feat: add proxy template origin field and implement socket utilities for log streaming

templates/tcp-block-message-length-threshold.yaml

@@ -0,0 +1,35 @@
+id: tcp-block-message-length-threshold
+name: Block oversized TCP messages
+protocol: tcp
+description: Cuts off client messages that exceed a fixed size threshold.
+category: tcp
+family: tcp-hardening
+tags:
+- length-limit
+- tcp
+- block
+action: block
+summary: Cuts off client messages that exceed a fixed size threshold.
+behavior: Checks every client TCP message size, logs the offending length, drops the
+  message, and kills the flow when the threshold is hit.
+source_url: https://docs.mitmproxy.org/stable/addons/examples/
+code: |
+  import logging
+
+  from mitmproxy import tcp
+
+  MAX_MESSAGE_BYTES = 4096
+
+
+  def tcp_message(flow: tcp.TCPFlow) -> None:
+      message = flow.messages[-1]
+      if not message.from_client:
+          return
+      size = len(message.content)
+      if size > MAX_MESSAGE_BYTES:
+          logging.warning(
+              "[tcp-block-message-length-threshold] blocked message size=%d",
+              size,
+          )
+          message.drop()
+          flow.kill()