bitbake: asyncrpc: Add support for server headers

Adds support for asyncrpc servers to send connection headers to clients
on connection. Since this is a breaking protocol change, clients must
opt-in to expect headers from the server, corresponding to a version
bump in the client protocol.

(Bitbake rev: 1cb2b8be6cc5269553f549285592e47b7d29db03)

Signed-off-by: Joshua Watt <JPEWhacker@gmail.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/asyncrpc/serv.py

@@ -39,10 +39,14 @@ class AsyncServerConnection(object):
                 "address": socket.address,
             },
         )
+        self.client_headers = {}
 
     async def close(self):
         await self.socket.close()
 
+    async def handle_headers(self, headers):
+        return {}
+
     async def process_requests(self):
         try:
             self.logger.info("Client %r connected" % (self.socket.address,))
@@ -64,12 +68,20 @@ class AsyncServerConnection(object):
                 )
                 return
 
-            # Read headers. Currently, no headers are implemented, so look for
-            # an empty line to signal the end of the headers
+            # Read headers
+            self.client_headers = {}
             while True:
                 header = await self.socket.recv()
                 if not header:
+                    # Empty line. End of headers
                     break
+                tag, value = header.split(":", 1)
+                self.client_headers[tag.lower()] = value.strip()
+
+            if self.client_headers.get("needs-headers", "false") == "true":
+                for k, v in (await self.handle_headers(self.client_headers)).items():
+                    await self.socket.send("%s: %s" % (k, v))
+                await self.socket.send("")
 
             # Handle messages
             while True: