Update handler.go

Bumps [github.com/cloudflare/circl](https://github.com/cloudflare/circl) from 1.6.3 to 1.6.4.
- [Release notes](https://github.com/cloudflare/circl/releases)
- [Commits](https://github.com/cloudflare/circl/compare/v1.6.3...v1.6.4)

---
updated-dependencies:
- dependency-name: github.com/cloudflare/circl
  dependency-version: 1.6.4
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

go.mod

@@ -4,7 +4,7 @@ go 1.26
 
 require (
 	github.com/apernet/quic-go v0.59.1-0.20260425001925-6c6cc9bcb716
-	github.com/cloudflare/circl v1.6.3
+	github.com/cloudflare/circl v1.6.4
 	github.com/ghodss/yaml v1.0.1-0.20220118164431-d8423dcdf344
 	github.com/golang/mock v1.7.0-rc.1
 	github.com/google/go-cmp v0.7.0

go.sum

@@ -4,8 +4,8 @@ github.com/apernet/quic-go v0.59.1-0.20260425001925-6c6cc9bcb716 h1:J1O+xpLuJWkd
 github.com/apernet/quic-go v0.59.1-0.20260425001925-6c6cc9bcb716/go.mod h1:Npbg8qBtAZlsAB3FWmqwlVh5jtVG6a4DlYsOylUpvzA=
 github.com/cespare/xxhash/v2 v2.3.0 h1:UL815xU9SqsFlibzuggzjXhog7bL6oX9BbNZnL2UFvs=
 github.com/cespare/xxhash/v2 v2.3.0/go.mod h1:VGX0DQ3Q6kWi7AoAeZDth3/j3BFtOZR5XLFGgcrjCOs=
-github.com/cloudflare/circl v1.6.3 h1:9GPOhQGF9MCYUeXyMYlqTR6a5gTrgR/fBLXvUgtVcg8=
-github.com/cloudflare/circl v1.6.3/go.mod h1:2eXP6Qfat4O/Yhh8BznvKnJ+uzEoTQ6jVKJRn81BiS4=
+github.com/cloudflare/circl v1.6.4 h1:pOXuDTCEYyzydgUpQ0CQz3LsinKjiSk6nNP5Lt5K64U=
+github.com/cloudflare/circl v1.6.4/go.mod h1:YxarevkLlbaHuWsxG6vmYNWBEsSp4pnp7j+4VljMavY=
 github.com/creack/pty v1.1.9/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ33E=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=

proxy/tun/handler.go

@@ -143,7 +143,14 @@ func (t *Handler) HandleConnection(conn net.Conn, destination net.Destination) {
 	defer cancel()
 	ctx = c.ContextWithID(ctx, session.NewID())
 
-	source := net.DestinationFromAddr(conn.RemoteAddr())
+	// if the connection is already closed, conn.RemoteAddr() will be nil
+	// due to gvisor weird behavior
+	remote := conn.RemoteAddr()
+	if remote == nil {
+		errors.LogInfo(t.ctx, "dropped quickly closed connection")
+		return
+	}
+	source := net.DestinationFromAddr(remote)
 	inbound := session.Inbound{
 		Name:          "tun",
 		Tag:           t.tag,