HTTP/2 prior knowledge (#333)

* introduce http2_prior_knowledge option for http connections

* add commentary to http2_prior_knowledge var

* unasync http2_prior_knowledge code

* add http2 enforcing in alpn negociation

* revert proxy changes for http2_prior_knowledge

* use http1 boolean instead of http2_prior_knowledge variable

* remove RemoteProtocolError when finding http1 string in http2 payload

* Tweak HTTP/2 prior knowledge support

* Tweak whitespacing

Co-authored-by: avy <alexandre.vaney@p1sec.com>

Author: lovelydinosaur

httpcore/_async/connection.py

@@ -1,5 +1,5 @@
 from ssl import SSLContext
-from typing import Optional, Tuple, cast
+from typing import List, Optional, Tuple, cast
 
 from .._backends.auto import AsyncBackend, AsyncLock, AsyncSocketStream, AutoBackend
 from .._exceptions import ConnectError, ConnectTimeout
@@ -23,6 +23,7 @@ class AsyncHTTPConnection(AsyncHTTPTransport):
     def __init__(
         self,
         origin: Origin,
+        http1: bool = True,
         http2: bool = False,
         uds: str = None,
         ssl_context: SSLContext = None,
@@ -32,15 +33,21 @@ def __init__(
         backend: AsyncBackend = None,
     ):
         self.origin = origin
+        self.http1 = http1
         self.http2 = http2
         self.uds = uds
         self.ssl_context = SSLContext() if ssl_context is None else ssl_context
         self.socket = socket
         self.local_address = local_address
         self.retries = retries
 
-        if self.http2:
-            self.ssl_context.set_alpn_protocols(["http/1.1", "h2"])
+        alpn_protocols: List[str] = []
+        if http1:
+            alpn_protocols.append("http/1.1")
+        if http2:
+            alpn_protocols.append("h2")
+
+        self.ssl_context.set_alpn_protocols(alpn_protocols)
 
         self.connection: Optional[AsyncBaseHTTPConnection] = None
         self.is_http11 = False
@@ -147,7 +154,7 @@ def _create_connection(self, socket: AsyncSocketStream) -> None:
         logger.trace(
             "create_connection socket=%r http_version=%r", socket, http_version
         )
-        if http_version == "HTTP/2":
+        if http_version == "HTTP/2" or (self.http2 and not self.http1):
             from .http2 import AsyncHTTP2Connection
 
             self.is_http2 = True

httpcore/_async/connection_pool.py

@@ -89,8 +89,10 @@ class AsyncConnectionPool(AsyncHTTPTransport):
         connections.
     keepalive_expiry:
         The maximum time to allow before closing a keep-alive connection.
+    http1:
+        Enable/Disable HTTP/1.1 support. Defaults to True.
     http2:
-        Enable HTTP/2 support.
+        Enable/Disable HTTP/2 support. Defaults to False.
     uds:
         Path to a Unix Domain Socket to use instead of TCP sockets.
     local_address:
@@ -110,6 +112,7 @@ def __init__(
         max_connections: int = None,
         max_keepalive_connections: int = None,
         keepalive_expiry: float = None,
+        http1: bool = True,
         http2: bool = False,
         uds: str = None,
         local_address: str = None,
@@ -131,6 +134,7 @@ def __init__(
         self._max_connections = max_connections
         self._max_keepalive_connections = max_keepalive_connections
         self._keepalive_expiry = keepalive_expiry
+        self._http1 = http1
         self._http2 = http2
         self._uds = uds
         self._local_address = local_address
@@ -140,6 +144,9 @@ def __init__(
         self._backend = backend
         self._next_keepalive_check = 0.0
 
+        if not (http1 or http2):
+            raise ValueError("Either http1 or http2 must be True.")
+
         if http2:
             try:
                 import h2  # noqa: F401
@@ -175,6 +182,7 @@ def _create_connection(
     ) -> AsyncHTTPConnection:
         return AsyncHTTPConnection(
             origin=origin,
+            http1=self._http1,
             http2=self._http2,
             uds=self._uds,
             ssl_context=self._ssl_context,

httpcore/_sync/connection.py

@@ -1,5 +1,5 @@
 from ssl import SSLContext
-from typing import Optional, Tuple, cast
+from typing import List, Optional, Tuple, cast
 
 from .._backends.sync import SyncBackend, SyncLock, SyncSocketStream, SyncBackend
 from .._exceptions import ConnectError, ConnectTimeout
@@ -23,6 +23,7 @@ class SyncHTTPConnection(SyncHTTPTransport):
     def __init__(
         self,
         origin: Origin,
+        http1: bool = True,
         http2: bool = False,
         uds: str = None,
         ssl_context: SSLContext = None,
@@ -32,15 +33,21 @@ def __init__(
         backend: SyncBackend = None,
     ):
         self.origin = origin
+        self.http1 = http1
         self.http2 = http2
         self.uds = uds
         self.ssl_context = SSLContext() if ssl_context is None else ssl_context
         self.socket = socket
         self.local_address = local_address
         self.retries = retries
 
-        if self.http2:
-            self.ssl_context.set_alpn_protocols(["http/1.1", "h2"])
+        alpn_protocols: List[str] = []
+        if http1:
+            alpn_protocols.append("http/1.1")
+        if http2:
+            alpn_protocols.append("h2")
+
+        self.ssl_context.set_alpn_protocols(alpn_protocols)
 
         self.connection: Optional[SyncBaseHTTPConnection] = None
         self.is_http11 = False
@@ -147,7 +154,7 @@ def _create_connection(self, socket: SyncSocketStream) -> None:
         logger.trace(
             "create_connection socket=%r http_version=%r", socket, http_version
         )
-        if http_version == "HTTP/2":
+        if http_version == "HTTP/2" or (self.http2 and not self.http1):
             from .http2 import SyncHTTP2Connection
 
             self.is_http2 = True

httpcore/_sync/connection_pool.py

@@ -89,8 +89,10 @@ class SyncConnectionPool(SyncHTTPTransport):
         connections.
     keepalive_expiry:
         The maximum time to allow before closing a keep-alive connection.
+    http1:
+        Enable/Disable HTTP/1.1 support. Defaults to True.
     http2:
-        Enable HTTP/2 support.
+        Enable/Disable HTTP/2 support. Defaults to False.
     uds:
         Path to a Unix Domain Socket to use instead of TCP sockets.
     local_address:
@@ -110,6 +112,7 @@ def __init__(
         max_connections: int = None,
         max_keepalive_connections: int = None,
         keepalive_expiry: float = None,
+        http1: bool = True,
         http2: bool = False,
         uds: str = None,
         local_address: str = None,
@@ -131,6 +134,7 @@ def __init__(
         self._max_connections = max_connections
         self._max_keepalive_connections = max_keepalive_connections
         self._keepalive_expiry = keepalive_expiry
+        self._http1 = http1
         self._http2 = http2
         self._uds = uds
         self._local_address = local_address
@@ -140,6 +144,9 @@ def __init__(
         self._backend = backend
         self._next_keepalive_check = 0.0
 
+        if not (http1 or http2):
+            raise ValueError("Either http1 or http2 must be True.")
+
         if http2:
             try:
                 import h2  # noqa: F401
@@ -175,6 +182,7 @@ def _create_connection(
     ) -> SyncHTTPConnection:
         return SyncHTTPConnection(
             origin=origin,
+            http1=self._http1,
             http2=self._http2,
             uds=self._uds,
             ssl_context=self._ssl_context,

tests/async_tests/test_interfaces.py

@@ -23,6 +23,11 @@ async def read_body(stream: httpcore.AsyncByteStream) -> bytes:
         await stream.aclose()
 
 
+def test_must_configure_either_http1_or_http2() -> None:
+    with pytest.raises(ValueError):
+        httpcore.AsyncConnectionPool(http1=False, http2=False)
+
+
 @pytest.mark.anyio
 async def test_http_request(backend: str, server: Server) -> None:
     async with httpcore.AsyncConnectionPool(backend=backend) as http:

tests/sync_tests/test_interfaces.py

@@ -23,6 +23,11 @@ def read_body(stream: httpcore.SyncByteStream) -> bytes:
         stream.close()
 
 
+def test_must_configure_either_http1_or_http2() -> None:
+    with pytest.raises(ValueError):
+        httpcore.SyncConnectionPool(http1=False, http2=False)
+
+
 
 def test_http_request(backend: str, server: Server) -> None:
     with httpcore.SyncConnectionPool(backend=backend) as http: