From: Yuchung Cheng Date: Tue, 2 Feb 2016 18:33:04 +0000 (-0800) Subject: tcp: retransmit after recovery processing and congestion control X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=e662ca40de846e0a2be6326a7c4668326ddb194c;p=linux-beck.git tcp: retransmit after recovery processing and congestion control The retransmission and F-RTO transmission currently happen inside recovery state processing (tcp_fastretrans_alert) but before congestion control. This refactoring moves the logic after both s.t. we can determine how much to send (cwnd) before deciding what to send. Signed-off-by: Yuchung Cheng Signed-off-by: Neal Cardwell Signed-off-by: Eric Dumazet Signed-off-by: David S. Miller --- diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 8194a250a01e..84a4ab9c05d1 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -126,6 +126,10 @@ int sysctl_tcp_invalid_ratelimit __read_mostly = HZ/2; #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH) #define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH)) +#define REXMIT_NONE 0 /* no loss recovery to do */ +#define REXMIT_LOST 1 /* retransmit packets marked lost */ +#define REXMIT_NEW 2 /* FRTO-style transmit of unsent/new packets */ + /* Adapt the MSS value used to make delayed ack decision to the * real world. */ @@ -2662,7 +2666,8 @@ static void tcp_enter_recovery(struct sock *sk, bool ece_ack) /* Process an ACK in CA_Loss state. Move to CA_Open if lost data are * recovered or spurious. Otherwise retransmits more on partial ACKs. */ -static void tcp_process_loss(struct sock *sk, int flag, bool is_dupack) +static void tcp_process_loss(struct sock *sk, int flag, bool is_dupack, + int *rexmit) { struct tcp_sock *tp = tcp_sk(sk); bool recovered = !before(tp->snd_una, tp->high_seq); @@ -2684,10 +2689,15 @@ static void tcp_process_loss(struct sock *sk, int flag, bool is_dupack) tp->frto = 0; /* Step 3.a. loss was real */ } else if (flag & FLAG_SND_UNA_ADVANCED && !recovered) { tp->high_seq = tp->snd_nxt; - __tcp_push_pending_frames(sk, tcp_current_mss(sk), - TCP_NAGLE_OFF); - if (after(tp->snd_nxt, tp->high_seq)) - return; /* Step 2.b */ + /* Step 2.b. Try send new data (but deferred until cwnd + * is updated in tcp_ack()). Otherwise fall back to + * the conventional recovery. + */ + if (tcp_send_head(sk) && + after(tcp_wnd_end(tp), tp->snd_nxt)) { + *rexmit = REXMIT_NEW; + return; + } tp->frto = 0; } } @@ -2706,7 +2716,7 @@ static void tcp_process_loss(struct sock *sk, int flag, bool is_dupack) else if (flag & FLAG_SND_UNA_ADVANCED) tcp_reset_reno_sack(tp); } - tcp_xmit_retransmit_queue(sk); + *rexmit = REXMIT_LOST; } /* Undo during fast recovery after partial ACK. */ @@ -2756,7 +2766,7 @@ static bool tcp_try_undo_partial(struct sock *sk, const int acked, */ static void tcp_fastretrans_alert(struct sock *sk, const int acked, const int prior_unsacked, - bool is_dupack, int flag) + bool is_dupack, int flag, int *rexmit) { struct inet_connection_sock *icsk = inet_csk(sk); struct tcp_sock *tp = tcp_sk(sk); @@ -2831,7 +2841,7 @@ static void tcp_fastretrans_alert(struct sock *sk, const int acked, } break; case TCP_CA_Loss: - tcp_process_loss(sk, flag, is_dupack); + tcp_process_loss(sk, flag, is_dupack, rexmit); if (icsk->icsk_ca_state != TCP_CA_Open && !(flag & FLAG_LOST_RETRANS)) return; @@ -2871,7 +2881,7 @@ static void tcp_fastretrans_alert(struct sock *sk, const int acked, if (do_lost) tcp_update_scoreboard(sk, fast_rexmit); tcp_cwnd_reduction(sk, prior_unsacked, fast_rexmit, flag); - tcp_xmit_retransmit_queue(sk); + *rexmit = REXMIT_LOST; } /* Kathleen Nichols' algorithm for tracking the minimum value of @@ -3506,6 +3516,27 @@ static inline void tcp_in_ack_event(struct sock *sk, u32 flags) icsk->icsk_ca_ops->in_ack_event(sk, flags); } +/* Congestion control has updated the cwnd already. So if we're in + * loss recovery then now we do any new sends (for FRTO) or + * retransmits (for CA_Loss or CA_recovery) that make sense. + */ +static void tcp_xmit_recovery(struct sock *sk, int rexmit) +{ + struct tcp_sock *tp = tcp_sk(sk); + + if (rexmit == REXMIT_NONE) + return; + + if (unlikely(rexmit == 2)) { + __tcp_push_pending_frames(sk, tcp_current_mss(sk), + TCP_NAGLE_OFF); + if (after(tp->snd_nxt, tp->high_seq)) + return; + tp->frto = 0; + } + tcp_xmit_retransmit_queue(sk); +} + /* This routine deals with incoming acks, but not outgoing ones. */ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag) { @@ -3520,6 +3551,7 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag) int prior_packets = tp->packets_out; const int prior_unsacked = tp->packets_out - tp->sacked_out; int acked = 0; /* Number of packets newly acked */ + int rexmit = REXMIT_NONE; /* Flag to (re)transmit to recover losses */ sack_state.first_sackt.v64 = 0; @@ -3616,7 +3648,7 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag) if (tcp_ack_is_dubious(sk, flag)) { is_dupack = !(flag & (FLAG_SND_UNA_ADVANCED | FLAG_NOT_DUP)); tcp_fastretrans_alert(sk, acked, prior_unsacked, - is_dupack, flag); + is_dupack, flag, &rexmit); } if (tp->tlp_high_seq) tcp_process_tlp_ack(sk, ack, flag); @@ -3634,13 +3666,14 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag) if (icsk->icsk_pending == ICSK_TIME_RETRANS) tcp_schedule_loss_probe(sk); tcp_update_pacing_rate(sk); + tcp_xmit_recovery(sk, rexmit); return 1; no_queue: /* If data was DSACKed, see if we can undo a cwnd reduction. */ if (flag & FLAG_DSACKING_ACK) tcp_fastretrans_alert(sk, acked, prior_unsacked, - is_dupack, flag); + is_dupack, flag, &rexmit); /* If this ack opens up a zero window, clear backoff. It was * being used to time the probes, and is probably far higher than * it needs to be for normal retransmission. @@ -3664,7 +3697,8 @@ old_ack: flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una, &sack_state); tcp_fastretrans_alert(sk, acked, prior_unsacked, - is_dupack, flag); + is_dupack, flag, &rexmit); + tcp_xmit_recovery(sk, rexmit); } SOCK_DEBUG(sk, "Ack %u before %u:%u\n", ack, tp->snd_una, tp->snd_nxt);