@@ -2892,8 +2892,8 @@ static void tcp_enter_recovery(struct sock *sk, bool ece_ack)
* tcp_xmit_retransmit_queue().
*/
static void tcp_fastretrans_alert(struct sock *sk, int pkts_acked,
- int prior_sacked, bool is_dupack,
- int flag)
+ int prior_sacked, int prior_packets,
+ bool is_dupack, int flag)
{
struct inet_connection_sock *icsk = inet_csk(sk);
struct tcp_sock *tp = tcp_sk(sk);
@@ -2959,7 +2959,8 @@ static void tcp_fastretrans_alert(struct sock *sk, int pkts_acked,
tcp_add_reno_sack(sk);
} else
do_lost = tcp_try_undo_partial(sk, pkts_acked);
- newly_acked_sacked = pkts_acked + tp->sacked_out - prior_sacked;
+ newly_acked_sacked = prior_packets - tp->packets_out +
+ tp->sacked_out - prior_sacked;
break;
case TCP_CA_Loss:
if (flag & FLAG_DATA_ACKED)
@@ -2981,7 +2982,8 @@ static void tcp_fastretrans_alert(struct sock *sk, int pkts_acked,
if (is_dupack)
tcp_add_reno_sack(sk);
}
- newly_acked_sacked = pkts_acked + tp->sacked_out - prior_sacked;
+ newly_acked_sacked = prior_packets - tp->packets_out +
+ tp->sacked_out - prior_sacked;
if (icsk->icsk_ca_state <= TCP_CA_Disorder)
tcp_try_undo_dsack(sk);
@@ -3605,9 +3607,10 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
bool is_dupack = false;
u32 prior_in_flight;
u32 prior_fackets;
- int prior_packets;
+ int prior_packets = tp->packets_out;
int prior_sacked = tp->sacked_out;
int pkts_acked = 0;
+ int previous_packets_out = 0;
bool frto_cwnd = false;
/* If the ack is older than previous acks
@@ -3687,14 +3690,14 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
sk->sk_err_soft = 0;
icsk->icsk_probes_out = 0;
tp->rcv_tstamp = tcp_time_stamp;
- prior_packets = tp->packets_out;
if (!prior_packets)
goto no_queue;
/* See if we can take anything off of the retransmit queue. */
+ previous_packets_out = tp->packets_out;
flag |= tcp_clean_rtx_queue(sk, prior_fackets, prior_snd_una);
- pkts_acked = prior_packets - tp->packets_out;
+ pkts_acked = previous_packets_out - tp->packets_out;
if (tp->frto_counter)
frto_cwnd = tcp_process_frto(sk, flag);
@@ -3709,7 +3712,7 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
tcp_cong_avoid(sk, ack, prior_in_flight);
is_dupack = !(flag & (FLAG_SND_UNA_ADVANCED | FLAG_NOT_DUP));
tcp_fastretrans_alert(sk, pkts_acked, prior_sacked,
- is_dupack, flag);
+ prior_packets, is_dupack, flag);
} else {
if ((flag & FLAG_DATA_ACKED) && !frto_cwnd)
tcp_cong_avoid(sk, ack, prior_in_flight);
@@ -3726,7 +3729,7 @@ no_queue:
/* If data was DSACKed, see if we can undo a cwnd reduction. */
if (flag & FLAG_DSACKING_ACK)
tcp_fastretrans_alert(sk, pkts_acked, prior_sacked,
- is_dupack, flag);
+ prior_packets, is_dupack, flag);
/* 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.
@@ -3746,7 +3749,7 @@ old_ack:
if (TCP_SKB_CB(skb)->sacked) {
flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una);
tcp_fastretrans_alert(sk, pkts_acked, prior_sacked,
- is_dupack, flag);
+ prior_packets, is_dupack, flag);
}
SOCK_DEBUG(sk, "Ack %u before %u:%u\n", ack, tp->snd_una, tp->snd_nxt);
This is a note to let you know that I have just added a patch titled tcp: bug fix in proportional rate reduction. to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree which can be found at: http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue This patch is scheduled to be released in version 3.8.13.4. If you, or anyone else, feels it should not be added to this tree, please reply to this email. For more information about the 3.8.y.z tree, see https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable Thanks. -Kamal ------ From 0b5aa2ae1a0c92f5621cb36587a55c903f8e0630 Mon Sep 17 00:00:00 2001 From: Nandita Dukkipati <nanditad@google.com> Date: Tue, 21 May 2013 15:12:07 +0000 Subject: tcp: bug fix in proportional rate reduction. [ Upstream commit 35f079ebbc860dcd1cca70890c9c8d59c1145525 ] This patch is a fix for a bug triggering newly_acked_sacked < 0 in tcp_ack(.). The bug is triggered by sacked_out decreasing relative to prior_sacked, but packets_out remaining the same as pior_packets. This is because the snapshot of prior_packets is taken after tcp_sacktag_write_queue() while prior_sacked is captured before tcp_sacktag_write_queue(). The problem is: tcp_sacktag_write_queue (tcp_match_skb_to_sack() -> tcp_fragment) adjusts the pcount for packets_out and sacked_out (MSS change or other reason). As a result, this delta in pcount is reflected in (prior_sacked - sacked_out) but not in (prior_packets - packets_out). This patch does the following: 1) initializes prior_packets at the start of tcp_ack() so as to capture the delta in packets_out created by tcp_fragment. 2) introduces a new "previous_packets_out" variable that snapshots packets_out right before tcp_clean_rtx_queue, so pkts_acked can be correctly computed as before. 3) Computes pkts_acked using previous_packets_out, and computes newly_acked_sacked using prior_packets. Signed-off-by: Nandita Dukkipati <nanditad@google.com> Acked-by: Yuchung Cheng <ycheng@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Kamal Mostafa <kamal@canonical.com> --- net/ipv4/tcp_input.c | 23 +++++++++++++---------- 1 file changed, 13 insertions(+), 10 deletions(-) -- 1.8.1.2