tcp: remove tcp_mark_lost_retrans()

Remove the existing lost retransmit detection because RACK subsumes
it completely. This also stops the overloading the ack_seq field of
the skb control block.

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 0 insertions, 65 deletions

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index eedb25db3947..5a776897a8c7 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -1048,70 +1048,6 @@ static bool tcp_is_sackblock_valid(struct tcp_sock *tp, bool is_dsack,
         return !before(start_seq, end_seq - tp->max_window);
 }
 
-/* Check for lost retransmit. This superb idea is borrowed from "ratehalving".
- * Event "B". Later note: FACK people cheated me again 8), we have to account
- * for reordering! Ugly, but should help.
- *
- * Search retransmitted skbs from write_queue that were sent when snd_nxt was
- * less than what is now known to be received by the other end (derived from
- * highest SACK block). Also calculate the lowest snd_nxt among the remaining
- * retransmitted skbs to avoid some costly processing per ACKs.
- */
-static void tcp_mark_lost_retrans(struct sock *sk, int *flag)
-{
-        const struct inet_connection_sock *icsk = inet_csk(sk);
-        struct tcp_sock *tp = tcp_sk(sk);
-        struct sk_buff *skb;
-        int cnt = 0;
-        u32 new_low_seq = tp->snd_nxt;
-        u32 received_upto = tcp_highest_sack_seq(tp);
-
-        if (!tcp_is_fack(tp) || !tp->retrans_out ||
-            !after(received_upto, tp->lost_retrans_low) ||
-            icsk->icsk_ca_state != TCP_CA_Recovery)
-                return;
-
-        tcp_for_write_queue(skb, sk) {
-                u32 ack_seq = TCP_SKB_CB(skb)->ack_seq;
-
-                if (skb == tcp_send_head(sk))
-                        break;
-                if (cnt == tp->retrans_out)
-                        break;
-                if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una))
-                        continue;
-
-                if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS))
-                        continue;
-
-                /* TODO: We would like to get rid of tcp_is_fack(tp) only
-                 * constraint here (see above) but figuring out that at
-                 * least tp->reordering SACK blocks reside between ack_seq
-                 * and received_upto is not easy task to do cheaply with
-                 * the available datastructures.
-                 *
-                 * Whether FACK should check here for tp->reordering segs
-                 * in-between one could argue for either way (it would be
-                 * rather simple to implement as we could count fack_count
-                 * during the walk and do tp->fackets_out - fack_count).
-                 */
-                if (after(received_upto, ack_seq)) {
-                        TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;
-                        tp->retrans_out -= tcp_skb_pcount(skb);
-                        *flag |= FLAG_LOST_RETRANS;
-                        tcp_skb_mark_lost_uncond_verify(tp, skb);
-                        NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSTRETRANSMIT);
-                } else {
-                        if (before(ack_seq, new_low_seq))
-                                new_low_seq = ack_seq;
-                        cnt += tcp_skb_pcount(skb);
-                }
-        }
-
-        if (tp->retrans_out)
-                tp->lost_retrans_low = new_low_seq;
-}
-
 static bool tcp_check_dsack(struct sock *sk, const struct sk_buff *ack_skb,
                             struct tcp_sack_block_wire *sp, int num_sacks,
                             u32 prior_snd_una)
@@ -1838,7 +1774,6 @@ advance_sp:
             ((inet_csk(sk)->icsk_ca_state != TCP_CA_Loss) || tp->undo_marker))
                 tcp_update_reordering(sk, tp->fackets_out - state->reord, 0);
 
-        tcp_mark_lost_retrans(sk, &state->flag);
         tcp_verify_left_out(tp);
 out: