MINOR: quic: mark quic-conn as jobs on socket allocation

To prevent data loss for QUIC connections, haproxy global variable jobs
is incremented each time a quic-conn socket is allocated. This allows
the QUIC connection to terminate all its transfer operation during proxy
soft-stop. Without this patch, the process will be terminated without
waiting for QUIC connections.

Note that this is done in qc_alloc_fd(). This means only QUIC connection
with their owned socket will properly support soft-stop. In the other
case, the connection will be interrupted abruptly as before. Similarly,
jobs decrement is conducted in qc_release_fd().

This should be backported up to 2.7.

doc/configuration.txt

@@ -3159,9 +3159,11 @@ tune.quic.socket-owner { listener | connection }
 
   When default "connection" value is set, a dedicated socket will be allocated
   by every QUIC connections. This option is the preferred one to achieve the
-  best performance with a large QUIC traffic. However, this relies on some
-  advanced features from the UDP network stack. If your platform is deemed not
-  compatible, haproxy will automatically switch to "listener" mode on startup.
+  best performance with a large QUIC traffic. This is also the only way to
+  ensure soft-stop is conducted properly without data loss for QUIC
+  connections. However, this relies on some advanced features from the UDP
+  network stack. If your platform is deemed not compatible, haproxy will
+  automatically switch to "listener" mode on startup.
 
   The "listener" value indicates that QUIC transfers will occur on the shared
   listener socket. This option can be a good compromise for small traffic as it

doc/management.txt

@@ -434,7 +434,7 @@ list of options is :
     is a list of pids to signal (one per argument). The list ends on any
     option starting with a "-". It is not a problem if the list of pids is
     empty, so that it can be built on the fly based on the result of a command
-    like "pidof" or "pgrep". QUIC connections will be aborted.
+    like "pidof" or "pgrep".
 
   -st <pid>* : send the "terminate" signal (SIGTERM) to older processes after
     boot completion to terminate them immediately without finishing what they
@@ -670,9 +670,6 @@ don't have enough load to trigger the race conditions. And for most high traffic
 users, the failure rate is still fairly within the noise margin provided that at
 least SO_REUSEPORT is properly supported on their systems.
 
-QUIC limitations: soft-stop is not supported. In case of reload, QUIC connections
-will not be preserved.
-
 5. File-descriptor limitations
 ------------------------------
 

src/quic_conn.c

@@ -5022,6 +5022,12 @@ static struct quic_conn *qc_new_conn(const struct quic_version *qv, int ipv4,
 	    is_addr(local_addr)) {
 		TRACE_USER("Allocate a socket for QUIC connection", QUIC_EV_CONN_INIT, qc);
 		qc_alloc_fd(qc, local_addr, peer_addr);
+
+		/* haproxy soft-stop is supported only for QUIC connections
+		 * with their owned socket.
+		 */
+		if (qc_test_fd(qc))
+			_HA_ATOMIC_INC(&jobs);
 	}
 
 	/* insert the allocated CID in the receiver datagram handler tree */
@@ -5144,6 +5150,9 @@ void quic_conn_release(struct quic_conn *qc)
 	/* We must not free the quic-conn if the MUX is still allocated. */
 	BUG_ON(qc->mux_state == QC_MUX_READY);
 
+	if (qc_test_fd(qc))
+		_HA_ATOMIC_DEC(&jobs);
+
 	/* Close quic-conn socket fd. */
 	qc_release_fd(qc, 0);
 
@@ -5235,6 +5244,7 @@ void quic_conn_release(struct quic_conn *qc)
 
 	pool_free(pool_head_quic_conn_rxbuf, qc->rx.buf.area);
 	pool_free(pool_head_quic_conn, qc);
+
 	TRACE_PROTO("QUIC conn. freed", QUIC_EV_CONN_FREED, qc);
 
 	TRACE_LEAVE(QUIC_EV_CONN_CLOSE, qc);
@@ -6537,6 +6547,7 @@ static int qc_handle_conn_migration(struct quic_conn *qc,
 		/* TODO try to reuse socket instead of closing it and opening a new one. */
 		TRACE_STATE("Connection migration detected, allocate a new connection socket", QUIC_EV_CONN_LPKT, qc);
 		qc_release_fd(qc, 1);
+		/* TODO need to adjust <jobs> on socket allocation failure. */
 		qc_alloc_fd(qc, local_addr, peer_addr);
 	}