 {
+		newReader = io.MultiReader(bytes.NewReader(remainingData), conn)
+	} else {
+		newReader = conn
+	}
+
+	// Create a wrapper connection that reads from the combined reader
+	wrappedConn := &proxyProtocolConn{
+		Conn:   conn,
+		reader: newReader,
+	}
+
+	proxyInfo := &ProxyProtocolInfo{
+		Protocol:     protocol,
+		SrcIP:        srcIP,
+		DestIP:       destIP,
+		SrcPort:      srcPort,
+		DestPort:     destPort,
+		OriginalConn: wrappedConn,
+	}
+
+	// Clear read timeout
+	if err := conn.SetReadDeadline(time.Time{}); err != nil {
+		return nil, conn, fmt.Errorf("failed to clear read deadline: %w", err)
+	}
+
+	return proxyInfo, wrappedConn, nil
+}
+
+// proxyProtocolConn wraps a connection to read from a custom reader
+type proxyProtocolConn struct {
+	net.Conn
+	reader io.Reader
+}
+
+func (c *proxyProtocolConn) Read(b []byte) (int, error) {
+	return c.reader.Read(b)
+}
+
+// buildProxyProtocolHeaderFromInfo creates a PROXY protocol v1 header using ProxyProtocolInfo
+func (p *SNIProxy) buildProxyProtocolHeaderFromInfo(proxyInfo *ProxyProtocolInfo, targetAddr net.Addr) string {
+	targetTCP, ok := targetAddr.(*net.TCPAddr)
+	if !ok {
+		// Fallback for unknown address types
+		return "PROXY UNKNOWN\r\n"
+	}
+
+	// Use the original client information from the PROXY protocol
+	var targetIP string
+	var protocol string
+
+	// Parse source IP to determine protocol family
+	srcIP := net.ParseIP(proxyInfo.SrcIP)
+	if srcIP == nil {
+		return "PROXY UNKNOWN\r\n"
+	}
+
+	if srcIP.To4() != nil {
+		// Source is IPv4, use TCP4 protocol
+		protocol = "TCP4"
+		if targetTCP.IP.To4() != nil {
+			// Target is also IPv4, use as-is
+			targetIP = targetTCP.IP.String()
+		} else {
+			// Target is IPv6, but we need IPv4 for consistent protocol family
+			if targetTCP.IP.IsLoopback() {
+				targetIP = "127.0.0.1"
+			} else {
+				targetIP = "127.0.0.1" // Safe fallback
+			}
+		}
+	} else {
+		// Source is IPv6, use TCP6 protocol
+		protocol = "TCP6"
+		if targetTCP.IP.To4() != nil {
+			// Target is IPv4, convert to IPv6 representation
+			targetIP = "::ffff:" + targetTCP.IP.String()
+		} else {
+			// Target is also IPv6, use as-is
+			targetIP = targetTCP.IP.String()
+		}
+	}
+
+	return fmt.Sprintf("PROXY %s %s %s %d %d\r\n",
+		protocol,
+		proxyInfo.SrcIP,
+		targetIP,
+		proxyInfo.SrcPort,
+		targetTCP.Port)
+}
+
 // buildProxyProtocolHeader creates a PROXY protocol v1 header
 func buildProxyProtocolHeader(clientAddr, targetAddr net.Addr) string {
 	clientTCP, ok := clientAddr.(*net.TCPAddr)
@@ -131,7 +333,7 @@ func buildProxyProtocolHeader(clientAddr, targetAddr net.Addr) string {
 }
 
 // NewSNIProxy creates a new SNI proxy instance
-func NewSNIProxy(port int, remoteConfigURL, publicKey, localProxyAddr string, localProxyPort int, localOverrides []string, proxyProtocol bool) (*SNIProxy, error) {
+func NewSNIProxy(port int, remoteConfigURL, publicKey, localProxyAddr string, localProxyPort int, localOverrides []string, proxyProtocol bool, trustedUpstreams []string) (*SNIProxy, error) {
 	ctx, cancel := context.WithCancel(context.Background())
 
 	// Create local overrides map
@@ -142,19 +344,36 @@ func NewSNIProxy(port int, remoteConfigURL, publicKey, localProxyAddr string, lo
 		}
 	}
 
+	// Create trusted upstreams map
+	trustedMap := make(map[string]struct{})
+	for _, upstream := range trustedUpstreams {
+		if upstream != "" {
+			// Add both the domain and potentially resolved IPs
+			trustedMap[upstream] = struct{}{}
+
+			// Try to resolve the domain to IPs and add them too
+			if ips, err := net.LookupIP(upstream); err == nil {
+				for _, ip := range ips {
+					trustedMap[ip.String()] = struct{}{}
+				}
+			}
+		}
+	}
+
 	proxy := &SNIProxy{
-		port:            port,
+		port:             port,
-		cache:           cache.New(3*time.Second, 10*time.Minute),
+		cache:            cache.New(3*time.Second, 10*time.Minute),
-		ctx:             ctx,
+		ctx:              ctx,
-		cancel:          cancel,
+		cancel:           cancel,
-		localProxyAddr:  localProxyAddr,
+		localProxyAddr:   localProxyAddr,
-		localProxyPort:  localProxyPort,
+		localProxyPort:   localProxyPort,
-		remoteConfigURL: remoteConfigURL,
+		remoteConfigURL:  remoteConfigURL,
-		publicKey:       publicKey,
+		publicKey:        publicKey,
-		proxyProtocol:   proxyProtocol,
+		proxyProtocol:    proxyProtocol,
-		localSNIs:       make(map[string]struct{}),
+		localSNIs:        make(map[string]struct{}),
-		localOverrides:  overridesMap,
+		localOverrides:   overridesMap,
-		activeTunnels:   make(map[string]*activeTunnel),
+		activeTunnels:    make(map[string]*activeTunnel),
+		trustedUpstreams: trustedMap,
 	}
 
 	return proxy, nil
@@ -270,14 +489,35 @@ func (p *SNIProxy) handleConnection(clientConn net.Conn) {
 
 	logger.Debug("Accepted connection from %s", clientConn.RemoteAddr())
 
+	// Check for PROXY protocol from trusted upstream
+	var proxyInfo *ProxyProtocolInfo
+	var actualClientConn net.Conn = clientConn
+
+	if len(p.trustedUpstreams) > 0 {
+		var err error
+		proxyInfo, actualClientConn, err = p.parseProxyProtocolHeader(clientConn)
+		if err != nil {
+			logger.Debug("Failed to parse PROXY protocol: %v", err)
+			return
+		}
+		if proxyInfo != nil {
+			logger.Debug("Received PROXY protocol from trusted upstream: %s:%d -> %s:%d",
+				proxyInfo.SrcIP, proxyInfo.SrcPort, proxyInfo.DestIP, proxyInfo.DestPort)
+		} else {
+			// No PROXY protocol detected, but connection is from trusted upstream
+			// This is fine - treat as regular connection
+			logger.Debug("No PROXY protocol detected from trusted upstream, treating as regular connection")
+		}
+	}
+
 	// Set read timeout for SNI extraction
-	if err := clientConn.SetReadDeadline(time.Now().Add(5 * time.Second)); err != nil {
+	if err := actualClientConn.SetReadDeadline(time.Now().Add(5 * time.Second)); err != nil {
 		logger.Debug("Failed to set read deadline: %v", err)
 		return
 	}
 
 	// Extract SNI hostname
-	hostname, clientReader, err := p.extractSNI(clientConn)
+	hostname, clientReader, err := p.extractSNI(actualClientConn)
 	if err != nil {
 		logger.Debug("SNI extraction failed: %v", err)
 		return
@@ -291,13 +531,20 @@ func (p *SNIProxy) handleConnection(clientConn net.Conn) {
 	logger.Debug("SNI hostname detected: %s", hostname)
 
 	// Remove read timeout for normal operation
-	if err := clientConn.SetReadDeadline(time.Time{}); err != nil {
+	if err := actualClientConn.SetReadDeadline(time.Time{}); err != nil {
 		logger.Debug("Failed to clear read deadline: %v", err)
 		return
 	}
 
-	// Get routing information
+	// Get routing information - use original client address if available from PROXY protocol
-	route, err := p.getRoute(hostname, clientConn.RemoteAddr().String())
+	var clientAddrStr string
+	if proxyInfo != nil {
+		clientAddrStr = fmt.Sprintf("%s:%d", proxyInfo.SrcIP, proxyInfo.SrcPort)
+	} else {
+		clientAddrStr = clientConn.RemoteAddr().String()
+	}
+
+	route, err := p.getRoute(hostname, clientAddrStr)
 	if err != nil {
 		logger.Debug("Failed to get route for %s: %v", hostname, err)
 		return
@@ -325,7 +572,14 @@ func (p *SNIProxy) handleConnection(clientConn net.Conn) {
 
 	// Send PROXY protocol header if enabled
 	if p.proxyProtocol {
-		proxyHeader := buildProxyProtocolHeader(clientConn.RemoteAddr(), targetConn.LocalAddr())
+		var proxyHeader string
+		if proxyInfo != nil {
+			// Use original client info from PROXY protocol
+			proxyHeader = p.buildProxyProtocolHeaderFromInfo(proxyInfo, targetConn.LocalAddr())
+		} else {
+			// Use direct client connection info
+			proxyHeader = buildProxyProtocolHeader(clientConn.RemoteAddr(), targetConn.LocalAddr())
+		}
 		logger.Debug("Sending PROXY protocol header: %s", strings.TrimSpace(proxyHeader))
 
 		if _, err := targetConn.Write([]byte(proxyHeader)); err != nil {
@@ -341,7 +595,7 @@ func (p *SNIProxy) handleConnection(clientConn net.Conn) {
 		tunnel = &activeTunnel{}
 		p.activeTunnels[hostname] = tunnel
 	}
-	tunnel.conns = append(tunnel.conns, clientConn)
+	tunnel.conns = append(tunnel.conns, actualClientConn)
 	p.activeTunnelsLock.Unlock()
 
 	defer func() {
@@ -350,7 +604,7 @@ func (p *SNIProxy) handleConnection(clientConn net.Conn) {
 		if tunnel, ok := p.activeTunnels[hostname]; ok {
 			newConns := make([]net.Conn, 0, len(tunnel.conns))
 			for _, c := range tunnel.conns {
-				if c != clientConn {
+				if c != actualClientConn {
 					newConns = append(newConns, c)
 				}
 			}
@@ -364,7 +618,7 @@ func (p *SNIProxy) handleConnection(clientConn net.Conn) {
 	}()
 
 	// Start bidirectional data transfer
-	p.pipe(clientConn, targetConn, clientReader)
+	p.pipe(actualClientConn, targetConn, clientReader)
 }
 
 // getRoute retrieves routing information for a hostname

proxy/proxy_test.go

@@ -76,3 +76,44 @@ func TestBuildProxyProtocolHeaderUnknownType(t *testing.T) {
 		t.Errorf("Expected %q, got %q", expected, result)
 	}
 }
+
+func TestBuildProxyProtocolHeaderFromInfo(t *testing.T) {
+	proxy, err := NewSNIProxy(8443, "", "", "127.0.0.1", 443, nil, true, nil)
+	if err != nil {
+		t.Fatalf("Failed to create SNI proxy: %v", err)
+	}
+
+	// Test IPv4 case
+	proxyInfo := &ProxyProtocolInfo{
+		Protocol: "TCP4",
+		SrcIP:    "10.0.0.1",
+		DestIP:   "192.168.1.100",
+		SrcPort:  12345,
+		DestPort: 443,
+	}
+
+	targetAddr, _ := net.ResolveTCPAddr("tcp", "127.0.0.1:8080")
+	header := proxy.buildProxyProtocolHeaderFromInfo(proxyInfo, targetAddr)
+
+	expected := "PROXY TCP4 10.0.0.1 127.0.0.1 12345 8080\r\n"
+	if header != expected {
+		t.Errorf("Expected header '%s', got '%s'", expected, header)
+	}
+
+	// Test IPv6 case
+	proxyInfo = &ProxyProtocolInfo{
+		Protocol: "TCP6",
+		SrcIP:    "2001:db8::1",
+		DestIP:   "2001:db8::2",
+		SrcPort:  12345,
+		DestPort: 443,
+	}
+
+	targetAddr, _ = net.ResolveTCPAddr("tcp6", "[::1]:8080")
+	header = proxy.buildProxyProtocolHeaderFromInfo(proxyInfo, targetAddr)
+
+	expected = "PROXY TCP6 2001:db8::1 ::1 12345 8080\r\n"
+	if header != expected {
+		t.Errorf("Expected header '%s', got '%s'", expected, header)
+	}
+}

relay/relay.go

@@ -64,6 +64,17 @@ type WireGuardSession struct {
 	LastSeen      time.Time
 }
 
+// Type for tracking bidirectional communication patterns to rebuild sessions
+type CommunicationPattern struct {
+	FromClient     *net.UDPAddr // The client address
+	ToDestination  *net.UDPAddr // The destination address
+	ClientIndex    uint32       // The receiver index seen from client
+	DestIndex      uint32       // The receiver index seen from destination
+	LastFromClient time.Time    // Last packet from client to destination
+	LastFromDest   time.Time    // Last packet from destination to client
+	PacketCount    int          // Number of packets observed
+}
+
 type InitialMappings struct {
 	Mappings map[string]ProxyMapping `json:"mappings"` // key is "ip:port"
 }
@@ -105,6 +116,9 @@ type UDPProxyServer struct {
 	// Session tracking for WireGuard peers
 	// Key format: "senderIndex:receiverIndex"
 	wgSessions sync.Map
+	// Communication pattern tracking for rebuilding sessions
+	// Key format: "clientIP:clientPort-destIP:destPort"
+	commPatterns sync.Map
 	// ReachableAt is the URL where this server can be reached
 	ReachableAt string
 }
@@ -156,6 +170,9 @@ func (s *UDPProxyServer) Start() error {
 	// Start the proxy mapping cleanup routine
 	go s.cleanupIdleProxyMappings()
 
+	// Start the communication pattern cleanup routine
+	go s.cleanupIdleCommunicationPatterns()
+
 	return nil
 }
 
@@ -445,6 +462,9 @@ func (s *UDPProxyServer) handleWireGuardPacket(packet []byte, remoteAddr *net.UD
 				return
 			}
 
+			// Track communication pattern for session rebuilding
+			s.trackCommunicationPattern(remoteAddr, destAddr, receiverIndex, true)
+
 			_, err = conn.Write(packet)
 			if err != nil {
 				logger.Debug("Failed to forward transport data: %v", err)
@@ -465,6 +485,9 @@ func (s *UDPProxyServer) handleWireGuardPacket(packet []byte, remoteAddr *net.UD
 					continue
 				}
 
+				// Track communication pattern for session rebuilding
+				s.trackCommunicationPattern(remoteAddr, destAddr, receiverIndex, true)
+
 				_, err = conn.Write(packet)
 				if err != nil {
 					logger.Debug("Failed to forward transport data: %v", err)
@@ -548,6 +571,9 @@ func (s *UDPProxyServer) handleResponses(conn *net.UDPConn, destAddr *net.UDPAdd
 					LastSeen:      time.Now(),
 				})
 				logger.Debug("Stored session mapping: %s -> %s", sessionKey, destAddr.String())
+			} else if ok && buffer[0] == WireGuardMessageTypeTransportData {
+				// Track communication pattern for session rebuilding (reverse direction)
+				s.trackCommunicationPattern(destAddr, remoteAddr, receiverIndex, false)
 			}
 		}
 
@@ -823,3 +849,117 @@ func (s *UDPProxyServer) UpdateDestinationInMappings(oldDest, newDest PeerDestin
 
 	return updatedCount
 }
+
+// trackCommunicationPattern tracks bidirectional communication patterns to rebuild sessions
+func (s *UDPProxyServer) trackCommunicationPattern(fromAddr, toAddr *net.UDPAddr, receiverIndex uint32, fromClient bool) {
+	var clientAddr, destAddr *net.UDPAddr
+	var clientIndex, destIndex uint32
+
+	if fromClient {
+		clientAddr = fromAddr
+		destAddr = toAddr
+		clientIndex = receiverIndex
+		destIndex = 0 // We don't know the destination index yet
+	} else {
+		clientAddr = toAddr
+		destAddr = fromAddr
+		clientIndex = 0 // We don't know the client index yet
+		destIndex = receiverIndex
+	}
+
+	patternKey := fmt.Sprintf("%s-%s", clientAddr.String(), destAddr.String())
+	now := time.Now()
+
+	if existingPattern, ok := s.commPatterns.Load(patternKey); ok {
+		pattern := existingPattern.(*CommunicationPattern)
+
+		// Update the pattern
+		if fromClient {
+			pattern.LastFromClient = now
+			if pattern.ClientIndex == 0 {
+				pattern.ClientIndex = clientIndex
+			}
+		} else {
+			pattern.LastFromDest = now
+			if pattern.DestIndex == 0 {
+				pattern.DestIndex = destIndex
+			}
+		}
+
+		pattern.PacketCount++
+		s.commPatterns.Store(patternKey, pattern)
+
+		// Check if we have bidirectional communication and can rebuild a session
+		s.tryRebuildSession(pattern)
+	} else {
+		// Create new pattern
+		pattern := &CommunicationPattern{
+			FromClient:    clientAddr,
+			ToDestination: destAddr,
+			ClientIndex:   clientIndex,
+			DestIndex:     destIndex,
+			PacketCount:   1,
+		}
+
+		if fromClient {
+			pattern.LastFromClient = now
+		} else {
+			pattern.LastFromDest = now
+		}
+
+		s.commPatterns.Store(patternKey, pattern)
+	}
+}
+
+// tryRebuildSession attempts to rebuild a WireGuard session from communication patterns
+func (s *UDPProxyServer) tryRebuildSession(pattern *CommunicationPattern) {
+	// Check if we have bidirectional communication within a reasonable time window
+	timeDiff := pattern.LastFromClient.Sub(pattern.LastFromDest)
+	if timeDiff < 0 {
+		timeDiff = -timeDiff
+	}
+
+	// Only rebuild if we have recent bidirectional communication and both indices
+	if timeDiff < 30*time.Second && pattern.ClientIndex != 0 && pattern.DestIndex != 0 && pattern.PacketCount >= 4 {
+		// Create session mapping: client's index maps to destination
+		sessionKey := fmt.Sprintf("%d:%d", pattern.DestIndex, pattern.ClientIndex)
+
+		// Check if we already have this session
+		if _, exists := s.wgSessions.Load(sessionKey); !exists {
+			session := &WireGuardSession{
+				ReceiverIndex: pattern.DestIndex,
+				SenderIndex:   pattern.ClientIndex,
+				DestAddr:      pattern.ToDestination,
+				LastSeen:      time.Now(),
+			}
+
+			s.wgSessions.Store(sessionKey, session)
+			logger.Info("Rebuilt WireGuard session from communication pattern: %s -> %s (packets: %d)",
+				sessionKey, pattern.ToDestination.String(), pattern.PacketCount)
+		}
+	}
+}
+
+// cleanupIdleCommunicationPatterns periodically removes idle communication patterns
+func (s *UDPProxyServer) cleanupIdleCommunicationPatterns() {
+	ticker := time.NewTicker(10 * time.Minute)
+	for range ticker.C {
+		now := time.Now()
+		s.commPatterns.Range(func(key, value interface{}) bool {
+			pattern := value.(*CommunicationPattern)
+
+			// Get the most recent activity
+			lastActivity := pattern.LastFromClient
+			if pattern.LastFromDest.After(lastActivity) {
+				lastActivity = pattern.LastFromDest
+			}
+
+			// Remove patterns that haven't had activity in 20 minutes
+			if now.Sub(lastActivity) > 20*time.Minute {
+				s.commPatterns.Delete(key)
+				logger.Debug("Removed idle communication pattern: %s", key)
+			}
+			return true
+		})
+	}
+}