Question about different listeners listen same port when enable_reuse_port set to true.

[pyrl247]

When enable_reuse_port set to ture,different listeners can listen same port without error,and the accept behavior depand on kernel,maybe cause route unpredictable?

admin:
  address:
    socket_address: { address: 127.0.0.1, port_value: 9901 }
stats_config:
  stats_matcher:
    reject_all: true
static_resources:
  listeners:
    - name: listener_0
      address:
        socket_address:
          address: 0.0.0.0
          port_value: 8888
      filter_chains:
        - filters:
            - name: envoy.filters.network.tcp_proxy
              typed_config:
                "@type": type.googleapis.com/envoy.extensions.filters.network.tcp_proxy.v3.TcpProxy
                stat_prefix: destination
                cluster: cluster_0
    - name: listener_1
      address:
        socket_address:
          address: 0.0.0.0
          port_value: 8888
      filter_chains:
        - filters:
            - name: envoy.filters.network.tcp_proxy
              typed_config:
                "@type": type.googleapis.com/envoy.extensions.filters.network.tcp_proxy.v3.TcpProxy
                stat_prefix: destination
                cluster: cluster_1
  clusters:
    - name: cluster_0
      connect_timeout: 30s
      type: STATIC
      load_assignment:
        cluster_name: cluster_0
        endpoints:
          - lb_endpoints:
              - endpoint:
                  address:
                    socket_address:
                      address: 127.0.0.1
                      port_value: 5001
    - name: cluster_1
      connect_timeout: 30s
      type: STATIC
      load_assignment:
        cluster_name: cluster_1
        endpoints:
          - lb_endpoints:
              - endpoint:
                  address:
                    socket_address:
                      address: 127.0.0.1
                      port_value: 5002

Since envoy1.20 ,enable_reuse_port is default to true.
When use the static config above,the request to port 8888 will randomly route to cluster_0 or cluster_1.
Is that a reasonable behavior?

[ggreenway]

No, this is a bug. The configuration should have failed validation in this case.

[ggreenway]

cc @mattklein123

[mattklein123]

Yeah definitely a bug. I can look into fixing.