cfilters: kill connection filter events attach+detach

Make transfer attach/detach to/from connections chepaer.

- the "attach" event was no longer implemented by any filter
- the "detach" did the same as the "done" event for the filters
  who still implemented it. It should be superfluous as the "done"
  must always happen.

Closes #16067

lib/cfilters.c

@@ -711,18 +711,6 @@ static CURLcode cf_cntrl_all(struct connectdata *conn,
   return result;
 }
 
-void Curl_conn_ev_data_attach(struct connectdata *conn,
-                              struct Curl_easy *data)
-{
-  cf_cntrl_all(conn, data, TRUE, CF_CTRL_DATA_ATTACH, 0, NULL);
-}
-
-void Curl_conn_ev_data_detach(struct connectdata *conn,
-                              struct Curl_easy *data)
-{
-  cf_cntrl_all(conn, data, TRUE, CF_CTRL_DATA_DETACH, 0, NULL);
-}
-
 CURLcode Curl_conn_ev_data_setup(struct Curl_easy *data)
 {
   return cf_cntrl_all(data->conn, data, FALSE,

lib/cfilters.h

@@ -132,8 +132,6 @@ typedef CURLcode Curl_cft_conn_keep_alive(struct Curl_cfilter *cf,
  *           to all filters in the chain. Overall result is always CURLE_OK.
  */
 /*      data event                          arg1       arg2     return */
-#define CF_CTRL_DATA_ATTACH           1  /* 0          NULL     ignored */
-#define CF_CTRL_DATA_DETACH           2  /* 0          NULL     ignored */
 #define CF_CTRL_DATA_SETUP            4  /* 0          NULL     first fail */
 #define CF_CTRL_DATA_IDLE             5  /* 0          NULL     first fail */
 #define CF_CTRL_DATA_PAUSE            6  /* on/off     NULL     first fail */
@@ -476,24 +474,6 @@ ssize_t Curl_cf_recv(struct Curl_easy *data, int sockindex, char *buf,
 ssize_t Curl_cf_send(struct Curl_easy *data, int sockindex,
                      const void *buf, size_t len, bool eos, CURLcode *code);
 
-/**
- * The easy handle `data` is being attached to `conn`. This does
- * not mean that data will actually do a transfer. Attachment is
- * also used for temporary actions on the connection.
- */
-void Curl_conn_ev_data_attach(struct connectdata *conn,
-                              struct Curl_easy *data);
-
-/**
- * The easy handle `data` is being detached (no longer served)
- * by connection `conn`. All filters are informed to release any resources
- * related to `data`.
- * Note: there may be several `data` attached to a connection at the same
- * time.
- */
-void Curl_conn_ev_data_detach(struct connectdata *conn,
-                              struct Curl_easy *data);
-
 /**
  * Notify connection filters that they need to setup data for
  * a transfer.

lib/http2.c

@@ -2636,9 +2636,6 @@ static CURLcode cf_h2_cntrl(struct Curl_cfilter *cf,
   case CF_CTRL_FLUSH:
     result = cf_h2_flush(cf, data);
     break;
-  case CF_CTRL_DATA_DETACH:
-    http2_data_done(cf, data);
-    break;
   case CF_CTRL_DATA_DONE:
     http2_data_done(cf, data);
     break;

lib/multi.c

@@ -946,7 +946,6 @@ void Curl_detach_connection(struct Curl_easy *data)
 {
   struct connectdata *conn = data->conn;
   if(conn) {
-    Curl_conn_ev_data_detach(conn, data);
     Curl_node_remove(&data->conn_queue);
   }
   data->conn = NULL;
@@ -967,7 +966,6 @@ void Curl_attach_connection(struct Curl_easy *data,
   Curl_llist_append(&conn->easyq, data, &data->conn_queue);
   if(conn->handler && conn->handler->attach)
     conn->handler->attach(data, conn);
-  Curl_conn_ev_data_attach(conn, data);
 }
 
 static int connecting_getsock(struct Curl_easy *data, curl_socket_t *socks)

lib/vquic/curl_ngtcp2.c

@@ -1990,9 +1990,6 @@ static CURLcode cf_ngtcp2_data_event(struct Curl_cfilter *cf,
   case CF_CTRL_DATA_PAUSE:
     result = h3_data_pause(cf, data, (arg1 != 0));
     break;
-  case CF_CTRL_DATA_DETACH:
-    h3_data_done(cf, data);
-    break;
   case CF_CTRL_DATA_DONE:
     h3_data_done(cf, data);
     break;

lib/vquic/curl_osslq.c

@@ -2200,9 +2200,6 @@ static CURLcode cf_osslq_data_event(struct Curl_cfilter *cf,
   case CF_CTRL_DATA_PAUSE:
     result = h3_data_pause(cf, data, (arg1 != 0));
     break;
-  case CF_CTRL_DATA_DETACH:
-    h3_data_done(cf, data);
-    break;
   case CF_CTRL_DATA_DONE:
     h3_data_done(cf, data);
     break;

lib/vquic/curl_quiche.c

@@ -1228,9 +1228,6 @@ static CURLcode cf_quiche_data_event(struct Curl_cfilter *cf,
   case CF_CTRL_DATA_PAUSE:
     result = h3_data_pause(cf, data, (arg1 != 0));
     break;
-  case CF_CTRL_DATA_DETACH:
-    h3_data_done(cf, data);
-    break;
   case CF_CTRL_DATA_DONE:
     h3_data_done(cf, data);
     break;