MINOR: session: remove redundant target argument from session_add_conn()

session_add_conn() uses three argument : connection and session
instances, plus a void pointer labelled as target. Typically, it
represents the server, but can also be a backend instance (for example
on dispatch).

In fact, this argument is redundant as <target> is already a member of
the connection. This commit simplifies session_add_conn() by removing
it. A BUG_ON() on target is extended to ensure it is never NULL.

include/haproxy/session.h

@@ -171,17 +171,21 @@ static inline void session_unown_conn(struct session *sess, struct connection *c
 	}
 }
 
-/* Add the connection <conn> to the private conns list of session <sess>. This
- * function is called only if the connection is private. Nothing is performed
- * if the connection is already in the session list.
+/* Add the connection <conn> to the private conns list of session <sess>. Each
+ * connection is indexed by their respective target in the session. Nothing is
+ * performed if the connection is already in the session list.
+ *
+ * Returns true if conn is inserted or already present else false if a failure
+ * occurs during insertion.
  */
-static inline int session_add_conn(struct session *sess, struct connection *conn, void *target)
+static inline int session_add_conn(struct session *sess, struct connection *conn)
 {
 	struct sess_priv_conns *pconns = NULL;
 	struct server *srv = objt_server(conn->target);
 	int found = 0;
 
-	BUG_ON(objt_listener(conn->target));
+	/* Connection target is used to index it in the session. Only BE conns are expected in session list. */
+	BUG_ON(!conn->target || objt_listener(conn->target));
 
 	/* A connection cannot be attached already to another session. */
 	BUG_ON(conn->owner && conn->owner != sess);
@@ -191,7 +195,7 @@ static inline int session_add_conn(struct session *sess, struct connection *conn
 		return 1;
 
 	list_for_each_entry(pconns, &sess->priv_conns, sess_el) {
-		if (pconns->target == target) {
+		if (pconns->target == conn->target) {
 			found = 1;
 			break;
 		}
@@ -201,7 +205,7 @@ static inline int session_add_conn(struct session *sess, struct connection *conn
 		pconns = pool_alloc(pool_head_sess_priv_conns);
 		if (!pconns)
 			return 0;
-		pconns->target = target;
+		pconns->target = conn->target;
 		LIST_INIT(&pconns->conn_list);
 		LIST_APPEND(&sess->priv_conns, &pconns->sess_el);
 

src/backend.c

@@ -1425,7 +1425,7 @@ struct connection *conn_backend_get(int reuse_mode,
 		if (reuse_mode == PR_O_REUSE_SAFE && conn->mux->flags & MX_FL_HOL_RISK) {
 			/* attach the connection to the session private list */
 			conn->owner = sess;
-			session_add_conn(sess, conn, conn->target);
+			session_add_conn(sess, conn);
 		}
 		else {
 			srv_add_to_avail_list(srv, conn);
@@ -2159,7 +2159,7 @@ int connect_server(struct stream *s)
 			         (reuse_mode == PR_O_REUSE_SAFE &&
 			          srv_conn->mux->flags & MX_FL_HOL_RISK)) {
 				/* If it fail now, the same will be done in mux->detach() callback */
-				session_add_conn(s->sess, srv_conn, srv_conn->target);
+				session_add_conn(s->sess, srv_conn);
 			}
 		}
 	}

src/connection.c

@@ -117,7 +117,7 @@ int conn_create_mux(struct connection *conn, int *closed_connection)
 		}
 		else if (conn->flags & CO_FL_PRIVATE) {
 			/* If it fail now, the same will be done in mux->detach() callback */
-			session_add_conn(sess, conn, conn->target);
+			session_add_conn(sess, conn);
 		}
 		return 0;
 fail:

src/http_ana.c

@@ -1641,7 +1641,7 @@ int http_wait_for_response(struct stream *s, struct channel *rep, int an_bit)
 				conn_set_owner(srv_conn, sess, NULL);
 				conn_set_private(srv_conn);
 				/* If it fail now, the same will be done in mux->detach() callback */
-				session_add_conn(srv_conn->owner, srv_conn, srv_conn->target);
+				session_add_conn(srv_conn->owner, srv_conn);
 				break;
 			}
 		}

src/mux_fcgi.c

@@ -3723,7 +3723,7 @@ static void fcgi_detach(struct sedesc *sd)
 	    (fconn->flags & FCGI_CF_KEEP_CONN)) {
 		if (fconn->conn->flags & CO_FL_PRIVATE) {
 			/* Add the connection in the session serverlist, if not already done */
-			if (!session_add_conn(sess, fconn->conn, fconn->conn->target)) {
+			if (!session_add_conn(sess, fconn->conn)) {
 				fconn->conn->owner = NULL;
 				if (eb_is_empty(&fconn->streams_by_id)) {
 					/* let's kill the connection right away */

src/mux_h1.c

@@ -1138,7 +1138,7 @@ static int h1s_finish_detach(struct h1s *h1s)
 
 		if (h1c->conn->flags & CO_FL_PRIVATE) {
 			/* Add the connection in the session server list, if not already done */
-			if (!session_add_conn(sess, h1c->conn, h1c->conn->target)) {
+			if (!session_add_conn(sess, h1c->conn)) {
 				h1c->conn->owner = NULL;
 				h1c->conn->mux->destroy(h1c);
 				goto released;

src/mux_h2.c

@@ -5533,7 +5533,7 @@ static void h2_detach(struct sedesc *sd)
 
 			if (h2c->conn->flags & CO_FL_PRIVATE) {
 				/* Add the connection in the session server list, if not already done */
-				if (!session_add_conn(sess, h2c->conn, h2c->conn->target)) {
+				if (!session_add_conn(sess, h2c->conn)) {
 					h2c->conn->owner = NULL;
 					if (eb_is_empty(&h2c->streams_by_id)) {
 						h2c->conn->mux->destroy(h2c);

src/mux_quic.c

@@ -3788,7 +3788,7 @@ static void qmux_strm_detach(struct sedesc *sd)
 			 * conn will be closed if idle, or insert will be
 			 * retried on next detach.
 			 */
-			if (!session_add_conn(sess, conn, conn->target)) {
+			if (!session_add_conn(sess, conn)) {
 				TRACE_ERROR("error during connection insert into session list", QMUX_EV_STRM_END, conn);
 				conn->owner = NULL;
 				if (!qcc->nb_sc)

src/mux_spop.c

@@ -2977,7 +2977,7 @@ static void spop_detach(struct sedesc *sd)
 	if (!(spop_conn->flags & (SPOP_CF_RCVD_SHUT|SPOP_CF_ERR_PENDING|SPOP_CF_ERROR))) {
 		if (spop_conn->conn->flags & CO_FL_PRIVATE) {
 			/* Add the connection in the session server list, if not already done */
-			if (!session_add_conn(sess, spop_conn->conn, spop_conn->conn->target)) {
+			if (!session_add_conn(sess, spop_conn->conn)) {
 				spop_conn->conn->owner = NULL;
 				if (eb_is_empty(&spop_conn->streams_by_id)) {
 					spop_conn->conn->mux->destroy(spop_conn);