cf-socket: improvements in socket I/O handling

- Curl_write_plain/Curl_read_plain have been eliminated. Last code use
  now uses Curl_conn_send/recv so that requests use conn->send/revc
  callbacks which defaults to cfilters use.
- Curl_recv_plain/Curl_send_plain have been internalized in cf-socket.c.
- USE_RECV_BEFORE_SEND_WORKAROUND (active on Windows) has been moved
  into cf-socket.c. The pre_recv buffer is held at the socket filter
  context.  `postponed_data` structures have been removed from
  `connectdata`.
- the hanger in HTTP/2 request handling was a result of read buffering
  on all sends and the multi handling is not prepared for this. The
  following happens:

   - multi preforms on a HTTP/2 easy handle
   - h2 reads and processes data
   - this leads to a send of h2 data
   - which receives and buffers before the send
   - h2 returns
   - multi selects on the socket, but no data arrives (its in the buffer already)
   the workaround now receives data in a loop as long as there is something in
   the buffer. The real fix would be for multi to change, so that `data_pending`
   is evaluated before deciding to wait on the socket.

io_buffer, optional, in cf-socket.c, http/2 sets state.drain if lower
filter have pending data.

This io_buffer is only available/used when the
-DUSE_RECV_BEFORE_SEND_WORKAROUND is active, e.g. on Windows
configurations. It also maintains the original checks on protocol
handler being HTTP and conn->send/recv not being replaced.

The HTTP/2 (nghttp2) cfilter now sets data->state.drain when it finds
out that the "lower" filter chain has still pending data at the end of
its IO operation. This prevents the processing from becoming stalled.

Closes #10280

1 files changed, 0 insertions, 46 deletions

diff --git a/lib/url.c b/lib/url.c
index ef3b3a4fd..3f9142e81 100644
--- a/lib/url.c
+++ b/lib/url.c
@@ -705,45 +705,6 @@ CURLcode Curl_open(struct Curl_easy **curl)
   return result;
 }
 
-#ifdef USE_RECV_BEFORE_SEND_WORKAROUND
-static void conn_reset_postponed_data(struct connectdata *conn, int num)
-{
-  struct postponed_data * const psnd = &(conn->postponed[num]);
-  if(psnd->buffer) {
-    DEBUGASSERT(psnd->allocated_size > 0);
-    DEBUGASSERT(psnd->recv_size <= psnd->allocated_size);
-    DEBUGASSERT(psnd->recv_size ?
-                (psnd->recv_processed < psnd->recv_size) :
-                (psnd->recv_processed == 0));
-    DEBUGASSERT(psnd->bindsock != CURL_SOCKET_BAD);
-    free(psnd->buffer);
-    psnd->buffer = NULL;
-    psnd->allocated_size = 0;
-    psnd->recv_size = 0;
-    psnd->recv_processed = 0;
-#ifdef DEBUGBUILD
-    psnd->bindsock = CURL_SOCKET_BAD; /* used only for DEBUGASSERT */
-#endif /* DEBUGBUILD */
-  }
-  else {
-    DEBUGASSERT(psnd->allocated_size == 0);
-    DEBUGASSERT(psnd->recv_size == 0);
-    DEBUGASSERT(psnd->recv_processed == 0);
-    DEBUGASSERT(psnd->bindsock == CURL_SOCKET_BAD);
-  }
-}
-
-static void conn_reset_all_postponed_data(struct connectdata *conn)
-{
-  conn_reset_postponed_data(conn, 0);
-  conn_reset_postponed_data(conn, 1);
-}
-#else  /* ! USE_RECV_BEFORE_SEND_WORKAROUND */
-/* Use "do-nothing" macro instead of function when workaround not used */
-#define conn_reset_all_postponed_data(c) do {} while(0)
-#endif /* ! USE_RECV_BEFORE_SEND_WORKAROUND */
-
-
 static void conn_shutdown(struct Curl_easy *data)
 {
   DEBUGASSERT(data);
@@ -792,7 +753,6 @@ static void conn_free(struct Curl_easy *data, struct connectdata *conn)
   Curl_safefree(conn->hostname_resolve);
   Curl_safefree(conn->secondaryhostname);
 
-  conn_reset_all_postponed_data(conn);
   Curl_llist_destroy(&conn->easyq, NULL);
   Curl_safefree(conn->localdev);
   Curl_free_primary_ssl_config(&conn->ssl_config);
@@ -1545,10 +1505,6 @@ static struct connectdata *allocate_conn(struct Curl_easy *data)
   conn->connection_id = -1;    /* no ID */
   conn->port = -1; /* unknown at this point */
   conn->remote_port = -1; /* unknown at this point */
-#if defined(USE_RECV_BEFORE_SEND_WORKAROUND) && defined(DEBUGBUILD)
-  conn->postponed[0].bindsock = CURL_SOCKET_BAD; /* no file descriptor */
-  conn->postponed[1].bindsock = CURL_SOCKET_BAD; /* no file descriptor */
-#endif /* USE_RECV_BEFORE_SEND_WORKAROUND && DEBUGBUILD */
 
   /* Default protocol-independent behavior doesn't support persistent
      connections, so we set this to force-close. Protocols that support
@@ -3399,8 +3355,6 @@ static void reuse_conn(struct Curl_easy *data,
   existing->hostname_resolve = temp->hostname_resolve;
   temp->hostname_resolve = NULL;
 
-  conn_reset_all_postponed_data(temp); /* free buffers */
-
   /* re-use init */
   existing->bits.reuse = TRUE; /* yes, we're re-using here */