BUG/MINOR: quic: Do not resend already acked frames

Some frames are marked as already acknowledged from duplicated packets
whose the original packet has been acknowledged. There is no need
to resend such packets or frames.

Implement qc_pkt_with_only_acked_frms() to detect packet with only
already acknowledged frames inside and use it from qc_prep_fast_retrans()
which selects the packet to be retransmitted.

Must be backported to 2.6 and 2.7.

diff --git a/src/quic_conn.c b/src/quic_conn.c
index 7c2ee64921779febbe13910a2ed73d63a7958886..61acd72c38d52b25a09decc04aee94227c254b90 100644 (file)
--- a/src/quic_conn.c
+++ b/src/quic_conn.c
@@ -2536,6 +2536,11 @@ static void qc_dup_pkt_frms(struct quic_conn *qc,
        list_for_each_entry_safe(frm, frmbak, pkt_frm_list, list) {
                struct quic_frame *dup_frm, *origin;
 
+               if (frm->flags & QUIC_FL_TX_FRAME_ACKED) {
+                       TRACE_DEVEL("already acknowledged frame", QUIC_EV_CONN_PRSAFRM, qc, frm);
+                       continue;
+               }
+
                switch (frm->type) {
                case QUIC_FT_STREAM_8 ... QUIC_FT_STREAM_F:
                {
@@ -2598,6 +2603,20 @@ static void qc_dup_pkt_frms(struct quic_conn *qc,
        TRACE_LEAVE(QUIC_EV_CONN_PRSAFRM, qc);
 }
 
+/* Boolean function which return 1 if <pkt> TX packet is only made of
+ * already acknowledged frame.
+ */
+static inline int qc_pkt_with_only_acked_frms(struct quic_tx_packet *pkt)
+{
+       struct quic_frame *frm;
+
+       list_for_each_entry(frm, &pkt->frms, list)
+               if (!(frm->flags & QUIC_FL_TX_FRAME_ACKED))
+                       return 0;
+
+       return 1;
+}
+
 /* Prepare a fast retransmission from <qel> encryption level */
 static void qc_prep_fast_retrans(struct quic_conn *qc,
                                  struct quic_enc_level *qel,
@@ -2622,9 +2641,10 @@ static void qc_prep_fast_retrans(struct quic_conn *qc,
                node = eb64_next(node);
                /* Skip the empty and coalesced packets */
                TRACE_PRINTF(TRACE_LEVEL_DEVELOPER, QUIC_EV_CONN_SPPKTS, qc, 0, 0, 0,
-                            "--> pn=%llu (%d %d)", (ull)p->pn_node.key,
-                            LIST_ISEMPTY(&p->frms), !!(p->flags & QUIC_FL_TX_PACKET_COALESCED));
-               if (!LIST_ISEMPTY(&p->frms)) {
+                            "--> pn=%llu (%d %d %d)", (ull)p->pn_node.key,
+                            LIST_ISEMPTY(&p->frms), !!(p->flags & QUIC_FL_TX_PACKET_COALESCED),
+                            qc_pkt_with_only_acked_frms(p));
+               if (!LIST_ISEMPTY(&p->frms) && !qc_pkt_with_only_acked_frms(p)) {
                        pkt = p;
                        break;
                }
@@ -2684,7 +2704,8 @@ static void qc_prep_hdshk_fast_retrans(struct quic_conn *qc,
                TRACE_PRINTF(TRACE_LEVEL_DEVELOPER, QUIC_EV_CONN_SPPKTS, qc, 0, 0, 0,
                             "--> pn=%llu (%d %d)", (ull)p->pn_node.key,
                             LIST_ISEMPTY(&p->frms), !!(p->flags & QUIC_FL_TX_PACKET_COALESCED));
-               if (!LIST_ISEMPTY(&p->frms) && !(p->flags & QUIC_FL_TX_PACKET_COALESCED)) {
+               if (!LIST_ISEMPTY(&p->frms) && !(p->flags & QUIC_FL_TX_PACKET_COALESCED) &&
+                   !qc_pkt_with_only_acked_frms(p)) {
                        pkt = p;
                        break;
                }