MINOR: quic: Shorten some handshakes

Move the "ACK required" bit from the packet number space to the connection level.
Force the "ACK required" option when acknowlegding Handshake or Initial packet.
A client may send three packets with a different encryption level for each. So,
this patch modifies qc_treat_rx_pkts() to consider two encryption level passed
as parameters, in place of only one.
Make qc_conn_io_cb() restart its process after the handshake has succeeded
so that to process any Application level packets which have already been received
in the same datagram as the last CRYPTO frames in Handshake packets.
diff --git a/src/xprt_quic.c b/src/xprt_quic.c
index 3afc761..7654940 100644
--- a/src/xprt_quic.c
+++ b/src/xprt_quic.c
@@ -388,7 +388,7 @@
 				              " qel=%c state=%s ack?%d cwnd=%llu ppif=%lld pif=%llu if=%llu pp=%u pdg=%llu",
 				              quic_enc_level_char_from_qel(qel, qc),
 				              quic_hdshk_state_str(HA_ATOMIC_LOAD(&qc->state)),
-				              !!(HA_ATOMIC_LOAD(&pktns->flags) & QUIC_FL_PKTNS_ACK_REQUIRED),
+				              !!(HA_ATOMIC_LOAD(&qc->flags) & QUIC_FL_PKTNS_ACK_REQUIRED),
 				              (unsigned long long)qc->path->cwnd,
 				              (unsigned long long)qc->path->prep_in_flight,
 				              (unsigned long long)qc->path->in_flight,
@@ -2039,7 +2039,7 @@
 				nb_ptos = HA_ATOMIC_LOAD(&qc->tx.nb_pto_dgrams);
 			} while (nb_ptos && !HA_ATOMIC_CAS(&qc->tx.nb_pto_dgrams, &nb_ptos, nb_ptos - 1));
 		}
-		ack = HA_ATOMIC_BTR(&qel->pktns->flags, QUIC_FL_PKTNS_ACK_REQUIRED_BIT);
+		ack = HA_ATOMIC_BTR(&qc->flags, QUIC_FL_PKTNS_ACK_REQUIRED_BIT);
 		/* Do not build any more packet if the TX secrets are not available or
 		 * if there is nothing to send, i.e. if no ACK are required
 		 * and if there is no more packets to send upon PTO expiration
@@ -2071,7 +2071,8 @@
 		if (err < 0) {
 			if (!prv_pkt && nb_ptos)
 				HA_ATOMIC_ADD(&qc->tx.nb_pto_dgrams, 1);
-			HA_ATOMIC_BTS(&qel->pktns->flags, QUIC_FL_PKTNS_ACK_REQUIRED_BIT);
+			if (ack)
+				HA_ATOMIC_BTS(&qc->flags, QUIC_FL_PKTNS_ACK_REQUIRED_BIT);
 		}
 		switch (err) {
 		case -2:
@@ -2567,27 +2568,35 @@
 /* Process all the packets at <el> encryption level.
  * Return 1 if succeeded, 0 if not.
  */
-int qc_treat_rx_pkts(struct quic_enc_level *el, struct ssl_sock_ctx *ctx)
+int qc_treat_rx_pkts(struct quic_enc_level *cur_el, struct quic_enc_level *next_el,
+                     struct ssl_sock_ctx *ctx, int force_ack)
 {
-	struct quic_tls_ctx *tls_ctx;
 	struct eb64_node *node;
 	int64_t largest_pn = -1;
+	struct quic_conn *qc = ctx->conn->qc;
+	struct quic_enc_level *qel = cur_el;
 
 	TRACE_ENTER(QUIC_EV_CONN_ELRXPKTS, ctx->conn);
-	tls_ctx = &el->tls_ctx;
-	HA_RWLOCK_WRLOCK(QUIC_LOCK, &el->rx.pkts_rwlock);
-	node = eb64_first(&el->rx.pkts);
+	qel = cur_el;
+ next_tel:
+	if (!qel)
+		goto out;
+
+	HA_RWLOCK_WRLOCK(QUIC_LOCK, &qel->rx.pkts_rwlock);
+	node = eb64_first(&qel->rx.pkts);
 	while (node) {
 		struct quic_rx_packet *pkt;
 
 		pkt = eb64_entry(&node->node, struct quic_rx_packet, pn_node);
-		if (!qc_pkt_decrypt(pkt, tls_ctx)) {
+		TRACE_PROTO("new packet", QUIC_EV_CONN_ELRXPKTS,
+		            ctx->conn, pkt, NULL, ctx->ssl);
+		if (!qc_pkt_decrypt(pkt, &qel->tls_ctx)) {
 			/* Drop the packet */
 			TRACE_PROTO("packet decryption failed -> dropped",
 			            QUIC_EV_CONN_ELRXPKTS, ctx->conn, pkt);
 		}
 		else {
-			if (!qc_parse_pkt_frms(pkt, ctx, el)) {
+			if (!qc_parse_pkt_frms(pkt, ctx, qel)) {
 				/* Drop the packet */
 				TRACE_PROTO("packet parsing failed -> dropped",
 				            QUIC_EV_CONN_ELRXPKTS, ctx->conn, pkt);
@@ -2596,13 +2605,12 @@
 				struct quic_arng ar = { .first = pkt->pn, .last = pkt->pn };
 
 				if (pkt->flags & QUIC_FL_RX_PACKET_ACK_ELICITING &&
-					!(HA_ATOMIC_ADD_FETCH(&el->pktns->rx.nb_ack_eliciting, 1) & 1))
-					HA_ATOMIC_BTS(&el->pktns->flags, QUIC_FL_PKTNS_ACK_REQUIRED_BIT);
-
+				    (!(HA_ATOMIC_ADD_FETCH(&qc->rx.nb_ack_eliciting, 1) & 1) || force_ack))
+					HA_ATOMIC_BTS(&qc->flags, QUIC_FL_PKTNS_ACK_REQUIRED_BIT);
 				if (pkt->pn > largest_pn)
 					largest_pn = pkt->pn;
 				/* Update the list of ranges to acknowledge. */
-				if (!quic_update_ack_ranges_list(&el->pktns->rx.arngs, &ar))
+				if (!quic_update_ack_ranges_list(&qel->pktns->rx.arngs, &ar))
 					TRACE_DEVEL("Could not update ack range list",
 					            QUIC_EV_CONN_ELRXPKTS, ctx->conn);
 			}
@@ -2610,14 +2618,20 @@
 		node = eb64_next(node);
 		quic_rx_packet_eb64_delete(&pkt->pn_node);
 	}
-	HA_RWLOCK_WRUNLOCK(QUIC_LOCK, &el->rx.pkts_rwlock);
+	HA_RWLOCK_WRUNLOCK(QUIC_LOCK, &qel->rx.pkts_rwlock);
 
 	/* Update the largest packet number. */
 	if (largest_pn != -1)
-		HA_ATOMIC_UPDATE_MAX(&el->pktns->rx.largest_pn, largest_pn);
-	if (!qc_treat_rx_crypto_frms(el, ctx))
+		HA_ATOMIC_UPDATE_MAX(&qel->pktns->rx.largest_pn, largest_pn);
+	if (!qc_treat_rx_crypto_frms(qel, ctx))
 		goto err;
 
+	if (qel == cur_el) {
+		qel = next_el;
+		goto next_tel;
+	}
+
+ out:
 	TRACE_LEAVE(QUIC_EV_CONN_ELRXPKTS, ctx->conn);
 	return 1;
 
@@ -2636,7 +2650,7 @@
 	struct quic_enc_level *qel, *next_qel;
 	struct quic_tls_ctx *tls_ctx;
 	struct qring *qr; // Tx ring
-	int prev_st, st;
+	int prev_st, st, force_ack;
 
 	ctx = context;
 	qc = ctx->conn->qc;
@@ -2644,6 +2658,7 @@
 	st = HA_ATOMIC_LOAD(&qc->state);
 	TRACE_ENTER(QUIC_EV_CONN_HDSHK, ctx->conn, &st);
 	ssl_err = SSL_ERROR_NONE;
+ start:
 	if (!quic_get_tls_enc_levels(&tel, &next_tel, st))
 		goto err;
 
@@ -2661,7 +2676,9 @@
 		qc_rm_hp_pkts(qel, ctx);
 
 	prev_st = HA_ATOMIC_LOAD(&qc->state);
-	if (!qc_treat_rx_pkts(qel, ctx))
+	force_ack = qel == &qc->els[QUIC_TLS_ENC_LEVEL_INITIAL] ||
+		qel == &qc->els[QUIC_TLS_ENC_LEVEL_HANDSHAKE];
+	if (!qc_treat_rx_pkts(qel, next_qel, ctx, force_ack))
 		goto err;
 
 	st = HA_ATOMIC_LOAD(&qc->state);
@@ -2673,6 +2690,7 @@
 		qc_set_timer(ctx);
 		if (!quic_build_post_handshake_frames(qc))
 			goto err;
+		goto start;
 	}
 
 	if (!qr)
@@ -2912,6 +2930,7 @@
 	qc->tx.nb_pto_dgrams = 0;
 	/* RX part. */
 	qc->rx.bytes = 0;
+	qc->rx.nb_ack_eliciting = 0;
 
 	/* XXX TO DO: Only one path at this time. */
 	qc->path = &qc->paths[0];